Ecological momentary assessment of physical activity: Validation study

Background: ecological momentary assessment (ema) may elicit physical activity (pa) estimates that are less prone to bias than traditional self-report measures while providing context. objectives: the objective of this study was to examine the convergent validity of ema-assessed pa compared with accelerometry. methods: the participants self-reported their pa using international physical activity questionnaire (ipaq) and behavioral risk factor surveillance system (brfss) and wore an accelerometer while completing daily emas (delivered through the mobile phone) for 7 days. weekly summary estimates included sedentary time and moderate-,vigorous-,and moderate-to vigorous-intensity physical activity (mvpa). spearman coefficients and lin's concordance correlation coefficients (lcc) examined the linear association and agreement for ema and the questionnaires as compared with accelerometry. results: participants were aged 43.3 (sd 13.1) years,51.7% (123/238) were african american,74.8% (178/238) were overweight or obese,and 63.0% (150/238) were low income. the linear associations of ema and traditional self-reports with accelerometer estimates were statistically significant (p<.05) for sedentary time (ema: ρ=.16),moderate-intensity pa (ema: ρ=.29; brfss: ρ=.17; ipaq: ρ=.24),and mvpa (ema: ρ=.31; brfss: ρ=.17; ipaq: ρ=.20). only ema estimates of pa were statistically significant compared with accelerometer for agreement. conclusions: the mobile ema showed better correlation and agreement to accelerometer estimates than traditional self-report methods. these findings suggest that mobile ema may be a practical alternative to accelerometers to assess pa in free-living settings.