Effects of Transcutaneous Electrical Nerve Stimulation (TENS) on Changes in Postural Balance and Muscle Contraction following Muscle Fatigue

[Purpose] The purpose of this study was to investigate the effects of transcutaneous electrical stimulation (TENS) applied to fatigued muscles on postural imbalance and decline in muscle strength following fatigue of the gastrocnemius. [Subjects] Eighteen subjects with muscle fatigue were allocated to either a sensory threshold group or a 2-3 times sensory threshold group and the study followed a randomized single-blind cross-over design. [Methods] Muscle fatigue of the gastrocnemius was induced by repeated exercise. After inducing fatigue, TENS was applied to the fatigued muscle. The postural sway length (PSL), postural sway velocity (PSV) and maximal voluntary contraction (MVC) were measured before and after the induction of fatigue, and during the application of TENS to the fatigued muscles. [Results] Muscle fatigue increased postural imbalance as expressed by length and velocity of body sway and decreased muscle strength, while TENS improved the postural imbalance and partially reversed the muscle strength decline induced by muscle fatigue. [Conclusion] Muscle fatigue is an important factor in postural balance control and muscle voluntary contraction, and TENS can be effective at relieving muscle fatigue.