Physical activity assessment in children and adolescents

Chronic disease risk factors, including a sedentary lifestyle, may be prese nt even in young children, suggesting that early prevention programmes may be critical to reducing the rates of chronic disease. Accurate assessment o f physical activity in children is necessary to identify current levels of activity and to assess the effectiveness of intervention programmes designe d to increase physical activity. This article summarises the strengths and limitations of the methods used to evaluate physical activity in children a nd adolescents. MEDLINE searches and journal article citations were used to locate 59 articles that validated physical activity measurement methods in children and adolescents. Only those methods that were validated against a more stringent measure were included in the review. Based on the definition of physical activity as any bodily movement resulti ng in energy expenditure (EE), direct observation of the individual's movem ent should be used as the gold standard for physical activity research. The doubly labelled water technique and indirect calorimetry can also be consi dered criterion measures for physical activity research, because they measu re EE, a physiologic consequence closely associated with physical activity. Devices such as heart rate monitors, pedometers and accelerometers have be come increasingly popular as measurement tools for physical activity. These devices reduce the subjectivity inherent in survey methods and can be used with large groups of individuals. Heart rate monitoring is sufficiently va lid to use in creating broad physical activity categories (e.g, highly acti ve, somewhat active, sedentary) but lacks the specificity needed to estimat e physical activity in individuals. Laboratory and field validations of ped ometers and accelerometers yield relatively high correlations using oxygen consumption (r = 0.62 to 0.93) or direct observation (r = 0.80 to 0.97) as criterion measures, although, they may not be able to capture all physical activity. Physical activity has traditionally been measured with surveys and recall i nstruments. These techniques must be used cautiously in a paediatric popula tion that has difficulty recalling such information. Still, some studies ha ve reported 73.4% to 86.3% agreement between these instruments and direct o bservation. Future investigations of physical activity instruments should v alidate the novel instrument against a higher standard. Additional studies are needed to investigate the possibility of improving the accuracy of meas urement by combining 2 or more techniques. The accurate measurement of phys ical activity is critical for determining current levels of physical activi ty, monitoring compliance with physical activity guidelines, understanding the dose-response relationship between physical activity and health and det ermining the effectiveness of intervention programmes designed to improve p hysical activity.