Comparing the 7-Day Physical Activity Recall with a Triaxial Accelerometer for Measuring Time in Exercise

SLOANE, R., D. C. SNYDER, W. DEMARK-WAHNEFRIED, D. LOBACH, and W. E. KRAUS. Comparing the 7-Day Physical Activity Recall with a Triaxial Accelerometer for Measuring Time in Exercise. Med. Sci. Sports Exerc., Vol. 41, No. 6, pp. 1334-1340, 2009. Purpose: The primary study aim was to evaluate associations of estimated weekly minutes of moderate-to-vigorous-intensity exercise from self-reports of the telephone-administered 7-Day Physical Activity Recall (7-Day PAR) with data captured by the RT3 triaxial accelerometer. Methods: This investigation was undertaken as part of the FRESH START study, a randomized clinical trial that tested all iteratively tailored diet and exercise mailed print intervention among newly diagnosed breast and prostate cancer survivors. A convenience sample of 139 medically eligible subjects living within a 60-mile radius of the study center provided both 7-Day PAR and accelerometer data at enrollment. Ultimately, substudy subjects (n = 115) were found eligible for the FRESH START study and randomized to one of two study treatment arms. Follow-up assessments at year I (n = 103) and year 2 (n = 99) provided both the 7-Day PAR and the accelerometer data. Results: There was moderate agreement between the 7-Day PAR and the accelerometer with longitudinal serial correlation coefficients of 0.54 (baseline), 0.24 (year 1), and 0.53 (year 2), all P values <0.01, although the accelerometer estimates for weekly time in moderate-to-vigorous physical activity (PA) were much higher than those of the 7-Day PAR at all time points. The two methods were poorly correlated in assessing sensitivity to change from baseline to year 1 (rho = 0.11, P = 0.30). Using mixed models repeated-measures analysis, both methods exhibited similar nonsignificant treatment arm x time interaction P values (7-Day PAR = 0.22, accelerometer = 0.23). Conclusions: The correlations for three serial time points were in agreement with findings of other studies that compared self reported time in exercise with PA captured by accelerometry. However, these methods capture somewhat different dimensions of PA and provide differing estimates of change over time.