Physical activity (PA) is presumed to decline during childhood and adolescence, but only few long-term studies about PA development during this period of life exist. We assessed PA and sedentary behavior (SB) over a 5-year period to gain a better understanding of the extent of change in activity and potential influencing factors.


PA and SB of 600 children from the Childhood Obesity Project were objectively measured with the SenseWear Armband 2 at the ages of 6, 8, and 11 years, resulting in 1254 observations. Longitudinal changes of total PA, moderate-to-vigorous physical activity (MVPA), light physical activity (LPA), and SB were modeled with mixed-effects models.


Total PA revealed a significant quadratic decline with age (P < .001), resulting in a change of total PA by –75.3 minutes per day from 6 to 11 years. LPA linearly declined (P < .001) by 44.6 minutes per day, MVPA quadratically declined (P < .001) by an overall 30.7 minutes, whereas SB increased significantly (+107 minutes; P = .001). Boys showed a steeper decline in LPA (P = .003) and MVPA (P < .001) than did girls. Higher fat mass index and BMI z scores were associated with lower levels of total PA and MVPA and higher levels of SB (all P < .001).


We showed that PA decreased, and SB increased in earlier years than previously thought. MVPA remained relatively stable until 8 years, but revealed a drop-off at 11 years, identifying this period as a crucial time for intervention.

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