Coordination Incoordination

A movement is the displacement of a certain body through a certain space in a certain interval of time. Since in piano-playing random movements are not considered, we may add aim as a fourth element of movement, to

1. weight,
2. distance, and
3. time.

Aim is the fourth element when considering coordination and incoordination.
A coordinated movement is a movement which fulfills the requirements of arm weight, space, and time with a minimum waste of physiological energy. An in-coordinated movement is a movement in which this minimum is not reached. Waste of psychological energy may be produced by incorrect weight, distance, or time, as a result of which the aim of the movement is either

1. not fulfilled, or
2. is fulfilled by an expenditure of energy greater than that necessary for the particular movement.

Suppose a "force of ten" is required to move the arm through one octave in a half-second, producing a tone of given loudness. A force of less than ten with the other elements constant, will then not suffice to meet these requirements. The tone will be too soft, or the time of the hand-movement will exceed one-half second.
A force greater than ten, no part of which is acting antagonistically to another part, will cause

1. too loud a tone, or
2. too great a leap, or
3. too quick a movement.

These excess effects may be counteracted by appropriate contraction of the antagonistic muscles. If, for example, the speed be sixteen units instead of twelve, a contraction of four in the antagonistic muscles will reduce the speed to the desired rate. But together there will be an expenditure of twenty units of work for which 12 units of work would have sufficed.