The Effects of British Army Footwear on Ground Reaction Force and Temporal Parameters of British Army Foot-Drill
High rates of occupational training-related lower-limb musculoskeletal [MSK] overuse injuries are reported for British Army recruits during basic training. Foot-drill is a repetitive impact loading occupational activity and involves striking the ground violently with an extended-knee [straight-leg] landing. Foot-drill produces vertical ground reaction forces [vGRF] equal to and/or greater than those reported for high-level plyometric exercises/activities. Shock absorbing footwear aid in the attenuation of the magnitude of vGRF, resulting in a reduced risk of lower-limb MSK overuse injury when running. The potential shock absorbing characteristics of standard issue British Army footwear on the magnitude of vGRF and temporal parameters of foot-drill are scant. Therefore, this study sought to determine the magnitude of, and examine changes in vGRF and temporal parameters of foot-drill across three types of British Army footwear. Sampled at 1000hz, the mean of eight-trials from fifteen recreationally active males were collected from four foot-drills; stand-at-ease [SaE], stand-at-attention [SaA], quick-march [QM] and halt. Analysis of a normal walk was included to act as a comparison with quick-march. Significant main effects [P<0.05] were observed between footwear and foot-drill. The training shoe demonstrated significantly greater shock absorbing capabilities when compared with the combat boot and ammunition boot. Foot-drill produced peak vGRF and peak vertical rate of force development in excess of 5bw, and 350bw/sec, respectively. Time to peak vGRF ranged from 0.016- 0.036ms across foot-drills, indicating that passive vGRF may not be under neuromuscular control. The marginal reductions in the magnitude of vGRF and temporal parameters in foot-drill associated with the training shoe may act to reduce the accumulative impact loading forces experienced by recruits, subsequently minimising the severity and rates of lower-limb MSK overuse injuries and recruit medical discharges during basic training.