Purpose The purpose of this study was to investigate the effect of midsole hardness on gait mechanisms by wearing a backpack. Methods Ten healthy adult males(age:23.20±1.33yrs, heights: 1.72±0.03cm, weights: 67.60±5.95kg) participated in this study. Subjects walked at a speed of 1.5m/s in an 8m section wearing randomly selected midsole hardness (Soft, Medium, Hard) shoes and backpack (30% of body weight). For measurement of body movement, 10 infrared cameras (Vicon motion capture system, UK) and force plate (AMTI, ORG-6, US) were used. Results First, in the shock phenomenon change, the ground contact time was longer when wearing a backpack. Second, in the shock absorption strategy, the pack plantarflexion velocity at the ankle joint was faster in Hard than Soft, and the pack dorsiflexion moment decreased when wearing a backpack (p<.05). Also, the pack extension moment of the knee increased significantly when wearing a backpack. Fourth, in the mechanical negative work, the ankle joint performed less work than the medium soft, and the knee joint increased as the backpack was worn (p<.05). Conclusion As a result of this study, the difference in the hardness of the midsole used in this study does not seem to affect the biomechanical movement of gait even when wearing a backpack. In future studies, it is necessary to investigate the effect of the midsole through the presence or absence of shoes or inducing muscle fatigue.
PURPOSE This study examined the biomechanical differences in running shoes with two midsole materials, ethylene-vinyl acetate (EVA) and polyether block amide (PEBA), and carbon fiber plate insertion. METHODS Ten recreational runners participated in the study and performed running trials on a 12m runway at a controlled speed of 3.89 m/s ± 5%. Biomechanical data were obtained for time-continuous variables of the metatarsophalangeal (MTP) joint (angle, moment, and power), as well as for discrete variables (push-off time, peak vertical impact force, peak anterior propulsion force, and timing of joint power transition). Data were analyzed using statistical parametric mapping for continuous data and the Wilcoxon signed-rank test for discrete variables (α = .05). RESULTS Compared with no-plate conditions, the EVA sole with plate significantly reduced push-off time, MTP joint range of motion, positive joint power, and peak anterior propulsion force, with an earlier timing of joint power transition (p < .05). In contrast, the PEBA sole with plate decreased MTP joint range of motion but increased plantar flexion moment, negative joint power, and push-off time (p < .05). Furthermore, under plate-inserted conditions, PEBA significantly increased plantar flexion moment, negative joint power, and push-off time, as well as exhibited a delayed timing of joint power transition compared with EVA (p < .05). CONCLUSIONS The interaction between midsole material and plate insertion causes complex variations in MTP joint energy management. Specifically, EVA shoes with a plate may facilitate rapid roll-off and promote swift turnover, thereby enhancing acceleration. In contrast, PEBA shoes with a plate may promote prolonged energy absorption, which could potentially reduce joint fatigue during long-distance running.
