The biophysical and physiological basis for mitigated elevations in heart rate with electric fan use in extreme heat and humidity

Ravanelli, Nicholas; Gagnon, Daniel; Hodder, Simon; Havenith, George; Jay, Ollie

doi:10.1007/s00484-016-1213-0

Cited by 15 publications

(21 citation statements)

References 47 publications

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“…However, these studies could not provide conclusive evidence regarding the effect of fan use, and there is currently no evidence to support or refute their use during heat waves (12, 14). Together with recent studies (11, 18, 29, 30), the current results represent an initial step towards understanding the consequence of fan use on cardiovascular and thermoregulatory responses in young and aged adults exposed to extreme heat and humidity. Such studies are particularly needed as climate change, urbanization and a rapidly aging population are placing an increasingly greater number of individuals at risk of heat-related morbidity and mortality (13, 23, 25).…”

Section: Discussionsupporting

confidence: 60%

“…Greater heat gain from the environment, and therefore the potential for increased physiological strain, is the main reason why public health agencies discourage fan use if air temperature exceeds 35–37°C (4, 36, 38, 39). However, such recommendations ignore the fact that fan use also improves evaporative capacity, particularly in humid environments (29). In young adults, fan use delayed the increase in heart rate and core temperature during exposure to air temperatures near (36°C) and well above (42°C) the threshold (e.g., 35–37°C) at which fan use is discouraged (30).…”

Section: Discussionmentioning

confidence: 99%

“…In young adults, fan use delayed the increase in heart rate and core temperature during exposure to air temperatures near (36°C) and well above (42°C) the threshold (e.g., 35–37°C) at which fan use is discouraged (30). Despite causing a greater rate of dry heat gain, fan use provided a “protective” effect by elevating evaporative capacity and maintaining sweating efficiency at greater levels (29). This delayed the humidity at which heat gain from the environment could no longer be balanced by evaporative heat loss (29).…”

Section: Discussionmentioning

confidence: 99%

“…Despite causing a greater rate of dry heat gain, fan use provided a “protective” effect by elevating evaporative capacity and maintaining sweating efficiency at greater levels (29). This delayed the humidity at which heat gain from the environment could no longer be balanced by evaporative heat loss (29). …”

Section: Discussionmentioning

confidence: 99%

“…Although fan use increased the rate of dry heat gain from the environment, this effect was marginal relative to a vast improvement in evaporative capacity (29). However, it is aged adults that are generally at the greatest risk of heat-related morbidity and mortality.…”

Section: Introductionmentioning

confidence: 99%

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Age Modulates Physiological Responses during Fan Use under Extreme Heat and Humidity

Gagnon

Romero

Cramer

et al. 2017

Medicine &Amp; Science in Sports &Amp; Exercise

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Purpose We examined the effect of electric fan use on cardiovascular and thermoregulatory responses of nine young (26 ± 3 years) and nine aged (68 ± 4 years) adults exposed to extreme heat and humidity. Methods While resting at a temperature of 42°C, relative humidity increased from 30 to 70% in 2% increments every 5 minutes. On randomized days, the protocol was repeated without or with fan use. Heart rate (HR), core (Tcore) and mean skin (Tsk) temperatures were measured continuously. Whole-body sweat loss (WBSL) was measured from changes in nude body weight. Other measures of cardiovascular (cardiac output), thermoregulatory (local cutaneous and forearm vascular conductance, local sweat rate), and perceptual (thermal and thirst sensations) responses were also examined. Results When averaged over the entire protocol, fan use resulted in a small reduction of HR (−2 beats/min, 95% CI: −8 to 3), and slightly greater Tcore (+0.05°C, 95% CI: −0.13 to 0.23) and Tsk (+0.03°C, 95% CI: −0.36 to 0.42) in young adults. In contrast, fan use resulted in greater HR (+5 beats/min, 95% CI: 0 to 10), Tcore (+0.20°C, 95% CI: 0.00 to 0.41) and Tsk (+0.47°C, 95% CI: 0.18 to 0.76) in aged adults. A greater WBSL during fan use was observed in young (+0.2 kg, 95% CI: −0.2 to 0.6) but not aged (0.0 kg, 95% CI: −0.2 to 0.2) adults. Greater local sweat rate and cutaneous vascular conductance were observed with fan use in aged adults. Other measures of cardiovascular, thermoregulatory and perceptual responses were unaffected by fan use in both groups. Conclusion During extreme heat and humidity, fan use elevates physiological strain in aged, but not young, adults.

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Section: Discussionsupporting

confidence: 60%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Age Modulates Physiological Responses during Fan Use under Extreme Heat and Humidity

Gagnon

Romero

Cramer

et al. 2017

Medicine &Amp; Science in Sports &Amp; Exercise

Self Cite

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Quantifying the impact of heat on human physical work capacity; part II: the observed interaction of air velocity with temperature, humidity, sweat rate, and clothing is not captured by most heat stress indices

et al. 2021

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Increasing air movement can alleviate or exacerbate occupational heat strain, but the impact is not well defined across a wide range of hot environments, with different clothing levels. Therefore, we combined a large empirical study with a physical model of human heat transfer to determine the climates where increased air movement (with electric fans) provides effective body cooling. The model allowed us to generate practical advice using a high-resolution matrix of temperature and humidity. The empirical study involved a total of 300 1-h work trials in a variety of environments (35, 40, 45, and 50 °C, with 20 up to 80% relative humidity) with and without simulated wind (3.5 vs 0.2 m∙s−1), and wearing either minimal clothing or a full body work coverall. Our data provides compelling evidence that the impact of fans is strongly determined by air temperature and humidity. When air temperature is ≥ 35 °C, fans are ineffective and potentially harmful when relative humidity is below 50%. Our simulated data also show the climates where high wind/fans are beneficial or harmful, considering heat acclimation, age, and wind speed. Using unified weather indices, the impact of air movement is well captured by the universal thermal climate index, but not by wet-bulb globe temperature and aspirated wet-bulb temperature. Overall, the data from this study can inform new guidance for major public and occupational health agencies, potentially maintaining health and productivity in a warming climate.

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Efficiency of three cooling methods for hyperthermic military personnel linked to water availability

et al. 2022

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The biophysical and physiological basis for mitigated elevations in heart rate with electric fan use in extreme heat and humidity

Cited by 15 publications

References 47 publications

Age Modulates Physiological Responses during Fan Use under Extreme Heat and Humidity

Age Modulates Physiological Responses during Fan Use under Extreme Heat and Humidity

Quantifying the impact of heat on human physical work capacity; part II: the observed interaction of air velocity with temperature, humidity, sweat rate, and clothing is not captured by most heat stress indices

Efficiency of three cooling methods for hyperthermic military personnel linked to water availability

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