Background: The decline in physical activity levels of young children seems to be combined with a high prevalence of obesity and overweight and a reduction in the participation in organized sport. With the ever-increasing interest in exploring the relationship between physical activity and obesity amongst children, it is important to provide a more precise estimate of both physical activity and body fatness. A significant proportion of previous research on this topic has relied on self-report methods to assess physical activity and body mass index as a proxy for actual body fatness. There is a need to investigate the relationships between physical activity and fatness in children using objective methods.
Aim: This study was conducted in order to explore the relationship between physical activity patterns and percentage body fat amongst a group of primary school children.
Subjects and methods: Forty-seven primary school children (boys, n = 23; girls, n = 24) participated in this study. They were randomly selected from children in years 5 and 6 (9-11 year olds) of four schools drawn from the same catchment area in the city of Birmingham, UK. The frequency, intensity and duration of physical activity were determined using continuous heart rate monitoring from 8:30 am to 8:30pm over three separate days (two weekdays and one weekend day). Percentage body fat was assessed using air displacement plethysmography.
Results: Results indicated that 52% of children did not achieve a single 15-min bout of sustained moderate physical activity over the three days of monitoring. Independent t-tests revealed that girls were significantly fatter (t44 = -3.126, p=0.003) than boys. There was no significant difference (t45 = 0.225, p > 0.05) between boys and girls in accumulated time spent with heart rates above the moderate physical activity threshold. Pearson's product moment correlation coefficients revealed no significant (r= -0.017, p> 0.05) relationship between per cent body fat and average daily time spent in moderate and vigorous activity.
Conclusion: Despite the prediction to the contrary, there was no evidence of a significant relationship between percentage body fat of children and time spent in moderate and vigorous activity. Additionally, while there were no significant gender differences in physical activity patterns, children were more physically active during weekdays than weekends.