The government used that scientific report to set the minimum activity levels.
The kind of exercise matters a lot, said Dr. William Kraus, a Duke University cardiologist and co-author of the scientific report. Runners such as Kraus can achieve the same health benefit in a fraction of the time of a walker.
"If you do it more intense, you can do less time," explained Kraus, who praised the guidelines for offering that flexibility. "This brings it back down to earth for a lot of people."
What's the right kind of exercise? The guidelines advise: