The impact of the mechanical whole-body vibration experienced during military land transit on the physical attributes underpinning dismounted combatant physical performance: A randomised controlled trial.

OBJECTIVES: The aim of this randomised controlled trial was to explore the impact of the mechanical WBV experienced during simulated military land transit on the physical attributes that underpin tasks performed by dismounted combatants. DESIGN: This study used a parallel group randomised control trial design. METHODS: Sixty participants were randomly assigned to one of four, 2-h laboratory-based simulations (restricted posture, sealed road, cross country or a control condition). A smaller sample of 16 Australian Defence Force infantry personnel served as a validation group and were exposed to the same conditions. Neither the restricted posture nor the control conditions were exposed to any WBV, but the former were secured in place using the built-in seat harness. Prior to, and following the assigned condition, participants performed a series of battlefield relevant physical performance tests including; drop jump, 20-m sprint, reactive agility, arm-hand steadiness, isometric mid-thigh pull, and sit-and-reach. RESULTS: Medium decreases in the drop jump were observed for both the sealed road (effect size [ES]=0.53) and cross-country (ES=0.97) simulation conditions indicating a decrease in performance of the jump phase. A large decrease in 20-m sprint performance was observed in both the sealed road (ES=1.37) and cross-country (ES=0.88) exposure conditions. Additionally, a large decrease in 20-m sprint performance was observed for the restricted posture (ES=1.02) exposure condition. CONCLUSIONS: These findings indicate that exposure to WBV experienced during motorised land transit has a negative influence on aspects of lower body explosive strength.

Time changes in the body dimensions of male Australian Army personnel between 1977 and 2012.

The aim of this study was to quantify time changes in the body dimensions of male Australian Army personnel. Following a systematic review, two studies were identified and matched for occupation and age (n = 669) with time changes in 12 absolute and 11 proportional body dimensions assessed between 1977 and 2010-12. Changes in means were expressed as absolute, percent and standardised changes, with changes in variability assessed visually and as the ratio of coefficients of variation (CVs). Time changes in absolute dimensions were typically positive (increases) and moderate in magnitude (median standardised change ± 95%CI: 0.53 ± 0.23), and while changes in proportional dimensions were typically negligible (median standardised change ± 95%CI: 0.16 ± 0.33), substantial changes (standardised changes ≥0.2 or ≤-0.2) were observed in several dimensions. Variability in body dimensions has also typically increased (median ratio of CVs ± 95%CI: 1.10 ± 0.07) and become more right-skewed. These findings have important implications for the design and acquisition of new military vehicles, body equipment and clothing.

Whole-body vibration and occupational physical performance: a review.

INTRODUCTION: In the occupational environment, there are a considerable number of stressors that can affect physical performance in job tasks. Whole-body vibration (WBV), which arises from vehicle transit, is one such stressor that has been demonstrated to alter human function in several ways. This study identifies the known physical changes to human function which result from WBV, to comment on changes which may translate to performance in physically demanding occupational tasks. METHODS: A systematic review is performed on the literature relating to changes in the neuromuscular, physiological and biomechanical properties of the human body, when exposed to WBV. Selection criteria are constructed to synthesise articles which strictly relate to in-vehicle WBV and physical responses. RESULTS: In total, 29 articles were identified which satisfied the criteria for inclusion. A range of physical responses produced from WBV are presented; however, little consistency exists in study design and the responses reported. DISCUSSION: Given the inconsistency in the reported responses, the precise changes to human function remain unknown. However, there is sufficient evidence to warrant the design of studies which investigate occupationally relevant physical performance changes following WBV.