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BOX 2-4
Recognizing the Value of Light-Intensity 
Physical Activity
Thirty to 40 years ago, only vigorous physical activity was thought to pro-
vide reductions in disease risk. By the early 1990s, however, it was clear 
that moderate-intensity physical activities were healthful, too. The joint 
Centers for Disease Control and Prevention (CDC) and American College 
of Sports Medicine (ACSM) recommendations of 1995 formalized accep-
tance of the health benefits of moderate-intensity physical activity (Pate 
et al., 1995). Recognition that the benefits of regular physical activity did 
not require the effort, commitment, and skill of an athlete solidified the 
public health value of physical activity and has guided epidemiologic, 
intervention, and clinical research ever since. That outcome has been 
good. It led, however, to a rigid categorization of physical activity into 
the good (vigorous- or moderate-intensity) and the bad (sedentary or 
light-intensity). In some scientific reports and even in official documents 
(PAGAC, 2008), “physical activity” has been used to mean vigorous- or 
moderate-intensity physical activity. This usage has become common, 
making it difficult for many to accept emerging evidence for the health 
benefits of light-intensity physical activity.
Recent research among adults indicates that replacing sedentary activi-
ties with light-intensity physical activity while holding the volume of 
vigorous- or moderate-intensity physical activity constant provides health 
benefits (Hu et al., 2003; Healy et al., 2008a,b; Katzmarzyk et al., 2009; 
Wijndaele et al., 2010, 2011; Grøntved and Hu, 2011; Matthews et al., 
2012). Data from a National Institutes of Health (NIH) and AARP study of 
more than 200,000 adults demonstrate that light-intensity physical activ-
ity augments the benefits of more intense physical activity (Matthews et 
al., 2012). At every volume of vigorous- or moderate-intensity physical 
activity, the risk of cardiovascular mortality increases as the volume of 
sedentary activity, assessed as hours of watching television, increases 
(see the figure on the next page). Worth noting is the essentially equiva-
lent risk among those who do the most vigorous- or moderate-intensity 
physical activity and the most television watching and those who do no 
vigorous- or moderate-intensity physical activity and the least television 
watching (see the arrows in the figure).
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Educating the Student Body: Taking Physical Activity and Physical Education to School
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