THE EFFECT OF NEUROMUSCULAR ELECTRICAL STIMULATION (NMES) IN INDUCING MUSCLE HYPERTROPHY AND IMPROVEMENT IN MUSCLE TORQUE WITHN THE QUADRICEPS MUSCLE OF ELDERLY PEOPLE

Aging is associated with structural changes in skeletal muscles. One such change is loss of muscle mass. Muscle fiber atrophy is another structural transformation. Muscle fiber atrophy is selective to type II muscle fibers. The reduced mass of aging muscles has functional consequences like reduced performance of daily activities. Although exercise can be used to hypertrophy type II muscle fibers, it requires high intensity training that may not be feasible for elderly people. Due to the ability of neuromuscular electrical stimulation (NMES) to activate type II muscle fiber at relatively low intensity compared to voluntary exercises, NMES might be an alternative method to train type II muscle fibers in the elderly population.\ud \ud The purpose is to test the effectiveness of NMES compared to exercise that is performed at the same intensity in inducing structural changes in quadriceps muscle of elderly subjects. The aims are to 1) compare changes in muscle hypertrophy, 2) compare changes in quadriceps muscle power output, and 3) Compare changes in the performance-based functional power tests in subjects who receive NMES and those who receive isometric strengthening exercise at the same intensity level.\ud \ud Twenty subjects (71.2 +/- 4.41) were randomized to receive NMES or exercise. Computed tomography (CT), and muscle biopsy were performed to assess changes in cross sectional area (CSA) and fiber types of the quadriceps. Isokinetic quadriceps muscle power and performance based functional power were measured to assess changes in quadriceps strength and performance based physical function.\ud \ud The patterns of change from pre to post training on total quadriceps CSA, lean quadriceps CSA, and type IIA CSA were significantly higher for the NMES group. There was no difference between the groups in isokinetic quadriceps muscle power. The change in ramp power test from pre to post training was significantly higher for the NMES group. \ud NMES might be an alternative to exercises in inducing type II fiber hypertrophy in older adults. \ud \ud NMES training induced improvements in performance based functional power tests compared to voluntary isometric exercise. There were no differences between the groups in the change in isokinetic quadriceps muscle power test scores.\u