Integrating Competing Demands of Osmoregulatory and Thermoregulatory Homeostasis

Martelli, Davide; Pennington, GL; Trevaks, David; McAllen, Robin M.

doi:10.1152/physiol.00037.2017

Cited by 32 publications

(25 citation statements)

References 103 publications

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“…Hypohydration-mediated reductions in sweating occur primarily via the inhibitory effect of increased intravascular osmolality 10,27-30 on the activity of warm-sensitive neurons in the PO/AH, 18,19 while a role may also exist for baroreceptor unloading (due to reduced circulating volume). Hypohydration-mediated reductions in sweating occur primarily via the inhibitory effect of increased intravascular osmolality 10,27-30 on the activity of warm-sensitive neurons in the PO/AH, 18,19 while a role may also exist for baroreceptor unloading (due to reduced circulating volume).…”

Section: The Impact Of Hypohydration On Heat Loss and Strain In Youmentioning

confidence: 99%

“…11 This occurs because of increased core and/or skin temperatures at the onset of sweating 12 and cutaneous vasodilation 1 along with attenuated activation of those heat loss responses with progressive elevations in body temperature. 18,19 It is therefore possible that older adults may display impaired sweat (fluid) conservation when faced with a matched reduction in body mass because of sweat loss. 15 While the independent influences of age and hydration status on thermoregulatory function are well established, the interaction of these factors has received considerably less attention.…”

Section: Introductionmentioning

confidence: 99%

“…16,17 Heat loss (sweating and cutaneous vasodilation) and thirst are both altered by increased intravascular osmolality and the control of these processes resides in the preoptic/anterior hypothalamus (PO/AH). 18,19 It is therefore possible that older adults may display impaired sweat (fluid) conservation when faced with a matched reduction in body mass because of sweat loss. Thus, ageing might also temper the impact of hypohydration on heat dissipation during exercise in the heat, since sweating is the primary mechanism providing heat loss under such conditions.…”

Section: Introductionmentioning

confidence: 99%

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Interactive effects of age and hydration state on human thermoregulatory function during exercise in hot‐dry conditions

et al. 2018

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Aim: Ageing and hypohydration independently attenuate heat dissipation during exercise; however, the interactive effects of these factors remain unclear. We assessed the hypothesis that ageing suppresses hypohydration-induced reductions in whole-body heat loss during exercise in the heat. Methods: On two occasions, eight young (mean [SD]: 24 [4] years) and eight middle-aged (59 [5] years) men performed 30-minute bouts of light (heat production of 175 W m −2 ) and moderate (275 W m −2 ) cycling (separated by 15-minute rest) in the heat (40°C, 15% relative humidity) when euhydrated and hypohydrated (~4% reduction in body mass). Heat production and whole-body net heat exchange (evaporative heat loss + dry heat gain) were measured via indirect and direct calorimetry (respectively) and heat storage was calculated via their temporal summation. Results: Net heat exchange was reduced, while heat storage was elevated, in the middle-aged men during moderate exercise when euhydrated (both P ≤ 0.01). In the young, evaporative heat loss (mean ± 95% confidence interval) was attenuated in the hypohydrated vs euhydrated condition during light (199 ± 6 vs 211 ± 10 W m −2 ; P ≤ 0.01) and moderate (287 ± 15 vs 307 ± 13 W m −2 ; P ≤ 0.01) exercise, but was similar in the middle-aged men, averaging 223 ± 6 and 299 ± 15 W m −2 , respectively, across conditions (both P ≥ 0.32). Heat storage was thereby exacerbated by hypohydration in the young (both P < 0.01), but not the middle-aged (both P ≥ 0.32) during both exercise bouts and, as a result, was similar between groups when hypohydrated (both P ≥ 0.50). Conclusion: Hypohydration attenuates heat loss via sweating in young but not middle-aged men, indicating that ageing impairs one's ability to mitigate further sweat-induced fluid loss during hypohydration.

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Section: The Impact Of Hypohydration On Heat Loss and Strain In Youmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Interactive effects of age and hydration state on human thermoregulatory function during exercise in hot‐dry conditions

et al. 2018

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“…Evaporation of sweat represents the major avenue of heat loss during exercise in the heat. However, excessive sweating can induce significant fluid loss leading to marked reductions in blood volume (BV) and elevated blood osmolality, both of which are associated with impairment of the body's ability to dissipate heat (Kenny & McGinn, ; McKinley, Martelli, Pennington, Trevaks, & McAllen, ; Shibasaki, Wilson, & Crandall, ). To minimize fluid loss, commercial sports beverages that contain a mixture of carbohydrate, such as glucose, fructose and/or maltodextrin, with electrolytes are commonly consumed by athletes, workers, servicemen and others during and following exercise.…”

Section: Introductionmentioning

confidence: 99%

“…In turn, changes in PV and P osm associated with ingestion of beverages containing carbohydrates such as isomaltulose may have a modulating effect on physiological heat loss responses thereby influencing core temperature (T co ) recovery following prolonged exercise (Kenny & McGinn, 2017;Kenny, Jay, & Journeay, 2007). This is because changes in PV and P osm can alter heat loss responses of cutaneous perfusion and sweating (Kenny & McGinn, 2017;McKinley et al, 2018;Shibasaki et al, 2006).…”

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confidence: 99%

Effects of isomaltulose ingestion on postexercise hydration state and heat loss responses in young men

Amano

Sugiyama

Okumura

et al. 2019

Experimental Physiology

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New Findings What is the central question of this study?What are the effects of isomaltulose, an ingredient in carbohydrate–electrolyte beverages to maintain glycaemia and attenuate the risk of dehydration during exercise heat stress, on postexercise rehydration and physiological heat loss responses? What is the main finding and its importance?Consumption of a 6.5% isomaltulose–electrolyte beverage following exercise heat stress restored hydration following a 2 h recovery as compared to a 2% solution or water only. While the 6.5% isomaltulose–electrolytes increased plasma volume and plasma osmolality, which are known to modulate postexercise heat loss, sweating and cutaneous vascular responses did not differ between conditions. Consequently, ingestion beverages containing 6.5% isomaltulose–electrolytes enhanced postexercise rehydration without affecting heat loss responses. Abstract Isomaltulose is a disaccharide carbohydrate widely used during exercise to maintain glycaemia and hydration. We investigated the effects of ingesting a beverage containing isomaltulose and electrolytes on postexercise hydration state and physiological heat loss responses. In a randomized, single‐blind cross‐over design, 10 young healthy men were hypohydrated by performing up to three 30 min successive moderate‐intensity (50% heart rate reserve) bouts of cycling, each separated by 10 min, while wearing a water‐perfusion suit heated to 45°C. The protocol continued until a 2% reduction in body mass was achieved. Thereafter, participants performed a final 15 min moderate‐intensity exercise bout followed by a 2 h recovery. Following cessation of exercise, participants ingested a beverage consisting of (i) water only (Water), (ii) 2% isomaltulose (CHO‐2%), or (iii) 6.5% isomaltulose (CHO‐6.5%) equal to the volume of 2% body mass loss within the first 30 min of the recovery. Changes in plasma volume (ΔPV) after fluid ingestion were greater for CHO‐6.5% compared with CHO‐2% (120 min postexercise) and Water (90 and 120 min) (all P ≤ 0.040). Plasma osmolality remained elevated with CHO‐6.5% compared with consumption of the other beverages at 30 and 90 min postexercise (all P ≤ 0.050). Urine output tended to be reduced with CHO‐6.5% compared to other fluid conditions (main effect, P = 0.069). Rectal and mean skin temperatures, chest sweat rate and cutaneous perfusion did not differ between conditions (all P > 0.05). In conclusion, compared with CHO‐2% and Water, consuming a beverage consisting of CHO‐6.5% and electrolytes during recovery under heat stress enhances PV recovery without modulating physiological heat loss responses.

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When water interacts with temperature: Ecological and evolutionary implications of thermo‐hydroregulation in terrestrial ectotherms

Rozen‐Rechels

Dupoué

Lourdais

et al. 2019

Ecology and Evolution

121

109

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The regulation of body temperature (thermoregulation) and of water balance (defined here as hydroregulation) are key processes underlying ecological and evolutionary responses to climate fluctuations in wild animal populations. In terrestrial (or semiterrestrial) ectotherms, thermoregulation and hydroregulation closely interact and combined temperature and water constraints should directly influence individual performances. Although comparative physiologists traditionally investigate jointly water and temperature regulation, the ecological and evolutionary implications of these coupled processes have so far mostly been studied independently. Here, we revisit the concept of thermo‐hydroregulation to address the functional integration of body temperature and water balance regulation in terrestrial ectotherms. We demonstrate how thermo‐hydroregulation provides a framework to investigate functional adaptations to joint environmental variation in temperature and water availability, and potential physiological and/or behavioral conflicts between thermoregulation and hydroregulation. We extend the classical cost–benefit model of thermoregulation in ectotherms to highlight the adaptive evolution of optimal thermo‐hydroregulation strategies. Critical gaps in the parameterization of this conceptual optimality model and guidelines for future empirical research are discussed. We show that studies of thermo‐hydroregulation refine our mechanistic understanding of physiological and behavioral plasticity, and of the fundamental niche of the species. This is illustrated with relevant and recent examples of space use and dispersal, resource‐based trade‐offs, and life‐history tactics in insects, amphibians, and nonavian reptiles.

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Integrating Competing Demands of Osmoregulatory and Thermoregulatory Homeostasis

Cited by 32 publications

References 103 publications

Interactive effects of age and hydration state on human thermoregulatory function during exercise in hot‐dry conditions

Interactive effects of age and hydration state on human thermoregulatory function during exercise in hot‐dry conditions

Effects of isomaltulose ingestion on postexercise hydration state and heat loss responses in young men

When water interacts with temperature: Ecological and evolutionary implications of thermo‐hydroregulation in terrestrial ectotherms

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