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Background: There have been concerns of an aging Australian volunteer firefighter workforce. Aims: To (1) determine the age distribution of Australian volunteer firefighters; (2) estimate the proportion of volunteer firefighters who met the Australian physical activity guidelines; (3) investigate the relationship between age and physical activity and exercise in volunteer firefighters. Methods: An online survey was electronically distributed to Rural Fire Service volunteers in Queensland, Australia. The survey included demographic and physical activity questions. National guidelines were used to determine whether respondents met the Australian physical activity recommendations. The relationships between age and weekly physical activity and weekly exercise minutes were modelled using Bayesian methods. Key results: The median age of responders (n = 480) was 54 years. Compared with Australian population data, volunteer firefighters were four times more likely to meet the physical activity guidelines and the exercise-only guidelines, but 1.4 times more likely to not meet the strength-based activity guidelines. Number of weekly physical activity minutes declined with age, by 61 min each decade. Conclusions: Volunteers were more likely to meet the national physical activity and exercise-only guidelines, but less likely to meet the strength-based activity guidelines. Implications: Volunteer firefighters could benefit from outreach programs that promote participation in strength-based training. This cross-sectional study investigated the age and physical activity status of Australian volunteer firefighters. The mean age was 51.4 years. We found that volunteer firefighters were more likely to meet the national physical activity and exercise-only guidelines, but less likely to meet the strength-based training guidelines compared with the general Australian population. [ABSTRACT FROM AUTHOR]

Whether glucose concentration increases during heat exposure because of reduced peripheral tissue uptake or enhanced appearance is currently unknown. This study aimed to report glucose concentrations in both capillary and venous blood in response to a glucose challenge during passive heating (PH) to assess whether heat exposure affects glucose uptake in healthy males. Twelve healthy male participants completed two experimental sessions, where they were asked to undertake an oral glucose tolerance test (OGTT) whilst immersed in thermoneutral (CON, 35.9 (0.6) °C) and hot water (HWI, 40.3 (0.5) °C) for 120 min. Venous and capillary blood [glucose], rectal temperature, and heart rate were recorded. [Glucose] area under the curve for HWI venous (907 (104) AU) differed from CON venous (719 (88) AU, all P < 0.001). No other differences were noted (P > 0.05). Compared with CON, HWI resulted in greater rectal temperature (37.1 (0.3) °C versus 38.6 (0.4) °C, respectively) and heart rate (69 (12) bpm versus 108 (11) bpm, respectively) on cessation (P < 0.001). An OGTT results in similar capillary [glucose] during hot and thermoneutral water immersion, whereas venous [glucose] was greater during HWI when compared with CON. This indicates that peripheral tissue glucose uptake is acutely reduced in response to HWI. Abbreviations: AUC: Area under the curve; CON: Thermoneutral immersion trial; HWI: Hot water immersion trial; OGTT: Oral glucose tolerance test; PH: Passive heating; $${\bar T_{{\rm{msk}}}}$$ T ˉ m s k : Mean skin temperature; Trec: Rectal temperature [ABSTRACT FROM AUTHOR]

This randomized cross-over study tested the hypothesis that heat acclimation training would detrimentally affect sleep variables and alter incidental physical activity compared to a thermoneutral training control condition. Eight recreationally trained males (V̇O2peak 49±4.9 mL.kg-1.min-1) completed two separate interventions separated by at least 31 days: 5 consecutive day training blocks of moderate-intensity cycling (60 min·day-1 at 50% peak power output) in a hot (34.9±0.7 °C and 53±4 % relative humidity) and a temperate (22.2±2.6 °C; 65±8 % relative humidity) environment. Wrist-mounted accelerometers were worn continuously for the length of the training blocks and recorded physical activity, sleep quality and quantity. Data were analysed in a Bayesian framework, with the results presented as the posterior probability that a coefficient was greater or less than zero. Compared to the temperate training environment, heat acclimation impaired sleep efficiency (Pr β<0 =.979) and wake on sleep onset (Pr β>0 =.917). Daily sedentary time was, on average, 35 min longer (Pr β>0 =.973) and light physical activity time 18 min shorter (Pr β>0 =.960) during the heat acclimation period. No differences were observed between conditions in sleep duration, subjective sleep quality, or moderate or vigorous physical activity. These findings may suggest that athletes and coaches need to be cognisant that heat acclimation training may alter sleep quality and increase sedentary behaviour. Highlights Five consecutive days of heat training negatively affected some objective measures of sleep quality and incidental physical activity in recreationally trained athletes. Athletes and coaches need to be aware of the potential unintended consequences of using heat acclimation on sleep behaviours. [ABSTRACT FROM AUTHOR]

Research to date provides equivocal evidence regarding the influence of heat stress, heat strain, and more specifically, elevated exercise-induced core temperature on cognitive performance. This review sought to identify differences in how specific cognitive tasks were affected by increases in core body temperatures. Included papers (n = 31) measured cognitive performance and core temperature during exercise, while experiencing heightened thermal stress. Cognitive tasks were classified as cognitive inhibition, working memory, or cognitive flexibility tasks. Independently, core temperature changes were not sufficient predictors of cognitive performance. However, reaction time, memory recall, and Stroop tasks appeared to be most effective at identifying cognitive changes during heightened thermal strain. Alterations in performance were more likely to arise under increased thermal loads, which were typically associated with cumulative physiological stressors, such as elevated core temperatures, occurring alongside dehydration, and prolonged exercise durations. Future experimental designs should consider the relevance, or futility of assessing cognitive performance in activities that do not elicit a considerable degree of heat strain, or physiological load. [ABSTRACT FROM AUTHOR]

Purpose: To examine the effects of daily cold- and hot-water recovery on training load (TL) during 5 days of heat-based training. Methods: Eight men completed 5 days of cycle training for 60 minutes (50% peak power output) in 4 different conditions in a block counter-balanced-order design. Three conditions were completed in the heat (35°C) and 1 in a thermoneutral environment (24°C; CON). Each day after cycling, participants completed 20 minutes of seated rest (CON and heat training [HT]) or cold- (14°C; HTCWI) or hot-water (39°C; HTHWI) immersion. Heart rate, rectal temperature, and rating of perceived exertion (RPE) were collected during cycling. Session-RPE was collected 10 minutes after recovery for the determination of session-RPE TL. Data were analyzed using hierarchical regression in a Bayesian framework; Cohen d was calculated, and for session-RPE TL, the probability that d > 0.5 was also computed. Results: There was evidence that session-RPE TL was increased in HTCWI (d = 2.90) and HTHWI (d = 2.38) compared with HT. The probabilities that d > 0.5 were.99 and.96, respectively. The higher session-RPE TL observed in HTCWI coincided with a greater cardiovascular (d = 2.29) and thermoregulatory (d = 2.68) response during cycling than in HT. This result was not observed for HTHWI. Conclusion: These findings suggest that cold-water recovery may negatively affect TL during 5 days of heat-based training, hot-water recovery could increase session-RPE TL, and the session-RPE method can detect environmental temperature-mediated increases in TL in the context of this study. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to model the effect of body armor coverage on body core temperature elevation and wet-bulb globe temperature (WBGT) offset. Background: Heat stress is a critical factor influencing the health and safety of military populations. Work duration limits can be imposed to mitigate the risk of exertional heat illness and are derived based on the environmental conditions (WBGT). Traditionally a 3°C offset to WBGT is recommended when wearing body armor; however, modern body armor systems provide a range of coverage options, which may influence thermal strain imposed on the wearer. Method: The biophysical properties of four military clothing ensembles of increasing ballistic protection coverage were measured on a heated sweating manikin in accordance with standard international criteria. Body core temperature elevation during light, moderate, and heavy work was modeled in environmental conditions from 16°C to 34°C WBGT using the heat strain decision aid. Results: Increasing ballistic protection resulted in shorter work durations to reach a critical core temperature limit of 38.5°C. Environmental conditions, armor coverage, and work intensity had a significant influence on WBGT offset. Conclusion: Contrary to the traditional recommendation, the required WBGT offset was >3°C in temperate conditions (<27°C WBGT), particularly for moderate and heavy work. In contrast, a lower WBGT offset could be applied during light work and moderate work in low levels of coverage. Application: Correct WBGT offsets are important for enabling adequate risk management strategies for mitigating risks of exertional heat illness. [ABSTRACT FROM AUTHOR]