Increasing Relative Humidity Impacts Low-Intensity Exercise in the Heat

Moyen, Nicole E.; Ellis, Carolyn L. V.; Ciccone, Anthony B.; Thurston, Taylor S.; Cochrane, Kristen C.; Brown, Lee E.; Coburn, Jared W.; Judelson, Daniel A.

doi:10.3357/asem.3787.2014

Cited by 30 publications

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“…The higher the relative humidity, the lower the heat transfer by perspiration evaporation. Therefore, hot and humid environments impose greater thermal strain by declining evaporative heat losses (Moyen et al 2014).…”

Section: Discussionmentioning

confidence: 99%

Environmental heat exposure and cognitive performance in older adults: a controlled trial

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Oliveira

et al. 2015

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Thermal stress has a negative effect on the cognitive performance of military personnel and industry workers exposed to extreme environments. However, no studies have investigated the effects of environmental thermal stress on the cognitive functions of older adults. We carried out a controlled trial with 68 healthy older adults (mean age 73.3 years, 69 % female), each of whom has been assessed twice on the same day with selected tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB). Repeated sessions were conducted with air temperatures set at 24 °C and 32 °C in a balanced order. Our primary analyses did not show significant differences when comparing the cognitive performance of the total sample under the two experimental temperatures. However, interaction analysis has shown that humidity levels modify the effect of temperature on cognitive outcomes. The subgroup exposed to relative humidity greater than the median value (57.8 %) presented worse cognitive performance in the heat session when compared to the control session. Reported exercising frequency explained individual vulnerability to heat stress. Volunteers with lower levels of physical activity (<4 times per week) were more likely to present worsened cognitive performance under heat stress. In a fully adjusted linear regression model, the performance under heat stress remained associated with relative humidity (β = -0.21; p = 0.007) and frequency of exercising (β = 0.18; p = 0.020). Our results indicate that heat stress may have detrimental effects on the cognitive functioning of some subgroups of older adults and under particular circumstances. Further research is needed for exploring a variety of potentially influential factors.

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Section: Discussionmentioning

confidence: 99%

Environmental heat exposure and cognitive performance in older adults: a controlled trial

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Oliveira

et al. 2015

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“…By contrast, Moyen et al 12 reported a greater heat storage and body temperatures at the higher end of the RH (55–70%) range even at a much lower exercise intensity.…”

Section: Introductionmentioning

confidence: 87%

“…More recently, the impact of a wider range of RH on the capacity to exercise was investigated at low 12 (5 RH levels) and moderate 13 (4 RH levels) intensity where it was concluded that exercise capacity was compromised at the higher end of the RH range when exposed to a hot (35°C), 12 and warm 13 (30°C) environment, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the investigations by Maughan et al 13 and Moyen et al 12 were conducted in a condition with minimal (1 m·s −1 ) and no convective cooling, respectively, which presents a challenge to thermoregulation 14,15 . During an outdoor running event, a well trained runner will experience a substantial convective cooling as they usually run at speeds ranging from 12–20 km·h −1 .…”

Section: Introductionmentioning

confidence: 99%

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The effects of a systematic increase in relative humidity on thermoregulatory and circulatory responses during prolonged running exercise in the heat

et al. 2016

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This study examined the thermoregulatory and circulatory responses, and exercise performance of trained distance runners during exercise in the heat (31°C) at varying relative humidity (RH). In a randomized order, 11 trained male distance runners performed 5 60 min steady-state runs at a speed eliciting 70% of VO2max in RH of 23, 43, 52, 61 and 71%. This was followed immediately with an incremental exercise test to volitional exhaustion. Core (Tre) and mean skin temperature (T¯sk), cardiac output (Q), heart rate (HR), and stroke volume (SV) were recorded at regular intervals. A significant (P = 0.003) main effect was detected for RH on mean body temperature (Tb), with a significantly higher Tb detected during steady-state exercise in the 61 and 71% RH compared to that in the 23% RH. During the steady-state exercise, no differences were detected in whole body sweat loss (P = 0.183). However, a significant main effect of RH was observed for HR and SV (P = 0.001 and 0.006, respectively) but not Q (P = 0.156). The time to exhaustion of the incremental exercise test was significantly reduced at 61 and 71% RH compared with 23% RH (P = 0.045 and 0.005, respectively). Despite an increase in dry heat loss, a greater thermoregulatory and circulatory stress was evident during steady-state exercise at 61 and 71% RH. This ultimately limits the capacity to perform the subsequent incremental exercise to exhaustion. This study highlighted that in a warm environment, the range of the prescriptive zone progressively narrows as RH increases.

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“…High humidity decreases the efficiency of cooling by decreasing the evaporation from the skin surface [10;12]. This leads to failure of cooling the body [13]. Further, the body responds by more sweating.…”

Section: Resultsmentioning

confidence: 99%

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Increasing Relative Humidity Impacts Low-Intensity Exercise in the Heat

Cited by 30 publications

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Environmental heat exposure and cognitive performance in older adults: a controlled trial

Environmental heat exposure and cognitive performance in older adults: a controlled trial

The effects of a systematic increase in relative humidity on thermoregulatory and circulatory responses during prolonged running exercise in the heat

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