Habitual physical activity and physical activity intensity: their relation to body composition in 5.0-10.5-y-old children

BACKGROUND: Concerns of a decrease in physical activity levels (PALs) of children and a concurrent increase in childhood obesity exist worldwide. The exact relation between these two parameters however has as yet to be fully defined in children. OBJECTIVE: This study examined the relation in 47 children, aged 5-10.5 y (mean age 8.4+/-0.9 y) between habitual physical activity, minutes spent in moderate, vigorous and hard intensity activity and body composition parameters. DESIGN: Total energy expenditure (TEE) was calculated using the doubly labelled water technique and basal metabolic rate (BMR) was predicted from Schofield's equations. PAL was determined by PAL=TEE/BMR. Time spent in moderate, vigorous and hard intensity activity was determined by accelerometry, using the Tritrac-R3D. Body fatness and body mass index (BMI) were used as the two measures of body composition. RESULTS: Body fat and BMI were significantly inversely correlated with PAL (r=-0.43, P=0.002 and r=-0.45, P=0.001). Times spent in vigorous activity and hard activity were significantly correlated to percentage body fat (r=-0.44, P=0.004 and r=-0.39, P=0.014), but not BMI. Children who were in the top tertiles for both vigorous activity and hard activity had significantly lower body fat percentages than those in the middle and lowest tertiles. Moderate intensity activity was not correlated with measures of body composition. CONCLUSIONS: As well as showing a significant relation between PAL and body composition, these data intimate that there may be a threshold of intensity of physical activity that is influential on body fatness. In light of world trends showing increasing childhood obesity, this study supports the need to further investigate the importance of physical activity for children.