Background: Epidemiologic evidence suggests that 8,368 kJ or 2000 kcal per week of moderate physical activity, including walking and stair climbing, can reduce risk of coronary heart disease (CHD). The goal of this study was to assess the effects of this amount of these two activities on physical fitness and risk factors for CHD.
Methods: Twenty-two healthy, slightly overweight, sedentary, normotensive, normolipemic men, age 22 to 44 years, were randomly assigned to an exercise or control group for 12 weeks followed by a 4-week washout period. The subjects then were crossed-over to the alternate group for an additional 12-week period. Exercise consisted of 5 days per week of supervised treadmill exercise plus stair climbing. Treadmill exercise consisted of walking for 45 minutes at 5.15 km per hour at 2% grade for a total of 19.3 km per week. Subjects also climbed 10 floors of stairs at a time at their own pace without prescribed target heart rates for a total of 50 floors per week. The estimated total weekly energy cost of the treadmill walking plus stair climbing was 8,368 kJ or 2,000 kcal. Mean observed heart rates were 55% and 82% of maximal heart rate during treadmill walking and stair climbing, respectively. Data from the two exercise periods and two control periods were pooled and compared by analysis of variance.
Results: Sixteen subjects completed all phases of the study. Maximal oxygen uptake (VO2max) by the Bruce treadmill exercise protocol with metabolic gas measurements was below average for age at baseline, and was not significantly affected by 12 weeks of training. No significant changes were noted between groups in body weight or percent body fat (hydrostatic weighing), although there was a trend for loss of weight and fat with exercise training. Mean systolic blood pressure (119 mm Hg) was unchanged in both groups. However, diastolic blood pressure (72 mm Hg and 78 mm Hg for the treatment and control groups, respectively) showed an unexpected 6 mm Hg increase during the exercise period and a 5 mm Hg decline during the control period. Mean plasma lipid and lipoprotein levels were unaffected by training, except for a 16% reduction in triglycerides (P < .05). However, a 28% increase in plasma high density lipoprotein (HDL)-cholesterol (P < .01) was noted during the initial 12-week training period, which regressed during the washout period, and was not replicated during the second 12-week exercise period.
Conclusions: Twelve weeks of walking and stair climbing at a moderate pace and intensity at an energy cost of about 2,000 kcal per week failed to improve physical fitness or risk factors for CHD. A reduction in physical activities other than the prescribed exercise program, as reported by a physical activity recall questionnaire, probably contributed to an absence of an exercise response. A longer and/or a more intense activity program is apparently required to improve these modalities.