What Children do all Day: The Physical Activity of 7-year-olds and its Impact on Adiposity (The Earlybird Diabetes Study)

Introduction physical activity (PA) is perceived to be a key determinant of childhood adiposity. This study objectively characterizes the daily PA of 7-year-olds and relates it to waking time, intensity, UK recommendations and body fat.

Methods and Participants MTI-Actigraph accelerometers were worn by 129 (88) healthy boys (girls) for seven days. Calibration studies defined three intensities of PA: low (2500 cpm ~ >4 km/h). BMI and fat% (DXA) were measured.

Results Three-quarters of waking time (B: 8.9 h, G: 9.2 h, P = 0.04) was spent in low intensity pursuits. High intensity PA, despite occupying only 8% (6%) of waking time in the boys (girls) contributed to 39% (34%) of total PA. Time spent in low intensity PA correlated inversely with high intensity PA counts (B: r = -0.63, G: r = -0.49, both P < 0.001) and total PA counts (B: r = -0.66, G: r = -0.52, both P < 0.001). Only 43% (17%) of the boys (girls) met UK recommendations: >1 h/day of ‘moderate’ intensity PA (~walking > 4 km/h). Importantly, there were no differences in BMI between those who met the recommendations and those who did not (B: 15.9 v 16.2 kg/m², P = 0.42 G: 17.1 v 17.1 kg/m², P = 0.99) and only a small difference in fat% in boys (B: 13.0 v 15.7%, P = 0.03. G: 21.5 v 22.4%, P = 0.72).

Conclusions Time spent in low intensity PA displaces time available for higher intensity PA, and thereby reduces total PA. Nevertheless, while PA is associated with a reduction in adiposity in boys, it is modest. There is an urgent need for evidence-based PA recommendations.