Definition of Coordination Revisited

If the definition given of coordination as a muscular reaction serving the aim of the movement with a minimum of waste of energy, is correct, it follows that this reaction will change with the speed of the movement ,

1. because as the speed changes,
2. the work done changes also,

and consequently demands a change in muscular reaction, if this is to retain its maximal efficiency. This change may take place in either of two ways:

1. the same muscles may contract more forcibly, thus increasing the output of work, or
2. the muscular reaction may spread to adjoining muscles.

If the first be the case, then we may rightfully speak of a fixed muscular reaction to any definite movement regardless of its speed. In earlier modules, the effect of range on coordination has already been pointed out . It was shown that as the range increases new muscles are brought into play, and that all movements of reasonable range, involve quite a transition of muscular activity, so that the combination of muscles functioning at the end of a movement is frequently quite different from those init iating the movement .
We have now to determine whether speed has a "similar effect".

Let us assume an arm-weight at five pounds.
This is to be moved through a distance of two feet in one second, and the work is done by a certain group of muscles. To move the same weight through the same distance in half the time will require twice the force, and the additional force must be balanced at appropriate points by a spread of tension in order to give fixed fulcra to the contraction.
The presence of this spread with any increase in force, has already been pointed out . It may also be readily inferred from the nature, size, and positions of the muscles themselves. If force variations depended solely upon intensity of contraction, large muscles would be superfluous, since the small muscles could do the necessary work by a more forceful contraction.
Both anatomy and physiology show clearly th at this is not true .