Measuring physical activity in patients after surgery for a malignant tumour in the leg - The reliability and validity of a continuous ambulatory activity monitor

A continuous ambulatory activity monitor allows objective measurement of th e amount and intensity of physical activity. We examined the reliability an d validity of this device in the assessment of seven aspects of function ov er a period of 24 hours in 20 patients who had undergone limb salvage or am putation for a tumour in the leg. The test-retest reliability was determined by undertaking identical assessm ents on two separate days. The measurements were compared with other indica tors of functional status and quality of life in order to determine the val idity of the monitor. Its reliability was satisfactory, with intraclass correlation coefficients ranging from 0.65 to 0.91. Significant correlations were seen between the ' time spent walking' and the Musculoskeletal Tumor Society rating scales and the Rand-36 physical functioning score. There was also a significant assoc iation between the 'movement intensity during walking' and the Musculoskele tal Tumor Society score. The satisfactory reliability and validity of the m onitor shows considerable promise for its use as a device for measuring phy sical activity objectively in patients after surgery for limb-salvage or an amputation.