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.
1School of Life, Sport & Social Sciences, Edinburgh Napier University, UK
2Department of Health and Human Performance, University of Houston, USA
3Exercises Science Department, East Stroudsburg University, USA
4Institute of Sport, Physical Education and Health Sciences, University of Edinburgh, UK
5Neuromuscular Research Laboratory, University of Pittsburgh, USA
Corresponding Author: Alex J Rawcliffe, BSc, Edinburgh Napier University, City of Edinburgh, UNITED KINGDOM