Purpose

The purpose of this study was to compare different methods of measuring physical activity (PA) in women by the doubly labeled water method (DLW).

Methods

Thirteen subjects participated in a 7-d protocol during which total daily energy expenditure (TDEE) was measured with DLW. Body composition, basal metabolic rate (BMR), and peak oxygen consumption were also measured. Physical activity-related energy expenditure (PAEE) was then calculated by subtracting measured BMR and the estimated thermic effect of food from TDEE. Simultaneously, over the 7 d, PA was assessed via a 7-d Physical Activity Recall questionnaire (PAR), and subjects wore secured at the waist, a Tritrac-R3D (Madison, WI), a Computer Science Application Inc. activity monitor (CSA; Shalimar, FL), and a Yamax Digi Walker-500 (Tokyo, Japan). Pearson-product moment correlations were calculated to determine the relationships among the different methods for estimating PAEE. Paired t-tests with appropriate adjustments were used to compare the different methods with DLW-PAEE.

Results

There was no significant difference between PAEE determined from PAR and DLW. The differences between the two methods ranged from-633 to 280 kcal. d (-1). Compared with DLW, PAEE determined from CSA, Tritrac, and Yamax was significantly underestimated by 59%(-495 kcal. d (-1)), 35%(-320 kcal. d (-1)) and 59%(-497 kcal. d (-1)), respectively. VO2peak explained 43% of the variation in DLW-PAEE.

Conclusion

Although the group average for PAR-PAEE agreed with DLW-PAEE, there were differences in the methods among the subjects. PAEE determined by Tritrac, CSA, and Yamax significantly underestimate free-living PAEE in women.