Effects of unilateral fatigue of triceps surae on undisturbed stance

Fatigue of lower limb presents various impacts on postural control. The purpose of this study was to explore the effects of a unilateral lower-limb muscle fatigue on undisturbed stance. Nine healthy men performed until exhaustion a fatiguing exercise of the limb extensor muscles of one leg (exercised leg). Just before and after the fatiguing exercise, postural sway measures (centre of pressure) were recorded simultaneously from a double force platform and an in-shoe pressure system in quiet standing conditions. Maximal plantar pressure was computed from each sensor of the in-shoe system, before being averaged for the medial and lateral heel, the external mid-foot, the external and internal foreparts. In undisturbed stance, the fatiguing exercise induced postural destabilisation for the non-exercised leg (P < 0.001). Changes in antero-posterior mean position of the exercised leg were also observed reflecting a mean loading in a more rear foot stance (P < 0.01). The in-shoe system parameters revealed for the exercised foot, an increase of the maximal pressure value for the heel region (P < 0.05) and a decrease for the mid-foot and forepart (P < 0.05). For the non-exercised foot, the maximal pressure decreased only in forepart (P < 0.05). Unilateral triceps surae fatigue revealed an immediate destabilisation of undisturbed stance and the observed postural strategy appears similar to these developed by patients who presented pain pathology and/or sensory deficits in lower limb.