Objective: Public health policies for physical activity presume that the gr
eatest health benefits are achieved by increasing physical activity among t
he least active. This presumption is based largely on studies of cardioresp
iratory fitness. Tn assess whether studies of cardiorespiratory fitness are
germane to physical activity :guidelines, we compared the dose-response re
lationships between cardiovascular disease endpoints with leisure-time phys
ical activity and fitness from published studies. Data Sources: Twenty-thre
e ses-specific cohorts of physical activity or fitness (representing 1,325,
004 person-years of follow-lip. cited in Tables 4-1 and 4-2 of the Surgeon
General's Report. Data Synthesis: Relative risks were plotted as a function
of the cumulative percentages of the samples when ranked from least fit or
active, to most fit or active. To combine study results, a weighted averag
e of the relative risks over the 16 physical activity or seven fitness coho
rts was computed at every 5th percentile between 5 and 100%. The analyses s
how that the risks of coronary heart disease or cardiovascular disease decr
ease linearly in association with increasing percentiles of physical activi
ty. In contrast, there is a precipitous drop in risk occurring before the 2
5th percentile of the fitness distribution. As a consequence of this drop,
then is a significant difference in the risk reduction associated with bein
g more physically active or physically fit (P less than or equal to 0.04).
Conclusions: Being unfit warrants consideration as a risk factor, distinctl
y from inactivity. and worthy of screening and intervention. Formulating ph
ysical activity recommendations oil the basis of fitness studies may inappr
opriately demote the status of physical fitness as a risk factor while exag
gerating the public health benefits of moderate amounts of physical activit
y.