A History Of Regular Exercise And Cardiac Vagal Tone

Abstract

Less Heart Rate Variability (HRV; a measure of parasympathetic or vagal activity) is indicative of parasympathetic withdrawal (or sympathetic dominance) and has been associated with difficulties in stress regulation. This suggests HRV could be a viable measure of physiological stress reactivity and recovery. Thus, understanding the relationship between exercise behavior and HRV reactivity could be of value in understanding how exercise may improve stress reactivity and recovery for regular exercisers. PURPOSE: Explore the relationship between exercise behavior participation and vagal tone reactivity in response to exercise. METHODS: Participants’ (N=25, 13 females, 23.3±4.0 yrs) reported retrospective exercise behavior [length of participation (LOP) in primary mode of exercise], then completed a 20-min exercise interval (5-blocks of 3-min exercise to 1-min rest) at high-intensity where heart rate (HR) and rating of perceived exertion (RPE) were measured during the session. HRV (High Frequency Power) was recorded prior to and 10-min post exercise. HRV reactivity was calculated by subtracting post from pre recordings, where a greater value equals more reactivity or less recovery. RESULTS: No differences in percentage of peak HR (>1 yr: 99%; <1 yr: 96%; F(3.4, 12.5)=0.7 P=0.59) and RPE (>1-yr: 14.6; <1-yr: 13.6; F(9.0, 50.9)=1.3, P=0.28) were observed during exercise between those LOPs of > 1-year and < 1-year, suggesting everyone engaged in exercise of the same intensity, duration, and mode. While HRV reactivity was not significantly different between those exercising >1-year (1.87±0.16) versus <1-year (3.98±0.99; F(3, 16.2)=2.21, P=0.14), LOP and HRV reactivity were inversely related (HI: r = -0.56, P=0.02). CONCLUSION: Participants who had been regular exercisers for longer experienced less HRV reactivity or recovered faster than their counterparts. This suggests that continued regular exercise over time is related to an advantageous response (i.e., less vagal reactivity and faster recovery) to an exercise stressor.