OBSERVATION OF CONTRACTION ON HUMAN SKELETAL MUSCLES IN SITU ― Fast and Slow Contracting Muscle ―
A simple device to pick up contraction force of a human skeletal muscle in situ as the muscle is electrically stimulated at the same point has been developed and used on eleven normal subjects. Some abnormal subjects were also studied. Latency of contraction with stimulation at the motor point was measured in deltoid, biceps brachii, triceps brachii, extensor digitorum communis, adductor pollicis, quadriceps femoris, soleus, gastrocnemius and tibialis antieus. The muscles in the upper extremity show uniform latencies and these are shorter than those of the lower extremity muscles. Critical fusion frequency of stimulation necessary to produce complete tetanus was measured in the same muscles mentioned above. Deltoid, biceps brachii, soleus and tibialis antieus muscles are classified as slow contraction muscles. Triceps brachii, extensor digitorum communis, adductor pollicis, quadriceps femoris and gastrocnemius are fast muscles.
