Prescribed Walking Can Improve Physical Fitness
Exercise counseling with a prescription for walking at either hard intensity or high frequency produces improvements in cardiorespiratory fitness, according to a study in the November 14 issue of the Archives of Internal Medicine, one of the JAMA/Archives journals.
The health benefits of regular physical activity have been well established. But most U.S. adults are not sufficiently active regularly, and 26 percent are not active at all, according to background information in the article. The exercise prescription needed to improve cardiovascular disease risk factors in free-living sedentary adults remains unclear.
Glen E. Duncan, Ph.D., R.C.E.P.S.M., of the University of Washington, Seattle, and colleagues conducted a randomized trial to examine the effects of exercise counseling prescriptions, varied in intensity and frequency. A total of 492 sedentary adults (177 men, 315 women) were randomized to one of four exercise counseling conditions, or to a physician advice comparison group. The duration of exercise (30 minutes) and type of exercise (walking) were the same in the four counseling groups, while exercise intensity and frequency was manipulated to form four prescriptions:
- Moderate intensity (ModI)-low frequency (LowF)
- Moderate intensity-high frequency (HiF)
- Hard intensity (HardI)-low frequency
- Hard intensity-high frequency
Intensity was defined by percentage of maximal heart rate (HR) reserve - 45-55 percent for ModI, and 65-75 percent for HardI. LowF was defined as three to four sessions per week, while HiF was five to seven sessions per week. Comparison group participants received physician advice and written materials regarding recommended levels of exercise for health. The researchers measured changes in cardiorespiratory fitness (maximum oxygen consumption), high-density lipoprotein cholesterol (HDL-C), and the ratio of total cholesterol to HDL-C.
"At six months, the HardI-HiF, HardI-low frequency, and moderate intensity-HiF conditions demonstrated significant increases in maximum oxygen consumption, but only the HardI-HiF condition showed significant improvements in HDL-C level, total cholesterol-HDL-C ratio, and maximum oxygen consumption, compared with physician advice" the authors write.
"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, but no significant effects on HDL-C or total cholesterol-HDL-C ratio were observed," they continue.
"The findings demonstrate that significant improvements in cardiorespiratory fitness can be achieved and maintained over 24 months via exercise counseling with a prescription for walking 30 minutes per day, either at a ModI five to seven days per week, or at a HardI three to four days per week," the authors conclude. "Additional benefits, including larger changes in fitness and increases in HDL-C level, may be achieved by prescribing either more exercise or the combination of HardI plus HiF exercise." (Arch Intern Med. 2005;165:2362-2369)