THE SCIENCE OF FORMLESS FLOW by Monya Gorelik, M.Sc. : How we coordinate rotary motion of our arms and legs

Monday, February 9, 2015

How we coordinate rotary motion of our arms and legs





It is well known fact that our body was created and developed to its present shape for one main reason – to move! We move mostly in specific environment in specific human manner and we move mostly by using our limbs – arms and legs.

This motion in the space has a special name – locomotion or locomotory motion. The typical examples of locomotion are walking, running and swimming.
In the basis of locomotion as well as of the other movements in the space there are stato-kinetic reflexes. Their name reflects their nature and destination – these reflexes are responsible for our postures and movements.


Of course locomotion and stato-kinetic reflexes employ not only our limbs until we move as living creatures and not as dolls or images in cartoons. The motions of trunk, neck and head play very important role and actually any restriction in these motions results in severe limitations and losses of our locomotory and stato-kinetic abilities. Actually the motions of the trunk and head precede and initiate the motions of the limbs. These motions are based on rotational motions of vertebra joins. The motions of pelvis and shoulders follow and continue the vertebral motions providing our body with additional degrees of freedom.

How our vertebra moves? It rotates in three planes clock-wise and counter-clock-wise directions in its joints. There is some delay in rotations when we proceed from one vertebral joint to another. These delays accumulate gradually so both ends of the vertebra finally will rotate in the some direction but can accumulate quite considerable delay. Our pelvis and shoulders will rotate in the same way as our vertebra. The pelvis has stiff bones joints so it will follow almost exactly the lower end vertebra rotations. The shoulders belt has much more freedom in its joints so inertia will add even more delay to the motion of two shoulders comparatively to the pelvis. Still both shoulders and pelvis will rotate in one direction.

The limbs, arms and legs, continue the motion of the shoulders and pelvis and rotate in the same direction, three-dimensionally, with additional delays as the motion progresses from one joint to another.

Try to imagine lizard walking on the ground or chameleon climbing on the tree. Their body moves like a wave and their legs rotate in unison. This, in main details, is our style of motion. We are not so much different!
This is a reason for the well-known fact that it is very difficult to rotate palms and feet on the same side in opposite directions. It is more complicated to explain why we can rotate leg and arm from the opposite sides of the body in opposite directions. This explanation needs special analyses.
During our sport activities sometimes can happen that our normal, natural course of motion is disturbed and we start to rotate leg and arm from the same side in the opposite directions. Such motion is dangerous as it can harm our vertebra. As a result we immediately and instinctively partially block this motion and stop moving our arm or leg. We can see this situation in many cases watching kicking in Martial Arts performances – the "frozen" arms during the kicking signalize a motor problem.  This partial blocking of the motion is not desirable in most of the cases as it weakens and slows down the motion. To avoid it we have to analyze and improve our once-learned motion.

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