By David Brown

Nearly 40 percent of American adults are sedentary in their leisure time, basically never exercising. In contrast, about 30 percent exercise on a regular basis, either vigorously several times a week, or even more often at lower intensity. The rest do something in between.

Those are among the findings of a survey, whose results will help the federal government track behaviors in the American population in the coming decades.

Regular exercise is more common in men than in women. It is also more common in the young and in the better educated. Whites are also more likely to exercise regularly or vigorously than blacks or Hispanics.

The information was collected as part of the National Health Interview Survey, which is conducted by the National Center for Health Statistics. Since 1957, interviewers have queried a representative sample of Americans about their health. In 1997, the survey was extensively revised and new exercise questions were added.

"Light-moderate physical activity" was defined as activity causing a light sweat and a slight increase in breathing or heart rate. "Vigorous activity" causes heavy sweating and large increases in breathing or heart rate. Only activity done during leisure time -- not on the job, in housework or as transportation -- was counted.

The new data are the combined results of the 1997 and 1998 surveys, in which a total of 68,556 people were interviewed. Most of the results have a margin of error of less than 1 percent. Among the findings:

• Sixty-two percent of adults reported doing "at least some" exercise. This category was very inclusive: any light-moderate or vigorous activity lasting at least 10 minutes qualified, regardless of how often a person did it.

• About 38 percent of adults are entirely sedentary in their leisure hours. For women, it's 41 percent; men, 35 percent; for people below poverty level, 57 percent; for people with incomes at least four times higher than poverty level, 24 percent; for southerners, 44 percent; for northeasterners, 38 percent; for westerners, 32 percent.

• Among all adults, 31 percent reported "regular physical activity." This was defined as either light-moderate activity lasting 30 minutes or more at least five times a week, or vigorous activity lasting 20 minutes three times a week. Among people who never graduated from high school, 18 percent said they did that much activity. Among people with graduate degrees, the fraction was 45 percent.

• About 12 percent of adults engaged in vigorous exercise five times a week or more. About 23 percent engaged in "strengthening activity," basically weight-lifting or calisthenics.

Schoenborn said there is some evidence that the prevalence of inactivity has increased, although she was hesitant to directly compare this survey to previous ones, which used different questions and methods.

Rates of obesity and adult-onset diabetes are increasing. Both conditions can be worsened by inactivity, and ameliorated by exercise.

"We have spent a long time concentrating on smoking, and have made real inroads," Schoenborn said. "We now need to turn our attention to these other activities, to make people realize these really are significant for their health."

The Department of Health and Human Services sets periodic health goals for the American population. Several goals in the recently ended "Healthy People 2000" program involved exercise, said Richard Klein, a biostatistician in the department.

One was to have 30 percent of people engage in "light to moderate physical activity." In 1990, only 23 percent of the population did, but by the end of the decade the goal had been reached "on the head," he said.

That was not true in the effort to increase the fraction of people engaging in vigorous physical activity. The goal was 20 percent. The decade began with 12 percent, and increased to only 14 percent by the end.

No progress was made on the inactivity front at all. The goal was to get the fraction of totally sedentary Americans down to 15 percent, but it remained at 24 percent throughout the decade, Klein said.

Washington Post April 8, 2002; Page A02