Accuracy and validity of a combined heart rate and motion sensor for the measurement of free-living physical activity energy expenditure in adults in Cameroon.
Résumé
Background: The increasing burden of non-communicable diseases in sub-Saharan Africa warrants rigorous studies of contributing lifestyle factors. Combined heart rate and movement monitoring make it possible to objectively measure physical activity in free-living individuals. We examined the validity of a combined heart rate and motion sensor in estimating physical activity energy expenditure (PAEE) in free-living adults in rural and urban Cameroon compared to doubly-labelled water (DLW) as criterion. Methods: PAEE was measured in 33 free-living rural and urban dwellers by DLW over 7 consecutive days. Simultaneously, the combined sensor recorded heart rate and uni-axial acceleration. Individual heart rate vs. PAEE calibration was done by a step test. Branched equation modelling was used to estimate PAEE from heart rate and acceleration. Validity and accuracy of prediction were expressed as mean bias and root mean square error (RMSE). Agreement was analyzed using Bland and Altman limits of agreement (LOA). Results: There was no significant mean bias between PAEE estimated from the combined sensor or measured by DLW [mean bias (standard error): -5.4 (5.1) kJ/kg/day; p=0.3; RMSE=29.3 kJ/kg/day]. The bias doubled for group compared to individual calibration of heart rate (-9.1 (5.0) kJ/kg/day, p=0.08). PAEE prediction was more accurate in urban compared to rural volunteers. The 95% LOA between predicted and measured PAEE were about 50 to 60 kJ/kg/day above or below perfect agreement. Conclusions: Combined heart rate and movement sensing is a valid method for estimating free-living PAEE on group level in adults in sub-Saharan Africa.
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