title: Prescribing exercise at varied levels of intensity and frequency: a randomized trial.
abstract: 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.
authors.affiliation: Department of Epidemiology, Nutritional Sciences Program, University of Washington, Seattle, USA.
authors.forename: Glen E
authors.initials: GE
authors.lastname: Duncan
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Anton
authors.forename: Sumner J
authors.initials: SJ
authors.lastname: Sydeman
authors.forename: Robert L
authors.initials: RL
authors.lastname: Newton
authors.forename: Joyce A
authors.initials: JA
authors.lastname: Corsica
authors.forename: Patricia E
authors.initials: PE
authors.lastname: Durning
authors.forename: Timothy U
authors.initials: TU
authors.lastname: Ketterson
authors.forename: A Daniel
authors.initials: AD
authors.lastname: Martin
authors.forename: Marian C
authors.initials: MC
authors.lastname: Limacher
authors.forename: Michael G
authors.initials: MG
authors.lastname: Perri
mesh_terms: D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000097:blood / Q000503:physiopathology / Q000517:prevention & control*; D002784:Cholesterol / Q000097:blood; D015444:Exercise / Q000502:physiology; D005081:Exercise Therapy / Q000145:classification / Q000379:methods*; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D010349:Patient Compliance; D010353:Patient Education as Topic / Q000379:methods*; D010809:Physical Fitness / Q000502:physiology; D011315:Preventive Medicine / Q000379:methods*; D012307:Risk Factors
chemical_list: D002784:Cholesterol