Abstract
Neuromuscular fatigue is known to impair balance ability, which is reflected in increased postural sway during quiet standing tasks. Recently, quantifying transient characteristics of postural sway has been suggested as an approach to obtain additional information regarding postural control. However, this approach is currently vastly unexplored. The purpose of this study was to investigate the effects of fatigue (induced by a repeated change of direction task) on postural sway and its transient characteristics during single-leg standing, including whole-trial estimates and indexes of transient behavior in young healthy active adults. The study involved 28 physically active students (14 females). Single-leg postural sway was recorded for 30s before and after a fatiguing protocol, which consisted of a repeated change of direction tasks. We calculated the traditional whole-trial estimates of postural sway [center-of-pressure (CoP) velocity and amplitude in anterior-posterior (AP) and medial-lateral (ML) directions] and corresponding transient behavior indexes, based on three 10-s intervals. Statistically significant sex×fatigue interaction with medium effect sizes was found for whole-trial CoP velocity in AP (p=0.028; η2=0.17) and ML directions (p=0.019; η2=0.19). Post-hoc test showed that both variables substantially decreased in female participants (p=0.041–0.045; d=0.54–0.56), but remained similar in males (p=0.194–0.294). There were small to medium statistically significant main effects of fatigue on transient index for CoP amplitude in both directions (p=0.042–0.049; η2=0.02–0.14). Notably, CoP AP amplitude increased in the first 10-s interval for males (before fatigue: 5.6±1.3mm; after fatigue: 6.3±1.6mm), while the CoP AP amplitude in the third interval remained similar after fatigue (before fatigue: 5.5±1.4mm; after fatigue: 5.1±1.2mm). In conclusion, the responses to fatigue in terms of postural sway were time interval specific, and there were certain sex-differences in responses to fatigue, which could be related to better ability to adapt balance strategies in females. Moreover, our results demonstrate that the indexes of transient behavior could perhaps detect smaller fatigue-induced changes in postural sway that are seen in whole-trial estimates.
Highlights
Balance and postural control are fundamental abilities underpinning normal human movement function (Pollock et al, 2000; Ivanenko and Gurfinkel, 2018)
The relative differences between the intervals were expressed as percentages (100% representing no change; >100% indicating an increase in time; and
The purpose of this study was to explore the effects of wholebody fatigue, induced by repeated CoD task on postural sway in single-leg stance and its transient characteristics
Summary
Balance and postural control are fundamental abilities underpinning normal human movement function (Pollock et al, 2000; Ivanenko and Gurfinkel, 2018). Dynamic balance tests have been used to assess injury risk (De Noronha et al, 2006; Plisky et al, 2006); the utility of static balance tests (e.g., assessment of postural sway during quiet standing) for athletic populations has not been explored as much. The role of balance assessment should not be neglected in athletes, both from injury prevention and performance enhancement aspects. It has been postulated that neuromuscular fatigue, owing to its effects on movement biomechanics, plays an important role in injury risk in sport (Barber-Westin and Noyes, 2017; Benjaminse et al, 2019; Bourne et al, 2019). It could be of particular interest to understand how neuromuscular fatigue affects balance
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