Force and acceleration characteristics of military foot drill: implications for injury risk in recruits.

ABSTRACT

BACKGROUND: Foot drill involving marching and drill manoeuvres is conducted regularly during basic military recruit training. Characterising the biomechanical loading of foot drill will improve our understanding of the contributory factors to lower limb overuse injuries in recruits. AIM: Quantify and compare forces, loading rates and accelerations of British Army foot drill, within and between trained and untrained personnel. METHODS: 24 trained soldiers (12 men and 12 women; TRAINED) and 12 civilian men (UNTRAINED) performed marching and five drill manoeuvres on force platforms; motion capture recorded tibial position. Peak vertical impact force (PF), peak vertical loading rate (PLR), expressed as multiples of body weight (BW) and peak tibial impact acceleration (PTA) were recorded. RESULTS: Drill manoeuvre PF, PLR and PTA were similar, but higher in TRAINED men (PF, PLR p<0.01; PTA p<0.05). Peak values in TRAINED men were shown for the halt (mean (SD); PF 6.5 (1.5) BW; PLR 983 (333) BW/s PTA; PTA 207 (57) m/s2) and left turn (PF 6.6 (1.7) BW; PLR 928 (300) BW/s; 184 (62) m/s2). Marching PF, PLR, PTA were similar between groups and lower than all drill manoeuvres (PF 1.1-1.3 BW; PLR 42-70 BW/s; p<0.01; PTA 23-38 m/s2; p<0.05). CONCLUSIONS: Army foot drill generates higher forces, loading rates and accelerations than activities such as running and load carriage, while marching is comparable to moderate running (10.8 km/h). The large biomechanical loading of foot drill may contribute to the high rate of overuse injuries during initial military training, and strategies to regulate/reduce this loading should be explored.