The synergy of elbow extensor muscles during dynamic work in man. II. Braking of elbow flexion.

The muscular synergy between the elbow extensors was studied during the braking of voluntary elbow flexion performed in a horizontal plane at various velocities and inertias. The braking of movements performed at very low velocity is effected by passive viscoelastic forces. For higher velocities there exists a chronology of muscular activities which depends on both velocity and inertia. From the characteristics of this muscular chronology it is inferred that: 1. The anconeus plays an important role in braking slow movements. 2. The motor output is distributed separately to the motoneurons of each muscle. The muscular activity patterns are of three distinct types. The agonist-antagonist timing is correlated with velocity and inertia. Its dependence on reciprocal inhibition mechanisms is discussed.