Disturbance of contralateral unipedal postural control after stimulated and voluntary contractions of the ipsilateral limb.

One session of sustained unilateral voluntary muscular contractions increases central fatigue and induces a cross-over of fatigue of homologous contralateral muscles. It is not known, however, how this cross-transfer affects contralateral unipedal postural control. Moreover, contralateral neurophysiological effects differ between voluntary muscular contractions and electrically stimulated contractions. The aims of this study were thus to examine the effects of muscle fatigue on contralateral unipedal postural control and to compare the effects of stimulated and voluntary contractions. Fifteen subjects took part in the protocol. Fatigue of the ipsilateral quadriceps femoris was generated either by neuromuscular electrical stimulation (NMES) or by isometric voluntary muscular contraction (VOL). Postural control on the contralateral limb was measured before (PRE condition) and after the completion of the two fatiguing exercises (POST condition) using a force platform. We analyzed body sway area and the spectral power density given by the wavelet transform. In POST condition, postural control recorded in the unipedal stance on the contralateral limb was disturbed after NMES and VOL fatiguing exercises. In addition, postural control was similarly disturbed for both exercises. These results suggest that cross-over fatigue is able to disturb postural control after both stimulated and voluntary contractions.