Article

The aim of the present study was to compare the effects of ankle muscle fatigue
on postural control when plantarflexors (PFs) and dorsiflexors (DFs) are fatigued
simultaneously compared with separately. This study also investigated the
recovery of postural control after fatigue. Sixteen adults (eight women and eight
men) performed postural trials before and after an isokinetic fatigue task
involving either (i) only PFs (30 degrees s(-1)), (ii) only DFs (120 degrees
s(-1)), or (iii) both PFs and DFs simultaneously. The fatigue task involved
maximal contractions repeated until the torque produced decreased below 50% of
the maximal torque. Postural trials lasted 30s and were performed on one leg with
eyes open (EO) or eyes closed (EC). Sway area, medio-lateral (ML) and
antero-posterior (AP) positions and velocities were calculated from the center of
pressure displacements. With EO, no effect of fatigue was found on postural
variables. With EC, sway area and AP velocity increased only when both PFs and
DFs were fatigued simultaneously. An effect of fatigue present only when both
muscle groups are fatigued simultaneously could be due to impairment in the
compensatory activity between agonist and antagonist muscles and/or a greater
decrease in proprioception due to a greater number of fatigued muscles. In
addition, when PFs and DFs were fatigued simultaneously, sway area and AP
velocity returned to pre-fatigue values within 2min, whereas a posterior shift in
AP position persisted for 10min. This last result may suggest a longer-lasting
change in postural strategy needed for optimal postural control.
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Langue : ANGLAIS