The methodology of **the Kadjchnikov Systema** is fundamentally different from all others. It is simple and accessible for understanding. **The Kadochnikov Systema** is based on the science, the laws of physics and mechanics and the synthesis of the scientific knowledge of the humanity. In other words there is no magic or some notions that an ordinary man can’t understand. Every motion the **russian hand-to-hand combat** includes has its explanation from the scientific point of view. **Alexey Alexeyevich Kadochnikov** in his system often makes reference to different laws of physics or mechanics. The model approximation of a man is very important part of the theoretical basis of **the Kadochnikov Systema**. It helps to understand certain mechanisms of **the russian hand-to-hand combat**.

Just like any physical agent a man can be regarded as a material point, a rigid body or complex biomechanical system of bodies. It depends on the purpose of the research.

A man is regarded as a material point when he relocates at distances much bigger than the size of his body and it is not necessary to research the motion of the parts of his body. It can be applied to a parachute jump. The man soaring under the canopy can be regarded as a point in a fixed system of reference XYZ. The position of this point is defined by the independent coordinates x1, y1, z1. In this case this man has three degrees of freedom.

The man is regarded as a rigid body of a finite size when it is important to consider not on only his dislocation but also the orientation of the body. For instance a parachutist performing a free-fall jump and doing the elements of skydiving is moving in space relatively to the fixed system of reference XYZ.

The axis Ox is directed to a normal along the ground, the axis Ox is tangential to the horizon and the axis Oz is perpendicular to the previous two exes.

The position of the axes of the system XYZ and consequently the turns of the parachutist in the terrestrial reference system are defined by three angles: ϕх, ϕy, ϕz. It means that the parachutist doing acrobatic figures can rotate about each axis.

For example when doing a somersault he rotates about frontal axis of the body Ox.

When doing “a somersault with a turn” the body of the parachutist is rotating about at least two axes. The first axis (for instance Ox) has constant orientation; the second one (for instance a long axis of the body Oy) changes its orientation in space.

Thus when a human body regarded as a rigid body of a finite size is in a free-flying operation it has six degrees of freedom.

Linear motions of a man in **the russian hand to hand combat** are defined by changing х1, у1, z1 coordinates of its center of mass in the fixed system of reference х1, у1, z1. The turns of the body relative to the center of mass are measured by three angles: ϕх, ϕy, ϕz. Thus the positions of the axis Ox and Oz of the bound coordinate system XYZ are determined by the turn of the human body about the vertical axis Oy at the angle ϕy.

When the longitudinal axis deviates from the vertical line in the frontal or basic plane the body is rotating around the axes Oz1 or Ox1 correspondingly.

A bearing surface x1Oz1 is a bond that restricts movements of the body along the axis Oy1

Thus a fighter on the straight legs has five degrees of freedom: ability to move along the axes Ox1, Oz1 and rotation about the coordinate axes Ox1, Oy1, Oz1. When the fighter bends his knees (when he squares up) he obtains additional limited degree of freedom that is motion along the axis Oy1.

In general cases in **the russian hand-to-hand fighting** each connection, that restricts the movements of the body, reduces the number of the degrees of freedom.

- Fixation of one point of the opponent’s body deprives him of three degrees of freedom – the linear motions along the three main coordinate axes.
- Fixation of two points of the body creates the axis that joins these two points. In this case the body is only left one degree of freedom – the rotation around this axis.
- Fixation of the third point that is not on this axis completely hog-tie the opponent.

The number of connections and consequently the number of the degrees of freedom can change during the motion!

For example a gymnast that does swings on a horizontal bar has only one degree of freedom that is the motion around the axis Oz – the axis of the bar. When he dismounts performing a curve and somersault the sportsman has three degrees of freedom (two additional degrees in the plane xOy). And when the gymnast dismounts doing a somersault with the turn he has up to six degree of freedom.

The parachutist who does acrobatic figures and the gymnast who performs breathtaking dismount do complicated movements. They both change posture by controlling their bodies. But in both cases it is important to trace the changes in the orientation of the body in space disregarding the mutual motions of the parts of the body limbs. This is the peculiarity of the model approximation of a man as a rigid body.

Finally a man can be regarded as a complex system of bodies. It means that we should consider not only position and orientation of the man in space but also mutual disposition of the parts of his body in their relation to each other. It can be in equal degree referred to many types of sports.

It is difficult to describe how to overbalance a man without taking into account the motion of all parts of his body. From the point of view of mechanics we’re talking now about representing a human body as a reconfigurable thing.

If it is so to describe the motions of the man we need a suitable model approximation. It should takes account of the peculiarities of motion of separate but interconnected parts of the body that influence the process of moving.

The complex biomechanical system of bodies can serve as such model approximation.

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