Refining the distinction between heat tolerant and intolerant individuals during a Heat tolerance test

Druyan, Amit; Ketko, Itay; Yanovich, Ran; Epstein, Yoram; Heled, Yuval

doi:10.1016/j.jtherbio.2013.09.005

Cited by 29 publications

(45 citation statements)

References 17 publications

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“…Resting and mean exercising T rec reduced after STHA, but were not further enhanced after LTHA for all methods in accordance with previous work (Buono et al, 1998;Kampmann et al, 2008). Though comparable with some previous data to determine temperature responses to heat stress (Druyan et al, 2013;Moran et al, 2006), the mean/change T rec observed during the HSTs were not as high as observed using alternative protocols to determine physiological responses to heat stress (Magalhães et al, 2010a;Périard et al, 2012). This may have affected the ability of the test to determine core temperature differences augmented by the different heat acclimation methods, or between STHA and LTHA.…”

Section: Physiological Mechanisms Of Heat Acclimationsupporting

confidence: 92%

Isothermic and fixed intensity heat acclimation methods induce similar heat adaptation following short and long-term timescales

Gibson

Mee

Tuttle

et al. 2015

Journal of Thermal Biology

103

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Heat acclimation requires the interaction between hot environments and exercise to elicit thermoregulatory adaptations. Optimal synergism between these parameters is unknown. Common practise involves utilising a fixed workload model where exercise prescription is controlled and core temperature is uncontrolled, or an isothermic model where core temperature is controlled and work rate is manipulated to control core temperature. Following a baseline heat stress test; 24 males performed a between groups experimental design performing short term heat acclimation (STHA; five 90 min sessions) and long term heat acclimation (LTHA; STHA plus further five 90 min sessions) utilising either fixed intensity (50% VO2peak), continuous isothermic (target rectal temperature 38.5 °C for STHA and LTHA), or progressive isothermic heat acclimation (target rectal temperature 38.5 °C for STHA, and 39.0 °C for LTHA). Identical heat stress tests followed STHA and LTHA to determine the magnitude of adaptation. All methods induced equal adaptation from baseline however isothermic methods induced adaptation and reduced exercise durations (STHA = -66% and LTHA = -72%) and mean session intensity (STHA = -13% VO2peak and LTHA = -9% VO2peak) in comparison to fixed (p < 0.05). STHA decreased exercising heart rate (-10 b min(-1)), core (-0.2 °C) and skin temperature (-0.51 °C), with sweat losses increasing (+0.36 Lh(-1)) (p<0.05). No difference between heat acclimation methods, and no further benefit of LTHA was observed (p > 0.05). Only thermal sensation improved from baseline to STHA (-0.2), and then between STHA and LTHA (-0.5) (p<0.05). Both the continuous and progressive isothermic methods elicited exercise duration, mean session intensity, and mean T(rec) analogous to more efficient administration for maximising adaptation. Short term isothermic methods are therefore optimal for individuals aiming to achieve heat adaptation most economically, i.e. when integrating heat acclimation into a pre-competition taper. Fixed methods may be optimal for military and occupational applications due to lower exercise intensity and simplified administration.

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Section: Physiological Mechanisms Of Heat Acclimationsupporting

confidence: 92%

Isothermic and fixed intensity heat acclimation methods induce similar heat adaptation following short and long-term timescales

Gibson

Mee

Tuttle

et al. 2015

Journal of Thermal Biology

103

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“…For example, sex-related differences in core temperature have been reported with exercise at a %VO 2max (Horstman and Christensen 1982), however, the greater VO 2max in males compared to females would have resulted in a greater H prod (in WÁkg À1 ), which may have been responsible for the greater change in core temperature based on present findings. Furthermore, the present findings can potentially augment existing heat tolerance test protocols that employ a fixed treadmill walking speed on an incline (Moran et al 2004;Druyan et al 2013;Cheuvront 2014). While walking at the same speed and incline with a similar movement economy will lead to a similar WÁkg À1 of H prod between participants of different body masses, alterations in H prod in WÁkg À1 secondary to differences in walking efficiency would, according to the present observations (Fig.…”

Section: Perspectivessupporting

confidence: 75%

“…; Druyan et al. ; Cheuvront ). While walking at the same speed and incline with a similar movement economy will lead to a similar W·kg −1 of H prod between participants of different body masses, alterations in H prod in W·kg −1 secondary to differences in walking efficiency would, according to the present observations (Fig.…”

Section: Discussionmentioning

confidence: 99%

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The optimal exercise intensity for the unbiased comparison of thermoregulatory responses between groups unmatched for body size during uncompensable heat stress

Ravanelli

Cramer

Imbeault

et al. 2017

Physiological Reports

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We sought to identify the appropriate exercise intensity for unbiased comparisons of changes in rectal temperature (ΔTre) and local sweat rates (LSR) between groups unmatched for body size during uncompensable heat stress. Sixteen males vastly different in body morphology were separated into two equal groups [small (SM): 65.8 ± 6.2 kg, 1.8 ± 0.1 m2; large (LG): 100.0 ± 13.1 kg, 2.3 ± 0.1 m2], but matched for sudomotor thermosensitivity (SM: 1.3 ± 0.6; LG: 1.1 ± 0.4 mg·cm−2·min−1·°C−1). The maximum potential for evaporation (Emax) for each participant was assessed using an incremental humidity protocol. On separate occasions, participants then completed 60 min of cycling in a 35°C and 70% RH environment at (1) 50% of VO 2max, (2) a heat production (Hprod) of 520 W, (3) Hprod relative to mass (6 W·kg−1), and (4) Hprod relative to mass above Emax (3 W·kg−1>Emax). Emax was similar between LG (347 ± 39 W, 154 ± 15 W·m−2) and SM (313 ± 63 W, 176 ± 34 W·m−2, P > 0.12). ΔTre was greater in SM compared to LG at 520 W (SM: 1.5 ± 0.5; LG 0.8 ± 0.3°C, P < 0.001) and at 50% of VO 2max (SM: 1.4 ± 0.5; LG 0.9 ± 0.3°C, P < 0.001). However, ΔTre was similar between groups when Hprod was either 6 W·kg−1 (SM: 0.9 ± 0.3; LG 0.9 ± 0.2°C, P = 0.98) and 3 W·kg−1>Emax (SM: 1.4 ± 0.5; LG 1.3 ± 0.4°C, P = 0.99). LSR was similar between LG and SM irrespective of condition, suggesting maximum LSR was attained (SM: 1.10 ± 0.23; LG: 1.07 ± 0.35 mg·cm−2·min−1, P = 0.50). In conclusion, systematic differences in ΔTre and LSR between groups unmatched for body size during uncompensable heat stress can be avoided by a fixed Hprod in W·kg−1 or W·kg−1>Emax.

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“…In particular, repeated exposure to heat stress causes health to be adversely affected (Hunter et al, 2017). Once heat stress is experienced chance of getting another heat stress during deployment gets higher (Druyan, Ketko, Yanovich, Epstein, & Heled, 2013).…”

Section: Introductionmentioning

confidence: 99%

Moses Health Monitoring System for Firefighters

Zaburnenko¹,

Prins²,

Salomons³

2019

17th International Conference on E-Society 2019

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When firefighting, the combination of exposition to high temperatures, high physical demands and wearing (heavy and insulated) personal protective equipment lead to increased risk of heat stress and exhaustion in firefighters. Heat stress can easily evolve into a life-threatening heat stroke. Once heat stress occurred, the chance of getting another heat stroke during deployment gets higher. Moreover, intermittent exposure to heat stress over several years, is a risk factor for heart diseases. Similarly, exhausted during a deployment, a firefighter needs more time to rehabilitate before he can safely be deployed again. Heat stress and exhaustion can lead to line-of-duty cardiovascular events. Therefore, preventing heat stress and exhaustion during deployment is beneficial for health, functioning and employability of firefighters. Since currently available measurement of the core temperature, such as thermometer pill or neck patch thermometer, are not reliable or practical for firefighters, an alternative approach may be used, namely, estimation of the core temperature based on non-invasive observation of the heart rate. Exhaustion is estimated using the training impulse model based on the heart rate reserve. Our achievement is a MoSeS health monitor system (as a smartphone application) that can real time analyze the health status of a firefighter and predict exhaustion and heat stress during deployment. The system is cheap (only a heart rate sensor and a smartphone application is needed), easy to use (intuitive "traffic light" signal), and objective (the health status is determined based on measurements of the heart rate). The only restriction is that the developed model is strongly dependent on personal maximum and minimum heart rate which need to be established beforehand.

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Refining the distinction between heat tolerant and intolerant individuals during a Heat tolerance test

Cited by 29 publications

References 17 publications

Isothermic and fixed intensity heat acclimation methods induce similar heat adaptation following short and long-term timescales

Isothermic and fixed intensity heat acclimation methods induce similar heat adaptation following short and long-term timescales

The optimal exercise intensity for the unbiased comparison of thermoregulatory responses between groups unmatched for body size during uncompensable heat stress

Moses Health Monitoring System for Firefighters

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