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Prescribing exercise at varied levels of intensity and frequency: a randomized trial
Duncan GE, Anton SD, Sydeman SJ, Newton RLJ, Corsica JA, Durning PE, Ketterson TU, Martin AD, Limacher MC, Perri MG
Archives of Internal Medicine 2005 Nov 14;165(20):2362-2369
clinical trial
5/10 [Eligibility criteria: Yes; Random allocation: Yes; Concealed allocation: No; Baseline comparability: Yes; Blind subjects: No; Blind therapists: No; Blind assessors: No; Adequate follow-up: No; Intention-to-treat analysis: Yes; Between-group comparisons: Yes; Point estimates and variability: Yes. Note: Eligibility criteria item does not contribute to total score] *This score has been confirmed*

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 < 0.01 for all), but only the HardI-HiF condition showed significant improvements in HDL-C level (p < 0.03), total cholesterol-HDL-C ratio (p < 0.04), and maximum oxygen consumption (p < 0.01) 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 < 0.01 for all), but no significant effects on HDL-C level (p = 0.57) or total cholesterol-HDL-C ratio (p = 0.64) 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.

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