Issn Print: 0195-9131
Publication Date: 2001/05/01
IMPACT OF EXERCISE TRAINING ON MYOCARDIAL OXYGEN SUPPLY/DEMAND RELATIONSHIP AND SYMPATHO-VAGAL ACTIVITY IN OBESE MIDDLE-AGED INDIVIDUALS
M Amano; H Ue; T Moritani
+ Author Information
Author Information: Laboratory of Applied Physiology, Graduate School of Human and Environmental Studies, Kyoto University, Japan
Excerpt
The purpose of this study was to investigate the effects of exercise training on myocardial oxygen supply/demand relationship and cardiac sympatho-vagal activities in 10 (male = 5, female = 5) obese middle-aged individuals (age: 42.5 ± 1.7 yr, BMI: 28.2 ± 0.4 kg/m2, %fat: 31.8 ± 1.7%, mean ± SE). Each subject performed an aerobic exercise training on an electronically controlled cycle ergometer consisting of 30 min/session (5-min warming up, 20-min anaerobic threshold (AT) work and 5-min cooling down), 3 times/wk for 12 consecutive weeks. Measurements were made before and after training for a beat-by-beat measurement of systolic and diastolic blood pressures and cardiac sympatho-vagal activities (R-R interval power spectral analysis) at rest. Potential subendcardial blood flow and myocardial oxygen requirement were estimated by the diastolic pressure time index (DPTI) and tension time index (TTI), respectively. The ratio DPTI/TTI thus, provided an estimate of myocardial oxygen supply/demand relationship. Results indicated that there were significant improvements in DPTI/TTI ratio (1.23 ± 0.07 vs. 1.30 ± 0.06, P < 0.05), low frequency component associated with the sympatho-vagal activity (0.03–0.15 Hz, 402.9 ± 111.0 vs. 800.0 ± 142.7 ms2, P < 0.01), high frequency vagal component (0.15–0.4 Hz, 127.8 ± 38.9 vs. 381.9 ± 159.4 ms2, P < 0.05), and over-all autonomic activity as evaluated by total power (0.03–0.4 Hz, 530.8 ± 138.0 vs. 1181.6 ± 296.7 ms2, P < 0.01) after the training. There was also a significant reduction in fat mass (P < 0.01) without losing lean body mass (P > 0.05) in addition to the improvement of AT VO2 (P < 0.01). These results suggest that 12 wk of exercise training has significantly improved the balance of myocardial oxygen supply/demand and sympatho-vagal activities which in turn might contribute for reducing myocardial stress in obese middle-aged individuals.
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