Bahman Adlou, Jerad J. Kosek, Meghan E. Hancock, Jordan E. Tompkins, Hannah H. Houde, John L. Grace, Christopher M. Wilburn, Wendi H. Weimar. Auburn University, Auburn, AL.

Background: Energy return plate (ERP) technology has been implemented in a variety of footwear to improve human locomotion, with a recent research interest in utilizing ERPs in tactical boots to improve gait and reduce injuries. However, inter-limb asymmetries when using these modified boots are overlooked; thus, this study aimed to evaluate the inter-limb walking gait of participants wearing modified tactical boots with different ERPs. Methods: Eleven healthy males college students were recruited to complete six successful walking trials (three over AMTI force platforms; three over an instrumented gait mat: Protokinetics LLC, Havertown, PA, USA) under four conditions: barefoot (BF); stock army boot (SB); modified army boot with 0.19mm ERP (ERP19); modified army boot with 0.30mm ERP (ERP30). Participants were provided a 5-minute acclimatization period between each condition. Repeated measures ANOVA with significance p < 0.05 was executed using SPSS (Version 27, IBM. Armonk, NY) to determine the differences in walking peak vertical force, stride velocity (SV), and stride length (SL) where each side’s SL had that respective foot contact twice. Results: Results showed no significant differences in peak vertical force between boot conditions. There were significant differences in both legs’ (system) SV between boot conditions (SB and ERP19: F(1,10)= 8.795, p = 0.014; SB and ERP30: (F(1,10)= 5.672, p = 0.039; ERP19 and ERP30: F(1,10)= 12.919, p = 0.005), but not when comparing each leg’s SV across boot conditions. There were no significant differences between system’s SL of SB and either ERP19 or ERP30 conditions. When comparing left and right leg’s SLs for each condition, there were significant differences in the SB (F(1,10)= 5.22, p = 0.045) and ERP19 (F(1,10)= 6.021, p = 0.034), but not in BF and ERP30. Inter-legs’ SL asymmetry difference reduced with ERP30 (0.201±1.246 cm), while it increased with SB (0.453±0.657 cm) and ERP19 (0.667±0.901 cm) compared to BF (0.446±0.810 cm). Conclusion: Inter-leg’s SV remained the same while SLs were different, suggesting time in a walking stride must also be different. ERP30 properties appear to reduce inter-leg’s SL asymmetries while walking, which can be useful for evaluating patterns of injuries related to lower-limb gait. Further research is warranted to specify the reason for these asymmetries and if there is a positive or negative impact on the motion.

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