Effect of Superimposed Electromyostimulation with Back Extension on Back Muscle Strengthening: a Pilot Study

Abstract

Objective: To determine the additional effect of superimposed electromyostimulation (EMS) on back muscle strength in healthy adults Design: Prospective, single blinded, randomized controlled trial Subjects: Twenty healthy male participants without low back pain, 20-29 years of age, were recruited. Methods: In EMS group, surface electrodes were attached to bilateral L2 and L4 paraspinal muscles. Intensity of the stimulation was set for maximally tolerabe intensity. With voluntary contraction of back extensors, EMS was superimposed for 10 seconds (s). Resting period was followed for 20s. In sham stimulation (SS) group, same procedure was applied except stimulation intensity set at the lowest stimulation intensity (5mA). All subjects performed back extension exercise using Swiss-ball, 10 contractions per set, 2 sets in a day, 5 times a week for 2 weeks. The primary outcome measure was the change in isokinetic strength of the trunk extensor at 60°s-1 by using isokinetic dynamometer (Biodex System 3, Biodex Medical Systems, Shirley, NY). In addition, endurance was measured by using Sorensen test. Outcome measures were assessed at baseline and 2 weeks after the each intervention. Results: After 2 weeks of back extension exercise, peak torque of trunk extensor and endurance increased significantly compared to baseline in both groups (P<0.05). The mean increase in the back muscle strength and gain of endurance after 2 weeks was greater in EMS group than SS group although there was no statistical significance. Conclusion: This study suggests that 2 weeks of back extensor strengthening exercise on Swiss-ball was effective for strength and endurance. Superimposed EMS on back extensor during strengthening exercise could provide additional effect on increasing strength.