Long‐term endurance training in older adults preserves cardiovagal control but not heart rate responses to exercise

Abstract

Parasympathetic nervous system (PNS) activity decreases with age. Estimates of baroreflex sensitivity (BRS) suggest endurance training may preserve PNS activity in older adults. But, do these estimates reflect the physiologic heart rate responses to exercise? We hypothesized that long term endurance training (ET) in older adults (O) would result in similar levels of PNS control, when compared to young healthy controls (Y). Older ET adults (n = 14; 55 ± 4 years; 4 females) and recreationally active controls (n=12; 26 ± 4 years; 6 females) completed repeated 30‐sec bouts of isometric hand grip exercise (IHG) at 30% of maximal voluntary contraction. Baseline PNS was estimated using cardiovagal BRS (sequence method). The ability to withdraw PNS during IHG was assessed by the reduction in high frequency heart rate variability (HRVhf; wavelet‐based power spectral analysis; ln normalized) and the heart rate (HR) response. Mean BRS (Y: 28.8 ± 18.4ms/mmHg vs O: 23.3 ± 15.2ms/mmHg; P>0.05) and decreases in HRVhf from rest (Y: −0.45 ± 0.63 ms2 vs O: −0.17 ± 0.36 ms2; P>0.05) were not different between groups. However, increases in HR (Y: 7.24 ± 3.36 vs. O: 2.53 ± 1.5 bpm; P=0.0002) from rest were greater in young compared to old. These data suggest that long term ET in older adults can preserve cardiovagal control but not HR responses to a moderate intensity IHG compared to young. Supported by CIHR.