Effects of Cold Water Immersion and Active Recovery on Post Exercise Heart Rate Variability

The aim of the present study was to investigate the potential benefits of cold water immersion (CWI) and active recovery (AR) on blood lactate concentration ([Lac]) and heart rate variability (HRV) indices following high-intensity exercise. Twenty male subjects were recruited. On the first visit, an incremental test was performed to determine maximal oxygen consumption and the associated speed (MAS). The remaining three visits for the performance of constant velocity exhaustive tests at MAS and different recovery methods (6 min) were separated by seven-day intervals [randomized: CWI, AR or passive recovery (PR)]. The CWI and AR lowered [Lac] (p<0.05) at 11, 13 and 15 minutes after exercise cessation in comparison to PR. There was a ‘time’ and ‘recovery mode’ interaction for two HRV indices: Standard deviation of normal R-R intervals (SDNN) (partial eta squared=0.114) and natural log of low-frequency power density (lnLF) (partial eta squared=0.090). For SDNN, CWI was significantly higher compared to PR at 15 min of recovery (p<0.05). In addition, we also found greater SDNN values in CWI vs AR following recovery , 30 and 75 minutes post-exercise (p<0.05 for all).The lnLF during the recovery and 75 min post-exercise was greater using CWI compared with AR (p < 0.05). For square root of the mean of the sum of the squares of differences between adjacent R-R intervals (RMSSD) and natural log of high-frequency power density (lnHF), a moderate effect size favoring CWI in comparison to PR was detected during technique as well as at T15. Our findings show that AR and CWI offer benefits regarding the removal of [Lac] following high-intensity exercise. While limited, CWI results in some improvement in post-exercise cardiac autonomic regulation compared to AR and PR. Further, AR is not recommended if the aim is to accelerate the parasympathetic reactivation.