Comparisons of four methods of estimating physical activity in adult women

Purpose: To compare four different methods of measuring physical activity ( PA) in adult women under free-living conditions, Methods: Twelve women part icipated in a 7-d period during which PA was assessed via self-report, acce lerometry and step-counting. Subjects wore at the waist a Tritrac-R3D accel erometer, a Computer Science Application Inc. activity monitor (CSA), both of which measure bodily accelerations in various planes, and a Yamax Digi-W alker-500(R) that records steps. After the 7-d period subjects responded to a 7-d Physical Activity Recall interview (PAR). Results: Physical activity -related energy expenditure (PAEE) determined from PAR was significantly hi gher than PAEE estimated from either the Tritrac, CSA, or the Yamax data. T ime spent in light, moderate, and hard physical activity was not significan tly different between PAR, CSA, and Tritrac. Log-transformed activity count s from CSA were highly correlated with log-transformed Tritrac results (r > 0.90). Number of steps recorded by the Yamax was significantly correlated with untransformed Tritrac and CSA results. Conclusions: Based upon compari sons with PAR, Tritrac, CSA, and Yamax underestimate the amount of PAEE by 25, 46, and 48%, respectively. The correspondence between the Tritrac and C SA results suggests that both devices produce similar estimates of bodily m ovement in free-living women. The relationships among results for Tritrac, CSA, and Yamax indicate that the number of steps recorded by the Yamax is r epresentative of the amount of physical activity performed during the day a s estimated by Tritrac and CSA. These results should be useful when selecti ng a method to measure PA in individuals under free-living conditions.