Assessment of physical activity using accelerometry, an activity diary, the heart rate method and the Indian Migration Study questionnaire in South Indian adults.

Objective: To validate questionnaire-based physical activity level (PAL) against accelerometry and a 24 h physical activity diary (24 h AD) as reference methods (Protocol 2), after validating these reference methods against the heart rate― oxygen consumption (HRVO 2 ) method (Protocol 1). Design: Cross-sectional study. Setting: Two villages in Andhra Pradesh state and Bangalore city, South India. Subjects: Ninety-four participants (fifty males, forty-four females) for Protocol 2; thirteen males for Protocol 1. Results: In Protocol 2, mean PAL derived from the questionnaire (1·72 (SD 0·20)) was comparable to that from the 24 h AD (1·78 (SD 0·20)) but significantly higher than the mean PAL derived from accelerometry (1·36 (SD 0·20); P< 0·001). Mean bias of PAL from the questionnaire was larger against the accelerometer (0·36) than against the 24 h AD (―0·06), but with large limits of agreement against both. Correlations of PAL from the questionnaire with that of the accelerometer (r = 0·28; P = 0·01) and the 24 h AD (r = 0·30; P= 0·006) were modest. In Protocol 1, mean PAL from the 24 h AD (1·65 (SD 0·18)) was comparable, while that from the accelerometer (1·51 (SD 0·23)) was significantly lower (P< 0·001), than mean PAL obtained from the HRVO 2 method (1·69 (SD 0·21)). Conclusions: The questionnaire showed acceptable validity with the reference methods in a group with a wide range of physical activity levels. The accelerometer underestimated PAL in comparison with the HRVO 2 method.