Force Effects during Coordination

Since all pianistic effects are secured through variations in speed and force, it is necessary to investigate the effects of intensity upon coordinated and in-coordinated movements. The speed effects which we have just considered in themselves point the way to intensity effects, because variations in either factor influence directly the other. An increase in speed, if the mass remains constant, results in an increase in force; and conversely, an increase in force, with constant mass, results in an increase in speed. We cannot, therefore, vary one without varying the other. There are certain phases of the problem, however, that can be better explained by a separate analysis.

Chief among these is the spread of activity with an increase of force, characteristic of all coordinated movements. The mechanical reason for such a spread of muscular activity can be easily observed.
Muscles do their best work along the middle of their range of action. Extreme contraction, when it does not actually injure the muscle or tear its tendon, does not permit the muscle to act at its greatest mechanical advantage. The function of the larger muscles of the body is not only to move the larger limbs, but also to aid in other forceful movements. Inertia, and resistance of flesh and t issue fix the joints passively up to a certain resistance.
When more resistance is needed, muscular contraction at the joints occurs, fixing them actively against the increase in resistance demanded. Two views are possible.

1. One that each muscle contracts until it exerts its maximal force, whereupon adjoining, more basically situated, larger muscles contract in turn, each waiting for maximal contraction of its predecessor before taking part in the movement.
2. The other view is that the spread to other muscles takes place before maximal contraction of anyone muscle is reached. The latter view agrees more closely with the facts.

What happens is this: As the intensity or resistance to be overcome increases, the parts of the body are so shifted that the force acts at the most advantageous part of the leverage system. When, for example, the entire body is suspended by the flexors of the fingers, as in hanging from a horizontal bar, the wrist is in line with the arm and the bar so held that it acts most directly against the first interphalangeal joint itself. Thus, tissues and above all the skeletal structure is opposed to the force, which considerably lessens the strain on the muscles. When a chord on the piano is played fortissimo, the hand is so held that the direction of key-resistance is toward the hand-knuckle itself, with a tendency to push the bone-ends together. This gives maximal strength to the movement without maximal contraction of the muscles of the fingers, which, in themselves, would be too weak to produce the desired intensity.
The larger muscles of the arm step in and take over the task, while the smaller hand-muscles place the finger-bones in such a position that when the key is set in motion the resistance will spend itself against the finger-joints themselves, that is to say, the skeletal part of the structure, so far as possible. (See Figs. 186 and 187b.)