Summary:
The purpose of the study was to assess the levels of physical activity and body fat in 4th, 5th and 6th grade school boys and to investigate: (1) the relationship between physical activity and body fat and (2) the validity of a physical activity questionnaire.
Methods: Were examined 254 boys, 9-12 years old (10.2 ± 0.8 yr). The measurements were included: the weight and the height for the calculation of the Body Mass Index (BMI), the triceps and the calf skinfolds thickness with skinfold caliper, the waist and hip circumferences for the calculation of the waist-to-hip- ratio (WHR) and the percentage of body fat by using bioelectrical impedance analysis. Physical activity was measured for three days by two methods: with self-administered questionnaire and with activity monitor (CSA, Model 7164). The questionnaire was completed by 204 boys. It consisted of a list of various athletic and recreational activities, plus sedentary pursuits. For each activity children engaged in the previous day, they reported the segment of the day, the number of minutes, and a subjective intensity rating. Self-reported data were summarized with the following three variables: (a) total minutes of physical activity; (b) weighted activity MET score(min of activity x MET value x intensity rating); (c) minutes in sedentary pursuits. Forty children were grouped into four fat categories based on percentiles for BMI (Underweight, Normal weight, Moderately overweight/Overweight, Obese), in which the
physical activity was assessed with the activity monitor, in order to investigate if there are
differences in levels of physical activity between them, and also to examine the validity of the questionnaire.
Results: The results showed that the obese children have lower levels of physical activity than children with normal weight. Physical activity, as assessed by means of the activity monitor, was significantly correlated with the BMI (r = -0,51, p 0,01), the % body fat (r = -0,57, p 0,01), the sum of two skinfolds (r = -0,60, p 0,01) and the hip circumference (r = -0,50 p 0,01). The total minutes of physical activity and the weighted activity MET score, as assessed by the questionnaire, showed small negative correlations with the above parameters, but statistically significant. In addition, minutes in sedentary pursuits were positive associated with the BMI (r=0,13, p 0,05), the waist circumference (r =0,15 p 0,05) and the hip circumference (r=0,12 p 0,05). The questionnaire used in this research, showed acceptable levels of validity in children 9-12 years old. The correlation coefficients of the total minutes of physical activity and the weighted activity MET score, were respectively (r=0,54 and r=0,59), (r=0,65 and r=0,68) and (r=0,69 and r=0,68) for the three days.
Conclusions: In 9 to 12 years old boys, the high levels of body fat are associated with low levels of physical activity and increased time of sedentary activities. These conclusions reinforce the beneficial role of physical activity in the weight control efforts of preadolescents boys and provide support to encourage physical activity during childhood.
