Force control characteristics for generation and relaxation compared between the upper and lower limbs

Abstract

We investigated the characteristics for force generation and relaxation compared between upper and lower limb. Participants were instructed to control the force of isometric elbow flexion or knee extension as quickly and accurately as possible. They performed the following two tasks: 1) Generation task, they increased their force from 0% maximum voluntary force (MVF) to 20%, 40%, or 60% MVF, 2) Relaxation tasks, they decreased their force from 60% MVF to 40%, 20%, or to 0% MVF. As a result, variable error of upper limb was greater than that of lower limb at all magnitudes in generation task. The peak rate of force development was greater in lower limb than in upper limb at all magnitudes in both tasks. The results indicate that it is more difficult to control relaxation of force accurately by upper limb than by lower limb under conditions that involve forces with low magnitude of control.