Russian style- studio support Black Ice(c) 1999-2002

Chapter 3. Fundamentals of Biomechanical Control

Science begins as soon as they begin to measure.

Accurate knowledge is unthinkable without measure.

D. I. Mendeleev

From intuition to exact knowledge!

A person’s motor skill, his ability to move quickly, accurately and beautifully in any conditions, depends on the level of physical, technical, tactical, psychological and theoretical preparedness. These five factors of movement culture are leading in sports, in physical education of schoolchildren, and in mass forms of physical education. To improve motor skills and even to maintain it at the same level, it is necessary to control each of these factors.

The object of biomechanical control is human motor skills, i.e. motor (physical) qualities and their manifestations. This means that as a result of biomechanical control we obtain information:

1) about the technique of motor actions and tactics of motor activity;

2) about endurance, strength, speed, agility and flexibility, the proper level of which is a necessary condition for high technical and tactical mastery (In the English literature on physical education, a wider list of motor qualities is accepted, including the ability to perform balance exercises, dance exercises and etc.).

To put it even more simply: biomechanical control answers three questions:

1) What does a person do?

2) How well does it do this?

3) Why does he do this?

The biomechanical control procedure corresponds to the following scheme:

Measurements in biomechanics

A person becomes an object of measurement from early childhood. A newborn's height, weight, body temperature, sleep duration, etc. are measured. Later, at school age, knowledge and skills are included in the variables measured. The older a person is, the wider his range of interests, the more numerous and varied the indicators that characterize him. And the more difficult it is to make accurate measurements. How, for example, can we measure technical and tactical readiness, the beauty of movements, the geometry of the masses of the human body, strength, flexibility, etc.? This is discussed in this section.

Measurement scales and units of measurement

A measurement scale is a sequence of quantities that allows one to establish a correspondence between the characteristics of the objects being studied and the numbers. In biomechanical control, scales of names, ratios and order are most often used.

The naming scale is the simplest of all. In this scale, numbers, letters, words or other symbols act as labels and serve to detect and distinguish the objects being studied. For example, when monitoring the tactics of a football team, field numbers help identify each player.

The numbers or words that make up the naming scale are allowed to be interchanged. And if they can be interchanged without compromising the accuracy of the value of the measured variable, then this variable should be measured on a scale of names. For example, the naming scale is used to determine the scope of equipment and tactics (this is discussed in the next section).

An order scale occurs when the numbers that make up the scale are ordered by rank, but the intervals between the ranks cannot be accurately measured. For example, knowledge of biomechanics or skills and abilities in physical education lessons are assessed on a scale: “poor” - “satisfactory” - “good” - “excellent”. The order scale makes it possible not only to establish the fact of equality or inequality of measured objects, but also to determine the nature of inequality in qualitative concepts: “more - less”, “better - worse”. However, to the questions: “How much more?”, “How much better?” - order scales do not give an answer.

Using order scales, they measure “qualitative” indicators that do not have a strict quantitative measure (knowledge, abilities, artistry, beauty and expressiveness of movements, etc.).

The scale of order is infinite, and there is no zero level in it. This is understandable. No matter how incorrect a person’s gait or posture may be, for example, an even worse option can always be found. And on the other hand, no matter how beautiful and expressive a gymnast’s motor actions are, there will always be ways to make them even more beautiful.

The relationship scale is the most accurate. In it, the numbers are not only ordered by rank, but also separated by equal intervals - units of measurement 1. The peculiarity of the ratio scale is that it defines the position of the zero point.

The ratio scale measures the size and mass of the body and its parts, the position of the body in space, speed and acceleration, strength, duration of time intervals and many other biomechanical characteristics. Illustrative examples of a ratio scale are: a scale of scales, a stopwatch scale, a speedometer scale.

The ratio scale is more precise than the order scale. It allows you not only to find out that one measurement object (technique, tactical option, etc.) is better or worse than another, but also gives answers to the questions of how much better and how many times better. Therefore, in biomechanics they try to use ratio scales and, for this purpose, record biomechanical characteristics.

TEXTBOOK FOR UNIVERSITIES.

IN AND. DUBROVSKY, V.N. FEDOROVA

Moscow

Reviewers:

Doctor of Biological Sciences, Professor A.G. Maxine; doctor technical sciences, Professor V.D. Kovalev;

Candidate of Medical Sciences, laureate of the USSR State Prize

I.L. Badnin

Drawings made by the artist N.M. Zameshaeva

Dubrovsky V.I., Fedorova V.N.

Biomechanics: Textbook. for medium and higher schools, institutions. M.: Publishing house VLADOS-PRESS, 2003. 672 p.: ill. ISBN 5-305-00101-3.

The textbook is written in accordance with the new program for the study of biomechanics in higher educational institutions. Much attention is paid to the biomechanical substantiation of the use of means of physical culture and sports using the example of various sports. Reflected modern approaches To assess the impact of various physical and climatic factors on an athlete’s technique, the biomechanical characteristics of various sports are given. Sections on medical biomechanics are presented for the first time, biomechanics of disabled athletes, biomechanical control of locomotion, etc.

The textbook is addressed to students of physical education faculties of universities, institutes of physical education and medical universities, as well as coaches, sports doctors, rehabilitation specialists involved in the development and forecasting of training, treatment and rehabilitation of athletes and other specialists.

© V.I. Dubrovsky, V.N. Fedorova, 2003 © VLADOS-PRESS Publishing House, 2003 © Serial cover design. ISBN 5-305-00101-3 “VLADOS-PRESS Publishing House”, 2003

PREFACE

Any branch of human knowledge, including such a discipline as biomechanics, operates with a certain set of initial definitions, concepts and hypotheses. On the one hand, fundamental definitions from mathematics, physics, and general mechanics are used. On the other hand, biomechanics is based on data from experimental studies, the most important of which are the assessment of various types of human motor activity and their control; determination of the properties of biomechanical systems under various methods of deformation; results obtained in solving medical and biological problems.

Biomechanics is at the intersection of different sciences: medicine, physics, mathematics, physiology, biophysics, involving various specialists in its field, such as engineers, designers, technologists, programmers, etc.

Biomechanics of sports as an academic discipline studies how a person moves in the process of performing physical exercise, during competitions, and the movement of individual sports equipment.

Significant importance in modern sports and physical culture is given to mechanical strength, resistance of tissues of the musculoskeletal system, organs, tissues to repeated physical activity, especially when training in extreme conditions (medium mountains, high humidity, low and high temperatures, hypothermia, changes in biorhythms) with taking into account the physique, age, gender, functional state of the person. All this data can be used to improve the methodology and technique of performing certain exercises and training systems, as well as to improve equipment, equipment and other factors.

Physical culture and sports in our country have lost their influence in the last decade. This does nothing to improve human health. This also affects the ability to withstand negative factors environment.

The importance of sport at all times has been significant in preventing premature aging and in restoring the body's functional capabilities after illnesses and injuries.

With the development of science, medicine is actively implementing its achievements, developing new treatment methods, assessing their effectiveness, and new diagnostic techniques. This, in turn, enriches sports medicine and physical education. This textbook offers knowledge of the physical foundations of many issues in sports medicine, which are necessary for a physical education teacher, coach, sports doctor, and massage therapist. This knowledge is no less important than knowledge of the basics of the training process. Depending on how the physical essence of a particular area of ​​sports medicine is understood, in conjunction with medical aspects it is possible to predict and dose the health (therapeutic) effect, as well as the level of sports achievements.

In therapeutic physical culture, various physical exercises are used, implemented in one or another sport.

This textbook, in comparison with previously published ones, is the first for the biomechanics of sports to present material showing the application of the laws of fundamental physics to many specific areas of this discipline. Issues considered: kinematics, dynamics of a material point, dynamics forward motion, types of forces in nature, dynamics of rotational motion, non-inertial frames of reference, conservation laws, mechanical vibrations, mechanical properties. A large section is presented showing physical basis the influence of various factors (mechanical, sound, electromagnetic, radiation, thermal), understanding the physical essence of which is absolutely necessary for the rational solution of many problems in sports medicine.

Professor V.I. Dubrovsky and Professor V.N. Fedorov, in addition to biomechanical methods of monitoring people involved in physical education and sports, presented biomechanical indicators in normal conditions and in pathology (injuries and diseases of the musculoskeletalapparatus, during fatigue, etc.), as well as during training in extreme conditions, in disabled athletes, etc.

Many issues are covered by the authors taking into account the development of elite sports, wheelchair sports, biomechanics of sports injury, various age periods development, taking into account the physique and technique of performing certain exercises in various sports.

The book shows the main directions in the development of biomechanics using modern control methods: stationary and remote control of locomotion; development modern technologies inventory, equipment; techniques for performing physical exercises in various sports; monitoring the performance of exercises by disabled athletes; biomechanical control for injuries and diseases of the musculoskeletal system, etc.

Essentially, in each chapter of the textbook, the authors emphasize that in order to successfully perform in competitions, an athlete must have a rational technique for performing the exercise, understanding its medical and physical essence, must be equipped with modern equipment, sports equipment, must be well prepared functionally and healthy.

A special place in the textbook is given to the influence of intense physical activity on structural (morphological) changes in the tissues of the musculoskeletal system, especially if the technique of performing physical exercises and methods of its correction are imperfect. It has been noted that the reaction of the musculoskeletal tissues to physical activity largely depends on the exercise technique, physique, age, functional state, climatic and geographical factors, etc.

The authors pay great attention to the possibilities of using mathematical and physical models both for various exercises, and for individual areas and systems of the human body, in particular the athlete, as well as the body as a whole, to predict the body’s reactions to physical activity and various adverse factors. external environment. Body type and age are important for the calculation and model assessment of the limits of tolerability of these effects, taking into account a variety of additional factors.

In our country and abroad, we still do not have a textbook that would systematize materials both on the theoretical physical and mathematical foundations of the biomechanics of sports, and on biomechanics in normal conditions and in pathology, taking into account the age, gender, physique and functional state of individuals, involved in physical education and sports. This is especially important when playing elite sports, where the requirements for the technique of performing exercises are exceptional, and the slightest deviations lead to injuries, sometimes to disability, and a decrease in sports results.

The textbook "Biomechanics" answers modern requirements requirements for textbooks on medical and biological disciplines, uniform for pedagogical, medical universities and institutes of physical education.

A large number of information tables, figures, diagrams, a uniform and clear division of material according to structure in each chapter, highlighted laconic definitions make the presented material very visual, interesting, easy to understand and remember.

This textbook will allow students, coaches, doctors, exercise therapy methodologists, physical education teachers to better understand the basics of sports biomechanics, sports medicine, physical therapy, and therefore, successfully and actively use them in their work. This textbook can be recommended to experts in applied mechanics specializing in biomechanics.

Head of the Department of Theoretical Mechanics, Perm State technical university,

Doctor of Technical Sciences, Professor, Honored Scientist of the Russian Federation

Yu.I. Nyashin

INTRODUCTION

The biomechanics of human movement is one part of a more general discipline, briefly called “biomechanics”.

Biomechanics is a branch of biophysics that studies the mechanical properties of tissues, organs and systems of a living organism and the mechanical phenomena that accompany life processes. Using the methods of theoretical and applied mechanics, this science studies the deformation of the structural elements of the body, the flow of liquids and gases in a living organism, the movement in space of body parts, the stability and controllability of movements and other issues accessible to these methods. Based on these studies, biomechanical characteristics of organs and systems of the body can be compiled, knowledge of which is the most important prerequisite for studying regulatory processes. Accounting bio mechanical characteristics makes it possible to make assumptions about the structure of systems that control physiological functions. Until recently, the main research in the field of biomechanics was associated with the study of human and animal movements. However, the scope of application of this science is progressively expanding; now it also includes the study of the respiratory system, circulatory system, specialized receptors, etc. Interesting data were obtained from the study of elastic and inelastic resistance of the chest, gas movements through the respiratory tract. Attempts are being made to generalize the analysis of blood movement from the perspective of continuum mechanics; in particular, elastic vibrations of the vascular wall are being studied. It has also been proven that, from a mechanical point of view, the structure of the vascular system is optimal for performing its transport functions. Rheological studies in biomechanics have discovered specific deformationproperties of many body tissues: exponential nonlinearity of the relationship between stresses and strains, significant dependence on time, etc. The knowledge gained about the deformation properties of tissues helps solve some practical problems In particular, they are used to create internal prostheses (valves, artificial heart, blood vessels, etc.). Classical solid mechanics is used especially fruitfully in the study of human movements. Biomechanics is often understood as precisely this application. When studying movements, biomechanics uses data from anthropometry, anatomy, physiology, nervous and muscular systems and other biological disciplines. Therefore, often, perhaps in educational purposes, the biomechanics of the musculoskeletal system includes its functional anatomy, and sometimes the physiology of the neuromuscular system, calling this association kinesiology.

The number of control influences in the neuromuscular system is enormous. However, the neuromuscular system has amazing reliability and wide compensatory capabilities, the ability not only to repeat the same standard sets of movements (synergy) over and over again, but also to perform standard voluntary movements aimed at achieving certain goals. In addition to the ability to organize and actively learn the necessary movements, the neuromuscular system ensures adaptability to rapidly changing environmental and internal conditions of the body, changing habitual actions in relation to these conditions. This variability is not only passive in nature, but has the features of an active search carried out by the nervous system when it achieves the best solution assigned tasks. The listed abilities of the nervous system are provided by the processing of information about movements in it, which arrives through feedback connections formed by sensory afferentation. The activity of the neuromuscular system is reflected in the temporal, kinematic and dynamic structures of movement. Thanks to this reflection, it becomes possible, by observing mechanics, to obtain information about the regulation of movements and its disorders. This opportunity is widely used in the diagnosis of diseases, in neurophysiological studies using special tests to monitor the motor skills and training of disabled people, athletes, astronauts, and in a number of other cases.

Chapter 1 HISTORY OF BIOMECHANICS DEVELOPMENT

Biomechanics is one of the oldest branches of biology. Its origins were the works of Aristotle and Galen, devoted to the analysis of animal and human movements. But only thanks to the work of one of the most brilliant men of the Renaissance, Leonardo da Vinci (14521519), biomechanics took its next step. Leonardo was particularly interested in the structure of the human body (anatomy) in connection with movement. He described the mechanics of the body during the transition from a sitting position to a standing position, when walking up and down, when jumping, and, apparently, gave the first description of gaits.

R. Descartes (15961650) created the basis of the reflex theory, showing that the cause of movements can be a specific environmental factor affecting the sense organs. This explained the origin of involuntary movements.

Subsequently, the Italian D. Borelli (16081679) - doctor, mathematician, physicist - had a great influence on the development of biomechanics. In his book “On the Movement of Animals,” he essentially laid the foundation for biomechanics as a branch of science. He viewed the human body as a machine and sought to explain breathing, blood movement and muscle function from a mechanical perspective.

Biological mechanics as the science of mechanical motion in biological systems uses the principles of mechanics as a methodological apparatus.

Human mechanicsThere is a new branch of mechanics that studies purposeful human movements.

Biomechanics this is a branch of biology that studies the mechanical properties of living tissues, organs and the organism as a whole, as well as the mechanical phenomena occurring in them (during movement, breathing, etc.).

Leonardo DO Vinci I.P. Pavlov

P.F. Lesgaft N.E. Vvedensky

The first steps in a detailed study of the biomechanics of movements were made only at the end XIX centuries by German scientists Braun and Fischer(V. Braune, O. Fischer), who developed a perfect method for recording movements, studied in detail the dynamic side of the movements of the limbs and the general center of gravity (GCG) of a person during normal walking.

K.H. Kekcheev (1923) studied the biomechanics of pathological gaits using the Brown and Fisher technique.

P.F. Lesgaft (18371909) created the biomechanics of physical exercises, developed on the basis of dynamic anatomy. In 1877 P.F. Lesgaft began giving lectures on this subject at physical education courses. At the Institute of Physical Education named after. P.F. Lesgaft this course was included in the subject “ physical education”, and in 1927 it was separated into an independent subject called “theory of movement” and in 1931 it was renamed the course “Biomechanics of Physical Exercises”.

N.A. made a great contribution to the knowledge of the interaction of levels of movement regulation. Bernstein (1880 1968). They are given theoretical basis movement control processes from the perspective of general theory large systems. Research by N.A. Bernstein was allowed to establish extremely important principle motion control, generally accepted today. Neurophysiological concepts N.A. Bernstein served as the basis for the formation of the modern theory of biomechanics of human movements.

Ideas N.M. Sechenov about the reflex nature of movement control through the use of sensitive signals was developed in the theory of N.A. Bernstein on the circular nature of management processes.

B.C. Gurfinkel et al. (1965) clinically confirmed this direction, identified the principle of synergy in the organization of the work of skeletal muscles in the regulation of vertical posture, and F.A. Severin et al. (1967) obtained data on spinal generators (motoneurons) of locomotor movements. R.Granit (1955) analyzed the mechanisms of movement regulation from the perspective of neurophysiology.

R.Granit (1973) noted that the organization of output responses is ultimately determined by the mechanical properties of motor units (MUs) and the specific hierarchy of activation processes involving slow or fast MUs, tonic or phasic motoneurons, alpha motor or alpha gamma control .

ON THE. Bernstein A.A. Ukhtomsky

THEM. Sechenov A.N. Krestovnikov

Great contributions to the biomechanics of sports were made by R.G. Osterhoud (1968); T. Duck (1970), R.M. Brown; J.E. Councilman (1971); S. Plagenhoef (1971); C. W. Buchan (1971); Dal Monte et al. (1973); M.Saito et al. (1974) and many others.

In our country, the study of human movement coordination has been carried out since the twenties. XX centuries. Research was carried out on the entire biomechanical picture of the coordination structure of human voluntary movements in order to establish general patterns that determine both central regulation and the activity of the muscular periphery in this most important life process. Since the thirties XX century in the institutes of physical education in Moscow (N.A. Bernstein), in Leningrad (E.A. Kotikova, E.G. Kotelnikova), in Tbilisi (L.V. Chkhaidze), in Kharkov (D.D. Donskoy) and In other cities, scientific work on biomechanics began to develop. In 1939, a textbook by E.A. was published. Kotikova “Biomechanics of Physical Exercises” and in subsequent years, textbooks and teaching aids began to include a section “Biomechanical justification of sports technique in various sports.”

Of the biological sciences, biomechanics used scientific data on anatomy and physiology more than others. In subsequent years, dynamic anatomy, physics and physiology, especially the doctrine of nervism by I.P., had a great influence on the formation and development of biomechanics as a science. Pavlov and about functional systems by P.K. Anokhina.

N.E. made a great contribution to the study of the physiology of the locomotor system. Vvedensky (18521922). He carried out studies of the processes of excitation and inhibition in nervous and muscle tissues. His works on the physiological lability of living tissues and excitable systems and on parabiosis are of great importance for modern physiology sports. His works on the coordination of movements are also of great value.

According to the definition of A.A. Ukhtomsky (18751942), biomechanics studies “how the resulting mechanical energy of movement and stress can acquire working application.” He showed that muscle strength, other things being equal, depends on the cross section. The more cross section muscles, the more she is able to lift the load. A.A. Ukhtomsky discovered the most important physiological phenomenon dominant in the activity of nerve centers, in particular during motor acts. A large place in his works is devoted to issues of physiology of the motor system.

Questions of the physiology of sports were developed by A.N. Krestovikov (18851955). They were associated with elucidating the mechanism of muscle activity, in particular, coordination of movements, formation of motor conditioned reflexes, the etiology of fatigue during physical activity and other physiological functions during exercise.

M.F. Ivanitsky (1895–1969) developed functional (dynamic) anatomy in relation to the tasks of physical education and sports, i.e., he determined the connection between anatomy and physical education.

The successes of modern physiology, and, first of all, the works of Academician P.K. Anokhin was given the opportunity to take a fresh look at the biomechanics of movements from the position of functional systems.

All this made it possible to summarize physiological data with biomechanical studies and approach the solution of important issues of the biomechanics of movements in modern sports, elite sports.

Mid XX century, scientists have created a prosthetic hand controlled by electrical signals coming from the nervous system. In 1957, in our country, a model of a hand (hand) was constructed, which carried out bioelectric commands such as “squeeze and unclench”, and in 1964 a prosthesis with feedback was created, i.e. a prosthesis from which continuously flows into the central nervous system information about the force of compression or release of the hand, the direction of movement of the hand, and similar signs.

PC. Anokhin

American specialists(E.W. Schrader et al., 1964) created a prosthetic leg amputated above the knee. A hydraulic model of the knee joint was made to achieve natural walking. The design provides for a normal heel lift and leg extension during abduction, regardless of walking speed.

Rapid development sports in the USSR served as the basis for the development of sports biomechanics. Since 1958, in all institutes of physical culture, biomechanics became a compulsory academic discipline, departments of biomechanics were created, programs were developed, teaching aids, textbooks were published, scientific and methodological conferences, specialists were preparing.

As an academic subject, biomechanics plays several roles. Firstly, with its help, the student is introduced to the most important physical and mathematical concepts that are necessary for calculating speed, repulsion angles, body weight, location of the central gravity and its role in the technique of performing sports movements. Secondly, this discipline has independent application in sports practice, because the system of motor activity presented in it, taking into account age, gender, body weight, physique, makes it possible to develop recommendations for the work of a coach, physical education teacher, physical therapy methodologist, etc.

Biomechanical research has made it possible to create new type shoes, sports equipment, equipment and control techniques (bicycles, alpine and jump skis, racing skis, rowing boats and much more).

The study of the hydrodynamic characteristics of fish and dolphins made it possible to create special suits for swimmers and change swimming techniques, which helped to increase swimming speed.

Biomechanics is taught in higher physical education institutions in many countries around the world. An international society of biomechanics has been created, conferences, symposia, and congresses on biomechanics are held. A Scientific Council on Problems of Biomechanics has been created under the Presidium of the Russian Academy of Sciences with sections covering problems of engineering, medical and sports biomechanics.

Chapter 2 TOPOGRAPHY OF THE HUMAN BODY. GENERAL DATA ABOUT THE HUMAN BODY

From a mechanical point of view, the human body is an object of the greatest complexity. It consists of parts that can be considered solid (skeleton) with a high degree of accuracy and deformable cavities (muscles, blood vessels, etc.), and these cavities contain fluid and filterable media that do not have the properties of ordinary liquids.

The human body in general retains the structure characteristic of all vertebrates: bipolarity (head and tail ends), bilateral symmetry, predominance of paired organs, the presence of an axial skeleton, preservation of some (relict) signs of segmentation (metamerism), etc. (Fig. 2.1 ).

Other morphofunctional features of the human body include: highly multifunctional upper limb; an even row of teeth; developed brain; upright walking; prolonged childhood, etc.

In anatomy, it is customary to study the human body in an upright position with the lower limbs closed and the upper limbs lowered.

In each part of the body, areas are distinguished (Fig. 2.2, a, b) of the head, neck, torso and two pairs of upper and lower limbs (see Fig. 2.1,6).

Rice. 2.1. Segmental division of the spinal cord. Formation of plexuses from the roots of the brain (a). Segmental inversion of organs and functional systems (b)

On the human body, two ends are designated: cranial, or cranial and caudal, or caudal, and four surfaces: abdominal, or ventral, dorsal, or dorsal and two laterals: right and left (Fig. 2:3).

On the limbs, two ends are determined in relation to the body: proximal, i.e. closer and distal, i.e. distant (see Fig. 2.3).

Axes and planes

The human body is built according to the type of bilateral symmetry (it is divided by the median plane into two symmetrical halves) and is characterized by the presence of an internal skeleton. Inside the body there is dismemberment into metamers, or segments, i.e. formations that are homogeneous in structure and development, located in a sequential order in the direction of the longitudinal axis of the body (for example, muscle, nerve segments, vertebrae, etc.); the central nervous system lies closer to the dorsal surface of the body, the digestive system lies closer to the abdominal surface. Like all mammals, humans have mammary glands and hairy skin; their body cavity is divided by the diaphragm into the thoracic and abdominal sections (Fig. 2.4).

Rice. 2.2. Areas of the human body:

a anterior surface: 7 parietal region; 2 frontal region; 3 orbital area; 4 mouth area; 5 chin area; b anterior neck area; 7 lateral neck area; 8 clavicle area; 9 palm of the hand; 10 anterior area of ​​the forearm; 11 anterior ulnar region; 12 back of the shoulder; 13 axillary region; 14 chest area; 15 subcostal region; 16 epigastrium; 17 umbilical region; 18 lateral abdominal area; 19 groin area; 20 pubic area; 21 medial thigh area; 22 anterior thigh area; 23 anterior knee area; 24 anterior area of ​​the leg; 25 posterior area of ​​the lower leg; 26 anterior ankle region; 27 dorsal foot; 28 heel area; 29 back of the hand; 30 forearm; 31 posterior area of ​​the forearm; 32 posterior ulnar region; 33 posterior shoulder area; 34 posterior area of ​​the forearm; 35 breast area; 36 deltoid region; 37 clavipectoral triangle; 38 subclavian fossa; 39 sternocleidomastoid region; 40 nose area; 41 temporal region.

Rice. 2.3. The relative position of the parts in human body

b back surface: 1 parietal region; 2 temporal region; 3 frontal region; 4 orbital area; 5 zygomatic region; b buccal region; 7 submandibular triangle; 8 sternocleidomastoid region; 9acromial region; 10 interscapular region; 11 scapular region; 12 deltoid region; 13 lateral thoracic region; 14 back of the shoulder; 15 subcostal region; 16 posterior ulnar region; 17 posterior area of ​​the forearm; 18 anterior area of ​​the forearm; 79 palm of the hand; 20 heel area; 21 sole of the foot; 22 dorsum of the foot; 23 anterior area of ​​the lower leg; 24 posterior area of ​​the lower leg; 25 back of the knee; 26 posterior thigh area; 27anal region; 28 gluteal region; 29 sacral region; 30 lateral abdominal area; 31 lumbar region; 32 subscapular region; 33 vertebral region; 34 posterior shoulder area; 35 posterior ulnar region; 36 posterior forearm; 37 back of the hand; 38 anterior shoulder area; 39 suprascapular region; 40 back of the neck; 41 occipital region

Rice. 2.4. Body cavities

Rice. 2.5. Diagram of axes and planes in the human body:

1 vertical (longitudinal) axis;

2 frontal plane; 3 horizontal plane; 4 transverse axis; 5 sagittal axis; 6 sagittal plane

To better navigate the relative position of parts in the human body, we start from some basic planes and directions (Fig. 2.5). The terms "upper", "lower", "front", "back" refer to the vertical position of the human body. The plane dividing the body in the vertical direction into two symmetrical halves is called median. Planes parallel to the median are called sagittal (lat. sagitta arrow); they divide the body into segments located in the direction from right to left. They run perpendicular to the median plane frontal, i.e. parallel to the forehead(fr. front forehead) plane; they cut the body into segments located in the direction from front to back. Perpendicular to the median and frontal planes are drawn horizontal or transverse planes dividing a body into segments located one above the other. An arbitrary number of sagittal (except for the median), frontal and horizontal planes can be drawn, i.e., through any point on the surface of the body or organ.

The terms “medial” and “lateral” are used to designate parts of the body in relation to the median plane: medialis located closer to the median plane, lateralis farther from her. These terms should not be confused with the terms “internal” interims and “external” externus, which are used only in relation to the walls of cavities. The words "abdominal" ventralis, “dorsal” dorsalis, “right” dexter, “left” sinister, "superficial" superficial, “deep” profundus don't need any explanation. To denote spatial relationships on the limbs, the terms"proximalis" and "distalis" i.e., located closer and further from the junction of the limb with the torso.

To determine the projection of the internal organs, a series of vertical lines are drawn: anterior and posterior median corresponding to the sections of the median plane; right and left sternal along the lateral edges of the sternum; right and left midclavicular through the middle of the clavicle; right and left parasternal in the middle between the sternum and midclavicular; right and left anterior axillary respectively, the anterior edge of the axillary fossa; right and left mid-axillary emanating from the depth of the fossa of the same name; right and left posterior axillary fossa, corresponding to the posterior edge of the axillary fossa; right and left scapula through the lower angle of the scapula; right and left paravertebral in the middle between the scapular and posterior midlines (corresponding to the apices of the transverse processes).

Brief information about the center of gravity of the human body

The function of a person's lower extremities, if we exclude many physical exercises, is determined mainly by support (standing position) and locomotion (walking, running). In bothIn this case, the function of the lower extremities, unlike the upper extremities, is significantly influenced by the general center of gravity (GC) of the human body (Fig. 2.6).

Rice. 2.6. Location of the general center of gravity for various types of standing: 1 when tense; 2 with anthropometric; 3 at quiet

In many problems of mechanics, it is convenient and acceptable to consider the mass of a body as if it were concentrated at one point - the center of gravity (CG). Since we have to analyze the forces acting on the human body during physical exercise and standing (at rest), we should know where the CG is located in a person normally and in pathology (scoliosis, coxarthrosis, cerebral palsy, amputation of a limb, etc.).

In general biomechanics, it is important to study the location of the center of gravity (CG) of the body, its projection onto the support area, as well as the spatial relationship between the CG vector and various joints (Fig. 2.7). This allows us to study the possibilities of joint blocking and evaluate compensatory and adaptive changes in the musculoskeletal system (MSA). In adult men (on average), the GCT is located 15 mm behind the anterior-inferior edge of the body V lumbar vertebra. In women, the CG is located on average 55 mm in front of the anterior inferior edge I sacral vertebra (Fig. 2.8).

In the frontal plane, the GCT is slightly shifted to the right (by 2.6 mm in men and 1.3 mm in women), i.e. the right leg takes on a slightly greater load than the left.

Rice. 2.7. Types of standing human body position: 1 anthropometric position; 2 calm position; 3 tense position: A circle with a dot in the center, located in the pelvic area, shows the position of the general center of gravity of the body; in the head area position of the center of gravity of the head; in the hand area the position of the general center of gravity of the hand. Black dots show the transverse axes of the joints of the upper and lower limbs, as well as same atlanto-occipital joint

Rice. 2.8. Center location

severity (CG): a in men; b in women

The general center of gravity (GCG) of the body is composed of the centers of gravity of individual parts of the body (partial centers of gravity) (Fig. 2.9). Therefore, when moving and moving the mass of body parts, the general center of gravity also moves, but in order to maintain balance, its projection should not extend beyond the support area.

Rice. 2.9. Location of centers of gravity of individual parts of the body

Rice. 2.10. The position of the general center of gravity of the body: a in men of the same height, but different builds; used men of different heights; in for men and women

The height of the GCT position varies significantly among different people depending on a number of factors, which primarily include gender, age, body type, etc. (Fig. 2.10).

In women, the BCT is usually “slightly lower than in men (see Fig. 2.8).

In young children, the center of gravity of the body is located higher than in adults.

When the relative position of body parts changes, the projection of its GCT also changes (Fig. 2.11). At the same time, the stability of the body also changes. In the practice of sports (teaching exercises and training) and when performing therapeutic gymnastics exercises, this issue is very important, since with greater body stability it is possible to perform movements with greater amplitude without disturbing balance.

Rice. 2.11. The position of the general center of gravity for various body positions

The stability of the body is determined by the size of the support area, the height of the body's central center of gravity, and the location of the vertical, lowered from the center of gravity, inside the support area (see Fig. 2.7). The larger the support area and the lower the body's central center is located, the greater the stability of the body.

The quantitative expression of the degree of stability of the body in a particular position isstability angle(UU). UU is the angle formed by a vertical lowered from the body's central center of gravity and a straight line drawn from the body's center of gravity to the edge of the support area (Fig. 2.12). The greater the angle of stability, the more degree body stability.

Rice. 2.12. Stability angles at Rice. 2.13. Shoulders of gravity

performing the “splits” exercise: in relation to the transverse axes

a backward stability angle; rotation in the hip, knee

p forward stability angle; and ankle joints supporting

P gravity of skater's legs

(according to M.F. Ivanitsky)

The vertical, lowered from the body's central center, passes at a certain distance from the axes of rotation of the joints. In this regard, the force of gravity in any position of the body has a certain force in relation to each joint.moment of rotation,equal to the product of the magnitude of gravity and its shoulder.Shoulder of gravityis a perpendicular drawn from the center of the joint to the vertical, lowered from the body's center of gravity (Fig. 2.13). The greater the arm of gravity, the greater the moment of rotation it has in relation to the joint.

The mass of body parts is determined in various ways. If the absolute mass of body parts varies significantly among different people, then the relative mass, expressed as a percentage, is quite constant (see Table 5.1).

Data on the mass of body parts, as well as on the location of partial centers of gravity and moments of inertia in medicine (for the design of prostheses, orthopedic shoes, etc.) and in sports (for the design of sports equipment, shoes, etc.) are very important. ).

Organism, organ, organ system, tissue

by the body called anything Living being, the main properties of which are: constant metabolism and energy (within oneself and with the environment); self-renewal; movement; irritability and reactivity; self-regulation; growth and development; heredity and variability; adaptability to living conditions. The more complex the organism is, the more it maintains the constancy of the internal environment - homeostasis (body temperature, biochemical composition of blood, etc.) regardless of changing environmental conditions.

Evolution took place under the sign of two opposing trends: differentiation, or division of the body into tissues, organs, systems (with a corresponding and simultaneous division and specialization of functions), and integration, or unification of parts into a whole organism.

Authority call a more or less separate part of the body (liver, kidney, eye, etc.) that performs one or more functions. Tissues of different structure and physiological roles take part in the formation of an organ, which arose during long evolution as a set of adaptive mechanisms. Some organs (liver, pancreas, etc.) have complex structure, and each component performs its own function. In other cases, the components of one or another organ (heart, thyroid gland, kidney, uterus, etc.) cellular structures subordinated to the implementation of a single complex function(blood circulation, urination, etc.).

The fourth lecture on the discipline “Biomechanics of Motor Activity” describes research methods in biomechanics (film and video recording, dynamometry, accelerometry and electromyography), measurement stages and the composition of the measuring system. When analyzing biomechanical methods, positive and negative features of the methods, as well as measurement errors, are discussed. Improvements in biomechanical research methods have made it possible to develop fully automatic systems that allow analysis of movements in real time.

Lecture 4

Research methods in biomechanics

4.1. The concept of research method

Method(Greek methodos - path to something) - in the most general sense - a way to achieve a goal, a certain way of ordering activity.

The research method is chosen based on the conditions and objectives of the study. The following requirements are imposed on the research method and the equipment that supports it:

• The method and equipment must ensure obtaining a reliable result, that is, the degree of measurement accuracy must correspond to the purpose of the study;
• The method and equipment should not affect the process being studied, that is, distort the results and interfere with the subject;
• The method and equipment must ensure the speed of obtaining the result.

Example. The coach and athlete set a goal to improve the result in the 100 m run by 0.1 s. A sprinter runs a distance of 100 m in 50 steps, therefore, the time of each step should be reduced on average by 0.002 s. Obviously, to obtain a reliable result, the error in measuring the step duration should not exceed 0.0001 s.

4.2. Measurement steps

There are three stages in the study of any phenomenon:

1. Measurement of mechanical characteristics.

Mechanical properties are measured using the methods described in this lecture.

1. Processing of research results.

Currently, special computer programs are used to process the results. So. For example, the Video Motion computer program, designed for athleticism, allows, based on video recording data, to calculate the trajectory, speed and acceleration of movement of any point of the athlete’s body, including the barbell.

1. Biomechanical analysis and synthesis.

At the final stage of measurements, based on the obtained mechanical characteristics, the technique of the athlete’s motor actions is assessed and recommendations are given for its improvement.

4.3. Composition of the measuring system

The measuring system includes:

• Information sensor;
• Communication line;
• Recording device;
• Computer;
• Data output device.

Sensor– an element of the measurement system that directly measures (perceives) a certain biomechanical characteristic of the athlete’s movement. Sensors can be attached to the athlete, sports equipment and equipment, as well as supporting surfaces.

Communication line serves to transmit information from the sensor to the recording device. The communication line can be wired or telemetric. Wired communication represents the transmission of information through a multi-core cable. Its advantage is its simplicity and reliability, its disadvantage is that it interferes with the athlete’s movements. Telemetric communication – data transmission via a radio channel. In this case, the transmitting antenna is most often located on the athlete, and the recording device has a receiving antenna through which the signal is perceived.

Recording device– a device in which the process of recording the biomechanical characteristics of an athlete’s movements occurs.

For a long time, there was an analog form of signal recording. For example, analog recording of a signal in video cameras on magnetic tape. Currently, the digital form of signal recording is widespread (in the form of a sequence of numbers on a specific digital medium, for example, a DVD).

ADC– analog-to-digital converter – a device that converts an analog signal into digital form.

PC– a personal computer in which the incoming signal is processed using a certain computer program. After this, information about the athlete’s biomechanical characteristics is displayed on a printer or monitor.

Currently, the following research methods are widely used in the field of athletics (weightlifting, powerlifting, bodybuilding):

• Optical methods (film and video recording with subsequent analysis, optoelectronic cyclography);
• dynamometry;
• accelerometry;
• electromyography.

We will talk about these methods in more detail.

4.4. Optical research methods

Filming– optical research method. This method refers to non-contact measuring instruments. The foundations of this method were laid by J.L. Daguerre, E.J. Marais, and E. Muybridge. This is especially important since the system does not interfere with the athlete when performing motor actions. Main technical means is a movie camera. To conduct biomechanical studies, movie cameras with a high shooting frequency (from 100 frames per second and above) are most often used. The disadvantage of filming is the need for special film processing. Therefore, at present, two other optical methods are most often used in biomechanical studies: video recording and optoelectronic cyclography.

Video shooting– an optical research method that allows you to record motor action on videotape or the electronic matrix of a video camera. Currently, high-speed video cameras are used for biomechanical studies, allowing recording up to 1000 frames per second and higher.

An example of such a camera is the CASIO EXILIM PRO EX-F1 digital camera (Fig. 4.1), which allows high-speed shooting at a frequency of up to 1200 fps. The resolution of the camera matrix is ​​6.6 Megapixels. To record an athlete performing strength exercises, this camera can use video recording, which must be done with a resolution of 1920x1080 pixels and a frame rate of 60 fps.

Rice. 4.1. Digital camera Casio Exlim Pro EX F1

The most important part of mechanical dynamometers is the spring, which must operate in the region of linear deformation. This means that the force being measured is directly proportional to the elongation of the spring. When measuring in sports, hand and backbone (Fig. 4.2) dynamometers are often used. For example, a deadlift dynamometer is used to measure pulling force in powerlifting. The measurement range is from 100 N to 1800 N with an error of +/-2% over the entire scale. Weight 1.8 kg, size 25.4x6.35 cm. Durable aluminum handle with convenient place for capture.

Fig.4.2. Deadlift dynamometer

The disadvantage of mechanical dynamometers is the assessment of one, most often the maximum, force value. In this regard, if it is necessary to study the change in force developed by a muscle group or athlete, electronic dynamometers are used. In this case, the sensor is not a spring, but a strain gauge, and the technique itself is called strain dynamometry.

Method strain dynamometry allows you to register the efforts developed by the athlete when performing various physical exercises.

In the process of performing sports movements, an athlete exerts a mechanical impact on a wide variety of objects: sports equipment, the floor, a track, which as a result are deformed. In order to measure the values ​​of the efforts developed by the athlete, special strain gauges are used that convert mechanical deformation into an electrical signal. The operation of strain gauges is based on the tensoelectric effect. The essence of the strain gauge effect is a change in the resistance of the conductor as it is lengthened.

The strain gauge is a wire with a diameter of 0.02-0.05 mm glued between two strips of paper. It is glued to an elastic element that absorbs the force set by the athlete.

In 1938, the first strain gauges were developed that operated on the basis of the strain effect. In 1947, strain gauges were first used in physical research.

For the first time in sports in 1954, M.P. Mikhailyuk secured the strain gauge to the barbell, P.I. Nikiforov (1957) developed a strain gauge platform for recording take-off forces in high jumps. In 1963 V.K. Balsevich used strain gauge insoles to analyze the running of sprinters of various qualifications. They established several types of repulsion.

The tensodynamometry technique is actively used in weightlifting. One of the key tasks of a coach is to provide information about errors, that is, feedback from the coach to the athlete. Feedback is an important element of learning. The athlete should receive information on a regular basis that allows him to compare his own performance with an ideal or model. As a result of such a comparison, the athlete will gain knowledge about his activities and have the opportunity to work to correct his mistakes.

This technique was developed by A.N. Furaev (1988) and modernized by I.P. Kozhekin (1998). The automated stand includes a strain gauge platform, an ADC (analog-to-digital converter) and a computer. The computer expert system contains samples that characterize the correct and incorrect performance of a motor action (snatch, upward jump and deep jump. By comparing the results obtained, the expert system, built on the analysis of a tensodynamogram, allows the athlete to obtain real-time information about errors in the technique of motor action and introduce adjustments to eliminate them.

4.6. Accelerometry

Accelerometry– a biomechanical method for recording accelerations of movement of an athlete’s body, or its individual parts, as well as accelerations of sports equipment. For example, in weightlifting, an informative indicator of an athlete’s movement technique is the acceleration of the center of mass of the barbell.

Special accelerometers are used as sensors. The operating principle of the accelerometer sensor is as follows. A mass is attached to the object under study using a connection that has a certain rigidity. The acceleration is then determined based on the known mass and bond stiffness. The main characteristics of accelerometers are the range and maximum frequency of change of measured accelerations.

If a three-component accelerometer is used, three components of acceleration can be recorded. By differentiating the received signal, it is possible to calculate the speed and movement of a sports equipment, for example, a barbell. Using a three-component accelerometric sensor A.V. Samsonova et al. (2015) recorded the acceleration of an athlete's head when performing power moves in ice hockey.

4.7. Electromyography

Electromyography I am a way of recording and analyzing the bioelectrical activity of muscles.

The essence of the phenomenon is the registration of electrical muscle potentials that appear when the muscle is excited. Thus, electromyography is a reliable method for recording muscle activity.

The following EMG (electromyogram) parameters are most often recorded; duration of electrical activity of muscles, frequency of biopotentials, amplitude of biopotentials and total electrical activity of muscles.

The duration of muscle electrical activity characterizes the time during which the muscle was excited.

The frequency and amplitude of muscle biopotentials characterizes the degree of muscle excitation and the nature of the activity of various motor units. The total electrical activity gives an idea of ​​the overall level of tension and strength being developed by the muscle. The greater the total electrical activity, the greater the degree of tension developed by the muscle.

The sensors used to record electrical activity are silver electrodes made in the form of small circles (cups). Their diameter is no more than 10 mm. A special electrically conductive paste is placed inside these cups for better electrical conductivity. Currently, the recording device is a personal computer, Fig. 4.3.

Fig.4.3. Electromyographic technique

One of the first works in which the electromyographic technique was used to study the motor actions of a weightlifter should be recognized as the dissertation work of A.S. Stepanova (1957). In this study, A.S. Stepanov (1957) subjected a detailed electromyographic analysis to the main competitive exercises of weightlifters: the clean and jerk, the snatch and the press.

In the study by S.S. Lapenkova (1985) was carried out biomechanical analysis weightlifting and auxiliary exercises using electromyography techniques. In the comparative analysis of movements, the following EMG characteristics were used: the time of electrical activity, which characterizes the duration of the application of forces developed by the muscles, the average EMG amplitude, which is interconnected with the level of development of muscle forces. The use of EMG techniques and the structural method of pattern recognition made it possible to evaluate the effectiveness of auxiliary exercises.

Abroad, serious studies of strength exercises using electromyographic techniques were undertaken by R.F. Escamilla et al. (2001). The squat with a barbell on the shoulders and the bench leg press were subjected to detailed electromyographic and biomechanical analysis (Fig. 4.4).

Fig.4.4. EMG recording of the strength exercise bench press with upper and lower feet (R.F. Escamilla et al., 2001)

It was found that when performing the squat, the activity of the quadriceps and hamstring muscles was higher than when performing the leg press. At the same time, a squat performed with a narrow foot placement causes greater electrical activity in the calf muscle compared to a wide foot position.

An analysis of muscle work was also carried out when performing strength exercises: squats with a barbell on the shoulders (N.B. Kichaikina, A.V. Samsonova, G.A. Samsonov, 2011). It has been established that at the lowest point (LP) the electrical activity of the gluteus maximus and hip extensor muscles (biceps femoris and semitendinosus) is minimal. A.V. Samsonova (2010) studied the characteristics of the electrical activity of the muscles of the lower extremities during strength exercises. The results obtained indicate that when performing a strength exercise, an increase in the mass of external weights leads to a decrease in the proportion of the total electrical activity of the quadriceps femoris muscle corresponding to the eccentric mode. When performing strength exercises in the “failure cycle,” the duration and amplitude of the electrical activity of the vastus lateralis muscle increases significantly (Fig. 4.5).

Rice. 3. Total electrical activity m. vastus lateralis when performing 2, 3 and 4 standard cycles (A) and a failure cycle (B) of strength exercises with weights of 40% of 1RM. Vertical lines correspond to the beginning of the cycle (A.V. Samsonova, E.A. Kosmina, 2011)

A positive feature of electromyography was that it made it possible to assess the degree of skeletal muscle activity in different movements. For this purpose, the study of the total electrical activity of the muscle is most often used. In addition, it became possible to evaluate the sequence of muscle activity when performing a motor action.

However, the electromyographic technique does not allow one to compare the voltage developed different muscles of an athlete when performing a strength exercise. That is, to quantify which muscle exhibits more or less effort. This is due to the fact that the level of force assessed by EMG is influenced by a number of technical factors, namely, the quality of electrode adhesive, skin resistance, degree of amplification, etc. Therefore, only on the basis of recording the electrical activity of muscles during a strength exercise, it is very difficult to compare the “contribution” of each muscle to the result; however, the electromyographic technique remains to date the most adequate for solving these problems.

Literature

1. Bilenko A.G., Govorkov L.P., Tsipin L.L. Measurements in the biomechanics of exercise. Practical course: Tutorial/A.G. Bilenko, L.P. Govorkov, L.L. Tsipin / NSU of Physical Culture, Sports and Health named after. P.F. Lesgafta, 2010.– 166 p.
2. Biomechanical research methods in sports: Textbook / Ed. G.P. Ivanova. – Leningrad, 1976. – 96 p.
3. Kichaikina, N.B. Peripheral mechanisms of movement organization in the study of squatting techniques with a barbell in powerlifting / N.B. Kichaikina, A.V. Samsonova, G.A. Samsonov // Proceedings of the Department of Biomechanics of the University. P.F. Lesgaft.- Issue. 5. – St. Petersburg, 2011.- pp. 42-65.
4. Kozhekin I.P. Improving the motor actions of weightlifters by controlling their biomechanical structure: 13.00.04: Abstract. dis. . Ph.D. ped. Sciences / Kozhekin Igor Petrovich. – Malakhovka: MOGIFK, 1998. - 19 p.
5. Popov G.I., Samsonova A.V. Biomechanics of motor activity / Textbook for students of higher professional institutions. Education /G.I. Popov. A.V. Samsonova. – M.: Academy, 2011. – 320 p.
6. Samsonova, A.V. History of biomechanics / A.V. Samsonova // Proceedings of the Department of Biomechanics: Interdisciplinary collection of articles / NSU named after. P.F. Lesgafta, St. Petersburg; comp. A.V. Samsonova, S.A. Pronin.- St. Petersburg: Publishing house "Olympus", 2009. – Issue 2. – P. 4-15.
7. Samsonova A.V. Characteristics of the total electrical activity of muscles when performing strength exercises // Bulletin of the Chernihiv State Pedagogical University. Issue 81. Series: Pedagogical sciences. Physical training and sports. - Chernihiv, 2010. - 427-431.
8. Samsonova, A.V. Urgent training effects of strength exercises until failure on human skeletal muscles / A.V. Samsonova, E.A. Kosmina // Bulletin of the Chernihiv State Pedagogical University. Issue 91. Volume 1 Series: Pedagogical sciences. Physical training and sports. - Chernihiv, 2011. – 407-410.
9. Samsonova, A.V. Acceleration of an athlete's head when performing power techniques in ice hockey / A.V. Samsonova, L.V. Mikhno, L.L. Tsipin, G.A. Samsonov, I.A. Chichelov // Russian Journal of Biomechanics, 2015.- T.19.- No. 3.- P. 307-315.
10. Furaev A.N. Operational regulation of the training process of weightlifters using an automated system for monitoring biomechanical parameters.: Author's abstract. dis... cand. ped. Sciences / A.N. Furaev.– M.: Malakhovka: 1988.–23 p.
11. Escamilla, R.F. Effects of technique variations on knee biomechanics during the squat and leg press / R.F. Escamilla, G.S. Fleisig, N. Zheng, J.E. Lander, S.W. Barrentine, J.R. Andrews, B.W. Bergemann, C.T. Moorman III //Med. Sci Sports Exerc., 2001.– V.33.– N. 9.– P. 1552-1566.

RESEARCH METHODS IN BIOMECHANICS

Statement of the problem and choice of research methods. The concept of a measuring system (sensors, transmission, conversion, recording of information).

Calculation methods (determination of coordinates, velocities, accelerations, forces, moments of forces).

Statement of the problem and choice of research methods.

Biomechanics how natural Science is largely based on experimental study the phenomena being studied. In the study itself, three successive stages are distinguished: measurement of biomechanical characteristics, transformation of measurement results, biomechanical analysis and synthesis. Usage computer technology allows you to perform these actions simultaneously.

To quantify a particular phenomenon, only objective (instrumental) research methods are used.

The specific method is chosen based on the problem and conditions of the experiment. In biomechanics, the following basic requirements are imposed on the research method and the equipment that supports it:

- the method and equipment must ensure obtaining a reliable result, that is, the degree of measurement accuracy must correspond to the purpose of the study;

- the method and equipment should not affect the process under study, that is, they should not distort the results and interfere with the test subject.

When conducting research, it is desirable to adhere to the principle of objective urgent information (V.S. Farfel, 1961), that is, information about the main factor of a sports movement should be received either during the execution of the movement or immediately after its completion.

The choice of research method is primarily determined by the nature of the change in the controlled quantity over time. On this basis, biomechanical characteristics can be divided into biomechanical parameters and biomechanical variables.

Biomechanical parameters are those characteristics whose values ​​do not change during the entire measurement process (for example, body mass, moment of inertia and coordinates of the central gravity in a fixed position, projectile weight). The value of the parameters may be unknown, but it does not change.

Biomechanical variables are characteristics whose value changes during the measurement process, as a rule. randomly(forces, accelerations, coordinates, etc.).

Requirements for the accuracy of measurements in the biomechanics of sports are primarily determined by the purpose and objectives of the study, as well as the characteristics of the movement itself. It is considered sufficient if the measurement error does not exceed ±5%.

Transformation of measurement results is used to increase the accuracy of the results obtained (statistical processing) and to determine by calculation the biomechanical characteristics that are not directly measured.

Calculation methods are based on the use of the laws of mechanics (statics and dynamics of a point, a body, a system of bodies), as well as statistical data on the geometry of the masses of the human body. These data can be presented in the form of tables characterizing the relationship between the mass of individual segments of the human body and its total weight (weight coefficients); characterizing the relationship between the length of a segment and the distance to its CG (radii of the centers of gravity). These data can also be presented in the form of regression coefficients (paired and multiple).

The concept of a measuring system (sensors, transmission, conversion, recording of information).

Instrumental methods of biomechanical control are based on measuring systems. A typical measuring system circuit consists of six blocks.

1. Object of measurement.

2. Perceiving device.

3. Converter.

4. Computing device.

5. Transmitting device.

6. Indicator (recorder).

Sensing device or sensor. Its main purpose is the perception of physical quantities. The following sensors are most often used in sports research.

Photodiodes (or photocells). They are used to measure time intervals. Their input value is illumination, the output value is direct current. Photodiodes are sensitive in the range from 0 to 500 Hz and have an error of 1-3%, which is not enough for particularly accurate measurements.

Rheostatic sensors (potentiometers). Used to measure linear and angular movements, can be used to measure forces. The input value of the potentiometer is the angular movement, the output value is the change in resistance. It has a relatively small error and high sensitivity.

Strain gauges. Used to measure forces. The use of strain gauges makes it possible to turn any sports equipment into a means for studying movement. The action of strain gauges is based on the same physical principle, as with rheostatic sensors - a change in the geometric dimensions of the conductors causes a change electrical resistance sensor R = r l / q – resistance is directly proportional to the resistivity and length of the conductor, and inversely proportional to its cross-sectional area. Changes in length and cross-sectional area within the elastic limits of the material are proportional to the force of action. The input value of strain gauges is displacement, the output value is change in resistance. The advantages of these sensors include: small measurement error, resistance to vibration. The disadvantages are low sensitivity and the need for careful gluing. The most significant error for strain gauges is the temperature error.

Accelerometers are designed to measure accelerations. The linear accelerations of points of the human body change quite significantly (for example, when swinging and hitting a ball - from 200 to -1000 m/s 2). Therefore, to achieve maximum measurement accuracy, accelerometers are selected according to their characteristics to measure very specific classes of movements.

The use of accelerometers is limited by the fact that the sensor does not measure the acceleration of the body, but the resultant of the linear acceleration and the acceleration of gravity. To determine the desired acceleration, you need to know the orientation of the sensor relative to the vertical at each moment of time, that is, the measurement must be accompanied by stereo filming. But when learning striking movements, this is not necessary.

Electrodes - needle and skin - are designed to remove biopotentials from working muscles.

Converters (aka sensor power supply and amplifiers) can be very different - from homemade devices to standard multi-channel. Allows you to amplify signals from sensors to a level sufficient to use a recording device.

The computing device compares the signal with a standard (calibration signal) and transmits the result via wire or using radio telemetry to an indicator or recording device.

In some cases, the measuring system does not include a computing device and the materials are analyzed separately using semi-automatic decoders or even manually. In such cases, there is no need to talk about compliance with the principle of urgent information.

Recorders (for example, an electrocardiograph), writing oscilloscopes, and printing devices can be used to record data. They have their own advantages and disadvantages. Thus, when recording fast processes, recorders may have too much inertia. Light-beam (loop) oscilloscopes do not have this drawback, but processing the film takes a lot of time and there is a danger of damaging the film during processing (and it is not so easy to get such film). Record made ultraviolet ray UV processing on photographic paper is not necessary, but the recording itself cannot be enlarged for decryption.

Experimental methods for determining biomechanical parameters (optical and optoelectronic, mechanoelectric, measurements of time intervals, complex).

To record biomechanical parameters, methods borrowed from many fields of knowledge are used. It is convenient to divide these methods into optical, optoelectronic, mechanoelectric, and complex.

Optical methods for recording movements. Depending on the research objectives, the following may be used:

1. 1. Regular photography to determine the structure of a pose.
2. 2. Multiple exposure photography - to obtain information about movements in the shooting plane. When using these types of photography, three synchronized devices produce an image of an object in three planes.
3. 3. Cyclographic (strobe) photography. This is done through a shutter or using pulsating markers, as well as light sources. Allows you to obtain a ready-made reliable measurement of movement.
4. 4. Stereostrobophotoraphy. Its advantage is the documented accuracy of localizing points in a frame along three coordinates at successive moments in time, the intervals between which are set by an electronic rather than a mechanical device.
5. 5. Filming is a publicly available informative pedagogical and biomechanical method for studying movements in sports. Depending on the speed of film advance, the equipment is divided into standard (24 fps), “time magnifying glass” (up to 300 fps), and special high-frequency (up to 5000 fps) film cameras.

Photographic and film film is a material for calculating the mechanical characteristics of movement, the accuracy of which depends on the reliability of taking the initial coordinates, which in turn is a consequence of the correct organization of the shooting.

The subject must wear a tight-fitting suit with contrasting marks above the axes of the joints. The study location is chosen based on the scope of the object’s movements. Lighting should provide sufficient short exposure. Long lenses are used to reduce distortion at the edges of the image. The optimal distance between the lens and the object (E 0) is determined by the formula:

E 0 = V F k / C f , where V – object speed, m/s, F – focal length, cm, k – ratio of exposure time to frame change time, C resolution of the device, cm, f – filming frequency, fps.

Optical-electronic recording of movements is mainly carried out using video recording. In this case, the movements can be immediately reproduced on the screen and used for applied pedagogical and biomechanical analysis. However, conventional video recorders are not suitable for quantitative assessment of technology due to their low resolution. In this regard, specialized video recorders (the so-called Speed ​​- Video ). In combination with a computing device, they allow you to provide urgent quantification movements.

Based on film and video materials, carried out in compliance with all technical requirements for their organization, it is possible to determine a number of mechanical characteristics of the position or movement of the body. An ordinary photograph or film frame is a document for determining the following indicators in the shooting plane.

1. coordinates of the centers of gravity of the links or GCT of the body;
2. moments of gravity forces of links;
3. articular angles;
4. moments and angles of stability;
5. moments of inertia of the links and body.

Analysis of several frames is associated with tracking these same characteristics over time.

The dependence of the coordinates of body points on time represents the law of their movement in the selected coordinate system. These data are necessary to quantify the quality of movements. The dynamics of joint angles, moments of gravity and muscle working conditions are the subject of analysis of human movements as a biomechanical system controlled by the central nervous system. Changes in the moment of inertia of the body reveal the mechanism for constructing complex rotational movements.

Mechanoelectric methods for determining biomechanical characteristics. Optical and optical-electronic research methods do not allow (with rare exceptions) to carry out a quantitative assessment of movement immediately after measurement, since final result preceded by the stages of chemical processing of materials (not always) and calculation of their biomechanical characteristics. This significantly limits the possibility of using the research results in the training process. Mechanical-electrical methods are largely free from this drawback. They consist in converting the measured mechanical quantity into an electrical signal and then measuring (or recording) and analyzing it.

The main advantage of mechanoelectric methods for measuring biomechanical variables is the speed of obtaining measured characteristics and the ability to automate the calculation of characteristics that are not directly measured. The most common of this group of methods is strain dynamometry. During the exercise, a person mechanically interacts with external bodies (support, apparatus, equipment). These bodies are deformed. Moreover, the magnitude of the deformation is usually proportional to the force of impact. To record these deformations, strain gauges are most often used, but rheostatic sensors can also be used.

In most cases, strain gauge equipment is used directly to determine the strength characteristics of sports movements and study on this basis dynamic structure motor actions.

Tenso platforms are widely used - devices that allow one to determine the interaction of a person with a support during repulsion. The components of the ground reaction (vertical and horizontal) are recorded regardless of the point of contact with the device.

Stabilometry. Using strain gauge equipment, it is also possible to study the movement of the point of application of force to the strain gauge platform. Such a movement can occur both due to the movement of the subject, and due to a change in the position of his GCP when changing posture. These measurements require a multicomponent strain gauge platform, with which the reaction components are measured separately in all supports installed at the corners of the platform.

Accelerometry. One of the most important characteristics of movement is linear acceleration. it can also be determined using strain gauge equipment. IN in this case The strain gauge records the deformation of an elastic plate connected to a moving object. Since the sensor mass ( m ) and plate elasticity ( C ) values ​​are constant, then the movement of the sensor mass relative to the object will be proportional linear acceleration object. The parameters of the accelerometer are selected in such a way that the natural frequency of oscillations of the sensor is 3-4 times greater than the maximum frequency of the process being studied.

Goniometry is the measurement of a person’s angles in the joints of the body. The joint angle is an important biomechanical characteristic, for example when determining a posture program. The traction force of the muscle (that is, its length and its shoulder relative to the axis of the joint) depends on the joint angle.

Mechanical and electromechanical goniometers are used to directly measure joint angles. The latter use rheostat potentiometers. The potentiometer body is rigidly connected to one of the goniometer bars, and to the other - its axis.

Mechanography is the recording of movement. This can also be done using potentiometers. The moving point is connected by a low-stretch thread to the sensor axis. Movements with large amplitude can be recorded if a ring (block) of the appropriate diameter is placed on the potentiometer axis.

Electromyography is a method of recording the electrical activity of muscles. Allows you to receive information directly while performing physical exercise. There are three main areas of using electromyography to study human motor activity. 1. Characteristics of the activity of individual motor units of muscles. 2. Determination of the activity of individual muscles in various motor acts. 3. Characteristics of coordination of the activity of muscles combined general participation in move. To solve biomechanical problems, mainly the second and third directions are used. When using electromyography to study sports movements, cutaneous electrodes are usually used, but needle electrodes are sometimes used. Skin electrodes can be mono- or bipolar. In any case, the electromyogram can reflect the electrical activity of those muscles over which the electrodes are located, or (with a monopolar lead) the activity of the muscles that are located between the active and indifferent electrodes.

It should be taken into account that the recorded value of biopotentials depends on three factors. Depending on the position of the electrodes relative to the muscle - when located along the fibers, as well as close to the motor point (the point of entry of the nerve into the muscle), the potentials are greater. From the electrical conductivity of the skin - the skin should be degreased with ether. From the shape and size of the electrodes - you should use the same ones or, in extreme cases, the same ones.

In any case, the electromyogram can be used as an indicator of the state of the mechanisms of coordination of movements as an equivalent of mechanical phenomena (tension, traction) that occur in the muscle when it is excited. N.V. Zimkin and M.S. Tsvetkov (1988) showed that a smoothed electromyogram can be used to judge the participation of muscle fibers in the movement different types(fast, intermediate and slow), and therefore about the composition of the muscle. A smoothed electromyogram is easier to process than a natural one; the smoothed electromyogram can be used to calculate the rate of muscle excitation.

Methods for measuring time indicators. If the trajectory is known in advance, and the amplitude of movement is large (several meters), then the time of passage of the segments can be recorded using photo sensors. Signals from the sensors either turn off the electric stopwatches (each sensor has its own stopwatch) or are recorded by a recorder (oscilloscope). IN the latter case The accuracy of the method is determined by the accuracy of the time marker or the accuracy of the tape drive mechanism. The degree of reliability of the results directly depends on the number of sensors installed at a distance.

Complex research methods. The goal of biomechanics is to study both the physical capabilities of an athlete and ways to solve a specific motor task. In the process of research, it is necessary to find out the patterns of movement construction, determine the relationship between mechanical and biological characteristics that reflect the coordination of movements. This task is very difficult, since the relationship between muscle tension and movement is not unambiguous, N.A. pointed out. Bernstein. The reason for the movement of body parts is muscle tension, which is determined by both the degree of excitation and the degree of stretching of the muscle. Thus, movement of the link changes the length of the muscle and, as a result, its tension.

Comprehensive registration of biological and mechanical characteristics of movement is a necessary condition for studying the patterns of human movement control. It is possible with simultaneous recording of electrophysiological and biomechanical indicators of movement. When the electrical activity of the muscles and the external picture of movement are recorded (kinogram, cyclogram, tensodynamogram, goniogram, mechanogram). When recording these processes on different media, it becomes necessary to use special devices to synchronize the recording. One such device is described in[4, p. 60].

When using mechano- and (or) strain dynamography, the problem of recording synchronization is solved more easily, since they are carried out on the same tape.

So, to date, the necessity and exceptional value of using multichannel simultaneous recording of parameters of kinematics, dynamics and electrical activity of muscles has been proven to establish a connection between various phenomena of movements and their causes, as well as to implement the idea of ​​optimal control of the training process.

However, the use of informative instrumental methods (tenso-, mechanical-, electromyography, filming, etc.) in natural conditions for the purpose of a comprehensive assessment of the technical skills of athletes is usually associated with great organizational and methodological difficulties.

At the same time, it has been proven that in artificially created conditions provided by the use of a simulator, it is possible to obtain reliable information about one or another aspect of technical or physical fitness. In addition, the simplified structure of the exercise allows you to more likely assess the nature of the change in the physical component, as the influence of the technical component on the result decreases. And although the simulator will never replace holistic movement, there is a lot of evidence that the simulator-research complex can successfully solve the problems of urgent reliable information, as well as determining the athlete’s state that guarantees him achievement desired result at competitions.

Calculation methods for studying movements (determination of coordinates, velocities, accelerations, forces, moments of forces).

Meaningful conclusions can be drawn based on reliable, reliable information. It follows that the methods and equipment used in biomechanical studies must ensure reliable results. This means that the degree of measurement accuracy must correspond to the purpose of the study, and the methods and equipment should not affect the process being studied, that is, they should not distort the result and interfere with the subject.

At first glance, these requirements are fully met (indirect measurements, mechanical and mathematical modeling), based on the use of physical laws and statistical data on the geometry of human body masses (tTables and illustrations are contained in ). Calculation methods are used to solve direct and inverse dynamics problems. In this case, kinematic or dynamic characteristics are usually used as initial data, that is, the analysis is carried out from the initial or final link of the phenomena that constitute the object of biomechanical research (human mechanical movement, causes and manifestations of this movement).

Calculation methods are often used to indirectly determine biomechanical characteristics that, for various reasons, cannot be measured (registered) directly, for example, in competition conditions.

Prominent biomechanists D.D. Donskoy and S.V. Dmitriev (1996) state that “... the development of precise recording equipment and computerization of studies of motor acts captivated researchers with the construction of mechanical and mathematical models, very complex and effective in revealing the finest details of movement (especially in engineering and medical biomechanics).” We have no right to dispute this statement completely, but the effectiveness of using mechanical-mathematical modeling to solve some problems in sports biomechanics is questioned by many equally well-known researchers.

In the domestic scientific and methodological literature, the capabilities of calculation methods have been demonstrated in isolated works that have confirmed well-known truths, for example, in determining the leading elements of technique in artistic gymnastics (Yu.A. Ippolitov, 1997), identifying factors that ensure results in ski jumping ( N.A. Bagin, 1997), identifying the relationship between kinematics and dynamics of rotations in figure skating (V.I. Vinogradova, 1999). The authors demonstrated the highest erudition, but in all cases the calculated results differed significantly from the results obtained by direct measurement under similar conditions.

Theoretically, this is explained by the fact that the basis of classical calculation methods in biomechanics is the hypothesis of the equivalence of inanimate and living mass. This hypothesis assumes that the biological body does not change its internal structure under the influence of control forces and moments, and also remains in an unchanged position. If this condition is not met, then the methods of classical biomechanics become inapplicable.

Experimental studies carried out for many years in the laboratory of biomechanics of VNIIFK showed that “... the limitations of classical calculation methods for obtaining from the movements of points data on the magnitude of accelerations and forces in motor actions with changes in posture arise from the circumstances that currently there is no opportunities for an objective assessment of the directions of displacement of internal organs, blood and lymph masses. The calculation algorithms also do not take into account the transfer of forces or energy from link to link or their absorption and dispersion” (I.P. Ratov, G.I. Popov, 1996). The same authors experimentally confirmed N.A.’s idea. Bernstein that there is no clear connection between muscle tension and mechanical movement(since every movement is the result of the interaction of active and reactive forces) and showed that in biomechanical systems the force-acceleration function is nonlinear, that is, significant accelerations when moving masses may not lead to the appearance of forces.

Thus, the disadvantage of computational methods in general and especially mechanical-mathematical modeling is that “... the developed models of human movements (questionably adequate to the living human body and its movements) are trying to be “stuffed” with the average geometry of masses and the real kinematics of live exercises” (M.L. Ioffe et al., 1995). “The results of this approach are disastrous from both scientific and practical points of view,” emphasizes N.G. Suchilin (1998).

Literature. 1. Godik M.A. Sports metrology: textbook for IFC. – M.: Physical culture and sport, 1988. P. 57-66.

2. Zatsiorsky V. M., Aruin A. S., Seluyanov V. N. Biomechanics of the human motor apparatus. – M.: Physical culture and sport, 1981. – 143 p.

3. Zimkin N.V., Tsvetkov M.S. Physiological characteristics of the characteristics of contractile muscle activity in sprinters and stayers // Human Physiology. – 1988. – T.14. – No. 1. – P. 129-137.

4. Workshop on biomechanics: A manual for the institute of physical culture /Under the general. ed. Ph.D. THEM. Kozlova. – M.: Physical culture and sport, 1980. – 106 p.

5. Seluyanov V.N., Chugunova L.G. Calculation of mass-inertial characteristics of the body of athletes using the method of geometric modeling // Theory and practice of physical culture. – 1989. – No. 2. – P. 38-39.

6. Suchilin N.G., Arkaev L.Ya., Savelyev V.S. Pedagogical and biomechanical analysis of the technique of sports movements based on a software and hardware video complex // Theory and practice of physical culture. – 1995. – No. 4. – P.12-21.

7. Shafranova E.I. Methods for processing bioelectrical activity of muscles // Theory and practice of physical culture. – 1993. – No. 2. – P. 34-44; No. 3 – pp. 16-18.

8. Utkin V.A. Biomechanics of physical exercises: Proc. manual for physical education departments. – M.: Education, 1989. – P. 56-79.

PROCESSING RESULTS OF BIOMECHANICAL STUDIES (2 hours)

Measurement scales (names, order, intervals, ratios).

Problems of processing biomechanical measurements. Processing of the results is carried out to assess the error of the obtained data, as well as to determine by calculation the biomechanical characteristics that are not directly measured.

The assessment of errors, as well as their reduction through further processing of measurement results, is of paramount importance in biomechanical studies of sports movements, since the specific requirements for research methods do not allow the use of highly accurate but cumbersome measurements. To solve this problem, a mathematical theory of measurement errors was developed. Below we will briefly give basic recommendations for assessing errors and reducing their impact on the final result.

Not all biomechanical characteristics can be directly measured to meet the requirements for measurement methods in sports research. But the use of the functional relationship between the sought and measured characteristics allows, as a rule, to determine all the biomechanical characteristics of interest to the researcher. This method is taken from technology, where it is widespread, and is called the “method of indirect measurements”.

Calculation of the required biomechanical characteristics based on indirect measurement data can be carried out both during the measurement process using computer technology, and in the process of analyzing the measurement results after the experiment. In both cases, the presence of measurement errors imposes certain restrictions on methods for processing the results of indirect measurements.

Assessment of measurement error and correct, that is, performed in accordance with GOST, presentation of measurement materials makes it possible to compare the results of studies carried out using different measurement methods or by different authors. And this, in turn, makes it possible to sharply reduce the number of additional studies of the same phenomena and thereby reduce the duration and cost of biomechanical studies in general.

Measurement errors, classification, sources and elimination methods. Measurement error – difference in measurement result X i and the true value of the measured quantity X source : e = X i – X source

According to the method of determination, they distinguish between absolute and relative; and by origin - systematic and random, as well as gross errors (misses).

We have just described the method for determining absolute errors. The absolute error is expressed in the same units as the measured value. The true value is usually taken to be the result obtained using a more accurate method.

Relative error is often used when carrying out complex control, when indicators of different dimensions are measured:erel. = e/X i *100%. Another argument for using relative error is that determining the relative error is necessary to assess the possibility of using this technique for research specific movement(the error should not exceed ±5.0% of the measured value).

Systematic errors are errors whose value remains unchanged (or changes in a known way) from experiment to experiment. Consequently, they can be excluded from the final result if their value is determined by preliminary calibration of the equipment before each experiment. There are 4 groups of systematic errors. 1. The cause of the occurrence is known and the value can be determined quite accurately (temperature error, ruler with a broken beginning...). 2. The cause is known, but the magnitude is not. These errors depend on the class of measuring equipment and fluctuate within the maximum permissible value. Accuracy class (1.0, 2.0, etc.) means the relative measurement error in percent. 3. The origin and magnitude of the error are unknown. Such errors appear in complex measurements when it is not possible to take into account all sources of possible errors. 4. errors associated with the properties of the measurement object. Systematic monitoring of athletes allows us to determine the measure of their stability and take into account possible measurement errors. Otherwise, it can be difficult to separate significant shifts (for example, due to fatigue) from measurement errors.

To eliminate systematic errors, two methods are used. The first is equipment calibration - checking instrument readings using standards over the entire range of possible values ​​of the measured value. The second method is calibration - determining errors and the magnitude of corrections.

Random errors are caused by uncontrollable factors that vary from experiment to experiment. Random errors appear during the simultaneous action of a very large number of factors independent of each other, each of which has a small impact on the measurement result, but in the aggregate these causes have a noticeable effect. Random error, by its very nature, cannot be taken into account and compensated for during the experiment.

Gross errors (misses) are significantly different in nature from random ones. If random errors occur when the equipment is in good working order and the experimenter is performing the correct actions, then the cause of the errors is malfunctions and (or) errors in operation. Gross errors are detected by a sharp drop in the result from general series the obtained numbers, which, as a rule, is in sharp contradiction with the physical picture of the phenomenon.

Processing the results of direct and indirect measurements of biomechanical parameters and variables. Methods for estimating and reducing random errors in the measurement of biomechanical parameters and variables vary significantly.

Processing the results of measurements of biomechanical parameters. The main way to reduce random errors when measuring biomechanical parameters is to carry out repeated measurements and process their results.

Processing the results of direct measurements of biomechanical parameters. In the absence of precise information about the physical causes of the observed scatter of measurement results, the most probable value of the measured quantity is taken to be an estimate of the mathematical expectation of the measurement results, that is. The degree of reliability of the obtained result can be assessed by the value of the interval ± q within which, with a given probability α, the quantity will be located: = t * S x , where t – Student’s t-test for a number equal n -1; Sx – average error of the arithmetic mean.

Processing the results of indirect measurements of biomechanical parameters. In a number of cases, the quantity we are interested in is not measured directly, but is calculated as a function of the measured values ​​of some other quantities. For example, that is. In such cases, to calculate the arithmetic mean and the mean error of the arithmetic mean, the most probable values ​​of the measured parameters (angle and departure speed) and their mean errors are first determined. In the following, it is assumed that the errors in determining the parameters are small compared to their true values, and the measurements of each of the parameters were carried out independently of each other. This assumption is valid for the vast majority of cases of biomechanical indirect measurements. Then the most probable value of the flight length is calculated from the average values ​​of the speed and departure angle: . The average error is calculated as follows: .

Processing the results of measuring biomechanical variables. Biomechanical variables (coordinates, speeds, accelerations) during movement are random functions of time. The result of their measurement is, as a rule, tables of values ​​recorded at certain intervals, or graphs drawn by a recorder (oscilloscope). Repeated measurements fundamentally cannot improve the accuracy of the result due to the variability of human movements. Simultaneous measurement of the desired variable using several similar instruments with subsequent processing is not recommended due to the bulkiness of the equipment and the influence of this factor on the measured process.

A relatively simple way to increase the accuracy of measuring biomechanical variables is to use the difference in the frequency composition of the measured process and the random errors (interference) that arise during the measurement, that is, when the equipment is operating, the error sinusoid (2) is superimposed on the process sinusoid (1).

The nature of the errors can be determined by trial recordings in the case when the measured variable is zero or constant. For example, in the absence of movement.

Errors during recording can be eliminated by smoothing the signal using a filter, the transmission coefficient of which is determined by the formula:, where f – frequency of the input signal, R is the resistance of the resistors, C is the value of the capacitance of the capacitor. Calculations are performed separately for the process signal frequency and the interference signal frequency, then the measurement and interference transfer coefficients are compared.

Tabular data can also be smoothed. This procedure is necessarily used when the derivative of the measured signal is calculated from tabular data, that is, velocities and accelerations are calculated from coordinates. In practice, this is done in such a way that displacements and then speed differences are calculated not between adjacent frames, but after 1 or more frames.

If the result is presented in the form of a graph in which the measured process contains a high-frequency error, then graphical averaging can be performed by plotting midline between high-frequency oscillations of the process.

The error of dynamic measurements is determined experimentally by checking the measuring equipment (calibration) under conditions close to the conditions of its practical use (in terms of strength, process speed).

Scales of measurements (names, order, intervals, ratios).

Scale	Characteristics	Mathematical methods	Examples
Items (nominal)	Objects are grouped and groups are designated by numbers. The fact that the number of one group is greater or less than the number of another group does not say anything about their properties, except that they differ	Number of cases. Fashion. Tetrachoric and polychoric correlation coefficients	Athlete number, role, specialization, sport, etc.
Order (rank)	The numbers assigned to objects reflect the number of properties belonging to these objects. It is possible to establish a ratio of “more” or “less”	Median. rank correlation. Rank criteria. testing hypotheses using nonparametric statistics methods	Results of ranking athletes in the test
Intervals	There is a unit of measurement with which objects can not only be ordered, but also numbers can be assigned to them so that equal differences mean equal differences in the amount of the property being measured. Zero point is arbitrary and does not indicate the absence of a property	All methods of statistics except for determining ratios (for example, degrees do not add or subtract, degrees by degrees divide by and do not multiply)	Body temperature, joint angles
relations	Numbers assigned to objects have all the properties of an interval scale. There is an absolute zero on the scale, which corresponds to the complete absence of any property in an object. The ratios of numbers assigned to objects after measurements reflect the quantitative relationships of the property being measured	All statistical methods	Length, mass, speed, acceleration, force, etc.

Presentation of measurement results. Correct presentation of the results of biomechanical measurements is an important factor in ensuring the reliability and clarity of the results of biomechanical studies. When presenting results, you should adhere to following rules. 1. All records relating to the study must be kept completely and accurately, and be fully understandable to any reasonably qualified reader. 2. All results of observations (measurements), as well as the final material calculated from them, should be presented along with errors. For each quantity, the dimension must be indicated in accordance with the SI system. 3. The number and its error should be written so that their last digits belong to the same decimal place. 4. The error resulting from the calculations should be approximately 10 times less than the measurement error.

When studying biomechanical variables, the results can be presented in graph form. The main advantage of the graph is clarity. The graph should be such that you can immediately capture the type of dependence obtained, get a quantitative idea of ​​it and note the presence various features– maximum, minimum, areas of highest and lowest rates of change, periodicity, etc. Rules are followed when drawing a graph. 1. The graph is drawn on graph paper, or paper with coordinate grids. 2. The abscissa (X) axis is the quantity that causes changes in other quantities (time – always). The axes must indicate the designation and dimension of the corresponding quantity. 3. The scale of the graph is determined by the measurement error of the quantities plotted along the axes (or based on the rules for grouping data). The scales along the axes may be different. The scale should be easy to read, so one cell of the scale grid should correspond to a convenient number (1, 2, 5, 10 ...) of units of the value depicted on the graph. 4. The graph shows only the experimentally determined area of ​​changes in indicators; You should not strive for the graph to start from a point with coordinates 0; 0. 5. As for drawing the curve, there are two opinions. Some believe that the line should be smooth, others believe that the points on the graph should be connected by straight lines - that is, not go into hypothetical areas (you get a broken line). 6. The title should indicate what is being depicted. Curves should be labeled or explained in the title.

Testing and pedagogical assessment in biomechanics.

Test – A measurement or test conducted to determine the condition or ability of an athlete. Only those tests that satisfy the following metrological requirements can be used as tests. 1. The purpose of testing must be defined. 2. The procedure must be standardized. 3. The reliability and information content of the test must be determined. 4. A system for assessing test results must be developed. 5. The type of control must be indicated (operational, current, stage-by-stage).

Depending on the purpose of testing, tests can be divided into several groups. 1. Indicators measured at rest - assessment of physical condition or determination of the “background” level for “dynamic” studies. 2. Standard tests - all subjects perform the same tasks, the load is not maximum and, thus, there is no motivation to achieve the maximum result. 3. Tests with maximum load– their results depend on preparedness and motivation.

Depending on the number of factors determining the test result, hetero- and homogeneous tests are distinguished. The first is the majority.

As a rule, the level of preparedness is assessed using a battery of tests.

The definition of the purpose of testing is selected based on the existence of three varieties (operational, current, staged) and three areas of control (competitive activity, training activity, level of preparedness).

Types and directions of complex control in sports

(according to M. Godik, 1988)

Types of control	Directions of control
	competitive activity	training activities	preparedness (in laboratory conditions)
Staged	Measurement and evaluation of various indicators at competitions that complete the qualifications. preparation stage, or at all competitions of the stage	Construction and analysis of the dynamics of load characteristics at the preparation stage. Summation of loads for all indicators for a stage and determination of their ratio	Measurement and evaluation of indicators and controls in specially organized conditions at the end of the preparation phase
Current	Measurement and evaluation of indicators at the competition that completes the microcycle (or it is provided for by the calendar)	Construction and analysis of the dynamics of load characteristics in a microcycle. Summation of loads for all indicators per microcycle and determination of their ratio	Registration and analysis of daily changes in athletes’ preparedness caused by systematic training sessions
Operational	Measuring and evaluating performance in any competition	Measurement and evaluation of the physical and physiological characteristics of an exercise load, a series of exercises, a training session	Measurement and analysis of indicators that informatively reflect the change in the condition of athletes during performance or shortly after performing an exercise or after a lesson

Standardization of measurement procedures determines the accuracy of control results. This is achieved by ensuring that the daily routine on the eve of testing, warm-up, performers, testing scheme and conditions, rest intervals and motor system during testing must remain unchanged.

Reliability and informativeness of the test. Test reliability is the degree to which results agree when repeated testing of the same people under the same conditions. The simplest way to determine reliability is to calculate the pair correlation coefficient of the results of the first and second testing. Test reliability is considered acceptable when r ³ 0.70.

Informativeness (validity) of a test is the property of a test to sufficiently fully reflect the essence of the process being studied. The information content of a test can be determined logically and empirically. The essence logical method consists of a logical (qualitative) comparison of the characteristics of the criterion and the test. The empirical method is to carry out correlation analysis criterion and test result.

The following criteria can be used: 1. result in a competitive exercise. 2. the most significant elements of a competitive exercise. 3. test results, the information content of which has been proven. 4. the sum of the test subject’s points when performing a battery of tests.

When used as a criterion for sports qualifications, compare the average values ​​of indicators among athletes of various qualifications (use t -Student's t-test). If the differences are reliable, the test is informative.

In addition to reliability and information content, tests are also characterized by stability, equivalence and consistency.

Stability is a type of reliability in the case of a significant dilution in test and retest time. High stability of the test indicates the stability of the quality being tested.

Test equivalence is the degree to which the result in a given test coincides with the results in other tests when studying the same sign (for example, pull-ups and push-ups, standing long and high jumps).

Test consistency is the independence of test results from the personal qualities of the researcher. Even when carrying out instrumental studies someone can motivate subjects better, which determines the amount of consistency.

Pedagogical assessment is the final stage of the testing procedure. It consists of: 1. selecting a scale for converting test results into points. 2. converting results into points. 3. comparison of achievements with standards and derivation of a final grade.

The results can be simply ranked, but this is not always fair. Therefore, you need to use special scales. There can be many of them. Four scales are considered main: proportional (a), progressive (b), regressive (c), S -shaped (sigmoid) (d).

The choice of rating scale depends on in which zone the growth of results should be stimulated.

In practice, the following scales are used: standard, percentile, GCOLIFKa.

The standard scale is based on a proportional scale. The standard scale is so named because its scale is standard deviation ( S ). When constructing this scale, the law is used normal distribution, saying that everything possible values characteristics are contained in the interval (three sigma rule for the general population: ). In this case, the following assessment zones (levels of manifestation of the studied characteristic) are usually distinguished:

But this scale does not allow you to give accurate assessment phenomena.

The most common is the T-scale, where T is the result in points, is the result i - participant, is the result of the group, S - standard deviation. This scale is more fair than simple ranking.

Percentile (percentage) scale. Its creation involves the following operation - each subject receives as many points for his result as the percentage of his opponents he is ahead of. This scale is most suitable for assessing large groups of people. Calculate how many results fit into one percentile (percentage) or how many percent per person. This scale superficially resembles a sigmoid scale - the greatest changes occur in the middle of the range.

The GCOLIFK scale is used to evaluate the testing results of the same athlete at different periods of the cycle or training stage: n = (best result– evaluated result / best result – worst result) x 100 (points). In this case, the test result is considered not as an abstract value, but in connection with the best and worst results.

Evaluation of a set of tests. Can be done using regression analysis. Equation like Y = a + b 1 x 1 + b 2 x 2 +…+ b n x n allows you to determine the result in a competitive exercise (U) based on the test results (x 1, x 2, ...). But we must keep in mind that the tests should be unequal. The importance (weight) of a test can be determined in three ways. 1. Expert review- For important test a multiplying factor is introduced. 2. Odds are set based on factor analysis. 3. A quantitative measure of the weight of a test can be the pair correlation coefficient with the result in a competitive exercise. These are ways to obtain a “weighted” test score.

The second option for assessing complex control is building a “profile” of an athlete - that is, a graphical representation of the assessment results in individual battery tests. The graph clearly shows the strengths and weaknesses of preparedness.

Point tables. In them maximum amount points (1000-1200) are given for a result exceeding the world record, and the result of a beginner is estimated at 100 points. Next comes one of the main scales. The choice is purely subjective. Difficult to compare different kinds sports. But these scales are needed to determine the course of team competitions and their results, and not the level of development of a particular trait.

Thus, biomechanical control (from a metrological point of view) consists of several stages.

Determining the purpose of testing based on the existence of three varieties (operational, current, staged) and three areas of control (competitive activity, training activity, level of preparedness).

I. Selecting a test (tests) - determining its (their) reliability, information content, as well as stability, equivalence and consistency based on the study of scientific and methodological literature or using methods of mathematical statistics. Definition of testing procedure. Selection of equipment. Determination of systematic measurement error.

II. Testing (measurement) – registration of biomechanical processes during motor activity using instrumental methods. Combating random errors.

III. Processing test results using appropriate methods of mathematical statistics, depending on what was measured (parameters or variables). Identifying errors and combating them.

IV. Presentation of research results in text, tabular or graphical form.

V. Selecting a scale for assessing test results (proportional, progressive, regressive, S -shaped, T-scale, percentile, GCOLIFKA, etc.).

VI. Evaluation of test results.

Literature.

1. Godik M.A. Sports metrology: textbook for IFC. – M.: Physical culture and sport, 1988. P. 10-44.

2. 2. Workshop on biomechanics: A manual for the Institute of Physics. cult /Under general ed. Ph.D. THEM. Kozlova. – M.: Physical culture and sport, 1980. – P. 65-75.

3. Utkin V.A. Biomechanics of physical exercises: Proc. manual for physical education faculties. – M.: Education, 1989. – P. 33-56.

AUTOMATION OF BIOMECHANICAL CONTROL

Biomechanical control can be carried out in different ways. The simplest thing is to observe and record the results of observations. But at the same time, much will be missed and no one will be able to vouch for the accuracy of the results obtained.

Much more fruitful, although more complex, is automated control. We can say that in our days Lenin’s formula “from living contemplation to abstract thinking and from there to practice” has acquired a new meaning. Today, the process of “living contemplation”, observation of the object of study is unthinkable without the use of measuring equipment.

All measuring systems in biomechanics include sensors of biomechanical characteristics with amplifiers and converters, a communication channel and a recording device. In recent years, storage and computing devices have been increasingly used, significantly expanding the capabilities of the teacher. To increase the accuracy of biomechanical control, all the latest engineering innovations are used: radio telemetry, lasers, ultrasound, infrared radiation, radioactivity, television, video recorders, and computer technology.

Biomechanical sensors

The sensor is the first link of the measuring system. Sensors directly perceive changes in the measured indicator and are fixed either on the human body or outside it.

A sensor attached to a person must have minimal weight and dimensions, high mechanical strength, ease of attachment, and at the same time must not restrict movement or create any discomfort. The following are placed on the human body: joint markers (Fig. 35, 36), electromyographic electrodes (see Fig. 3), joint angle sensors (They are more often called goniometric (from the words gonios - angle, metreo - measure); in addition to measuring joint angles, goniometric sensors are used to measure angular movements in sports equipment, for example the angle of rotation of an oar in a rowlock) and acceleration (Fig. 37).

But it has long been noted that the accuracy of biomechanical control is higher if a person’s movements are not constrained by anything. Therefore, they try to place biomechanical sensors on sports equipment so that the conditions under which control is carried out do not differ from the natural conditions of training and competition.

Dynamographic platforms have become popular. They are installed secretly in the sector for jumping or throwing, under the covering of a running track, gymnastics platform, playground, etc. The most advanced dynamo platforms allow you to measure all three components of the force (vertical and two horizontal) and, in addition, the twisting moment at the point of application force, and the measurement result does not depend on the point to which the force is applied.

The sensitive elements in the dynamography platform are piezoelectric sensors (similar to the one found in the pickup of an electric record player) or less fragile force sensors - strain gauges (strain cells) (About the design of biomechanical sensors and about physical phenomena, underlying their design, can be read in the book: Ducks N. V. L. Measurements in sports (introduction to sports metrology).— M., 1978.—-S. 103-120; Minenkov B.V. Technique and methodology of strain gauge research in biology and medicine. - M., 1976).

Rice. 37. “Exoskeleton” - a system for attaching goniometric (1) and accelerometric (2) sensors to the human body; it is possible to adjust the exoskeleton to the lengths of the arm and leg segments (according to A. N. Laputin)

Strain gauges are used to measure force in many sports. In gymnastics, they are glued to the crossbar, parallel bars, rings, horse handles, etc. In weightlifting, they are glued to the barbell. In shooting sports and biathlon - on the trigger, stock and butt. In rowing - on the cone of the oarlock or oar (between the handle and the oarlock), on the footrest and on the can. In cycling, speed skating and skiing, the design of the pedal, skate, ski and ski pole is slightly modified to measure strength, and these changes do not in any way affect the natural technique of movement. In athletics, tensile insoles are used, which are placed in sports shoes. Interestingly, sneakers have appeared with tensile insoles and a miniature computer that automatically calculates the pace and force of repulsion and signals the training person if the force of repulsion and step frequency are higher or lower than optimal.

Strain gauges are used not only to measure force, but also to measure acceleration, as well as to record body vibrations (Fig. 38). In this case, the strain gauges are glued onto a vertical rod connecting the centers of the lower and upper areas of the stabilographic platform. A stabilogram shows how great a person’s ability to maintain body stability is, which is an important factor in achievements in gymnastics, acrobatics, rowing, figure skating, etc. In addition, stabilography is useful in treating people with impaired ability to maintain balance, when testing the state of the nervous system ( for example, before a competition).

Like strain gauges, photoelectric sensors do not distort natural movements, in which electricity occurs under the influence of light. They are used to measure walking and running speed. A runner (as well as a skater, skier, etc.) while moving interrupts the light rays falling on the photocells (Fig. 39). Since each optocoupler pair (light source - photocell) is located at a certain distance (S) from the next one, and the time (Dt) to cover this distance is measured, it is easy to calculate the average speed over this distance segment:

If the light source (for example, a laser) produces a narrow beam, then the duration and length of each step can be measured. This information is useful in training sprinters, jumpers and hurdlers.

Telemetry and methods for recording biomechanical characteristics

In order to use information from biomechanical sensors, it must be transmitted via a telemetry channel and registered.

The term "telemetry", made up of the Greek words tele - far and metron - measure, means "measurement at a distance." Information about measurement results can be transmitted via wires, radio, light rays and infrared (heat) rays.

Wired telemetry is simple and resistant to interference. Its main disadvantage is the inability to transmit signals via wires from sensors placed on the body of a person in motion. Therefore, wired telemetry should be used in combination with a dynamography platform or permanently installed sports equipment equipped with biomechanical sensors.

Let's give an example. To record a water skier’s dynamogram (Fig. 40), you need to glue the strain gauges to a vertical post installed at the stern of the boat. The end of the halyard is attached to the top of the stand, the other end of which holds the skier. In this case, it is advisable to transmit the electrical signal from the strain gauges to the recording device (which is also located on the boat) via wires.

Radio telemetry is a branch of radio engineering that provides radio transmission of information about measurement results.

Radiotelemetry makes it possible to monitor a person’s technical and tactical skills in natural conditions of motor activity. To do this, it must carry biomechanical sensors and a miniature transmitting device for a radiotelemetry system. An example of radiotelemetric recording of biomechanical information is presented in Fig. 41. The electromyograms depicted on it were obtained in an athletics arena, under the treadmill of which the receiving antenna of the radiotelemetry system was placed.

Rice. 41. Radiotelemetric recording of electromyograms in a running person:

1 - gluteus maximus; 2 - straight line of the thigh; 3 - vastus lateralis? 4 - biceps femoris; 5 - anterior tibial m.; 6 - gastrocnemius m.; 7 - soleus m.; single oblique hatching - inferior work; double oblique hatching - overcoming work (according to I.M. Kozlov)

Question for self-control of knowledge

What telemetry options can be used to record the repulsion force from a support:

a) in cross-country skiing;

b) long jump;

c) in rhythmic gymnastics?

Registration of electrical signals containing information about the results of biomechanical control is carried out by recorders and indicators of various designs. When recording measurement results, a document remains (graph on paper, magnetic recording, photograph, etc.). Unlike recording, indication consists of perceiving the information received visually or auditorily.

Recorders help to find out how one or several measured indicators change over time (see Fig. 40, 41). But there are also two-coordinate recorders that draw a graph of the dependence of one indicator on another. They give the teacher additional features. So, in Fig. 42 there are automatically drawn dependences of the force applied to the oar on the horizontal; a lot of movement of the oar. The area limited by this. curve, proportional to the amount of external mechanical work.

Task for self-control and consolidation of knowledge Subject the last statement to critical analysis and prove its truth or fallacy.

Image registration has long been of great practical benefit in physical education and sports.

Sports competitions are an exciting spectacle. In sports such as gymnastics and figure skating, the success of an athlete directly depends on the beauty and expressiveness of movements. In other sports, the external picture of movements is, although secondary, also very important, since the strength, speed and accuracy of motor actions depend on it. Yes and in Everyday life The ability to move beautifully is important.

The kinematics of movements is recorded by optical methods, which have been continuously improved since 1839, when Francois Arago at a meeting French Academy Sciences reported the discovery of photography (“light painting”). Already in 1882, E. J. Marey installed a rotating disk with slots in front of the camera lens and for the first time obtained several poses of a moving person (“chronophotogram”) on one photographic plate.

Another innovation, later called cyclic photography by N.A. Bernstein, consisted of recording only a schematic image of the body. For this purpose, miniature electric bulbs or light reflectors are attached to a person’s head and joints or at certain points on sports equipment (see Fig. 35, 36). In this case, a sequence of luminous dots (“cyclogram”) is recorded on the photographic plate. By connecting the points related to any joint, we obtain the trajectory of this joint (Fig. 43).

Rice. 42. Graphic recording (with a recorder) or indication (on a cathode-ray indicator) of the relationship between the force applied to the oar handle and the horizontal movement of the oar in two rowing cycles; below is a boat equipped with measuring equipment:

1 - computing device and electron beam indicator; 2 — oar angular movement sensor; 3 — strain gauge (according to A. P. Tkachuk)

As measuring equipment improved, stereo photography was mastered, which made it possible to obtain a three-dimensional image, and high-speed photography, which made it possible to record fast processes (Fig. 44).

The variety of optical measurement methods is clearly illustrated in Fig. 45. From the words written in the figure, the names of most known methods of recording the external picture of movements can be made. For example, low-speed planar video cycle photography is the recording of markers on the human body with one video camera at a normal frame rate.

Rice. 44. Film of a tennis ball bouncing off the court; with high-speed shooting (4000 frames per second), you can see how the shape of the ball changes (according to Hay)

Please note that modern video technology is gradually replacing film and photographic measurement methods. Thanks to video recording, a thorough and objective analysis of technology and tactics is possible. It is also a powerful teaching tool. A VCR gives you the opportunity to look at yourself from the outside. But “it’s better to see once than to hear seven times.” Repeated viewing of video footage, freeze frame; slow playback allows you to detect errors and outline ways to eliminate them. Finally, video recording is more durable than film. And with all these advantages, modern color video recorders (for example, “Electronics VM-12”) are relatively cheap and widely available.

Biomechanical control and computer

Biomechanical control is a necessary, but very labor-intensive job. And this is the main reason why it is not implemented in every school and sports team.

In Fig. 46 schematically shows 10 poses of a running man whose body weight is 70 kg. These graphs were obtained as a result of planar cyclic photography. The vertical and horizontal coordinates of the six joints, the center of mass of the head and the tip of the foot are placed in Table 9.

The data provided is sufficient to calculate the velocities and accelerations of the main body segments, determine the coordinates of the general center of mass in each pose, and construct kinematic graphs ( Kinematic graphs It is customary to call graphs showing how the coordinates, velocities and accelerations of parts of a body change over time).

Rice. 46. ​​Cinematic cyclogram of a person running (according to D. D. Donskoy, L. S. Zaitseva)

Assignment for independent work

Perform all the listed calculations and constructions.

Having completed this task, you are convinced that the complexity of biomechanical control is indeed very high. But it also took a lot of time to compile Table 9. Now imagine that you received all the necessary information without spending any effort, immediately after the person being studied finished the exercise. Isn't it true that this is already in the realm of science fiction? Nevertheless, today such a fantastic opportunity has become real, and this happened thanks to the achievements of electronic computing technology.

The creation of computers, the significance of which academician N. N. Moiseev compares with the conquest of fire, is associated the most important stage scientific and technological revolution of the 20th century. “Improving their working organs and sense organs over thousands of years, man until the middle of the 20th century. retained for his brain the function of an intermediate link between them.

But with the modern level of development of science and technology, the mental load of a person... has become enormous, and sometimes debilitating and unbearable. The further development of mankind required “completion” natural system control - the human brain... From this need, electronic computing technology was born" (Quote (with abbreviations) taken from the book by I. M. Feigenberg "Brain, psyche, health" (M., 1972. - P. 32)).

Note. The numerator contains horizontal coordinates, and the denominator contains vertical coordinates of the markers, see

As you know, computers are divided into universal and specialized. Mainframe computers (including personal computers) make it possible to solve many problems of biomechanical control. Including:

- calculations and graphic work similar to what you did while completing the task on p. 75 and more complex;

— testing of motor qualities;

- identification of optimal options for technology and tactics through their mathematical and simulation modeling on a computer (see Fig. 23, 24);

— monitoring the effectiveness of equipment and tactics.

We illustrate the latter by those shown in Fig. 47 results of dynamographic control over the symmetry of posture when a person is standing. Such control not only allows you to give healthy recommendations, but is also necessary when tailoring sports shoes individually. The picture shows that the two toes of the left foot are not interacting with the support. Therefore, an instep support should be placed under these fingers.

Even these few examples give an idea of ​​how the use of computer technology in biomechanical control expands the capabilities of the teacher. It is not for nothing that the ability to use a computer is called the second literacy.