Military-Type Workload and Footwear Alter Lower Extremity Muscle Activity During Unilateral Static Balance: Implications for Tactical Athletic Footwear Design

Postural stability of polish special forces operators

The level of balance can play an essential role in a soldier's performance. For a Special Forces soldier, the footwear used or extra weight may be important factors affecting their balance level during combat operations or trainings. Therefore, the purpose of the study was to assess the level of static balance of Special Forces Operators and to determine the influence of select elements of a soldier's combat uniform and equipment on balance levels. The study group consisted of 37 Polish Special Forces Operators. To assess the level of static balance, the Romberg test was used in three variants (barefoot, with shoes, and with shoes, helmet, and vest). The measurements were made using the AMTI AccuGait portable force platform. The results of the analysis showed that the calculated average values of selected static balance parameters of soldiers differed depending on the variant of the Romberg test used, and in most cases, those differences were statistically significant ( α < 0.05 ). The lowest average values of parameters characterizing the level of static balance of Special Forces soldiers were calculated for barefoot measurements. The measurements with shoes and additional loads showed a statistically significant increase in almost all analysed parameters compared to barefoot measurements.

Increased Barefoot Stride Variability Might Be Predictor Rather than Risk Factor for Overuse Injury in the Military

Footwear usage could be a promising focus in reducing musculoskeletal injury risk in lower extremities commonly observed among the military. The goal of this research was to find potential gait-related risk factors for lower leg overuse injuries. Cases (n = 32) were active-duty infantry soldiers who had suffered an overuse injury in the previous six months of service before enrolling in the study. The control group (n = 32) included infantry soldiers of the same age and gender who did not have a history of lower leg overuse injury. In the gait laboratory, individuals were asked to walk on a 5-m walkway. Rearfoot eversion, ankle plantar/dorsiflexion and stride parameters were evaluated for barefoot and shod conditions. Barefoot walking was associated with higher stride time variability among cases. According to the conditional regression analysis, stride time variability greater than 1.95% (AUC = 0.77, 95% CI (0.648 to 0.883), p < 0.001) during barefoot gait could predict lower leg overuse injury. Increased barefoot gait variability should be considered as a possible predictive factor for lower leg overuse injury in the military, and gait with military boots masked stride-related differences between soldiers with and without lower leg overuse injury.

The Bionic High-Cushioning Midsole of Shoes Inspired by Functional Characteristics of Ostrich Foot

The sole is a key component of the interaction between foot and ground in daily activities, and its cushioning performance plays a crucial role in protecting the joints of lower limbs from impact injuries. Based on the excellent cushioning performance of the ostrich foot and inspired by the structure and material assembly features of the ostrich foot's metatarsophalangeal skeletal-tendon and the ostrich toe pad-fascia, a functional bionic cushioning unit for the midsole (including the forefoot and heel) area of athletic shoes was designed using engineering bionic technology. The bionic cushioning unit was then processed based on the bionic design model, and the shoe soles were tested with six impact energies ranging from 3.3 J to 11.6 J for a drop hammer impact and compared with the conventional control sole of the same size. The results indicated that the bionic forefoot area absorbed 9.83-34.95% more impact and 10.65-43.84% more energy than the conventional control forefoot area, while the bionic heel area absorbed 26.34-44.29% more impact and 28.1-51.29% more energy than the conventional control heel area when the controlled impact energy varied from 3.3 J to 11.6 J. The cushioning performance of the bionic cushioning sole was generally better than that of the conventional control sole, and the cushioning and energy-absorption performances of the heel bionic cushioning unit were better than those of the forefoot bionic cushioning unit. This study provides innovative reference and research ideas for the design and development of sports shoes with good cushioning performance.