TABLE OF CONTENTS One need only watch a few slow-motion instant replays on the sports channels to be amazed by the variety and complexity of ways a human can carry, swing, toss, glide, and otherwise propel his body through space. Orientation, balance, and control are maintained at all times without apparent effort, while the ball is dunked, the bar is jumped, or the base is stolen, and such spectacular performance is not confined to the sports arena only. Behavior observable at any local playground is equally impressive from a mechanical engineering, sensory motor integration point of view. The final wonder comes when we observe the one-year-old infant s wobble with the knowledge that running and jumping will soon be learned and added to the repertoire.
Two-legged walking, running, jumping, and skipping are some of the most sophisticated movements that occur in nature, because the feet are quiet small and the balance at all times has to be dynamic; even standing still requires sophisticated control. If one falls asleep on ones feet he falls over. The human stabilizes the movement by integrating signals from:
Vision, which includes ground position and estimates of the firmness of the ground and the coefficient of friction.
Proprioception, that is, knowledge of the positions of all the interacting muscles, the forces on them and the rate of movement of the joints.
The vesicular apparatus, the semicircular canals used for orientation and balance.
A very large number of muscles are used...
