Comparing the 7-day physical activity recall with a triaxial accelerometer for measuring time in exercise.
OBJECTIVE
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 an 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 1 (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.
Sloane
Richard
R
The Center for the Study of Aging and Human Development, Duke University Medical Center, Durham, NC 27710, USA. sloane@geri.duke.edu
Snyder
Denise Clutter
DC
Demark-Wahnefried
Wendy
W
Lobach
David
D
Kraus
William E
WE
D000054:Acceleration; D003430:Cross-Sectional Studies; D015444:Exercise; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D011939:Mental Recall; D008875:Middle Aged; D009043:Motor Activity; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D013997:Time Factors