The training of coordination.

The training of coordination is generally considered a volitional activity, during which, by trial and perception of results, an individual selects the muscular activity resulting in the desired performance. This concept of volitionally directed complex coordination of multiple muscles with speed, skill, and strength does not stand the test of thorough evaluation. Attention is limited to 1 activity at a time, with the ability to shift attention not more frequently than 3 times per second. Only under special conditions can activity be limited to specific muscles during an untrained contraction without cocontraction of other muscles. However, with repeated practice of the desired activity, a pattern of performance is developed which can be carried out rapidly and forcefully without activation of other muscles. At that time, the consciousness is no longer directing the components of the activity but merely starting, maintaining, and stopping the performance. The development of these patterns, or engrams, by practice develops the capacity to automatically inhibit muscles that do not contribute to the performance of the desired pattern. The capacity for inhibition results in coordinated activation of the muscles contributing to the performance desired. Investigation of the development of coordination in many types of normal activities, as well as in neuromuscularly impaired patients, shows that engrams develop progressively by slow, precise practice of simple patterns, combined as they develop into more and more complex patterns, until the final skill is attained.