EFFECTS OF ACUTE EXERCISE ON RESTING HEART RATE VARIABILITY

Abstract

PURPOSE Chronic exercise training has been shown to have a positive influence on cardiac autonomic function as assessed by frequency domain measures of heart rate variability (HRV). Recent evidence indicates that several of the benefits associated with exercise training (e.g. improved insulin sensitivity, reduced blood pressure) may be realized transiently as a result of a single bout of exercise. As many of these effects of recent exercise are linked to cardiovascular control systems, the purpose of this investigation was to test the hypothesis that a single bout of exercise would result in favorable changes in HRV. METHODS Subjects were 11 healthy males ages 18–34 yr. Resting HRV measures were obtained during 5 minutes of paced, supine breathing at baseline and 1,3,6 and 22 hours after a 60-minute bout of cycling at 65% of maximal oxygen uptake. Subjects served as their own controls in a randomized crossover design. RESULTS Acute exercise resulted in increased high-frequency HRV (HFNU), decreased low-frequency HRV (LFNU), and consequently a decrease in the ratio of low-frequency to high-frequency HRV (LF:HF). An overall measure of HRV (pnn50) was significantly higher in the exercise condition as compared to control. CONCLUSION The changes in HRV observed in the present study are similar to those seen in investigations of long-term training. These changes indicate a shift in autonomic function toward increased parasympathetic nervous system activity and decreased sympathetic nervous system activity, suggesting a more stable autonomic environment for the heart. These results provide further evidence of the cardio-protective effects of a single bout of exercise.Table: No Caption AvailablePercent change between exercise and control conditions at 4 timepoints following one hour of exercise or rest (control) in 4 frequency domain measures of HRV.* = p < 0.10, ** = p < 0.05 This study was funded in part by a grant from LifeFitness.