Background: The age of boots is a significant factor that can impact the risk of injury during daily activities. Conversely, military personnel rely on their footwear to meet the physical demands of their daily professional tasks. Objectives: This study aimed to evaluate how wearing thermoplastic polyurethane (TPU) and rubber military boots for six months affects lower limb muscle activity during running. Methods: Thirty healthy male participants were provided with two new pairs of rubber and TPU military boots and instructed to wear them for six months. Electromyography signals were recorded during a pre-test and after six months while the participants ran at a speed of 3.2 m/s. Statistical analysis was conducted using a two-way ANOVA with repeated measures, with a significance level of 0.05. Results: The results did not show a significant overall effect of "boots" or "time" on muscle activities during running. However, there were significant boot-by-time interactions for muscle activities during different phases of the running cycle. These interactions were observed for the tibialis anterior (P = 0.037, η2p = 0.146), gastrocnemius medialis (P = 0.023, η2p = 0.172), and gluteus medius (P = 0.038, η2p = 0.144) activities during the loading phase, tibialis anterior activity at the mid-stance phase (P = 0.003, η2p = 0.278), and gastrocnemius medialis activity during the push-off phase (P = 0.046, η2p = 0.135). Conclusions: Wearing military boots appears to affect muscle activities, particularly the tibialis anterior, in healthy males. These findings underscore the importance of careful boot selection for running activities. Understanding the reasons behind differences in muscle activity between TPU and rubber military boots can inform further research and the development of specialized footwear tailored to specific operational needs.
