Leisure-time physical activity levels, cardiovascular fitness and coronary risk factors in 1015 white Zimbabweans.

To determine a 'threshold' level of habitual physical activity for the reduction of coronary risk factors, a cross-sectional study of 646 male and 369 female White Zimbabweans aged 20 - 70 years was undertaken. Results showed that light exercise, even up to four times a week, was not associated with meaningful changes in maximum oxygen intake (VO2MAX) or reduction in body fat or the incidence of smoking, but such changes were seen in subjects involved in vigorous exercise. Ischaemic changes on exercise ECGs were less frequent among those participating in strenuous exercise more than twice a week than among those performing either mild exercise or strenuous exercise less than twice a week. These data show that a 'threshold' level of exercise might exist above which there is a reduction in the percentage of body fat, the incidence of smoking and abnormal ST-segment depression during exercise, increased VO2MAX values and a reduced rate of fall of VO2MAX with age. Whereas participation in only light exercises had little effect, more strenuous exercise was associated with beneficial alterations in all these parameters. This level of exercise is also the 'threshold' level for elevations in serum high-density lipoprotein cholesterol levels. The results suggest that future longitudinal studies should employ only more vigorous exercise, to be undertaken at least three or preferably more times a week.