Energy cost determination using a portable accelerometer

The purpose of this study was to determine the physical activity of physical therapists during clinical practice. Nineteen physical therapists from three clinical facilities wore portable accelerometers on their waist belts or chest pockets for the duration of their work shifts. The subjects repeated the experiment on the second day. The accelerometer readings (in arbitrary units) were converted to oxygen consumption VO2 and energy expenditure (kcal) values using previously derived regression equations. The PTs worked an average of 7.9 hours during each shift. The total energy expended during the work shift ranged from 933.6 to 1,689.6 kcal. A correlation coefficient of .91 was found between the accelerometer readings (count X hr-1) recorded on day 1 and day 2 of the study. The analysis of variance revealed that the PTs in the three clinical facilities were not significantly different in age, height, and work-shift duration, but were significantly different (p less than .05) in weight, mean accelerometer readings, and estimated VO2 (L X min-1). When the VO2 was expressed in mL X kg-1 X min-1, no significant difference was found between the PTs in the three clinical facilities. The implications and limitations of the findings are discussed.