The researchers split participants into four groups:

• Low amount of moderate exercise (equivalent to walking about 12 miles per week)
• Low amount of vigorous exercise (equivalent to jogging about 12 miles per week)
• High amount of vigorous exercise (equivalent to jogging nearly 20 miles per week)
• No exercise

Participants in the exercise group didn't plunge into their workouts. They spent two to three months working up to their assigned exercise level to avoid injuries.

After that, they followed their exercise assignment for six months. They wore heart rate monitors so that the researchers could monitor their progress.