Antti Kiviniemi | PubMed Health

PubMed2004

Heart rate dynamics after controlled training followed by a home-based exercise program.

Daily aerobic training results in autonomic control of the heart toward vagal dominance. The constancy of vagal dominance after controlled training followed by a home-based training program in accordance with contemporary guidelines is not known. We set out here to study whether the vagal dominance induced by 8 weeks of controlled aerobic training is preserved after a 10-month home-based training program. For the controlled study, healthy men were randomized as training (n=18) and control subjects (n=6). The training was started by a supervised 8-week period with six training sessions a week [45 (15) min each] at an intensity of 70-80% of maximum heart rate, followed by a home-based training program for 10 months in accordance with the American College of Sports Medicine recommendations. Cardiovascular autonomic function was assessed by analyzing HR variability over a 24-h period and separately during the night hours (midnight-6 a.m.). Maximal running performance improved during the controlled training 16 (7)% (range 4-31%, P<0.001) and remained 8 (8)% (range -3 to 23%, P<0.001) above the baseline level after the home-based training program. At night, the vagally mediated high-frequency (HF) power of R-R intervals increased during the controlled training from 6.7 (1.3) to 7.3 (1.1) ln ms2 ( P<0.001) and remained higher than the baseline after the home-based training [7.0 (1.3) ln ms2, P<0.05]. The changes in running performance correlated with the changes in HF power at night (r=0.41, P<0.05) and over 24 h (r=0.44, P<0.05) after the home-based training program. Similarly, the changes in body mass index correlated with the changes in HF power over 24 h (r=-0.44, P<0.05) after the home-based training program. The high vagal outflow to the heart after the home-based training is associated with good physical performance and body mass control.

Adaptation, Physiological↗

PubMed2003

Cardiovascular autonomic function correlates with the response to aerobic training in healthy sedentary subjects.

Individual responses to aerobic training vary from almost none to a 40% increase in aerobic fitness in sedentary subjects. The reasons for these differences in the training response are not well known. We hypothesized that baseline cardiovascular autonomic function may influence the training response. The study population included sedentary male subjects (n = 39, 35 +/- 9 yr). The training period was 8 wk, including 6 sessions/wk at an intensity of 70-80% of the maximum heart rate for 30-60 min/session. Cardiovascular autonomic function was assessed by measuring the power spectral indexes of heart rate variability from 24-h R-R interval recordings before the training period. Mean peak O2 uptake increased by 11 +/- 5% during the training period (range 2-19%). The training response correlated with age (r = -0.39, P = 0.007) and with the values of the high-frequency (HF) spectral component of R-R intervals (HF power) analyzed over the 24-h recording (r = 0.46, P = 0.002) or separately during the daytime hours (r = 0.35, P = 0.028) and most strongly during the nighttime hours (r = 0.52, P = 0.001). After adjustment for age, HF power was still associated with the training response (e.g., P = 0.001 analyzed during nighttime hours). These data show that cardiovascular autonomic function is an important determinant of the response to aerobic training among sedentary men. High vagal activity at baseline is associated with the improvement in aerobic power caused by aerobic exercise training in healthy sedentary subjects.

Adult↗