Teun Remmers

20 | Chapter 2 (± 1) weeks of pregnancy (6). Figure 2 depicts the number of children participating in each assessment period. Figure 2: Flowchart Measurements Physical activity PA was measured with the uniaxial ActiGraph 7164 in the first assessment period, and with the ActiGraph 7164 and GT1M accelerometers (ActiGraph, Fort Walton Beach, FL) in the second assessment period. Participants were instructed to wear the accelerometer during waking hours on the right hip for seven days, and to remove the accelerometer during activities in which water was involved, such as swimming. Accelerometers express PA in “counts”, and were initialized to capture the frequency of these counts every 15 seconds (i.e. epochs). Although efforts were made to prevent the occurrence of measurements in non-regular weeks, occasional measurement-days within holidays were excluded from further analyses. In addition, the exact dates at which PA measurement commenced were categorized into four seasons (i.e. spring, summer, autumn, winter) to control for seasonality effects.