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BOX 2-5 Continued
these two types of physical activity. One of the difficulties has been deciding 
which sedentary behaviors to monitor. Use of accelerometers in recent years 
has enabled researchers to measure total sedentary time, but long-term 
trends have depended on self-reported data, primarily regarding television 
viewing time and more recently also time spent watching videos, play-
ing video games, and using a computer. Television viewing time has been 
monitored, often for business reasons, for a number of years. The average 
number of hours children and teens spent watching television daily declined 

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Copyright © National Academy of Sciences. All rights reserved.
Educating the Student Body: Taking Physical Activity and Physical Education to School
Status and Trends of Physical Activity Behaviors and Related School Policies
 
67
FIGURE 2-11
Percentage of students walking or bicycling to school.
SOURCE: McDonald, 2007.
Figure 2-11.eps
0
10
20
30
40
50
60
70
80
90
100
1970 1975 1980 1985 1990 1995 2000
Pe
rc
enta
ge
Year
W/B Sch (K-12)
W/B Sch <1m (K-12)
slightly during the early 1990s, from about 3.3 hours per day to about 3 
hours per day, and rose during the 2000s to about 3.4 hours per day (see 
Figure 2-12) (TVB, 2012). If television use includes DVDs, pre recorded 
shows, or television shows on other platforms (e.g., Internet, cell phone), 
then total television use has increased since the late 1990s, as has the use 
of computers for purposes other than schoolwork (Rideout et al., 2010). 
The prevalence of high school students reporting on the YRBS that they 
watched at least 3 hours per day of television declined from 38 percent in 
2003 to 32 percent in 2011, while the prevalence of using computers for at 
least 3 hours per day increased from 21 percent in 2005 to 31 percent in 
2011 (CDC, 2012a).