Key result
Heat acclimation is linked to lower heart rate and increased sympathetic tone during exercise.
Why the study?
The study aimed to investigate changes in sympatho-vagal balance during heat acclimation in healthy individuals.
Does a 10-day heat acclimation procedure alter sympatho-vagal balance in healthy individuals?
Observational (n=8)
Does a 10-day heat acclimation procedure alter sympatho-vagal balance in healthy individuals?
Heat acclimation leads to a decrease in heart rate but an increase in sympathetic tone, suggesting peripheral factors play a major role in cardiac adaptation.
Hypothesis-generating for autonomic shifts during heat acclimation in healthy subjects; leaves open relevance to patients with cardiovascular disease.
We studied the sympatho-vagal balance during acclimation to heat in eight healthy individuals. The subjects, dressed in shorts and tennis shoes, underwent a 10 d procedure of acclimation. Daily exposure lasted 115 min--5 min rest followed by 2 bouts of 50 min exercise (walking on a treadmill at a work load of approximately 350 watt) separated by 10 min rest-at 40 degrees C and 40% relative humidity. We analyzed the time and frequency domains of 256 R-R intervals, toward the end of the second bout of exercise, on the first and tenth days of acclimation. Typical changes for heat acclimation (a reduction in rectal temperature and heart rate, an increase in sweat rate) were observed. Concomitant to a decrease in the final heart rate on the tenth day, sympathetic tone increased. We suggest that, except for the chronotropic response, changes in the sympatho-vagal balance may reflect several adaptive mechanisms of the cardiovascular system. Peripheral factors rather than intrinsic cardiac factors are of relatively greater importance in the direct control of cardiac function.
No takes yet. Share an insight, caveat, or question.
Belokopytov et al. (2001) conducted an observational in Healthy (n=8). Heat acclimation vs. First day of acclimation was evaluated on Sympatho-vagal balance (time and frequency domains of R-R intervals). Heat acclimation over 10 days in 8 healthy individuals reduced final heart rate and increased sympathetic tone, suggesting peripheral factors are important in direct control of cardiac function.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: