Accelerometer-measured patterns of shared physical activity among mother-young child dyads

Background: Many mothers and young children are not meeting physical activity guidelines. Parent–child coparticipation in physical activity (ie, shared physical activity) provides opportunities for social modeling and might be associated with child physical activity. There is very little information about shared physical activity using objective measures. Methods: Participants (N = 17 mother–young child dyads) completed a demographic survey and height/weight measurements, and wore a Bluetooth® accelerometer for 1 week. Accelerometers were initialized using the proximity function to yield both individual and proximity [a minute-by-minute log of whether the 2 accelerometers were in- or out-of-range (~50 m or less)] data. Shared physical activity was calculated in MATLAB by overlaying individual and proximity accelerometer data. Results: Mother–child dyads spent approximately 2 hours per day in shared time that was mostly shared sedentary activities. Less than 1% of shared minutes per day were spent in shared moderate to vigorous physical activity. Conclusions: Mothers and young children spent a small portion of their day in shared activities. Most mother–child shared time was spent in sedentary or light activities rather than moderate to vigorous physical activity. This method for objectively measuring shared physical activity provides novel information about the context in which physical activity occurs and could be used to understand patterns of physical activity among other dyads.