Article

This study assessed effects of unilateral leg muscle fatigue (ULMF) on balance
control in gait during the stance and swing phases of the fatigued leg in healthy
elderly, to test the assumption that leg muscle strength limits balance control
during the stance-phase. Ten subjects (aged 63.4, SD 5.5 years) walked on a
treadmill in 4 conditions: unperturbed unfatigued, unperturbed fatigued,
perturbed unfatigued, and perturbed fatigued. The perturbations were lateral
trunk pulls just before contralateral heel contact. ULMF was evoked by unilateral
squat exercise until task failure. Isometric knee extension strength was measured
to verify the presence of muscle fatigue. Between-stride standard deviations and
Lyapunov exponents of trunk kinematics were used as indicators of balance
control. Required perturbation force and the deviation of trunk kinematics from
unperturbed gait were used to assess perturbation responses. Knee extension
strength decreased considerably (17.3% SD 8.6%) as a result ULMF. ULMF did not
affect steady-state gait balance. Less force was required to perturb subjects
when the fatigued leg was in the stance-phase compared to the swing-phase.
Subjects showed a faster return to the unperturbed gait pattern in the fatigued
than in the unfatigued condition, after perturbations in swing and stance of the
fatigued leg. The results of this study are not in line with the hypothesized
effects of leg muscle fatigue on balance in gait. The healthy elderly subjects
were able to cope with substantial ULMF during steady-state gait and demonstrated
faster balance recovery after laterally directed mechanical perturbations in the
fatigued than in the unfatigued condition.
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Langue : ANGLAIS