1. 1. General concept

The movements of a person largely depend on the structure of the body and its properties. This, on the one hand, makes the movements themselves and their management very difficult.

But, on the other hand, it causes an extraordinary richness and variety of movements, which is still inaccessible in General to any most perfect machine. Biomechanics is the science that studies the mechanical movements of biological bodies and in these biological bodies.

Consider a simplified model of the human body – a biomechanical system. It has the main properties essential for the performance of motor function.

Thus, the biomechanical system is a simplified copy, a model of the human body, on which you can study the laws of movement.

From the point of view of mechanics, the human motor apparatus is a mechanism consisting of a complex system of levers driven by muscles. However, it is necessary to keep in mind the biological nature of the "mechanisms" of the human body. Analysis of the activity of the motor apparatus from a biological point of view allows us to reveal the uniqueness of the device and the principle of action of "living mechanisms".

The main biological features that distinguish the motor apparatus of animals and humans from non-living technical mechanisms are as follows:

1. The Apparatus of movement of animal beings is built from living tissues and organs, in which constantly, including at rest, there is a metabolism. Chemical transformations of molecules that enter into various reactions with other organic and inorganic substances are the essence of intracellular metabolism and specific working activity of cells (for example, contractile). In this regard, the extreme dependence of the structure and function of cells and organs on their working use, on the intensity of their metabolism becomes clear. To maintain the tissues and organs of the motor apparatus in a state of high efficiency, their constant and proper use is necessary. Morphological and functional improvement under the influence of work and degradation during inactivity are an important feature of the motor apparatus of animals and humans.
2. in a technical machine, the movements produced by it are predetermined once and for all by the very shape of the joints between the moving parts. On the contrary, the human motor apparatus is built in such a way that from the same structural units (bones with their joints, ligaments, muscles) can be formed many different mechanisms with different working tasks, different speeds and trajectories of movement.
3. Motor activity of animals and humans, including arbitrary, is a system of unconditional and conditional reflexes to stimuli from the external and internal world, acting at this time or acting previously and preserved in the nerve centers in the form of traces.

Thus, motor activity is provided not only by the work of the motor apparatus itself, but also by the work of the sensory organs and the Central nervous system. Multiple use of the same structures of the motor apparatus is provided by the ability of the reflex mechanism to form temporary connections. There is a continuous adaptation of movements to the current conditions of the environment, i.e. "balancing" of the organism with the environment.

All motor actions of humans and animals are performed as a result of tension and relaxation of the muscles, which are caused by nerve impulses coming to the muscles through the motor nerves.

The first step from anatomical to mechanical concepts is the idea of a biokinematic pair.

A biokinematic pair is a mobile (kinematic) connection of two bone links, in which the possibilities of movement are determined by its structure and the controlling influence of the muscles.

In technical mechanisms, the connection of two links-kinematic pairs – is usually arranged in such a way that only certain predetermined movements are possible. Some possibilities are not limited (they are characterized by degrees of freedom of the body), others are completely limited (they are characterized by degrees of connection).

Degrees of freedom are understood as independent movements of a body or its parts in space. These independent movements can be either translational or rotational (simple forms of mechanical movement). In the case of a complex (composite) movement, it is always decomposed into components of simple forms. In this case, the incoming is understood to be a movement in which a line mentally drawn in the body moves parallel to itself. And in a rotational motion, all points of the body describe circles, the centers of which are on a single straight line, called the axis of rotation.

If a physical body has no restrictions (connections), it can move in space relative to three mutually perpendicular axes (translationally), as well as around them (rotationally). Hence: such a body has six degrees of freedom.

Each link reduces the number of degrees of freedom. Having fixed one point of a free body, making it a link of a biokinematic pair, you can immediately deprive it of 3 degrees of freedom – possible linear movements along the three main coordinate axes.

Almost all the joints (except the interphalangeal, radioulnar and atlantoaxial) degrees of freedom more than one. Therefore, the device of the passive apparatus in them causes the uncertainty of movements, a lot of possible movements ("incompletely connected mechanism"). The control actions of the muscles cause additional connections and leave only one degree of freedom for movement ("fully connected mechanism"). This provides a single opportunity for movement – exactly the one that is required. The set of degrees of freedom of the biokinematic pair in multi-axis joints requires each specific movement to be performed:

1. Selecting the necessary trajectory,
2. Control of movement along the trajectory (direction and speed),
3. Regulation of movement, understood as the fight against interference that leads off the trajectory.

Biokinematic pairs, connecting in series or in parallel, form biokinematic chains.

A biokinematic chain in which the final link is free is called an open chain. For example, free limbs when their end links are free (the fighter is ready for hand-to-hand combat).

If there is no free end link in the biokinematic chain, then it is closed (for example, two opponents locked in a grip with each other).

In a closed or open circuit, it is not possible to have a single, isolated movement, i.e. movement in a single connection. So, bending and unbending the leg in a blow, you can make sure that movement in any joint necessarily causes movement in others. Thus, in closed circuits, there are fewer possibilities of movement, but their control is more precise than in open circuits.

Considering the human body as a complex biomechanism, bones as rigid links, and joints as kinematic pairs of certain classes, for the whole person we have:

• mobile bones – 148,
• joints with 3 degrees of freedom – 29,
• joints with 2 degrees of freedom – 33,
• joints with the 1st degree of freedom – 85,
• total degrees of freedom for the entire biomechanism – 244.

The concept of "kinematic chain" was transferred to biomechanics from technical mechanics, where it is used to describe and analyze the kinematics of mechanisms. Accordingly, in biomechanics, it is applicable to the study and analysis of the kinematics of the musculoskeletal system, i.e., in the process of considering linear and angular movements, speeds, accelerations of body parts-relative and absolute (in the selected report system). Kinematics refers to the external picture of motion that occurs in space and time.

In the same cases, when the dynamics of movements, the developed moments of joint forces and the forces of interaction of the body's links with each other and with other bodies are of interest, when the power and energy capabilities of the motor apparatus are analyzed, the concept of "biokinematic chain" can no longer satisfy. Here we introduce the concept of "dynamic chain", which refers to a system of power links connected in series or parallel.

Dynamics is understood as the essence of movement and its causes: first of all, power and mass-inertia characteristics.

Both biokinematic and biodynamic chains can be sequential (simple) and branched. However, for dynamic circuits, the concept of "closed" is devoid of expediency, since it means only the imposition of new dynamic (power) factors, i.e. it does not introduce anything fundamentally new.

The functional characteristics of the same power links are not the same for different people. In this regard, the most appropriate structure of movements is very often individual, i.e. it differs from the generally accepted structure of movements determined by rational control techniques. This is based on the desire to compensate for the functional insufficiency of some links at the expense of the functional redundancy of other links in the dynamic chain.

Compensation is made at the expense of:

• load changes on power links;
• redistribution of the velocities of the motions of the links.

Movements of links-joint movements-are made as a result of the presence of joint moments.

Mechanical movement of biological bodies is called motor action.

In order to quantify the motor action, including calculating the joint moments, you should go to the mechanical representation of the lever.

2. Levers, their characteristics and types

A lever is a solid body that has a fulcrum and can rotate around this point-the axis of rotation; a device that serves to convert force.

In the lever, there are at least two forces with opposite moments.

Bone levers-links of the body that are movably connected in the joints under the action of applied forces, can either maintain their position or change it. They serve to transmit movement and work over a distance.

When forces are applied on both sides of the axis (fulcrum) of the lever, it is called two-shoulder, and when on one side-one-shoulder. For different muscles attached in different places of the bone link, the lever can be of different types. There are three types of levers in nature: levers of the I-th, II-th and III-th genera (Fig. 1).

            two-shoulder                                                   single-shoulder

Each lever has the following elements (Fig. 1a):

- support point (axis of rotation, point O),

- at least two forces (f and F),

- points of application of these forces (A and B),

- lever arms (distances from the pivot point to the points of application of forces-AO and VO),

- arms of forces (the shortest distance from the fulcrum to the lines of action of forces-the perpendiculars lowered on it – A¢O and S¢).

The measure of the force on the lever is its moment relative to the fulcrum – the rotational moment. The moment of force is determined by the product of the force on the shoulder of this force.

М_f= F^. ОВ¢

М_f= f^. АО¢

The moment of force is a vector quantity. If the force does not lie in a plane perpendicular to the axis, then find the component of the force lying in this plane. It causes the moment of force relative to the axis. The other components do not affect the moment of force (Fig. 2).

When the moments of forces opposite to the axis of the joint are equal, the link either retains its position or continues to move at a constant speed (the moments of forces are balanced). If one of the moments of force is greater than the other, the link receives acceleration in the direction of its action.

In the musculoskeletal system there are levers of all three kinds, and much more levers of the third kind, levers of speed, because the muscles are attached mainly near the joints.

Thus, the human motor system is by nature more fast and agile than strong. In addition, all bone levers have a loss in strength due to the fact that the muscles are attached to the bones at an acute or obtuse angle.

Melee power that performs work is applied to the enemy force and counteracting force – the force of the enemy. To overcome the counteracting force on the lever, you must either increase the force that performs the work, or change the length of the shoulder through which the work is performed. Since the power capabilities are almost always limited, and the fight can be conducted with a significantly superior opponent, the main way to work with the help of levers is to move the fulcrum. Any body parts (your own and your opponent's), as well as weapons and improvised means can be used as a fulcrum.

       3. Fundamentals of muscle biomechanics

It is known that a muscle is a control organ of the Central nervous system. Biomechanics considers what happens to the mechanics of the muscle as a result of neural influences, i.e. the relationship between linear movements of the ends of the muscles (kinematics of movement) and the forces developed by it (dynamics of movement). The mechanics of muscle contraction consists in the connection of stress in the muscle with its deformation.

To fully describe the biomechanical properties of muscles, use the following definitions:

rigidity – the ability to resist applied forces. It manifests as elasticity and quasi rigidity;

relaxation – voltage drop (tension) over time;

strength – is understood as the tensile strength.

Often, when studying the mechanical properties of the human body and its individual elements, the influence of tendons is not taken into account. Tendons are often considered as an absolutely inextensible, flexible part of the muscle. And tendons are able to absorb sharp shocks and have hard-damping properties.

The strength of tendons exceeds the strength of muscles by 2 times. The tendons of a person are torn mainly at the place of attachment to the muscles.

The strength, speed and economy of movements depend on the extent to which you can use the biomechanical properties of your motor apparatus. The force and speed of movement can be increased by using elastic forces, efficiency – by using the recovery (reuse) of mechanical energy and reducing the loss of dispersion.

In addition, it is necessary to know that with increasing speed of active muscle contraction, the value of its maximum tension decreases and Vice versa, i.e. in order to inflict as fast (sharp) a blow (hand or foot) as possible, it is necessary to relax as much as possible the part of the body that this blow is applied to.

The biomechanical properties of muscles have a decisive influence on this. It is well known that in jumping up from a place performed from a squat after a pause, the result will be lower than in a jump from a squat without a pause, because in the second case, the forces of elastic deformation of pre-stretched muscles are used. It is believed that the energy recovery of elastic deformation is the main reason for the high efficiency of human running and kangaroo jumping.

A significant amount of elastic strain energy can accumulate in muscle and tendon structures. However, the accumulated energy of elastic deformation is not always fully used. The degree of its use depends on the conditions for performing movements, in particular, on the time between stretching and shortening the muscle. It is necessary to learn how to use this energy correctly in hand-to-hand combat.

In the course of training, it should be taken into account that the mechanical strength of tendons and ligaments increases relatively slowly. With the accelerated development of speed-power qualities, there may be a discrepancy between the increased speed-power capabilities of the muscle apparatus and the insufficient strength of ligaments and tendons. This could lead to potential injuries. Therefore, during training, it is necessary to pay attention to the strengthening of the tendon-ligamentous apparatus. This is achieved by volume training work of low intensity. It is desirable that the movements are performed with the maximum possible amplitude for this joint and in all directions.

       4. Structure of impacts and their biomechanics

The element of motor action is a temporary structural unit-the phase.

A phase is a sequence of motor actions that solves a specific motor task; a motor task changes – the phase changes.

When considering actions in hand-to-hand combat, we suggest considering the concept of "impact" and the processes associated with it.

A blow, as a physical phenomenon , is a short-term interaction of two (or more) bodies, in which large forces occur.

In biomechanics, the following impact phases are distinguished:

Swing – movement that precedes the impact movement and leads to an increase in the distance between the impact link of the body and the object that is being struck. This phase is the most variable.

Pre-stroke movement-from the end of the swing to the beginning of the strike.

Impact interaction (or actual impact) – the collision of striking bodies.

Post-impact movement – the movement of the impact link of the body after contact with the object – target, which is struck.

The main phase is the shock interaction, which is characterized by a force pulse (Fig. 3).

Graphically, the force impulse is determined by the area under the curve of force versus time (t1 and t2 – moments of time corresponding to the beginning and end of the shock interaction; t = t2 – t1).

Force impulse is the product of force for the duration of forces (translational movement); it is a measure of the impact force on the body over a period of time.

The mechanics of the strokes are divided into

• Central (if the bodies before impact move along a straight line passing through their centers of mass);
• straight lines (if the velocity V Of the center of mass of the body at the beginning of the impact is directed along the normal n in the direction of another body);
• oblique (if the velocity vector of the center of mass is different from the normal).

In the process of shock interaction, the mechanical deformation of the body occurs; the kinetic energy of motion passes into the potential energy of elastic deformation, then this energy is again partially converted into kinetic energy of movement, and partially dissipated (goes into heat). Depending on the losses on the energy dissipation of elastic deformation, the impacts are divided into:

1. a) quite elastic (there are no losses on scattering, for example, a blow to a billiard ball);
2. b) not completely elastic (only part of the elastic strain energy is converted into kinetic energy; for example, blows in sports games on the ball);
3. c) inelastic (the energy of elastic deformation is all converted into heat, for example, blows in boxing, karate, landing in jumps, jumps).

In the theory of impact in mechanics, it is assumed that the impact occurs so quickly and the shock forces are so large that all other forces can be ignored. However, many actions in hand-to-hand combat can not be considered as a "clean" blow and in them such assumptions are not justified.

The impact time in hand-to-hand combat (and in such sports as Boxing, karate, etc.), although small, can not be ignored; the path of impact interaction, along which the colliding bodies move together during the impact (for example, in sports RB, Boxing, etc.), can reach 20-30 cm.

In such cases, the impact interaction appears externally as a complex movement, i.e. it includes elements of both translational and rotational motion, i.e. the phase of the impact interaction is characterized by the sum of the force pulse and the momentum of the moment of force:

F^. t + M_f^. t 

where: Mf – moment of force,     t – time of action of the moment of force.

When performing during the impact, in addition to translational, also rotational movement of the impact surface, the body that is struck is transmitted mechanical movement in the form of rotational. In this case, the so-called "shock" mass increases. Its value is not constant. If, for example, you perform a blow by bending the hand or with a relaxed hand, the body that is being hit will interact only with the mass of the hand. If, at the moment of impact, the striking link is fixed by the activity of the antagonist muscles (hand-forearm) and is a single – solid body, then the mass of all the rigidly fixed links will take part in the impact interaction. You can not differ in large muscle mass, but at the same time own a very strong blow. The larger the element of rotational motion, the greater the "shock" mass and the stronger the impact can be applied. Thus, in hand-to-hand combat, a blow is mainly intended to provide a greater force of impact interaction and, due to a given trajectory of movement, to ensure that it hits a specific end point. It is possible to provide a greater impact force, first, by giving the maximum speed to the striking link at the moment of impact interaction and, secondly, by increasing the "shock" mass.

From the point of view of mechanics, it is clear that the smaller the mass of a link, the more speed this link can develop, and anatomically less massive links of the body are capable of more coordinated movements.

You can also increase the impact force by increasing the "shock" mass at the moment of impact interaction. This is achieved by "fixing" (for example, in Boxing, karate, etc.) individual links of the striking segment by simultaneously turning on the antagonist muscles and increasing the radius of rotation. Melee on the system of COLLECTING such "consolidation" the separate segments is not achieved by muscle tension (strikes are unstressed limb), but a simple shutdown of degrees of freedom in joints of rotating the limb at the moment of interaction with the target.

The impact time is so short that it is almost impossible to correct the mistakes made. Therefore, the accuracy of the blow is decisively ensured by correct actions during the swing and pre-impact movement.

When considering the concept of "blow" in hand-to-hand combat, the following is important for us:

1. in oncoming traffic, when bodies hit (collide), their speeds add up.
2. the smaller the area of impact, all other things being equal, the greater the impact effect.
3. The time of the strike has direct dependence of body weight, value of joint displacement and inverse dependence on the force of impact.

It should be noted that the blow is a powerful means of sudden defeat of the enemy and often, but not always, decides the outcome of the battle.

Strikes have three main drawbacks:

- the impact cannot be dosed;

- when striking a blow, you can get injured, which will reduce the combat capability;

- against some attacks, equipment ("unloading", bulletproof vest, etc.) and clothing, especially winter clothing, is a good protection.

         5. Control of motor action

Every position of a biological body is a vibrational process. The point of the common center of gravity (CCT) of the body in a static position experiences fluctuations in the range of 2-3 cm, due to blood circulation, lymph flow, respiration, muscle tremor, etc.of the biological body; this is a controlled process. A person can change the stability of their body by varying the stability factors, which are:

1. The magnitude of the support area. This is the area enclosed between the boundary points of the support. It includes the active area of the support that arose when the biological body came into contact with the support, and the passive area.

In practice, we are more able to change the passive area of support (for example, by placing our feet wider than our shoulders).The larger the total area of support, the more stable the position of the body. The optimal support area in hand – to-hand combat is when the feet are placed shoulder-width apart.

2. The height of the point of the BCT. The lower the BCC point of the body, the more stable the body is.
3. The course of the line of gravity. The line of gravity is a perpendicular lowered from the body's BCC to the support area. Passing the line of gravity allows you to assess the stability of the body in different directions (for a flat image – in the front-back direction). If the line of gravity passes through the center of the support area, the degree of stability of the body is the same in all directions; if it is shifted to one side, the degree of stability is reduced in this direction.
4. the Magnitude of the stability angles. The angle of stability is the angle formed by the line of gravity and the line connecting the BCC to the edge of the support area.

The stability angle is a dynamic stability factor that combines the three previous static factors. Try changing one of the previous stability factors, this will immediately affect the stability angles. The meaning of this angle is as follows: it is the angle at which the body returns to its original position when rotated. If the body is rotated at an angle greater than the value of the stability angle, the body will lose stability and move to a different position. The angles of stability of the body when viewing a flat image characterize the stability in the front and back directions. The greater the stability angles, the more stable the body is in this direction.

5. The coefficient of stability of the body determines the body's ability to maintain stability under the action of overturning forces. Be able to manage the stability coefficient (changing the position to change the moment of stability)- this is the task of everyone involved in hand-to-hand combat.

Within the framework of the proposed manual and for simplicity of explanation, we will focus on the first three factors and introduce the concept of "stability" from the point of view of its use in the Republic of Belarus.

From the point of view of biomechanics in hand-to-hand combat, we pursue the following goals:

- maintaining and using your balance;

- unbalancing the enemy and using his loss of stability for their own purposes.

Consider the concept of "stability", its loss and recovery.

Figure 4 shows schematically the figure of a person, which is conventionally called "the enemy".

1. Imagine that we are attacking, and he (the enemy) is defending (Fig. 4a).

In this case, the enemy's position is static and stable. The whole system is in balance. The opponent in a stand leans on both legs-supports. The gravity vector P is directed at the center of the support platform. The sum of the moments is 0, and the resultant of the forces along the axes (X, Y,Z) is 0.

2. Start to bring the system out of balance (Fig. 4 б). Removing one support (foot at point B), we get the following:

under the action of its own weight, a tipping moment appears, which is equal to the product of the weight on the shoulder relative to the support at point A:

M opr. = P • l/2

The system has become unbalanced, and the sum of moments is not equal to 0.

          3. Due to the fact that there was a tipping moment, the system turned into a dynamic, the enemy began to fall.

We use this and, in order to accelerate the fall, additionally apply the force F with the shoulder l1 (Fig. 4 в).

The calculated tipping moment is equal to

М _{р. opr.} =   Р ^{. 1}/₂l + F^. l₁

In this case, the larger the lever l1, the less force F is required for tipping or tipping control. Formally, we did everything to ensure that the enemy (this system) fell, but in reality it can try to restore the lost stability in some way.

         4. To prevent this from happening, we apply a couple of forces (in this case, to the head) and create additional torque, while continuing to remove one support (Fig 4r). This action will speed up the enemy's rollover.

In this example, we have considered only a special case. There can be many ways to use these or other forces.

Let's go to the actions of the defender.

1. If the enemy has brought us to an unstable position, you need to go to the hinge-movable support and lower the center of gravity (Crouch) (Fig. 5 a). Simultaneously turn around ("go") in the direction of the enemy force. In this way, we equalize the speed of our rotation and the rotation of the enemy, and being on a pivot-movable support, we are ready to move our system in any direction, while simultaneously maintaining the position of balance.

2. Now, in order to take the initiative, we add the force F1k to the enemy, in this case to the head, create a fixed support point at point A, remove the support at point B. As a result, the enemy loses stability, and we, being in a stable position, begin to control it (the enemy) (Fig. 5 b).

Conclusions:

1. Knowledge of anatomical and biomechanical bases is necessary for understanding the motor processes occurring in hand-to-hand combat, as well as for the correct organization and conduct of training for hand-to-hand combat.

2. When conducting RB, it is necessary to use the principles of minimum energy consumption. It consists in the following: a mentally normal living being arbitrarily organizes its motor activity so as to minimize the expenditure of energy. Avoid unnecessary, unproductive muscle contractions and strains, and reduce unnecessary unproductive movements.

3. It is advisable to use energy recovery, i.e.:

- choose the least energy-intensive combination of displayed strength and speed;

- use the energy that passes from one segment of the body to another (for example, the lashing of the lower leg due to the energy accumulated during the swing of the hip),

- use the energy of elastic deformation accumulated in the muscles in the previous phases of motor action.

4. In hand-to-hand combat, it is necessary to use levers, inertia gained by the enemy, and torque to control and defeat the enemy. Using these elements will reduce the energy consumption of the leading RB.

5. It is necessary to carry out optimal motor switching, namely:

- changes in the intensity of muscle work (for example, the speed of movement);

- a change in the motor action of force and speed (for example, the length and frequency of steps),

- switching from one method of performing motor actions to another (for example, attacking or defensive alternating actions with hands and feet).