Alison L. Fogarty

Influence of postexercise cooling techniques on heart rate variability in men.

The reduction of core body temperature (TC) is vitally important in the treatment of hyperthermia; however, little is known regarding the impact of cooling treatments on the autonomic control of heart rate (HR). The aim of the present study was to examine the influence of three field‐based hyperthermia treatments on the neural control of HR via heart rate variability (HRV). Following exercise‐induced hyperthermia (TC∼40.0°C) in a warm environment (34.2 ± 0.5°C), nine healthy, active men were treated during recovery, in a randomized order, with intravenous cold saline infusion (IV) or ice packs (ICE) or fan cooling with intermittent water spray (FAN) for 40 min. During each treatment, HR dynamics via power spectral (VLF, LF, HF), Poincare plot (SD1, SD2), approximate entropy (ApEn) and short‐ (α1) and long‐term (α2) fractal scaling analyses were determined every 10 min. At recovery onset, HR and TC were similar between treatments and were significantly reduced over the 40 min recovery period. During recovery, HR and α2 were significantly reduced from initial levels but were significantly greater for IV compared with ICE and FAN. In contrast, VLF, LF, HF, SD1, SD2 and ApEn increased during recovery, with all being significantly lower for IV compared with ICE and/or FAN. The present results demonstrated that IV, compared with ICE and FAN, resulted in significantly greater HR, reduced spectral and geometrical HRV, lower HR complexity and reduced long‐term HR control, indicative of reduced vagal and/or increased sympathetic modulation. Specific treatments for exercise‐induced hyperthermia may result in an altered sympathovagal balance that requires further examination.

Balancing ballistic protection against physiological strain: evidence from laboratory and field trials

This project was based on the premise that decisions concerning the ballistic protection provided to defence personnel should derive from an evaluation of the balance between protection level and its impact on physiological function, mobility, and operational capability. Civilians and soldiers participated in laboratory- and field-based studies in which ensembles providing five levels of ballistic protection were evaluated, each with progressive increases in protection, mass (3.4-11.0 kg), and surface-area coverage (0.25-0.52 m(2)). Physiological trials were conducted on volunteers (N = 8) in a laboratory, under hot-dry conditions simulating an urban patrol: walking at 4 km·h(-1) (90 min) and 6 km·h(-1) (30 min or to fatigue). Field-based trials were used to evaluate tactical battlefield movements (mobility) of soldiers (N = 31) under tropical conditions, and across functional tests of power, speed, agility, endurance, and balance. Finally, trials were conducted at a jungle training centre, with soldiers (N = 32) patrolling under tropical conditions (averaging 5 h). In the laboratory, work tolerance was reduced as protection increased, with deep-body temperature climbing relentlessly. However, the protective ensembles could be grouped into two equally stressful categories, each providing a different level of ballistic protection. This outcome was supported during the mobility trials, with the greatest performance decrement evident during fire and movement simulations, as the ensemble mass was increased (-2.12%·kg(-1)). The jungle patrol trials similarly supported this outcome. Therefore, although ballistic protection does increase physiological strain, this research has provided a basis on which to determine how that strain can be balanced against the mission-specific level of required personal protection.

Soldiers' perceived versus actual heat strain in a jungle environment

Soldiers are regularly required to work in hot environments whilst wearing protective body armour (BA). However, BA is impermeable and decreases the torso surface area available for evaporative heat losses [1]. Consequently, an elevation in body core temperature was observed with early versions of BA [2,3]. In recent years, the size (and surface area coverage) of BA has decreased and laboratory simulations have shown that this newer BA does not increase the physiological load to the same extent as previous systems [4]. Anecdotally, however, Australian soldiers continue to report feeling an increased thermal burden when wearing BA. Therefore, we investigated the disconnect between experience and laboratory trials of the thermal impact of wearing BA in a warm jungle environment.

The effects of flame resistant protective clothing on heat exchange and thermal strain

Soldiers may be required to wear flame resistant protective clothing to mitigate the risk of burns in the event of a fire or exposure to flames. Flame resistance is provided by either including fibres of inherent flame resistance into the garments or by applying a flame retardant treatment to fibres that are usually flammable, which may affect the thermal properties of the clothing. The aim of this study was to evaluate the heat exchange properties of flame resistant protective clothing and predict the effects on thermal strain during prolonged work.

Do weak postural muscles contribute to pain when wearing body armour

Military personnel regularly wear body armour. There is a growing body of evidence that suggests pain or discomfort experienced whilst wearing body armour may, in part, be due to weaknesses in key stabilising and postural muscles of the upper body. This study seeks to investigate the association between pain symptoms and muscle weakness of the upper body.