Developments in Brief : Exercise Study Shaves Standards; 45% Pass

A new study shows only 45% of Americans get enough exercise to do them any good, federal health officials said.

The percentage of people not getting appropriate exercise would have been even greater if the “intensity standard” had not been relaxed, said Carl Calperson, a statistician with the federal Centers for Disease Control in Atlanta.

The findings were based on a telephone survey of 25,221 people in 21 states and the District of Columbia conducted by state health departments for the CDC.

Calperson said although physical activity is complex and difficult to assess, “progress has been made in the ability to characterize national levels of physical activity.

“Unfortunately, these results indicate that less than half of the American population is physically active at a level likely to confer health benefits.”

The 1990 health objectives for the nation define “appropriate physical activity” as exercise involving large muscle groups for periods of 20 minutes or longer, three or more days per week, and which is performed at an intensity of 60% or greater of an individual’s heart and lung capacity.

Calperson said “that’s pretty vigorous,” and researchers recognized “many people who might want to do it simply can’t do it.”

He said since evidence indicates less intense, yet regular physical activity--like walking--also may confer health benefits, “we relaxed the intensity standard,” and the study results are based on physical activity less than three times per week, less than 20 minutes per occasion, or both, regardless of the intensity of participation.