RALEIGH, N.C. — Schools need more mandatory physical education classes and parents need to unplug TVs and video games, say researchers who concluded that most young Americans, particularly blacks and females, are far too sedentary.
The nationwide study of adolescent physical activity was conducted by researchers at the University of North Carolina and published in the June Pediatrics.
Lead author Penny Gordon-Larsen blamed the problems on the decline in comprehensive physical education curricula in U.S. schools and habitual TV viewing and video-game playing among youngsters.
"Even though it's a particular problem for minorities, it's a problem for all kids," said Gordon-Larsen, a postdoctoral fellow at the university's Carolina Population Center.
Youngsters who don't get enough exercise could be at greater risk for problems such as obesity, diabetes, cancer and heart disease.
Gordon-Larsen and her colleagues analyzed data on more than 17,700 middle school and high school students from a 1996 population center survey of adolescent health and behavior.
Based on self-reported data, students were grouped by levels of activity and inactivity. Activity was characterized by frequency, from zero to five times a week, and by intensity, with cycling and martial arts ranking higher than less-strenuous activities.
Inactivity was characterized by the number of hours spent each week watching TV or videos and playing video and computer games.
Researchers also studied environmental and demographic variables, finding that involvement in physical education classes and use of community recreation centers were key to healthy activity rates.
Overall, youngsters who had PE class five times a week were more than twice as likely to be highly active. The rate was just 44 percent for those who had PE once a week.
"The fact that PE had such a dramatic impact was a big surprise," Gordon-Larsen said. "We knew it had an impact, but we had no idea that it was this strong."
Only one-fifth of the youngsters surveyed were enrolled in a PE class, and 15 percent had PE five times a week. Middle school students were more likely than high school students to take PE and males more likely than females.
Michael Goran of the Institute of Prevention Research at the University of Southern California said the study helps quantify factors associated with inactivity.
"I think this may be one of the first studies that shows this can be partially explained by environmental constraints or environmental factors," he said.
In a seemingly contradictory finding, blacks were more likely than whites to be enrolled in PE classes and use recreation centers but were found to be less active.
"It's a little confusing; we really need more information to understand why that is happening," said Gordon-Larsen.
Moreover, some highly active youngsters could simultaneously be considered highly inactive, based on their television viewing habits.
Russell Pate of the University of South Carolina's School of Public Health said the trend toward fewer PE requirements in high schools, as outlined in a 1996 report by the U.S. surgeon general, is only one factor in childhood inactivity.
"I don't think solving this problem is nearly as simple as saying, 'Let's get kids in PE classes more frequently," he said.
Educators must ensure that students enrolled in PE actually participate, and that they learn the physical and behavioral skills, including time management and goal-setting, they will need later, Pate said.