Author(s): PARADISIS, G., BELECHRIS, N. , Institution: NATIONAL & KAPODISTRIAN UNIVERSITY OF ATHENS, Country: GREECE, Abstract-ID: 562

INTRODUCTION:
Running with a weighted vest (WV) is commonly employed to augment external mechanical load and increase neuromuscular and metabolic demand; however, its effects on gait mechanics are not fully characterized and may differ from unloaded locomotion [1]. Symmetrical loading is assumed but there is limited evidence on the effect of WV on bilateral symmetry. The addition of external mass may compel the locomotor system to reorganize spatiotemporal step characteristics to accommodate the elevated load, yet it is presently unclear whether these adjustments occur uniformly across limbs. This study examined the acute effects of WV on spatiotemporal variables and their asymmetries (ASI).
METHODS:
Participants (N = 15; age = 21.4 ±2.9 years; body weight (BW) = 68.9 ± 7.6 kg; height = 1.77 ± 0.04 m; maximal oxygen uptake (VO2max) = 60.9 ± 5.8 ml·kg⁻¹·min⁻¹; maximal aerobic speed (MAS) = 4.96 ± 0.46 m·s⁻¹) completed 2 min running bouts on a treadmill (running at MAS) under three loading conditions, Unloaded, 5% BW and 10% BW with a WV. During each condition, spatiotemporal parameters, Contact (CT) and Flight time (FT) were recorded using a high-speed camera (300 fps) at the last 30 s of each condition. Step rate (SR) and length (SL) were calculated. The dominant leg of each participant was defined by the triple jump test [2]. ASI was determined using the formula: ASI = 2 * |Dominant - NonDominant| / (Dominant + NonDominant) * 100. Differences were assessed via two-way and one-way repeated measures ANOVAs. Post hoc analysis utilized Bonferroni adjustments, while Cohen’s d and percentage changes (Δ%) characterized the magnitude of effects.
RESULTS:
A significant main effect of Load was found for CT (p < 0.001, partial η2 = 0.475), which increased by 1.46% (d = 0.19) at 5% BW and 2.93% (d = 0.35) at 10% BW. Significant Dominance effects were observed for FT (10% BW; Δ% = 3%, p < 0.05, d = 0.21), SR (10% BW; Δ% = 1.23%, p < 0.05, d = 0.2), or SL (10% BW; Δ% = 1.23%, p < 0.05, d =.15), with no significant interactions. Analysis of ASI revealed that 10% BW significantly reduced ASI-CT (p < 0.05, partial η2 = 0.212). Post hoc analysis showed a non-significant decrease at 5% BW (Δ% = -13.24%, d = -0.15) but a large, significant reduction at 10% BW (Δ% = -64.15%, d = -0.85). Non-significant reductions in ASI were observed for SL and SR.
CONCLUSION:
While running with a WV acutely alters CT, it does not negatively impact the ASI of most spatiotemporal parameters. Conversely, 10% BW appears to enhance gait symmetry by reducing ASI-CT, suggesting an adaptive mechanism to maintain stability under increased load.

REFERENCES:
1. Silder, A., Besier, T., & Delp, S. L. (2015). Running with a load increases leg stiffness. Journal of biomechanics, 48(6), 1003-1008.
2. Risberg, M. A., Holm, I., & Ekeland, A. (1995). Reliability of functional knee tests in normal athletes. Scandinavian journal of medicine & science in sports, 5(1), 24-28.