Assessment of free-living daily physical activity in older claudicants: validation against the doubly labeled water technique.

BACKGROUND: The purpose of this study was to compare physical activity assessed by monitoring devices and questionnaires with the criterion method of physical activity using doubly labeled water (DLW) in free-living peripheral arterial occlusive disease (PAOD) patients.
METHODS: Twenty-two older nonsmoking PAOD patients with intermittent claudication (age = 68.7 +/- 7.3 years, ankle/brachial index = 0.67 +/- 0.21) were recruited from the Vascular Clinic at the Baltimore Veterans Affairs Medical Center. The energy expenditure of physical activity (EEPA) was calculated using DLW. Physical activity values were also obtained by activity monitors (an accelerometer and a pedometer worn on each hip over a 48-h period) and by three activity questionnaires (the Minnesota Leisure-Time Physical Activity, the Peripheral Arterial Disease Physical Activity Recall, and the NASA Johnson Space Center questionnaire).
RESULTS: As expected, the claudicants were sedentary, as EEPA was 378 +/- 190 kcal/day. The activity value from the accelerometer was highly correlated with EEPA, yielding a regression equation of EEPA (kcal/day) = 81.6 + (0.599 x accelerometer kcal/day); R = .834, R2 = .696, standard error of estimate = 77 kcal/day, p = .001. The activity value from the pedometer was also correlated with EEPA, yielding a regression equation of EEPA (kcal/day) = 76.6 + (0.048 x pedometer steps/day); R = .614, R2 = .377, standard error of estimate = 124 kcal/day, p = .002. None of the physical activity questionnaires was significantly correlated with EEPA, as the correlation coefficients ranged between .037 and .326.
CONCLUSION: Free-living daily physical activity of older PAOD patients with intermittent claudication can be accurately predicted with an accelerometer, and to a lesser extent with a pedometer, worn over a 48-h period.