Menstrual cycle phase does not modulate whole body heat loss during exercise in hot, dry conditions

Notley, Sean R.; Dervis, Sheila; Poirier, Martin P.; Kenny, Glen P.

doi:10.1152/japplphysiol.00735.2018

Cited by 42 publications

(35 citation statements)

References 44 publications

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“…Third, all female participants were eumenorrhoeic, but were not tested within a specific menstrual cycle phase. The menstrual cycle phase has long been thought to influence thermoregulatory function (Stephenson & Kolka, ), but it has been demonstrated recently that menstrual phase does not significantly modulate whole‐body heat exchange in comparable exercise and environmental conditions (Notley, Dervis, Poirier, & Kenny, ). Finally, we used a model involving exercise at increasing fixed rates of metabolic heat production, each separated by brief resting recovery periods.…”

Section: Discussionmentioning

confidence: 99%

Revisiting the influence of individual factors on heat exchange during exercise in dry heat using direct calorimetry

Notley

Lamarche

Meade

et al. 2019

Experimental Physiology

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New Findings What is the central question of this study?The aim was to identify the greatest contributor(s) to the variation in whole‐body heat exchange, as assessed using direct calorimetry, among young men and women with heterogeneous characteristics during exercise at increasing metabolic heat production rates in dry heat. What is the main finding and its importance?The evaporative heat loss requirement, body morphology and aerobic fitness made the greatest contributions to the individual variation in evaporative and dry heat exchange, with the variance explained being exercise intensity dependent. These findings provide a foundation on which to build our ability to explain the individual variation in heat exchange during exercise‐induced heat stress. Abstract Numerous individual factors (e.g. fitness, sex, body morphology) are known to independently modulate heat exchange during exercise in the heat. However, in our view, the individual factor(s) making the greatest contribution to the variation in heat exchange among men and women remains poorly understood, despite several studies. We therefore sought to revisit this question by assessing whole‐body dry and evaporative heat exchange using direct calorimetry in a heterogeneous sample of 100 young men (n = 57) and women (n = 43). Participants performed three 30 min bouts of cycling at very light (men/women; 300/250 W), light (400/325 W) and moderate (500/400 W) metabolic heat production rates, separated by a 15 min recovery, in dry heat (40°C, ∼12% relative humidity). Positive associations were observed between the evaporative heat loss requirement (metabolic heat production ± dry heat exchange) and evaporative heat loss (all P < 0.01), especially during moderate exercise (men, r = 0.62; women, r = 0.82), which explained 19–67% of individual variation. Peak aerobic power (in millilitres per kilogram per minute) was also positively related to evaporative heat loss in both sexes, albeit only during light and moderate exercise (r = 0.33–0.43; all P < 0.05), explaining a further 5–9% of individual variation. Dry heat exchange shared negative associations with body mass and surface area during all exercise bouts in both sexes (r = −0.29 to −0.55; all P < 0.05), explaining 9–30% of individual variation. We therefore demonstrate that the evaporative heat loss requirement, peak aerobic power and body morphology are the greatest contributors to the variation in whole‐body heat exchange among young men and women exercising in dry heat, with the strength of those relationships being heat‐load dependent.

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Section: Discussionmentioning

confidence: 99%

Revisiting the influence of individual factors on heat exchange during exercise in dry heat using direct calorimetry

Notley

Lamarche

Meade

et al. 2019

Experimental Physiology

Self Cite

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“…Two examples of this were noted above, with respect to the impact of sex and chronological age on sweating. Another example is the menstrual cycle: during the luteal phase regional sweating rate is lower at a given body core temperature (increased threshold and decreased slope) [122][123][124][125], but there are no differences in whole-body sweating rate across the menstrual cycle phases [123,[126][127][128][129]. Additionally, for trained females their menstrual phase is of little physiological or performance consequence during exercise in the heat [103,130].…”

Section: Chronicmentioning

confidence: 99%

Physiology of sweat gland function: The roles of sweating and sweat composition in human health

2019

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The purpose of this comprehensive review is to: 1) review the physiology of sweat gland function and mechanisms determining the amount and composition of sweat excreted onto the skin surface; 2) provide an overview of the well-established thermoregulatory functions and adaptive responses of the sweat gland; and 3) discuss the state of evidence for potential non-thermoregulatory roles of sweat in the maintenance and/or perturbation of human health. The role of sweating to eliminate waste products and toxicants seems to be minor compared with other avenues of excretion via the kidneys and gastrointestinal tract; as eccrine glands do not adapt to increase excretion rates either via concentrating sweat or increasing overall sweating rate. Studies suggesting a larger role of sweat glands in clearing waste products or toxicants from the body may be an artifact of methodological issues rather than evidence for selective transport. Furthermore, unlike the renal system, it seems that sweat glands do not conserve water loss or concentrate sweat fluid through vasopressin-mediated water reabsorption. Individuals with high NaCl concentrations in sweat (e.g. cystic fibrosis) have an increased risk of NaCl imbalances during prolonged periods of heavy sweating; however, sweat-induced deficiencies appear to be of minimal risk for trace minerals and vitamins. Additional research is needed to elucidate the potential role of eccrine sweating in skin hydration and microbial defense. Finally, the utility of sweat composition as a biomarker for human physiology is currently limited; as more research is needed to determine potential relations between sweat and blood solute concentrations.

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“…First, the pre‐menopausal women studied were eumenorrhoeic, but were not tested within a specific menstrual cycle phase. However, while fluctuations in sex hormones during the menstrual cycle have long been thought to influence thermoregulatory function (Stephenson & Kolka, 1985), more recent data indicate that menstrual phase does not significantly modulate whole‐body heat exchange under comparable exercise and environmental conditions (Notley, Dervis, Poirier, & Kenny, 2019a). Thus, we feel it is unlikely that any effects of menstrual phase would modify our observations.…”

Section: Discussionmentioning

confidence: 99%

Effect of aerobic fitness on the relation between age and whole‐body heat exchange during exercise‐heat stress: a retrospective analysis

Notley

Meade

Kenny

2020

Experimental Physiology

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New Findings What is the central question of this study?Does higher aerobic fitness, indexed by peak oxygen uptake (V̇O2normalpeak), attenuate the age‐related decline in thermoregulatory function during exercise in the heat? What is the main finding and its importance?When assessed in aerobically fit and less fit adults (V̇O2normalpeak: ∼30 vs. ∼50 ml kg−1 min−1) aged 18–66 years, a steeper decline in whole‐body total heat loss (evaporative + dry heat exchange) was observed with increasing age in less aerobically fit adults. These outcomes indicate that increased aerobic fitness may attenuate the age‐related decline in thermoregulatory function during exercise‐heat stress. Abstract Ageing is associated with decrements in cutaneous vasodilatation and sweating that attenuate whole‐body total heat loss (evaporative + dry heat exchange) during exercise‐heat stress. However, it remains uncertain whether increased aerobic fitness, as indexed by peak oxygen uptake (V̇O2normalpeak), slows that age‐related decline. To evaluate this possibility, we conducted a retrospective analysis of data from aerobically fit (n = 38; V̇O2normalpeak: (mean (SD)) 49 (4) ml kg−1 min−1) and less fit (n = 35; V̇O2normalpeak: 32 (3) ml kg−1 min−1) adults spanning a broad age range (18–65 vs. 18–66 years). Participants performed three, 30 min bouts of cycling at metabolic heat productions of 150, 200 and 250 W m−2, each separated by 15 min recovery, in dry heat (40˚C, ∼15% relative humidity). Metabolic heat production and whole‐body total heat loss were measured using indirect and direct calorimetry, respectively. Total heat loss (mean (95% CI)) declined at a rate of 5 (2, 8), 6 (3, 8) and 5 (3, 10) W m−2 per decade during exercise at metabolic heat productions of 150, 200 and 250 W m−2, respectively, in less aerobically fit individuals (all P ≤ 0.002), due primarily to reductions in evaporative heat loss. In contrast, no significant associations between age and total heat loss were observed in aerobically fit individuals (all P ≥ 0.146). As such, the slope of the age‐related reduction in total heat loss was steeper in less fit compared to fit individuals across all three exercise bouts (all P ≤ 0.029). These outcomes indicate that increased aerobic fitness attenuates the age‐related decline in exercise thermoregulation.

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Menstrual cycle phase does not modulate whole body heat loss during exercise in hot, dry conditions

Cited by 42 publications

References 44 publications

Revisiting the influence of individual factors on heat exchange during exercise in dry heat using direct calorimetry

Revisiting the influence of individual factors on heat exchange during exercise in dry heat using direct calorimetry

Physiology of sweat gland function: The roles of sweating and sweat composition in human health

Effect of aerobic fitness on the relation between age and whole‐body heat exchange during exercise‐heat stress: a retrospective analysis

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