Effect of hypohydration on thermoregulatory responses in men with low and high body fat exercising in the heat

Tucker, Matthew A.; Caldwell, Aaron R.; Butts, Cory L.; Robinson, Forrest B.; Reynebeau, Haley C.; Kavouras, Stavros A.; McDermott, Brendon P.; Washington, Tyrone A.; Turner, Ronna C.; Ganio, Matthew S.

doi:10.1152/japplphysiol.00768.2016

Cited by 14 publications

(14 citation statements)

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“…For example, there are well-appreciated deleterious effects of acute hypohydration including reduced exercise performance [3,4,10,12,13,14,16,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88], worsened mood [18,89,90,91], impaired cognitive function [19,20,21,91,92], altered thermoregulatory function [73,74,80,82,84,87,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108], and decreased glycemic regulation [11,109] (Figure 1). Chronic systemic hypohydration is a proposed pathogenic factor for hypertension, venous thromboembolism,...…”

Section: Clinical Relevancementioning

confidence: 99%

“…This hypothesis is supported by evidence that more methacholine chloride (an endothelium-dependent vasodilator) is required to achieve the drug concentration that provides half of the maximal response (EC 50 ) during hypohydration to ~2% body mass loss via exercise in the heat following fluid restriction compared to euhydration [25]. While only one [22] of these particular three studies examining vascular function [22,23,25] reported greater increases in body temperature in the hypohydrated state, several other studies have found hydration status to affect thermoregulatory function [73,74,80,82,84,87,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,134]. As a result, specific guidelines for hydration status have been set in certain populations, such as industrial workers in the heat [135], to minimize the potential for heat-stress and hypohydration-induced increases in cardiovascular strain and potential risk for adverse cardiovascular events.…”

Section: Vascular Health and Functionmentioning

confidence: 99%

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Hydration Status and Cardiovascular Function

Watso

Farquhar

2019

Nutrients

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Hypohydration, defined as a state of low body water, increases thirst sensations, arginine vasopressin release, and elicits renin–angiotensin–aldosterone system activation to replenish intra- and extra-cellular fluid stores. Hypohydration impairs mental and physical performance, but new evidence suggests hypohydration may also have deleterious effects on cardiovascular health. This is alarming because cardiovascular disease is the leading cause of death in the United States. Observational studies have linked habitual low water intake with increased future risk for adverse cardiovascular events. While it is currently unclear how chronic reductions in water intake may predispose individuals to greater future risk for adverse cardiovascular events, there is evidence that acute hypohydration impairs vascular function and blood pressure (BP) regulation. Specifically, acute hypohydration may reduce endothelial function, increase sympathetic nervous system activity, and worsen orthostatic tolerance. Therefore, the purpose of this review is to present the currently available evidence linking acute hypohydration with altered vascular function and BP regulation.

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Section: Clinical Relevancementioning

confidence: 99%

Section: Vascular Health and Functionmentioning

confidence: 99%

Hydration Status and Cardiovascular Function

Watso

Farquhar

2019

Nutrients

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“…Laboratory investigations have examined the effect of body fat on thermoregulation during exercise in the heat, but these studies are limited in number with small sample sizes with conflicting conclusions. 5,9,13,14 Some studies reported significant differences in Tcore and Tsk between high-body fat (Hi-BF) and low-body fat (Lo-BF) [15][16][17] where others suggest that there are no differences in any thermoregulatory outcome. [18][19][20][21] Moreover, individuals with higher body fat tend to have lower fitness levels, greater body mass and a smaller body surface area to mass ratio compared to those with lower body fat, which makes it difficult to ascertain the independent influence of body fat on thermoregulatory responses during exercise in the heat.…”

Section: Introductionmentioning

confidence: 99%

The impact of body fat on thermoregulation during exercise in the heat: A systematic review and meta-analysis

Morrissey

Zuk

et al. 2021

Journal of Science and Medicine in Sport

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Objectives: We performed a systematic review and meta-analysis to examine the effect of body fat on thermoregulatory responses to exercise in the heat. Design: Systematic Review and Meta-analysis. Methods: We systematically searched databases (N = 8) for studies that included: healthy participants; an aerobic exercise intervention under heat stress; a measure of body fat by a high and low body fat group; pre-and post-exercise internal temperature, and/or post-exercise mean skin temperature and whole body sweat loss. Criteria to distinguish high body fat and low body fat were determined by each qualifying study. Out of 1222 potential studies, 10 qualified. Robust variance estimation models were utilized to determine the pooled effect size (ES, 95% CI) for interventions that performed unbias comparisons between groups. Results: Participants (n = 211) were mostly male (70%) and young (19.3 ± 7.1 years) with a maximal oxygen consumption of 50.42 ± 9.3 ml•kg −1 •min −1 by high body fat (36.7 ± 11.8%) and low body fat (17.8 ± 5.7%). Exercise duration was between 30 and 60 min at moderate-high intensity (44.1-71.4% VO 2 max) at 28-40.3°C and 26-50% humidity. Of the 7 interventions that normalized metabolic heat production to body mass and 5 interventions that normalized to external workload, there were no differences in any of the three outcome variables between groups. Conclusions: Many of the included studies did not control for confounding factors that may affect the relationship between body fat and thermoregulation during exercise in the heat such as metabolic heat production and body mass. Given the small number of interventions included, future work must make unbiased comparisons to appropriately assess the independent influence of body fat.Published by Elsevier Ltd on behalf of Sports Medicine Australia. Practical implications• There are current methodological concerns in research studies surrounding the influence of body fat on thermoregulation during exercise in the heat • Future investigations need to make unbiased comparisons (i.e. control for confounding factors such as metabolic heat production, body mass, heat acclimatization, body surface area, etc.) between Hi-BF and Lo-BF to examine the independent influence of body fat on thermoregulation during exercise in the heat.

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“…Although there is a paucity of data with obese individuals, some studies suggest obesity is linked with poorer cognitive performance compared to lean controls ( Boeka & Lokken, 2008 ; Lokken et al, 2009 ; Lokken et al, 2010 ). Poor cognitive performance may be exacerbated in obese individuals when heat stressed because of impaired thermoregulatory control ( Bar-Or, Lundegren & Buskirk, 1969 ; Buskirk, Bar-Or & Kollias, 1969 ; Tucker et al, 2017 ). However, the independent and combined effects of hyperthermia and hypohydration on cognition and mood in obese individuals have not been investigated.…”

Section: Introductionmentioning

confidence: 99%

Obesity, but not hypohydration, mediates changes in mental task load during passive heating in females

Caldwell

Burchfield

Moyen

et al. 2018

PeerJ

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BackgroundThe independent effects of hypohydration and hyperthermia on cognition and mood is unclear since the two stresses often confound each other. Further, it is unknown if obese individuals have the same impairments during hyperthermia and hypohydration that is often observed in non-obese individuals.MethodsThe current study was designed to assess the independent and combined effects of mild hypohydration and hyperthermia on cognition, mood, and mental task load in obese and non-obese females. Twenty-one healthy females participated in two passive heating trials, wherein they were either euhydrated or hypohydrated prior to and throughout passive heating. Cognition (ImPACT), mental task load (NASA-TLX), and mood (Brunel Mood Scale; BRUMS) were measured before and after a 1.0 °C increase in core temperature (TC).ResultsAfter a 1.0 °C TC elevation, hypohydration resulted in greater (p < 0.05) body mass loss (−1.14 ± 0.48 vs −0.58 ± 0.48 kg; hypohydrated and euhydrated, respectively) and elevation in serum osmolality (292 ± 4 vs 282 ± 3 mOsm; p < 0.05) versus euhydration. Hypohydration, independent of hyperthermia, did not affect mental task load or mood (p > 0.05). Hyperthermia, regardless of hydration status, impaired (∼5 A.U) measures of memory-based cognition (verbal and visual memory), and increased mental task load, while worsening mood (p < 0.05). Interestingly, obese individuals had increased mental task load while hyperthermic compared to the non-obese individuals (p < 0.05) even while euhydrated. Hypohydration did not exacerbate any heat-related effects on cognition between obese and non-obese females (p > 0.05).ConclusionThese data indicate that hyperthermia independently impairs memory-based aspects of cognitive performance, mental task load, and leads to a negative mood state. Mild hypohydration did not exacerbate the effects of hyperthermia. However, obese individuals had increased mental task load during hyperthermia.

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Effect of hypohydration on thermoregulatory responses in men with low and high body fat exercising in the heat

Cited by 14 publications

References 45 publications

Hydration Status and Cardiovascular Function

Hydration Status and Cardiovascular Function

The impact of body fat on thermoregulation during exercise in the heat: A systematic review and meta-analysis

Obesity, but not hypohydration, mediates changes in mental task load during passive heating in females

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