Changes in central circulation and body fluid spaces during acclimatization to heat.

Wyndham, C. H.; Benadé, A. J. S.; Williams, C. G.; Strydom, N. B.; Goldin, Alan R.; Heyns, Arne

doi:10.1152/jappl.1968.25.5.586

“…Interestingly, by the 7 th sauna exposure, PV trended back towards pre-sauna levels (unclear whether values were elevated) despite subsequent sauna exposure and remained stable for the 7 days (possible-to-likely small-to-moderate elevation above pre-sauna levels) after the final sauna exposure (Fig. 3a), supporting the observation that PV expansion regresses toward baseline levels if the exercise stimulus and/or thermal load exposures remain constant (Wyndham et al 1968). Although evidence linking PV expansion and exercise performance is not definitive (Warburton et al 2000), the transient nature of this response highlights that periodization of sauna exposure/heat acclimation within the training/competition cycle requires consideration if intended for ergogenic benefit.…”

Section: Discussionsupporting

confidence: 61%

Effect of sauna-based heat acclimation on plasma volume and heart rate variability

Stanley

¹

,

Halliday

²

,

D’Auria

³

et al. 2014

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Anthony S. (2015) Effect of sauna-based heat acclimation on plasma volumeand heart rate variability. European Journal of Applied Physiology, 115 (4). pp. immediately following normal training. Capillary blood samples were collected to assess PV changes while resting seated. HR (HR wake ) and vagal-related HR variability (natural logarithm of square-root mean squared differences of successive R−R intervals, ln rMSSD wake ) were assessed daily upon waking. A sub-maximal cycle test (5 min at 125 W) was performed on days 1, 8, 15, 22, 25, 29, and 35 and HR recovery (HRR 60s ) and ln rMSSD postex were assessed post-exercise. Effects were examined using magnitude-based inferences. Conclusions: Sauna-bathing following normal training largely expanded PV in well-trained cyclists after just 4 Resultsexposures. The utility of HR and HRV indices for tracking changes in PV was however uncertain. Future studies will clarify mechanisms and performance benefits of post-training sauna bathing.

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“…The end- T at end-exercise decreased across EUH and DEH acclimation with no difference between regimes. These physiological adaptations are characteristic features of heat acclimation (Armstrong and Maresh 1991) and reflected by greater cardiovascular stability (Wyndham et al 1968;Strydom and Williams 1969;Senay et al 1976;Sawka et al 1985). In summary, these findings indicates that after acclimation per se, the cardiovascular system is not under as much physiological strain and more so after the DEH regime.…”

Section: Adaptation To Repeated Heat Stressmentioning

confidence: 69%

Induction and decay of short-term heat acclimation

Garrett

¹

,

Goosens

²

,

Rehrer

³

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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“…Further, in the present study sk T and b T at end-exercise decreased across EUH and DEH acclimation with no difference between regimes. These physiological adaptations are characteristic features of heat acclimation (Armstrong and Maresh 1991) and reflected by greater cardiovascular stability (Wyndham et al 1968;Strydom and Williams 1969;Senay et al 1976;Sawka et al 1985). In summary, these findings indicates that after acclimation per se, the cardiovascular system is not under as much physiological strain and more so after the DEH regime.…”

Section: Adaptation To Repeated Heat Stressmentioning

confidence: 69%

The Induction and Decay of Short-Term Heat Acclimation

Garrett

¹

,

Goossens

²

,

Rehrer

³

et al. 2003

Medicine & Science in Sports & Exercise

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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 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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Changes in central circulation and body fluid spaces during acclimatization to heat.

Cited by 114 publications

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Effect of sauna-based heat acclimation on plasma volume and heart rate variability

Effect of sauna-based heat acclimation on plasma volume and heart rate variability

Induction and decay of short-term heat acclimation

The Induction and Decay of Short-Term Heat Acclimation

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