Electrical stimulation superimposed onto voluntary muscular contraction reduces deterioration of both postural control and quadriceps femoris muscle strength

Fatiguing exercise of the quadriceps femoris muscle degrades postural control in human subjects. The aim of this work was to compare the effects of the fatigue of the quadriceps femoris induced by voluntary muscular contraction (VC), and by electrical stimulation (ES) superimposed onto voluntary muscular contraction (VC+ES), on postural control and muscle strength. Fourteen healthy young adults participated in the study. Postural control and muscle strength were evaluated using a stable force platform and an isokinetic dynamometer, respectively, before (PRE condition) and after the completion of each fatiguing exercise (immediately: POST condition; after a 5 min recovery time: POST 5 condition). In POST, both postural control and muscle strength were impaired by both fatiguing exercises. However, the impairment was higher for VC than for VC+ES. In POST 5, for both fatiguing exercises, postural control recovered its initial level while muscle strength did not. These results suggest that superimposing ES onto voluntary muscular contractions (VCs) impaired muscle strength and postural control less than did VCs alone. However the duration of recovery of these two neurophysiological functions did not differ for the two fatiguing exercises. For both exercises, postural control was restored faster than the ability to produce muscular strength.