Prescribing exercise at varied levels of intensity and frequency: a randomized trial.
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.
Duncan
Glen E
GE
Department of Epidemiology, Nutritional Sciences Program, University of Washington, Seattle, USA.
Anton
Stephen D
SD
Sydeman
Sumner J
SJ
Newton
Robert L
RL
Corsica
Joyce A
JA
Durning
Patricia E
PE
Ketterson
Timothy U
TU
Martin
A Daniel
AD
Limacher
Marian C
MC
Perri
Michael G
MG
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
D002784:Cholesterol