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. 20 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 3 visits for the performance of constant velocity exhaustive tests at MAS and different recovery methods (6 min) were separated by 7-day intervals [randomized: CWI, AR or passive recovery (PR)]. The CWI and AR lowered [Lac] (p<0.05) at 11, 13 and 15 min after exercise cessation in comparison to PR. There was a 'time' and 'recovery mode' interaction for 2 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). CWI presented significantly higher SDNN compared to PR at 15 min of recovery (p<0.05). In addition, greater SDNN values were found in CWI vs. AR during the application of recovery interventions, and at 30 and 75 min post-exercise (p<0.05 for all differences). The lnLF during the recovery interventions and at 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 was found between CWI and PR during the recovery interventions and at 15 min post-exercise. 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.

The effects of physical fitness and body composition on oxygen consumption and heart rate recovery after high-intensity exercise.

The aim of this study was to investigate the potential relationship between excess post-exercise oxygen consumption (EPOC), heart rate recovery (HRR) and their respective time constants (tvo2 and t HR) and body composition and aerobic fitness (VO2max) variables after an anaerobic effort. 14 professional cyclists (age=28.4±4.8 years, height=176.0±6.7 cm, body mass=74.4±8.1 kg, VO2max=66.8±7.6 mL·kg - 1·min - 1) were recruited. Each athlete made 3 visits to the laboratory with 24 h between each visit. During the first visit, a total and segmental body composition assessment was carried out. During the second, the athletes undertook an incremental test to determine VO2max. In the final visit, EPOC (15-min) and HRR were measured after an all-out 30 s Wingate test. The results showed that EPOC is positively associated with % body fat (r=0.64), total body fat (r=0.73), fat-free mass (r=0.61) and lower limb fat-free mass (r=0.55) and negatively associated with HRR (r= - 0.53, p<0.05 for all). HRR had a significant negative correlation with total body fat and % body fat (r= - 0.62, r= - 0.56 respectively, p<0.05 for all). These findings indicate that VO2max does not influence HRR or EPOC after high-intensity exercise. Even in short-term exercise, the major metabolic disturbance due to higher muscle mass and total muscle mass may increase EPOC. However, body fat impedes HRR and delays recovery of oxygen consumption after effort in highly trained athletes.