Abstract
This paper aims at clarifying the movement control system of skeletal muscles.
The authors paid attention to the small oscillation (tremor) that is observed in the movement control system and proposed the hypothesis that this small oscillation is caused in the closed loop called the stretch reflex arc consisting of an α motor neuron, a muscle and a muscle spindle.
The experiments on the elbow joint were carried out under the following conditions and the EMG, the EMG envelope, the joint angle and the joint angular velocity were recorded.
a) To maintain a preassigned joint angle precisely under constant torque disturbance.
b) To rotate the elbow joint by a preassigned angle at the highest possible speed.
c) To maintain the integrated value of the joint angle constant precisely.
In these experiments oscillations of the EMG envelope and the joint angle at about 10Hz were observed.
Then the model of the movement control system was proposed, the parameters of a muscle were measured experimentally, and those of a muscle spindle could be determined such that the existing oscillation was explained.
Analog simulation of the movement control system showed good agreement with the results of our experiments.
