| Abstract | Musculoskeletal injuries are a major concern for the military resulting in substantial burdens for both recruits and the service. Recruits report high incidence of musculoskeletal injuries with the majority occurring to the lower limbs. Consequences of recruit injuries can be considerable for the individual including reduced participation, injury chronicity, training time loss and career pathway change due to backsquad or discharge. For the military, recruit injuries can result in increased health care expenditure, additional costs related to training, and recruitment and retention to replace injured recruits. Potentially, deployment capability may be impacted as fewer recruits progress from basic training to trade training or operational units, whereby they gain essential skills to become deployable.
Injury incidence data were limited for New Zealand Army recruits with a current understanding of the recruit injury problem unknown. It was unknown whether recruits present for basic training with pre-existing injuries or risk factors that could predispose them to injury, and if a prevention program using neuromuscular training could lower recruit injury incidence.
The aim of the current program of research was to establish the extent of the New Zealand Army recruit injury problem, the profile and aetiology of recruit injuries and the effect of six weeks neuromuscular training compared to usual training on incidence of lower limb injury of New Zealand Army recruits undertaking basic training. Additionally, this program of research investigated if baseline personal, lifestyle and physical performance characteristics could predict actual injury sustained during training.
This program of research comprised four studies based on the sequence of injury prevention model. The first study explored the extent of the New Zealand Army recruit injury problem through surveillance of four years of physiotherapy provisions for injuries sustained during basic training. Commencing basic training were 1896 recruits (1697 males, 199 females), who required 1683 physiotherapy provisions for injury sustained during training, across four years. Lower limb injuries accounted for more than 75% (n = 1285) of the total demand for physiotherapy service and injuries sustained at the knee and below accounted for 67% of all injury presentations.
Studies 2, 3 and 4 investigated injury risk and injury outcomes in 248 New Zealand Army recruits (228 male, 20 female). Study 2 investigated personal profiles, lifestyle and physical performance characteristics of recruits presenting to basic training to identify if pre-existing conditions or risk factors for injury existed at the commencement of training. Recruits were predominantly male (91.9%) with an average age of 20.3 ± 2.8 years. Approximately 30% of recruits reported injury in the year prior to training commencing, with 44.8% of those injuries in the lower limbs. Approximately one fifth of recruits were self-reported current smokers. Recruits who passed the 2.4 km timed run for distance were 53.8% of males and 28.6% of females. Weight-bearing dorsiflexion lunge test performance was within a normal range (left = 10.2 ± 3.2 cm); although, 30.9% of recruits had limb asymmetry (>1.5 cm). Outcomes of the Y Balance TestTM for dynamic lower limb stability, found 70% of female recruits had high posterolateral reach asymmetry (8.1 ± 6.0 cm), while normalised composite reach scores were low (right) for male (92.2 ± 8.1%) and female recruits (89.0 ± 7.5%).
Findings from Studies 1 and 2 informed the development of a neuromuscular injury prevention intervention program for army recruit injuries occurring at the knee and below. Study 3, a cluster randomised controlled trial design, was used to investigate if a six-week neuromuscular training program led to fewer lower limb injuries in basic training army recruits, across two intakes compared to usual training. Neuromuscular exercises did not change recruit injury incidence but did lower health care encounters for overall lower limb per recruit (control 4.83 ±7.58, intervention 3.45 ± 5.79, p = 0.041), and overall number of knee injuries (control 262, intervention 120) (p < 0.010) during basic training. Additionally, more intervention recruits completed training on time (p = 0.026).
Study 4 considered whether personal, lifestyle, and physical performance characteristics can predict actual injuries sustained by recruits during training. From 248 participants commencing basic training, 46 (18.5%) recruits had missing data, which resulted in 202 (81.5%) remaining for the regression analysis. Backwards stepwise logistic regression had two variables associated with injury risk in the final model: passing the 2.4 km timed run and right Y Balance TestTM posterolateral reach. This model accurately predicted 60.9% of recruits with 36 correctly assigned as not injured and 87 correctly assigned as injured. Findings support the use of physical performance injury screening to identify recruits at risk of injury at entry to training so that mitigation measures could be taken to reduce this risk.
This program of research identified several clinical implications and recommendations for future directions. Firstly, knee injuries are common in army recruits and need to be targeted by prevention programs. Secondly, recruits enter training with injury risk factors and therefore screening is important to identify individuals at higher risk so that measures could be taken to lower this risk. Thirdly, neuromuscular training reduces health care burdens associated with common lower limb injuries. Future recommendations include investigation of recruit injury risk factors and neuromuscular training over longer study durations and with larger samples. Investigation of the effectiveness of neuromuscular training delivered prior to basic training or as part of a recruit preconditioning program to lower injury and associated burdens requires consideration. Finally, injury consensus statements are required to improve consistency and accuracy reporting military recruit injury and to improve comparability of findings across military recruit research. |
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