Agonist contractions against electrically stimulated antagonists¹

Schematic model of the exercise method. Note that both the volitionally activated agonist and the electrically stimulated antagonist contract during joint motion. The result is that both muscles are exercised and that a longitudinal compressive load is placed on the bone

The subject exercises the left arm for the hybrid method and the right arm for the control method. Specially made gel-coated metal fiber electrodes are placed over the motor points of the biceps and triceps brachii. One pair of electrodes is placed over the each muscle of each upper limb. To avoid the influence of gravity, the subjects set their upper limbs onto the cushions, which have a 30° angular surface. The hybrid exercise is performed from 15° to 105° of flexion during elbow flexion and extension motion

Muscle force measurements of isometric (A) elbow extension and (B) flexion torque (Nm) at before, 6 weeks, and 12 weeks after exercise were presented, respectively. Muscle force had increased significantly after 12 weeks

Example of the changes revealed by MRI in the CSA of the muscles in the right-hybrid-trained brachium. Note that the CSAs of both muscles increased and became rounded after 6 weeks. (A) Before exercise; (B) 6 weeks after hybrid exercise; and (C) 12 weeks after hybrid exercise

Increased ratio of the CSA of brachial muscles, comparing hybrid exercise with control exercise. It was remarkably greater than that of the control exercise both in biceps and triceps brachii. Abbreviation: W, week