Catriona A Burdon

Employment Standards for Australian Urban Firefighters: Part 4: Physical Aptitude Tests and Standards.

Objective: Firefighter physical aptitude tests were administered to unskilled subjects and operational firefighters to evaluate the impact that testing bias associated with gender, age, activity-specific skills, or task familiarity may have upon establishing performance thresholds. Methods: These tests were administered in sequence, simulating hazmat incidents, ventilation fan carriage (stairs), motor-vehicle rescues, bushfire incidents, fire attacks, and a firefighter rescue. Participants included two unskilled samples (Nu200a=u200a14 and 22) and 143 firefighters. Results: Firefighter performance was not significantly different from the unskilled subjects. Participants from both genders passed the test, with scores unrelated to performance skill or age; however, familiarization significantly improved performance when the test was repeated. Conclusion: These outcomes confirmed this test to be gender-, age-, and skill-neutral. Familiarization effects could be removed through performing a single, pre-selection trial of the test battery.

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.

Indirect hand and forearm vasomotion: regional variations in cutaneous thermosensitivity during normothermia and mild hyperthermia

In this experiment, hand and forearm vasomotor activity was investigated during localised, but stable heating and cooling of the face, hand and thigh, under open-loop (clamped) conditions. It was hypothesised that facial stimulation would provoke the most potent vascular changes. Nine individuals participated in two normothermic trials (mean body temperature clamp: 36.6°C; water-perfused suit and climate chamber) and two mildly hyperthermic trials (37.9°C). Localised heating (+5°C) and cooling (-5°C) stimuli were applied to equal surface areas of the face, hand and thigh (perfusion patches: 15min), while contralateral forearm or hand blood flows (venous-occlusion plethysmography) were measured (separate trials). Thermal sensation and discomfort votes were recorded before and during each thermal stimulation. When hyperthermic, local heating induced more sensitive vascular responses, with the combined thermosensitivity of both limb segments averaging 0.011mL·100mL-1·min-1·mmHg-1·°C-1, and 0.005mL·100mL-1·min-1·mmHg-1·°C-1 during localised cooling (P<0.05). Inter-site comparisons among the stimulated sites yielded minimal evidence of variations in local thermal sensation, and no differences were observed for vascular conductance (P>0.05). Therefore, regional differences in vasomotor and sensory sensitivity appeared not to exist. When combined with previous observations of sudomotor sensitivity, it seems that, during mild heating and cooling, regional representations within the somatosensory cortex may not translate into meaningful differences in thermal sensation or the central integration of thermoafferent signals. It was concluded that inter-site variations in the cutaneous thermosensitivity of these thermolytic effectors have minimal physiological significance over the ranges investigated thus far.

Cutaneous thermosensitivity differences among the face, hand or thigh appear not to exist for skin blood flow during normothermic states

Variations in the volume of the sensory cortex (homunculus) assigned to different skin regions may lead one to postulate that thermal stimulation of some body segments (e.g. face, hand) may evoke more powerful autonomic responses. That is, there may exist a mosaic of cutaneous thermosensitivity. To study thermosensitivity, thermal feedback from sites other than the treated site needs to be minimised. This is achieved via whole-body clamping of deep-body and skin temperatures. Previously, greater sensitivity of the face was observed for sudomotor control in mildly hyperthermic individuals [1], so the aim of this investigation was to explore possible sensitivity variations in the control of skin blood flow during isolated stimulation of three sites, but after a normothermic clamp had been established.

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.

Does the skin of mildly hyperthermic individuals display local variations in thermosensitivity for the control of skin blood flow

In an accompanying communication, it was revealed that local variations in cutaneous thermosensitivity, with respect to the control of skin blood flow, were not evident in normothermic individuals. Previously, greater thermosensitivity of the face relative to other sites, including the hand and thigh, was observed for sudomotor control in mildly hyperthermic individuals. Therefore, the possibility was tested that such variations may also exist for vasomotor control when subjects were first rendered mildly hyperthermic.

Is the dermatomal recruitment of sweating a physiological reality or a misinterpretation

A caudal-to-rostral (sympathetic dermatomal) recruitment pattern for human eccrine sweating was first described by Randall and Hertzman [1], and is widely accepted. Nevertheless, neither sudomotor activation nor sweat gland recruitment patterns were actually measured during that, or their subsequent supporting research. Instead, recruitment was derived using curves fitted to data obtained over several months, with data for separate skin regions not necessarily obtained from the same individuals. Since such data are ill-suited for drawing interpretations relative to sympathetic activation, and since Kuno [2] reported a simultaneous glandular activation across all skin regions, this hypothesis was revisited.

Does acute radio-frequency electromagnetic field exposure affect visual event-related potentials in healthy adults?

OBJECTIVEnTo use improved methods to address the question of whether acute exposure to radio-frequency (RF) electromagnetic fields (RF-EMF) affects early (80-200u202fms) sensory and later (180-600u202fms) cognitive processes as indexed by event-related potentials (ERPs).nnnMETHODSnThirty-six healthy subjects completed a visual discrimination task during concurrent exposure to a Global System for Mobile Communications (GSM)-like, 920u202fMHz signal with peak-spatial specific absorption rate for 10u202fg of tissue of 0u202fW/kg of body mass (Sham), 1u202fW/kg (Low RF) and 2u202fW/kg (High RF). A fully randomised, counterbalanced, double-blind design was used.nnnRESULTSnP1 amplitude was reduced (pu202f=u202f.02) and anterior N1 latency was increased (pu202f=u202f.04) during Exposure compared to Sham. There were no effects on any other ERP latencies or amplitudes.nnnCONCLUSIONSnRF-EMF exposure may affect early perceptual (P1) and preparatory motor (anterior N1) processes. However, only two ERP indices, out of 56 comparisons, were observed to differ between RF-EMF exposure and Sham, suggesting that these observations may be due to chance.nnnSIGNIFICANCEnThese observations are consistent with previous findings that RF-EMF exposure has no reliable impact on cognition (e.g., accuracy and response speed).

Postural influences on sweating: exploring the effects of gravity and pressure

The distribution of thermal sweating is neither uniform nor does it commence simultaneously at all sites. One reason for this variability may be associated with gravitational influences. That is, localised and posture-dependent compression of tissues containing pressure-sensitive receptors is believed to inhibit sweating from the compressed and ipsilateral sites, whilst enhancing secretion from contralateral surfaces [1]. To evaluate the possibility that local sweat rates might be influenced by gravity, it is necessary to test subjects with and without gravitational loading. This can be achieved by using water immersion to simulate zero gravity, and this experimental model was used for this pilot investigation.