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Habitual physical activity, body composition and health risk factors of Singaporean children and adolescents
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Type
Thesis
Author
Sun, David Xiaoqian
Supervisor
Schmidt, Gordon James
Teo-Koh, Sock Miang
Abstract
Many studies have shown that physical activity plays an important role in reducing cardiovascular disease (CVD) risk factors in adults. However, the association between childhood physical activity and CVD risk factors or obesity is not conclusive. This study seeks to explain the relationships between habitual physical activity, body composition, diet and lipid-lipoproteins concentrations in Singaporean school children.
A total of 55 boys (age: 13.00 ± 0.60 yrs; body mass: 49.50 ± 16.20 kg; height: 1.59 ± 0.10 m) and 39 girls (age: 13.10 ± 0.60 yrs; body mass: 44.80 ± 9.20 kg; height: 1.53 ± 0.10 m) took part in this study. In the validation phase, 25 subjects and 18 subjects completed designated activities in indoor and outdoor settings respectively to establish the validity of the accelerometer. They wore a RT3 acceIerometer, a heart rate monitor (HRM) and a portable indirect calorimeter (Cosmed K4b2) simultaneously when they engaged in each of designated activities. In collecting information phase, after subjects completed a physical activity questionnaire, they wore the accelerometer and a HRM concurrently for three consecutive weekdays and a weekend day. Subjects also completed a dietary and activity log for the four days. Body composition was determined using dual energy X-ray absorptiometry (DXA) scanning. Energy expenditure (EE) was assessed using the Cosmed K4b2. A fasting blood sample was collected for the analysis of blood lipid-lipoproteins, and glucose concentrations. Resting blood pressure was taken by the auscultatory method with a sphygmomanometer and a stethoscope. Aerobic fitness (peak V02) was evaluated on the treadmill via the Bruce protocol.
The results showed that the RT3 accelerometer was a valid tool for measuring physical activity of children. Moderate to high correlations were found (outdoor: r = 0.76, p = 0.001 vs indoor: r = 0.96, p = 0.001) between accelerometer estimated EE and metabolic measurement. Physical activity was positively correlated with peak VO2 and inversely correlated with body fat. However, after adjusting for peak VO2, the relationship between physical activity and body fat disappeared. There was no significant difference of CVD risk factors between accelerometer outputs (Wilks' Lambda = 0.679, F [Z, 731 = 1.367, p = 0.15, multivariate = 0.176). Correlation analysis indicated that, except for triglyceride concentrations, there were no significant relationships between physical activity and lipid-lipoprotein concentrations. However, significant relationships between percent of body fat (%BF), lipid-lipoprotein and glucose concentrations were found. TC and LDL-C seem to be more influenced by diet. Furthermore, %BF significantly predicted LDL-C concentrations while trunk fat significantly predicted blood pressure.
Physical activity seems to have an indirect influence on CVD risk factors mainly through changing body composition in children. This study provides some evidence that an active lifestyle, more moderate to vigorous activity and a healthy diet may reduce CVD risk factors in children and adolescents.
A total of 55 boys (age: 13.00 ± 0.60 yrs; body mass: 49.50 ± 16.20 kg; height: 1.59 ± 0.10 m) and 39 girls (age: 13.10 ± 0.60 yrs; body mass: 44.80 ± 9.20 kg; height: 1.53 ± 0.10 m) took part in this study. In the validation phase, 25 subjects and 18 subjects completed designated activities in indoor and outdoor settings respectively to establish the validity of the accelerometer. They wore a RT3 acceIerometer, a heart rate monitor (HRM) and a portable indirect calorimeter (Cosmed K4b2) simultaneously when they engaged in each of designated activities. In collecting information phase, after subjects completed a physical activity questionnaire, they wore the accelerometer and a HRM concurrently for three consecutive weekdays and a weekend day. Subjects also completed a dietary and activity log for the four days. Body composition was determined using dual energy X-ray absorptiometry (DXA) scanning. Energy expenditure (EE) was assessed using the Cosmed K4b2. A fasting blood sample was collected for the analysis of blood lipid-lipoproteins, and glucose concentrations. Resting blood pressure was taken by the auscultatory method with a sphygmomanometer and a stethoscope. Aerobic fitness (peak V02) was evaluated on the treadmill via the Bruce protocol.
The results showed that the RT3 accelerometer was a valid tool for measuring physical activity of children. Moderate to high correlations were found (outdoor: r = 0.76, p = 0.001 vs indoor: r = 0.96, p = 0.001) between accelerometer estimated EE and metabolic measurement. Physical activity was positively correlated with peak VO2 and inversely correlated with body fat. However, after adjusting for peak VO2, the relationship between physical activity and body fat disappeared. There was no significant difference of CVD risk factors between accelerometer outputs (Wilks' Lambda = 0.679, F [Z, 731 = 1.367, p = 0.15, multivariate = 0.176). Correlation analysis indicated that, except for triglyceride concentrations, there were no significant relationships between physical activity and lipid-lipoprotein concentrations. However, significant relationships between percent of body fat (%BF), lipid-lipoprotein and glucose concentrations were found. TC and LDL-C seem to be more influenced by diet. Furthermore, %BF significantly predicted LDL-C concentrations while trunk fat significantly predicted blood pressure.
Physical activity seems to have an indirect influence on CVD risk factors mainly through changing body composition in children. This study provides some evidence that an active lifestyle, more moderate to vigorous activity and a healthy diet may reduce CVD risk factors in children and adolescents.
Date Issued
2005
Call Number
GV481 Sun
Date Submitted
2005