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Prescribing Exercise at Varied Levels of Intensity and Frequency

2005; American Medical Association; Volume: 165; Issue: 20 Linguagem: Inglês

10.1001/archinte.165.20.2362

1538-3679

Glen E. Duncan,

Cardiovascular Effects of Exercise

Background Regular physical activity produces beneficial effects on health, but the exercise prescription needed to improve cardiovascular disease risk factors in free-living sedentary individuals remains unclear. Methods Sedentary adults (N = 492, 64.0% women) were randomized to 1 of 4 exercise-counseling conditions or to a physician advice comparison group. The duration (30 minutes) and type (walking) of exercise were held constant, while exercise intensity and frequency were manipulated to form 4 exercise prescriptions: moderate intensity–low frequency, moderate intensity–high frequency (HiF), hard intensity (HardI)–low frequency, and HardI-HiF. Comparison group participants received physician advice and written materials regarding recommended levels of exercise for health. Outcomes included 6- and 24-month changes in cardiorespiratory fitness (maximum oxygen consumption), high-density lipoprotein cholesterol (HDL-C) level, and the total cholesterol–HDL-C ratio. Results At 6 months, the HardI-HiF, HardI–low-frequency, and moderate-intensity–HiF conditions demonstrated significant increases in maximum oxygen consumption ( P <.01 for all), but only the HardI-HiF condition showed significant improvements in HDL-C level ( P <.03), total cholesterol–HDL-C ratio ( P <.04), and maximum oxygen consumption ( P <.01) compared with physician advice. At 24 months, the increases in maximum oxygen consumption remained significantly higher than baseline in the HardI-HiF, HardI–low-frequency, and moderate-intensity–HiF conditions and in the HardI-HiF group compared with physician advice ( P <.01 for all), but no significant effects on HDL-C level ( P = .57) or total cholesterol–HDL-C ratio ( P = .64) were observed. Conclusions Exercise counseling with a prescription for walking at either a HardI or a HiF produced significant long-term improvements in cardiorespiratory fitness. More exercise or the combination of HardI plus HiF exercise may provide additional benefits, including larger fitness changes and improved lipid profiles.