Characteristics of Standing Postural Control in Women under Additional Load

Relationship between backpack load location, sex, anthropometric and body composition factors with postural sway in healthy young adults

Objective

Evaluate the effect of backpack load location on postural sway and correlate sway path length (PL) to anthropometrics and body composition.

Methods

Fifteen participants aged 18-25 stood on a force plate with backpack load located high (LH), low (LL) or without backpack (NL). Body composition and anthropometric variables were correlated to PL.

Results

Load increased PL, 95% confidence ellipse, and mean velocity while it reduced mediolateral SampEn (p<0.05). Females had increased mean velocity and PL of sway (p<0.05). Larger phase angles correlated with reduced PL under NL. Taller individuals correlated with reduced PL under LL. Greater mass correlated with reduced PL under LH.

Conclusions

Load carriage regardless of load location increased postural sway metrics except mediolateral SampEn. Females had greater PL and mean velocity compared to males. Select anthropometric and body composition variables correlated with postural sway under different load conditions.

Effects of load carriage on measures of postural sway in healthy, young adults: A systematic review and meta-analysis

Load carriage (LC) is a contributing factor to musculoskeletal injury in many occupations. Given that falls are a common mechanism of injury for those frequently engaging in LC, understanding the effects of LC on postural stability (PS) is necessary. A systematic review and meta-analysis was conducted to examine effects of LC on PS. Sixteen and 9 studies were included in the qualitative and quantitative synthesis, respectively. In most studies, it was found that LC leads to a decrease in PS with significant effects on center of pressure (COP) sway area (standardized mean difference = 0.45; p < 0.005) and COP anterior-posterior excursion (standardized mean difference = 0.52; p < 0.05). Furthermore, load magnitude and load placement are factors which can significantly affect COP measures of PS. It is recommended to minimize load magnitude and equally distribute load when possible to minimize LC effects on PS. Future research should examine additional factors contributing to differences in individual PS responses to LC such as changes in muscle activation and prior LC experience.

Effect of Different Landing Heights and Loads on Ankle Inversion Proprioception during Landing in Individuals with and without Chronic Ankle Instability

Proprioception is essential for neuromuscular control in relation to sport injury and performance. The effect of landing heights and loads on ankle inversion proprioceptive performance in individuals with or without chronic ankle instability (CAI) may be important but are still unclear. Forty-three participants (21 CAI and 22 non-CAI) volunteered for this study. The Ankle Inversion Discrimination Apparatus for Landing (AIDAL), with one foot landing on a horizontal surface and the test foot landing on an angled surface (10°, 12°, 14°, 16°), was utilized to assess ankle proprioception during landing. All participants performed the task from a landing height of 10 cm and 20 cm with 100% and 110% body weight loading. The four testing conditions were randomized. A repeated measures ANOVA was used for data analysis. The result showed that individuals with CAI performed significantly worse across the four testing conditions (p = 0.018). In addition, an increased landing height (p = 0.010), not loading (p > 0.05), significantly impaired ankle inversion discrimination sensitivity. In conclusion, compared to non-CAI, individuals with CAI showed significantly worse ankle inversion proprioceptive performance during landing. An increased landing height, not loading, resulted in decreased ankle proprioceptive sensitivity. These findings suggest that landing from a higher platform may increase the uncertainty of judging ankle positions in space, which may increase the risk of ankle injury.

Nonlinear Analyses Distinguish Load Carriage Dynamics in Walking and Standing: A Systematic Review

Load carriage experiments are typically performed from a linear perspective that assumes that movement variability is equivalent to error or noise in the neuromuscular system. A complimentary, nonlinear perspective that treats variability as the object of study has generated important results in movement science outside load carriage settings. To date, no systematic review has yet been conducted to understand how load carriage dynamics change from a nonlinear perspective. The goal of this systematic review is to fill that need. Relevant literature was extracted and reviewed for general trends involving nonlinear perspectives on load carriage. Nonlinear analyses that were used in the reviewed studies included sample, multiscale, and approximate entropy; the Lyapunov exponent; fractal analysis; and relative phase. In general, nonlinear tools successfully distinguish between unloaded and loaded conditions in standing and walking, although not in a consistent manner. The Lyapunov exponent and entropy were the most used nonlinear methods. Two noteworthy findings are that entropy in quiet standing studies tends to decrease, whereas the Lyapunov exponent in walking studies tends to increase, both due to added load. Thus, nonlinear analyses reveal altered load carriage dynamics, demonstrating promise in applying a nonlinear perspective to load carriage while also underscoring the need for more research.