Seven consecutive days of hot water heat acclimation did not significantly modulate the decrease in SDNN (-52.2 ms vs -54.1 ms) or other heart rate variability indices during passive heat exposure.
Does 7 days of hot water heat acclimation modulate the change in heart rate variability during passive heat exposure in healthy adults?
Seven consecutive days of hot water heat acclimation does not alter the modulation of cardiac autonomic activity, as measured by heart rate variability, during passive heat exposure in healthy adults.
Absolute Event Rate: -52.2% vs -54.1%
p-value: p=0.85
We examined if the change in heart rate variability during passive heat exposure is modified by hot water heat acclimation (HA). Sixteen healthy adults (28 ± 5 years, 5 females/11 males) underwent heat exposure in a water-perfused suit, before and after 7 days of HA (60 min at rectal temperature ≥38.6 °C). During passive heat exposure, heart rate, the standard deviation of NN intervals (SDNN), the square root of the mean squared differences of successive NN intervals (RMSSD), and the power in the high-frequency range (HF) were measured. No difference in heart rate (P = 0.22), SDNN (P = 0.87), RMSSD (P = 0.79), and HF (P = 0.23) was observed at baseline. The increase in HR (pre-HA, 43 ± 10; post-HA, 42 ± 9 bpm; P = 0.57) and the decrease of SDNN (pre-HA, −54.1 ± 41.0; post-HA, −52.2 ± 36.8 ms; P = 0.85), RMSSD (pre-HA, −70.8 ± 49.5; post-HA, −72.7 ± 50.4 ms; P = 0.91) and HF (pre-HA, −28.0% ± 14.5; post-HA, −23.2% ± 17.1%; P = 0.27) were not different between experimental visits at fixed increases in esophageal temperature. These results suggest that 7 consecutive days of hot water HA does not modify the change in heart rate variability indices during passive heat exposure. Novelty: It remains unclear if HA alters the change in heart rate variability that occurs during passive heat exposure. At matched levels of thermal strain, 7 consecutive days of hot water immersion did not modulate the change in indices of heart rate variability during passive heat exposure.
Gendron et al. (Thu,) conducted a other in Healthy (n=16). Hot water heat acclimation vs. Pre-acclimation (baseline) was evaluated on Decrease in SDNN during passive heat exposure at fixed increases in esophageal temperature (p=0.85). Seven consecutive days of hot water heat acclimation did not significantly modulate the decrease in SDNN (-52.2 ms vs -54.1 ms) or other heart rate variability indices during passive heat exposure.