Responses to Moderate and Low Sodium Diets during Exercise-Heat Acclimation

1993 ◽  
Vol 3 (2) ◽  
pp. 207-221 ◽  
Author(s):  
Lawrence E. Armstrong ◽  
Roger W. Hubbard ◽  
E. Wayne Askew ◽  
Jane P. De Luca ◽  
Catherine O'Brien ◽  
...  
Keyword(s):  
Heart Rate ◽  
Plasma Volume ◽  
Rectal Temperature ◽  
Prolonged Exercise ◽  
Heat Acclimation ◽  
Treadmill Walking ◽  
Heat Illness ◽  
Low Sodium ◽  
Physiologic Function ◽  
Physiologic Responses

This investigation examined whether low sodium (Na+) (LNA; 68 mEq Na+·d-1) or moderate Na+(MNA; 137 mEq Na+.d-1) intake allowed humans to maintain health, exercise, and physiologic function during 10 days of prolonged exercise-heat acclimation (HA). Seventeen volunteers, ages 19 to 21, consumed either LNA (n=8) or MNA (n=9) during HA (41°C, 21% RH; treadmill walking for 30 min.h-1, 8 h·d-1at 5.6 kmh-l, 5% grade), which resulted in significantly reduced heart rate, rectal temperature, and urine Na+for both groups. There were few between-diet differences in any variables measured. Mean plasma volume in LNA expanded significantly less than in MNA by Days 11 and 15, but reached the MNA level on Day 17 (+12.3 vs. +12.4%). The absence of heat illness, the presence of normal physiologic responses, and the total distance walked indicated successful and similar HA with both levels of dietary Na+.

Heat acclimation in cystic fibrosis

1984 ◽  
Vol 57 (2) ◽  
pp. 408-412 ◽  
Author(s):  
D. M. Orenstein ◽  
K. G. Henke ◽  
C. G. Green
Keyword(s):  
Cystic Fibrosis ◽  
Rectal Temperature ◽  
Heat Acclimation ◽  
Heat Illness ◽  
Cycle Exercise ◽  
Control Temperature ◽  
Control Subjects ◽  
Sweat Chloride ◽  
Before And After ◽  
Normal Controls

Cystic fibrosis (CF) patients may be at risk for heat illness because of their high sweat chloride and sodium concentrations ([Cl-], [Na+]), but it is not known if they can heat acclimate. We studied 10 CF patients and 10 normal controls on 8 consecutive days of cycle exercise in the heat (37 degrees C dry bulb, 24–29 degrees C wet bulb). Both groups acclimated. CF peak rectal temperature (Tre) was 38.2 +/- 0.3 degrees C on day 1 and 37.8 +/- 0.4 degrees C on day 8 (P less than .005), and peak heart rates (HR) were 151 +/- 24 beats/min on day 1 and 136 +/- 22 beats/min on day 8 (P less than 0.025). Control temperature (T) and HR were similar. Controls decreased sweat [Cl-] from 37.2 +/- 14.6 meq/l on day 1 and to 24.9 +/- 10.6 meq/l on day 8 (P less than 0.005). CF sweat [Cl-] was significantly higher and did not change with acclimation (day 1, 71.1 +/- 20.9 meq/l; day 8, 72.6 +/- 21.6 meq/l, NS). Before and after acclimation, exercise-heat sessions resulted in significant decreases in serum [Cl-] in CF patients (104.5 +/- 4.6 to 101.3 +/- 4.4 meq/l on day 1, P less than 0.05; 103.5 +/- 5.1 to 99.7 +/- 4.2 meq/l on day 8, P less than 0.025) but not in controls. Serum [Cl-] was significantly lower in CF than control subjects at every measurement. Both groups had significant renal Na+ conservation after exercise on both days.(ABSTRACT TRUNCATED AT 250 WORDS)

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

2014 ◽  
Vol 115 (4) ◽  
pp. 785-794 ◽  
Author(s):  
Jamie Stanley ◽  
Aaron Halliday ◽  
Shaun D’Auria ◽  
Martin Buchheit ◽  
Anthony S. Leicht
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Plasma Volume ◽  
Heat Acclimation

Fluid replacement and glucose infusion during exercise prevent cardiovascular drift

1991 ◽  
Vol 71 (3) ◽  
pp. 871-877 ◽  
Author(s):  
M. T. Hamilton ◽  
J. Gonzalez-Alonso ◽  
S. J. Montain ◽  
E. F. Coyle
Keyword(s):  
Heart Rate ◽  
Body Weight ◽  
Cardiac Output ◽  
Rectal Temperature ◽  
Prolonged Exercise ◽  
Blood Glucose Concentration ◽  
Fluid Replacement ◽  
O2 Uptake ◽  
Trained Subjects ◽  
Cardiovascular Drift

This study examined the influence of both hydration and blood glucose concentration on cardiovascular drift during exercise. We first determined if the prevention of dehydration during exercise by full fluid replacement prevents the decline in stroke volume (SV) and cardiac output (CO) during prolonged exercise. On two occasions, 10 endurance-trained subjects cycled an ergometer in a 22 degrees C room for 2 h, beginning at 70 +/- 1% maximal O2 uptake (VO2max) and in a euhydrated state. During one trial, no fluid (NF) replacement was provided and the subject's body weight declined 2.09 +/- 0.19 kg or 2.9%. During the fluid replacement trial (FR), water was ingested at a rate that prevented body weight from declining after 2 h of exercise (i.e., 2.34 +/- 0.17 1/2 h). SV declined 15% and CO declined 7% during the 20- to 120-min period of the NF trial while heart rate (HR) increased 10% and O2 uptake (VO2) increased 6% (all P less than 0.05). In contrast, SV was maintained during the 20- to 120-min period of FR while HR increased 5% and thus CO actually increased 7% (all P less than 0.05). Rectal temperature, SV, and HR were similar during the 1st h of exercise during NF and FR. However, after 2 h of exercise, rectal temperature was 0.6 degree C higher (P less than 0.05) and SV and CO were 11–16% lower (P less than 0.05) during NF compared with FR.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Post-exercise hot water immersion elicites heat acclimation responses in endurance and recreational athletes. A systematic review and meta-analysis

2020 ◽  
Vol 13 (2) ◽  
Author(s):  
Jack Paul Martin
Keyword(s):  
Heart Rate ◽  
Rectal Temperature ◽  
Meta Analysis ◽  
Water Immersion ◽  
Heat Acclimation ◽  
Hot Water ◽  
Design Studies ◽  
Post Exercise ◽  
Study Results ◽  
Hot Water Immersion

Aims  This meta-analysis aims to evaluate the effectiveness of heat acclimation (HA) via hot water immersion protocols and their effect on time trial (TT) performance, heart rate (HRE, HRM and HRTT), rectal temperature (Tre), Rate of perceived exertion (RPE), psychological stress index (PhSI), thermal comfort (Tcomf), thermal sensation (Tsen) and maximum oxygen uptake (Vo2max).  Methods  Pubmed, Scopus, Sportdiscus and Web of Science databases were used alongside the grey matter sites Google Scholar and Researchgate. The databases were then searched for randomised control trials and mixed-method design studies. Two RTCs, six repeated measure design studies and one randomised crossover design study were included after screening a total of 50 titles and 28 full-text articles. Sample sizes range from 1 - 13 with all participants having not participated in any form of heat training 6 months before their inclusion in the study.  Results  The mean difference (MD) for Heart rate (HR) was -9.1125 BPM (95% CI p = 0.026) and was considered to be statistically significant. The MD for Rectal temperature (Tre) effect size was -0.3814 Tre (°C) (95% CI; p = 0.05). The MD for sweat rate was 0.085; (96% CI; p = 0.0179) The changes in RPE, PhSI, Tcomf and Tsen were too small to be considered statistically significant. There was no significant difference between pre and post HA for Vo2max and PV.  This meta-analysis implies that HA via HWI may improve tolerance to discomfort during heat exposure and thus subsequently improve physical performance during exercise in hot conditions. Conclusion  The primary finding of this meta-analysis is that athletic performance is improved with post-exercise hot water immersion heat acclimation training.  HWI HA protocols should focus on the following guidelines:  40-50 minutes of submaximal exercise (>65% of Vo2max) should be followed directly (within 10 minutes) by 40 minutes of hot water immersion at 40°C with the individual immersed up to their neck.  The HA protocol should last between 6-9 days with a single bout of HWI every day for this period. 

A Comparison of Three Fluid Replacement Strategies for Maintaining Euhydration During Prolonged Exercise

1997 ◽  
Vol 22 (1) ◽  
pp. 48-57 ◽  
Author(s):  
Jan M. Schroeder ◽  
Kris L. Heck ◽  
Jeffrey A. Potteiger
Keyword(s):  
Heart Rate ◽  
Plasma Volume ◽  
Prolonged Exercise ◽  
Fluid Intake ◽  
Fluid Replacement ◽  
Water Delivery ◽  
Total Water ◽  
Significant Difference ◽  
Ad Libitum ◽  
Total Water Intake

The effectiveness of a new water delivery system (the Water-Del) was examined for maintaining euhydration compared to other fluid replacement strategies. Subjects (N = 10) performed three 60-min cycling trials (@ 50% of VO2max) in an environmental chamber (27 °C; RH = 50%). Trials were randomly assigned from Water-Del (metered: 200 ml water every 15 min), ad libitum every 15 min (ad-lib-15), and ad libitum (ad-lib). Total water intake (TWI), changes in plasma volume (ΔPV), body Weight (ΔBW), thirst, skin temperature (Tsk), and heart rate (HR) were measured. A significant difference (p ≤.05) among trials was observed for TWI, with metered (1.200 ± 0.12 ml) being greater than ad-lib-15 (358 ± 48 ml) and ad-lib (522 ± 106 ml). No significant difference was found for ΔPV. A significant difference (p ≤.05) for ΔHW was observed with metered (0.28 ± 0.16 kg) being different than ad-lib-l5 (−0.63 ± 0.12 kg) and ad-lib (−0.34 ± 0.14 kg). No significant differences (p > .05) were found for thirst, Tsk, or HR. The Water-Del provides for greater fluid intake during exercise compared to other replacement strategies. Key words: hydration, dehydration, plasma volume

Heat Strain in Protective Clothing Following Hot-Wet or Hot-Dry Heat Acclimation

1996 ◽  
Vol 21 (2) ◽  
pp. 90-108 ◽  
Author(s):  
Tom M. McLellan ◽  
Yukitoshi Aoyagi
Keyword(s):  
Heart Rate ◽  
Skin Temperature ◽  
Rectal Temperature ◽  
Protective Clothing ◽  
Intermittent Exercise ◽  
Sweat Rate ◽  
Heat Acclimation ◽  
Heat Strain ◽  
Mean Skin Temperature ◽  
Time Required

The purpose of the present study was to compare the heat strain while wearing nuclear, biological, and chemical (NBC) protective clothing following a hot-wet (HW) or hot-dry (HD) heat acclimation protocol. Twenty-two males were assigned to groups HW (n = 7), HD (n = 8), or control (C, n = 7). Subjects were evaluated during continuous treadmill walking while wearing lightweight combat clothing and during intermittent exercise while wearing the NBC protective clothing. While wearing Combat clothing, greater decreases in rectal temperature (Tre), mean skin temperature [Formula: see text], and heart rate were observed for both acclimation groups. For the NBC clothing trials, lower Tre, [Formula: see text], and heart rates were observed only for group HW. The time required for Tre to increase 1.0 °C and 1.5 °C was significantly delayed for groups HW and HD. Sweat evaporation increased for HW, whereas no change was found for HD. The most significant changes in Tre, [Formula: see text], and heart rate while wearing the NBC protective clothing occur following heat acclimation that involves wearing the clothing during exercise. Key words: rectal temperature, mean skin temperature, heart rate, sweat rate

scholarly journals Provision of instructions to drink ad libitum or according to thirst sensation: impact during 120 km of cycling in the heat in men

2021 ◽  
Author(s):  
Pascale Claveau ◽  
Thomas A. Deshayes ◽  
David Jeker ◽  
Timothée Pancrate ◽  
Eric D.B. Goulet
Keyword(s):  
Heart Rate ◽  
Rectal Temperature ◽  
Fluid Balance ◽  
Perceived Exertion ◽  
Prolonged Exercise ◽  
The Body ◽  
Drinking Patterns ◽  
Fluid Ingestion ◽  
Ad Libitum ◽  
The Difference

The terms drinking to thirst and ad libitum drinking are used interchangeably, but should they? We investigated the differences in how athletes consume fluids during exercise when instructed to drink according to thirst or ad libitum. Using a randomized, crossover and counterbalanced design, 10 males (27 ± 4 y) cycled 120 km (48 ± 4% of peak power, 33°C, 40% relative humidity) on two occasions, while drinking water according to thirst or ad libitum. Participants covered the cycling trials in 222 ± 11 min (p = 0.29). Although the body mass loss at the end of exercise and total volume of water consumed were similar between trials, thirst perception before each sip and the volume consumed per sip were significantly higher with thirst than ad libitum drinking, whereas the total number of sips was significantly lower with thirst than ad libitum drinking. Perceived exertion, rectal temperature and heart rate were all significantly higher with thirst than ad libitum drinking, but the difference was trivial. In conclusion, thirst and ad libitum drinking are associated with different drinking patterns, but equally maintain fluid balance during prolonged exercise. The terms drinking to thirst and ad libitum drinking can be used interchangeably for guiding fluid intake during prolonged exercise. NOVELTY • Both strategies are associated with different patterns of fluid ingestion during prolonged exercise, but are equally effective in maintaining fluid balance; • Perceived exertion, rectal temperature and heart rate are regulated dissimilarly by thirst and ad libitum drinking, but the difference is trivial.

Orthostatism and heat acclimation

1975 ◽  
Vol 39 (4) ◽  
pp. 590-595 ◽  
Author(s):  
E. Shvartz ◽  
N. B. Strydom ◽  
H. Kotze
Keyword(s):  
Heart Rate ◽  
Rectal Temperature ◽  
Sweat Rate ◽  
Heat Acclimation ◽  
Exercise Heart Rate ◽  
Post Exposure ◽  
Group A ◽  
Head Up Tilt ◽  
Group B

Three groups of subjects (6 subj in each group) underwent the following precedures: group A was given a 20-min head-up tilt at 21 degrees C followed by 4 h of exercise at 33.9 degrees C DB, 32.2 degrees C WB, and a repetition of tilting after exercise in heat; group B underwent the same procedure at 21 degrees C; group C was tilted at 21 degrees C, rested in heat for 4 h and was retilted in heat. The above procedures were repeated for 8 days, and on the last day groups B and C underwent the same treatment as group A. Group A showed the usual decreases in heart rate and rectal temperature and an increase in sweat rate on acclimation. This corresponded to marked improvements in heat-orthostatism. While five subjects in group A fainted during post-exposure tilting on the first exposure, none fainted on the last day. Resting in heat (group C) did not cause any acclimation to work in heat. This corresponded to poor heat-orthostatism after the work-heat procedure when five subjects fainted. Mild training at 21 degrees C (group B) resulted in minor improvements to work in heat as evident by some improvements in heart rate responses after the 1st and 2nd h of exposure. This corresponded to better heat-orthostatism and fewer men fainting than in group C. The results indicated that heat-orthostatism improves on acclimation to the same extent as exercise heart rate and rectal temperature.

scholarly journals Does Dehydration Affect the Adaptations of Plasma Volume, Heart Rate, Internal Body Temperature, and Sweat Rate During the Induction Phase of Heat Acclimation?

2020 ◽  
Vol 29 (6) ◽  
pp. 847-850
Author(s):  
Yasuki Sekiguchi ◽  
Erica M. Filep ◽  
Courteney L. Benjamin ◽  
Douglas J. Casa ◽  
Lindsay J. DiStefano
Keyword(s):  
Heart Rate ◽  
Body Temperature ◽  
Skin Temperature ◽  
Plasma Volume ◽  
Sweat Rate ◽  
Physiological Responses ◽  
Heat Acclimation ◽  
Hydration Status ◽  
Induction Phase ◽  
Internal Body

Clinical Scenario: Exercise in the heat can lead to performance decrements and increase the risk of heat illness. Heat acclimation refers to the systematic and gradual increase in exercise in a controlled, laboratory environment. Increased duration and intensity of exercise in the heat positively affects physiological responses, such as higher sweat rate, plasma volume expansion, decreased heart rate, and lower internal body temperature. Many heat acclimation studies have examined the hydration status of the subjects exercising in the heat. Some of the physiological responses that are desired to elicit heat acclimation (ie, higher heart rate and internal body temperature) are exacerbated in a dehydrated state. Thus, euhydration (optimal hydration) and dehydration trials during heat acclimation induction have been conducted to determine if there are additional benefits to dehydrated exercise trials on physiological adaptations. However, there is still much debate over hydration status and its effect on heat acclimation. Clinical Question: Does dehydration affect the adaptations of plasma volume, heart rate, internal body temperature, skin temperature, and sweat rate during the induction phase of heat acclimation? Summary of Findings: There were no observed differences in plasma volume, internal body temperature, and skin temperature following heat acclimation in this critically appraised topic. One study found an increase in sweat rate and another study indicated greater changes in heart rate following heat acclimation with dehydration. Aside from these findings, all 4 trials did not observe statistically significant differences in euhydrated and dehydrated heat acclimation trials. Clinical Bottom Line: There is minimal evidence to suggest that hydration status affects heat acclimation induction. In the studies that met the inclusion criteria, there were no differences in plasma volume concentrations, internal body temperature, and skin temperature. Strength of Recommendation: Based on the Oxford Centre for Evidence-Based Medicine Scale, Level 2 evidence exists.

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