Average patient walking activity approaches 2 million cycles per year: pedometers under-record walking activity

A two-dimensional accelerometer worn on the ankle (step activity monitor [SAM]; Prosthetic Research Study, Seattle, WA) has been proved to be highly accurate for assessing walking activity. The walking activity of 33 patients with well-functioning total hip arthroplasties was measured continuously during daily life, simultaneously with a pedometer and a SAM. The SAM recorded an average of 1.9 million cycles/y. The pedometer under-recorded an average of 34% cycles per day compared with the SAM (P=.0007), but the 2 measures were highly correlated (r=0.66; P=.001). No difference was seen in the number of gait cycles per day between men and women. The previously reported difference in average walking activity between men and women is due to greater under-recording of the pedometer in women, especially those with a body mass index > or =27. The pedometer is more reliable in quantifying the walking activity of men, less obese women, and patients with >1 million gait cycles/y.