Participants in the study were questioned about which activities caused leg pain and the characteristics of the pain when it occurred. The researchers then tested participants' physical ability by measuring the distance they could walk in 6 minutes and by observing their ability to get up from a chair unassisted, how well they maintained balance in a standing position, and how fast they could walk over a short distance. The researchers also asked participants how often they walked for exercise and how long each walking session lasted. Participants were divided into 3 groups: those who walked for exercise at least 3 times per week, those who walked fewer than 3 times per week, and those who did no walking for exercise. Measurements of physical ability were repeated annually for an average of 3 years.