The Effect of Fatigue on Single-Leg Postural Sway and Its Transient Characteristics in Healthy Young Adults

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.

The Function of the Proprioceptive, Vestibular and Visual Systems Following Fatigue in Individuals With and Without Chronic Ankle Instability

“…The separate patterns of improvement/deterioration in the function of each of the three sensory systems has not been well-specified previously (Zemkova & Hamar, 2014). Reduced vestibular ability following fatigue protocols was expected (Coco et al, 2021; Derave et al, 2002; Kozinc et al, 2021) as the otolithic organs are known to be sensitive to head accelerations (Zemkova & Hamar, 2014), with horizontal movements induced by running known to show a decreased sensitivity. Thus, following fatigue, there is diminished vestibular information for regulating postural control (Coco et al, 2021; Derave et al, 2002; Kozinc et al, 2021).…”

Postural Control in Unipedal Quiet Stance in Young Female Gymnasts and the Effects of Training with Consideration of Transient Behavior of Postural Sway

“…Firstly, we calculated the traditional whole-trial estimates (i.e., averaged CoP characteristics, as defined above, over the whole 30 s of the trial). Then, we also calculated the quotients between the 1st and the 2nd (DIF_21) and the 1st and the 3rd (DIF_31) 10 s time intervals within the whole trial, which were expressed as percentages (100% representing no change, >100% indicating an increase in time, <100% indicating a decrease in time) [ 18 , 19 ]. For all the outcome variables, we used the mean value of the three repetitions.…”

“…It was reported that indices of the transient behavior of postural sway are largely independent of the whole-trial estimates and were sensitive to age-related impairments in postural control, as well as to sensory conditions (vision elimination) [ 17 ]. Moreover, the sensitivity to leg preference [ 18 ], fatigue [ 19 ], and history of ballet dance training has also been shown [ 20 ]. Indices of transient behavior are purported to provide additional information regarding an individual’s balance control that are masked (e.g., initial less stable period) by averaging the data across the whole trial [ 17 ].…”

“…We hypothesized that the gymnasts would exhibit better postural balance (lower CoP velocity and amplitude) and that they would stabilize more quickly than non-gymnasts (which will be reflected in different indices of transient behavior). According to recent evidence regarding the effects of fatigue and ballet dance training history [ 19 , 20 ], we hypothesized that the transient behavior indices, but not the whole-trial estimates of postural sway, would be affected by supplementary exercise training in gymnasts. We chose to study children and young adolescents, as postural control has been mostly investigated in youth and adult gymnasts so far.…”

Effects of Fatigue on Postural Sway and Electromyography Modulation in Young Expert Acrobatic Gymnasts and Healthy Non-trained Controls During Unipedal Stance

“…Post-fatigue postural assessments were similar to those described initially (pre-fatigue). However, as a transient effect of fatigue-inducing protocols on postural control has been reported ( Paillard, 2012 ; Kozinc et al, 2021 ), the fatigue protocol (submaximal contraction until exhaustion, as described above) was repeated before each trial to ensure the participants performed the postural task under the effects of muscle fatigue ( Paillard, 2012 ). For each of the 5 repetitions, the postural task was initiated immediately after the fatiguing contraction was finished, thereby ensuring the presence of the fatigue effect in all post-fatigue trials.…”