EFFECTS OF CONTRAST WATER THERAPY ON THE RECOVERY OF HEART RATE VARIABILITY FOLLOWING ECCENTRIC EXERCISE

Abstract

PURPOSE: The aim of this study was to compare the effects of hot/cold immersion therapy and passive recovery following maximal eccentric exercise of the bilateral knee extensors on heart rate variability. METHODS: 14 health college males (18-22 yrs) were recruited and randimly assigned into the contrast water therapy (CWT) or passive recovery (CON) group (n=7 per group). Each participant performed 10 sets of 10 maximal isokinetic (30°/s) eccentric contractions (MaxECC) of each knee extensors. Contrast water therapy (8°C × 1 min and 45°C × 4 minutes, 3 reps), or the passive recovery interventions (15-min consecutive rest) were taken at 30 minutes post-MaxECC. Heart rate variability (HRV) parameters were collected by the portable heart rate monitor at 5 mins before, and 0-5, 10-15 and 25-30 mins after interventions. RESULTS: During the first 5 mins after interventions, mean HR (95.4 ± 11.1 bpm) and the normalized units of high frequency power (23.6 ± 10.3 nu) of the CWT group showed significantly higher value than the CON group (81.5 ± 11.6 bpm, 18.5 ± 9.0 nu; P<0.05), the mean R-R intervals (636.8 ± 78.8 ms), the standard deviation of normal R-R intervals (26.1 ± 6.6 ms) and the square root of the mean squared differences between adjacent R-R intervals (17.2 ± 7.7 ms) for CWT showed significantly lower than that of CON (749.3 ± 105.4 ms, 46.1 ± 17.7 ms, 33.0 ± 12.8 ms; P < .05). However, 10-15 and 25-30 mins after interventions, all HRV parameters between the two groups showed no significant difference (P > .05). CONCLUSION: These findings supported the hypothesis and suggested that one session of 15 mins CWT after eccentric exercise could be increased parasympathetic-related activation in cardiac autonomic regulation, but the effect only lasting for 10 mins. Keywords: autonomic nervous system, parasympathetic activation, normalization of high-frequency power