Zora Szabo1, Maddie Seidner1, Maddie Fulk1, William D. Hale1, & Roger O. Kollock1

1The University of Tulsa, Tulsa, Oklahoma

Heavy load carriage has the potential to negatively impact dynamic stability in basic training recruits (BTR). The inability to quickly recover balance may increase susceptibility to injury.

PURPOSE: The purpose of the study was to explore the combined influence of load and sex on dynamic postural stability. METHODS: 33 recreationally active participants were recruited, 16 males and 17 females. Participants completed 3 trials of single-leg landing (SLL) tasks under two conditions: unloaded and loaded (≈22 kg). Participants wore shorts, a t-shirt, and combat boots for the unloaded condition and a combat helmet, improved outer tactical vest, rucksack, and combat boots for the loaded condition. The SLL task required participants to drop onto a force plate from the top of a 30 cm box placed 10% of their height from a force plate. Upon landing on the dominant limb, participants maintained a quiet stance for 10 seconds. The force plate data was sampled at 1500 Hz. The first 3 seconds of the ground reaction forces following initial ground contact were used to calculate the average DPSI values for each condition. Initial ground contact was defined as the instant the vertical ground reaction force exceeded 5% of body weight. A higher DPSI value represents worse dynamic postural stability. A 2-way Mixed ANOVA was used to determine the effects of load condition and sex (male and female) on DPSI. RESULTS: There was no statistically significant interaction between load condition and sex, F(1, 31) = 4.09, p = .052, partial η2 = .117. The main effect of load condition showed a statistically significant difference in mean DPSI (unloaded, .380 vs. loaded .533) at the different conditions, F(1, 31) = 122.54, p < .1 partial η2 = .798. The main effect of the group showed that there was a statistically significant difference in SS between groups F(1, 32) = 17.13, p < .001, partial η2 = .349, with males having significantly higher DPSI values for both the unloaded (.450 vs. .313) and loaded (.575 vs. .494) conditions. CONCLUSION: Findings suggest females have better dynamic postural stability than males for both load conditions of the SLL task. The donning ≈ 22 kg of military loads resulted in statistically significant greater DPSI values in both males and females during the SLL task.

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