Effect of hydration state of circulatory and thermal regulations

Nadel, E. R.; Fortney, S. M.; Wenger, C. B.

doi:10.1152/jappl.1980.49.4.715

Cited by 305 publications

(177 citation statements)

References 26 publications

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“…Heatand-exercise induced hypohydration manifests itself as hyperosmotic hypovolaemia (Nadel et al 1980), which impairs cutaneous blood flow and sweat rate, and raises heart rate, core temperature, glycogenolysis, perceived exertion and permeability of tight-membranes (Mack and Nadel 1996;Gonzalez-Alonso et al 1998;Gonzalez-Alonso et al 1999;Blatteis 2000;Gonzalez-Alonso and Calbert 2003;Maughan 2003;Watson et al 2005). The consequence is impaired exercise tolerance and performance in temperate conditions which has previously been debated (Sawka and Noakes 2007).…”

Section: Introductionmentioning

confidence: 99%

Induction and decay of short-term heat acclimation

et al. 2009

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Abstract:Most advice for heat adaptation is to use long-term (>10 d) regimes, in which hydration status is maintained. We tested the hypothesis that short-term (5-day) heat acclimation would confer substantial improvements in physiological strain and exercise tolerance for exercise in the heat, and fluid regulatory strain provides a thermally-independent stimulus for such adaptations. Ten moderately-fit males were heat acclimated using controlled hyperthermia (rectal temperature 38.5°C) for 90 min on five consecutive days (T a = 40°C, 60% RH), on two occasions separated by a five-week washout, in a randomly assigned, cross-over design; one with euhydration (EUH) and one with dehydration (DEH) during acclimation bouts. One week before, then on the 2 nd day after each acclimation regime, a heat stress test (HST) was completed, comprising cycling at 40% peak power output for 90 min (T a = 35°C, 60% RH), before incrementing to exhaustion. Plasma volume (PV) at rest was measured using CO rebreathing. Acclimation exercise-induced response of[aldo] p became more pronounced across DEH (  178 pg . mL -1 ; 95%CI: 33 to 324) but not EUH (  -47 pg . mL -1 : -209 to 115) and this difference was significant (P=0.02).Compared to EUH, permissive DEH during acclimation bouts conferred larger acclimation-induced increases in resting PV (4.1%: -1.5 to 9.8%; P=0.06), F Q  (4.2: 0.7 to 7.8 ml . min -1. 100 ml -1 ; P=0.009), FVC (0.06: 0.02 to 0.10 ml . 100ml Tissue -1. min -1. mmHg -1 ; P=0.006) and decreased end-exercise c f by 17% (19: -29 to 9 b·min-1; P=0.05). In conclusion, short-term (5-day) heat acclimation was effective with several adaptations more pronounced after fluid-regulatory strain from a dehydration acclimation regime.

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Section: Introductionmentioning

confidence: 99%

Induction and decay of short-term heat acclimation

et al. 2009

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“…In an upright walking man the muscle pump empties the veins during each contraction, but the arterial inflow is so high that the average venous pressure and volume are increased (10). Dehydration also reduces venous return to the heart by lowering circulating blood volume (19). In spite of the unchanged mean cardiac output in the heat, there was substantial variation in the individual cardiac output responses (figure 3).…”

Section: Circulatory Adjustmentsmentioning

confidence: 99%

Circulatory and thermal responses of men with different training status to prolonged physical work in dry and humid heat.

Smolander¹,

Ilmarinen²,

Korhonen³

et al. 1987

Scand J Work Environ Health

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(1987) 37 -46. Eight ph ysicalIy tra ined and eight untrained , una cclimated men walked on a treadmill at 30 010 of their maximum oxygen consumption up to 3.5 h in a the rmoneutral [20°C / 40 010 relative humid ity {RH) J, a warm hum id (30°C /8 0 % RH), and a hot dry (40°C I2 0 010 RH ) environment while wearing indu str ial work clothing. Their oxygen consumption, rectal and skin temperat ures, sweat ing, card iac output, hea rt rate, stroke volume, and peripheral blood pressure were measured du ring the tests . Thirteen of the 32 heat stress tests were prematurely stopped du e to high rectal temperature, high heart rate, subjective fa tigue, or heat syncope . The physiological str ain, as indicated by the rectal tempe ratur e and heart rate, was not significantl y different between th e warm humid and hot dr y environmen ts (wet bulb globe temperature -28°C). Th e rectal temp eratur e and heart rat e responses of the physicalIy train ed and untrained subjects did not diff er in any of the environments . In th e heat, the heart ra te was significa ntly higher than in the thermoneut ral environm ent , but becau se of the markedly redu ced stroke volume the average ca rdiac output was not differen t between the three environ ments. The impaired work perform an ce in the hea t seemed mainly to be related to the circulat ory instability accompanying the increased cuta neous circulation .Key terms: bod y temp erature, central circulation, heat stress indices, hot dry environment, peripheral circulati on , physical fitn ess, prol onged exercise, sweating, warm humid environment, work perform an ce.

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“…heat and humidity [Armstrong, 2000]. An increase in core temperature and parallel decrease in body fluid results in impaired cardiovascular function [Costill et al, 1976;Harrison, 1985;Nadel et al, 1980] and physical performance [Armstrong et al, 1985;Callister et al, 1991;Hickner et al, 1991;Hoffman et al, 1995].…”

Section: Introductionmentioning

confidence: 99%

Effects of acute dehydration on brain morphology in healthy humans

Kempton

Ettinger

Schmechtig

et al. 2007

Human Brain Mapping

100

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Dehydration can affect brain structure which has important implications for human health. In this study, we measured regional changes in brain structure following acute dehydration. Healthy volunteers received a structural MRI scan before and after an intensive 90-min thermal-exercise dehydration protocol. We used two techniques to determine changes in brain structure: a manual point counting technique using MEASURE, and a fully automated voxelwise analysis using SIENA. After the exercise regime, participants lost (2.2% 6 0.5%) of their body mass. Using SIENA, we detected expansion of the ventricular system with the largest change occurring in the left lateral ventricle (P 5 0.001 corrected for multiple comparisons) but no change in total brain volume (P 5 0.13). Using manual point counting, we could not detect any change in ventricular or brain volume, but there was a significant correlation between loss in body mass and third ventricular volume increase (r 5 0.79, P 5 0.03). These results show ventricular expansion occurs following acute dehydration, and suggest that automated longitudinal voxelwise analysis methods such as SIENA are more sensitive to regional changes in brain volume over time compared with a manual point counting technique. Hum Brain Mapp 30: [291][292][293][294][295][296][297][298] 2009. V V C 2007 Wiley-Liss, Inc.

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Effect of hydration state of circulatory and thermal regulations

Cited by 305 publications

References 26 publications

Induction and decay of short-term heat acclimation

Induction and decay of short-term heat acclimation

Circulatory and thermal responses of men with different training status to prolonged physical work in dry and humid heat.

Effects of acute dehydration on brain morphology in healthy humans

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