Abstract
The reduction in the quality and integration of sensory information with aging could increase the alterations in postural control associated with muscle fatigue observed in younger adults. This study aimed to compare changes in postural control and attentional demands due to ankle muscle fatigue, with intact and reduced proprioceptive information at the ankle, between young and older adults. Eleven young (24 ± 4 years) and 13 older (65 ± 4 years) men stood quietly on a force platform (blindfolded) under four experimental conditions (combinations of firm (FS)/compliant (CS) surfaces and single/dual tasks), before and immediately after a fatiguing exercise. The fatiguing exercise, performed on a dynamometer, consisted of maintaining an isometric contraction of the plantarflexors at 50 % of maximum until exhaustion. Both COP sway area and COP sway velocity were greater on the CS compared to FS and increased with fatigue for both groups in all conditions. COP sway area showed a greater increase with fatigue in older adults when standing on the CS. Reaction time (secondary task) increased significantly after fatigue, but only for older adults when standing on the CS. The effects of fatigue on postural control are more important when proprioceptive information at the ankle is altered. In particular, older adults had more difficulty and may have needed more attention to stand quietly, compared with young adults.
Highlights
Neuromuscular or muscle fatigue can alter postural control, with most studies showing an increase in sway amplitude or velocity in young adults (Paillard 2012)
Studies have shown a modulation of the effect of fatigue on postural control according to available sources of sensory information (Boyas et al 2011; Thedon et al 2011; Gimmon et al 2011; Bisson et al 2010)
Center of pressure (COP) sway during feet-together stance was characterized with three time-domain variables using BioAnalysis 2.1 software (Watertown, MA): the 95 % ellipse sway area, and medio-lateral (ML) and anterior– posterior (AP) COP sway velocity
Summary
Neuromuscular or muscle fatigue can alter postural control, with most studies showing an increase in sway amplitude or velocity in young adults (Paillard 2012). Numerous studies examining the effect of ankle muscle fatigue on postural control have suggested a link between an alteration in proprioception and an increase in sway with fatigue (Salavati et al 2007; Gribble and Hertel 2004; Vuillerme et al 2002a). When proprioceptive input is less reliable [e.g., on a compliant surface (CS)], postural control alterations due to ankle muscle fatigue can be exaggerated (Bisson et al 2012) due to an additive effect: altered joint position sense (Allen et al 2010) and force sense (Vuillerme and Boisgontier 2008) as a result of muscle fatigue and further alteration in kinesthesia caused by the CS (Horak and Hlavacka 2001).
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