Carrying Police Load Increases Gait Asymmetry in Ground Reaction Forces and Plantar Pressures Beneath Different Foot Regions in a Large Sample of Police Recruits

Background: Although carrying external load has negative effects on gait biomechanics, little evidence has been provided regarding its impact on body asymmetry. The main purpose of the present study was to examine, whether standardized equipment produced greater gait asymmetries in ground reaction force and plantar pressure. Methods: For the purpose of this study, we recruited 845 police recruits (609 men and 236 women; 72.1% men and 27.9% women) measured in two conditions: (i) 'no load' and (ii) 'a 3.5 kg load'. Absolute values in ground reaction forces and plantar pressures beneath the different foot regions were assessed with pedobarographic platform (Zebris FDM). Asymmetry was calculated as (xright - xleft)/0.5 x (xright + xleft) x 100%, where 'x' represented a given parameter being calculated and a value closer to 0 denoted greater symmetry. Results: Significant differences in ground reaction forces and plantar pressures between the left and right foot were observed, when adding 'a 3.5 kg load'. Compared to the 'no load' condition, carrying 'a 3.5 kg load' significantly increased gait asymmetries for maximal ground reaction forces beneath the forefoot (ES = 0.29), midfoot (ES = 0.20) and hindfoot (ES = 0.19) regions of the foot. For maximal plantar pressures, only the asymmetry beneath the midfoot region of the foot significantly increased (ES = 0.19). Conclusions: Findings of this study indicate that 'a 3.5 kg load' significantly increases ground reaction force and plantar pressure gait asymmetries beneath the forefoot and midfoot regions, compared to 'no load' condition. Due to higher loads, increases in kinetic gait asymmetries may have negative effects on future pain and discomfort in the foot area, possibly causing stress fractures and deviated gait biomechanics in police recruits.