Effects Of Marathon Running On Nocturnal Autonomic Modulation

Abstract

The nocturnal autonomic modulation is dominated by parasympathetic nervous system but is disturbed after a hard training period. Even though the effects of overreaching and overtraining on nocturnal autonomic modulation have been studied, no result of the effects of a single exercise session is available. PURPOSE: To study the effects of a single light and a heavy endurance exercise session on nocturnal autonomic modulation. METHODS: Nocturnal R-R intervals were collected after a rest day, after a light training day (on average 52 ± 26 min, average heart rate 133 ± 9 bpm) and after a marathon run (on average 217 ± 28 min, average heart rate 156 ± 5 bpm) in ten recreational athletes (37 ± 5 yrs, VO2max 52 ± 5 mL·kg-1·min-1). The heart rate variability (HRV) was analyzed as a continuous four-hour period starting 30 min after going to bed for the sleep. The HRV values after the rest day were set as 100% and the later values were calculated in relation to these baseline values. Comparisons between the nights were run with ANOVA for repeated measures. RESULTS: The average nocturnal heart rate (HR), standard deviation of R-R intervals (SDRRI), root-mean-square of differences between adjacent R-R intervals (RMSSD), low frequency power (LFP) and high frequency power (HFP) results are presented in Table 1.Table: HR and HRV indices from the resting value (%). Mean ± SD.CONCLUSION: Endurance exercise sessions resulted parasympathetic withdrawal and possibly enhanced sympathetic activation during the following night sleep. There seemed to be a dose - response relationship in these effects. Supported by TEKES Grant 1009/07.