Physical activity was measured using a Step Watch Activity Monitor (SAM, Ortho Care Innovations, Seattle,Washington) following the manufacturers’ recommendations.The SAM is a research-grade pedometer for assessment of walking activity. It is a small (70 9 50 9 20 mm;38 g), waterproof, self-contained device that is worn on the ankle and records the number of steps taken every min and the data are also time-stamped. The SAM provides no feedback to the subject and, thus, does not encourage‘‘performance behavior.’’ The sensitivity of the SAM is tuned to each subject by specifying the subjects’ height and gait characteristics during programming. Step detection
accuracy varies according to walking speed, but at average walking speeds (2 mph), accuracy is approximately 98%