Altered Dynamic Postural Stability and Joint Position Sense Following British Army Foot-Drill.

Katrina L Hinde,Chris Connaboy,Alex J Rawcliffe,Scott M Graham,Andrew Morrison,Kellen T Krajewski,Russell Martindale

doi:10.3389/fspor.2020.584275

Abstract

Impaired proprioceptive acuity negatively affects both joint position sense and postural control and is a risk factor for lower-extremity musculoskeletal injury in athletes and military personnel. British Army foot-drill is an occupational military activity involving cyclical high impact loading forces greater than those observed in athletes during high level plyometrics. Foot-drill may contribute to the high rates of lower-extremity overuse injuries observed in recruits during basic training. There is limited research investigating foot-drill specific injury risk factors in women, despite greater incidences of musculoskeletal injury reported in women (522 vs. 417 per 1,000 personnel, OR: 1.53) when compared to men during basic training. This study aimed to quantify changes in ankle joint proprioception and dynamic postural stability following a period of British Army foot-drill. Fourteen women of similar age to British Army female recruits underwent pre-post foot-drill measures of frontal plane ankle joint position sense (JPS) and dynamic postural stability using the dynamic postural stability index (DPSI). Passive ankle JPS was assessed from relative test angles of inversion 30% (IN30%) and eversion 30% (EV30%) and IN60% of participants range of motion using an isokinetic dynamometer. The DPSI and the individual stability indices (medio-lateral [MLSI], anterior-posterior [APSI], and vertical [VSI]) were calculated from lateral and forward jump-landing conditions using force plates. Foot-drill was conducted by a serving British Army drill instructor. Significantly greater absolute mean JPS error for IN30% and EV30% was observed post foot-drill (p ≤ 0.016, d ≥ 0.70). For both the lateral and forward jump-landing conditions, significantly greater stability index scores were observed for MLSI, APSI, and DPSI (p ≤ 0.017, d ≥ 0.52). Significantly greater JPS error and stability index scores are associated with the demands of British Army foot-drill. These results provide evidence that foot-drill negatively affects lower-extremity proprioceptive acuity in recruit age-matched women, which has implications for increased injury risk during subsequent military physical activity, occurring in a normal training cycle.

Highlights

The aim of initial military training or Phase one Basic Training (BT) is to transform civilians into trained soldiers
Significant increases in IN30% and EV30% were observed post foot-drill
Participants demonstrated a 29 and 32% increase in absolute joint position sense (JPS) error post foot-drill for IN30% and EV30%, respectively

Summary

Introduction

The aim of initial military training or Phase one Basic Training (BT) is to transform civilians into trained soldiers. British Army foot-drills are characterized by their own unique movement patterns; quick-march involves marching at two paces per second whilst impacting the ground with an exaggerated heel strike; stand-at-attention, stand-at-ease, halt and about-turn (left and right) all involve raising the active limb to 90-degree (◦) hip flexion and forcefully stamping down onto the ground with an extended-knee (i.e., straight-leg landing) It is these regimental movement patterns that have been implicated in the high impact loading forces and tibial accelerations of foot-drill irrespective of sex, experience (i.e., trained [soldiers] vs untrained [recruits]) (Carden et al, 2015) and footwear (drill shoe vs combat boot and gym training shoe) (Rawcliffe et al, 2020)

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