Water Intake Accelerates Parasympathetic Reactivation After High-Intensity Exercise

It has been shown that water intake (WI) improves postexercise parasympathetic recovery after moderate-intensity exercise session. However, the potential cardiovascular benefit promoted by WI has not been investigated after high-intensity exercise. Purpose: To assess the effects of WI on post high-intensity parasympathetic recovery. Methods: Twelve recreationally active young men participated in the study (22 +/- 1.4 years, 24.1 +/- 1.6 kg.m(-2)). The experimental protocol consisted of two visits to the laboratory. Each visit consisted in the completion of a 30-min high-intensity [similar to 80% of maximal heart rate (HR)] cycle ergometer aerobic session performing randomly the WI or control (CON, no water consumption) intervention at the end of the exercise. HR and RR intervals (RRi) were continuously recorded by a heart rate monitor before, during and after the exercise. Differences in HR recovery [e.g., absolute heart rate decrement after 1 min of recovery (HRR60s) and time-constant of the first order exponential fitting curve of the HRR (HRR tau)] and in postexercise vagal-related heart rate variability (HRV) indexes (rMSSD(3os), rMSSD, pNN50, SD1 and HF) were calculated and compared for WI and CON. Results: A similar HR recovery and an increased postexercise HRV [SDI = 9.4 +/- 5.9 vs. 6.0 +/- 3.9 millisecond, HF(ln) = 3.6 +/- 1.4 vs. 2.4 +/- 1.3 millisecond(2), for WI and CON, respectively; p < .05] was observed in WI compared with CON. Conclusion: The results suggest that WI accelerates the postexercise parasympathetic reactivation after high-intensity exercise. Such outcome reveals an important cardioprotective effect of WI.