Physical activity in overweight and nonoverweight preschool children.

OBJECTIVE: To compare the physical activity levels of overweight and non overweight 3- to 5-y-old children while attending preschool. A secondary aim was to evaluate weight-related differences in hypothesized parental determinants of child physical activity behavior. DESIGN: Cross-sectional study. SUBJECTS: A total of 245, 3- to 5-y-olds (127 girls, 118 boys) and their parent(s) (242 mothers, 173 fathers) recruited from nine preschools. Overweight status determined using the age- and sex-specific 85th percentile for body mass index (BMI) from CDC Growth Charts. MEASUREMENTS: Physical activity during the preschool day was assessed on multiple days via two independent objective measures-direct observation using the observation system for recording activity in preschools (OSRAP) and real-time accelerometry using the MTI/CSA 7164 accelerometer. Parents completed a take-home survey assessing sociodemographic information, parental height and weight, modeling of physical activity, support for physical activity, active toys and sporting equipment at home, child's television watching, frequency of park visitation, and perceptions of child competence. RESULTS: Overweight boys were significantly less active than their nonoverweight peers during the preschool day. No significant differences were observed in girls. Despite a strong association between childhood overweight status and parental obesity, no significant differences were observed for the hypothesized parental influences on physical activity behavior. CONCLUSIONS: Our results suggest that a significant proportion of overweight children may be at increased risk for further gains in adiposity because of low levels of physical activity during the preschool day.

Physical activity assessment in children and adolescents.

Chronic disease risk factors, including a sedentary lifestyle, may be present even in young children, suggesting that early prevention programmes may be critical to reducing the rates of chronic disease. Accurate assessment of physical activity in children is necessary to identify current levels of activity and to assess the effectiveness of intervention programmes designed to increase physical activity. This article summarises the strengths and limitations of the methods used to evaluate physical activity in children and 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 resulting in energy expenditure (EE), direct observation of the individual's movement should be used as the gold standard for physical activity research. The doubly labelled water technique and indirect calorimetry can also be considered criterion measures for physical activity research, because they measure EE, a physiologic consequence closely associated with physical activity. Devices such as heart rate monitors, pedometers and accelerometers have become 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 valid to use in creating broad physical activity categories (e.g. highly active, somewhat active, sedentary) but lacks the specificity needed to estimate physical activity in individuals. Laboratory and field validations of pedometers 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 instruments. These techniques must be used cautiously in a paediatric population that has difficulty recalling such information. Still, some studies have reported 73.4% to 86.3% agreement between these instruments and direct observation. Future investigations of physical activity instruments should validate the novel instrument against a higher standard. Additional studies are needed to investigate the possibility of improving the accuracy of measurement by combining 2 or more techniques. The accurate measurement of physical activity is critical for determining current levels of physical activity, monitoring compliance with physical activity guidelines, understanding the dose-response relationship between physical activity and health and determining the effectiveness of intervention programmes designed to improve physical activity.

Field evaluation of the Computer Science and Applications, Inc. physical activity monitor.

PURPOSE: The purpose of this study was to evaluate the Computer Science and Applications, Inc. (CSA) activity monitor to quantify physical activity in free living subjects using an activity diary as the criterion measure. METHODS: Subjects also completed a 7-d physical activity recall at the end of the monitoring period. Nine male and 10 female subjects (mean, SD) (25.0, 3.6 yr) wore the CSA monitor for 7 consecutive days. On 3 of those days, subjects completed an activity diary (2 weekdays and 1 weekend day). Total kcal per day (Dkcal(tot)) was calculated from the self-reported diary classifications of the subject's activities. For the 3 days that coincided with the diary, total number of counts accumulated per day (cnt(tot)) was obtained from the monitor. RESULTS: The amount of activity per day recorded by the CSA monitor followed the same pattern of change as the activity diary. The cnt(tot) and Dkcal(tot) were significantly (P < or = 0.05) correlated on day 1 (r = 0.65), day 2 (r = 0.49), day 3 (r = 0.55), and for the 3 days pooled (r = 0.51). Subjects were classified as low, moderate, or highly active based on tertiles of kcal from the diary and counts from the CSA monitor. The percentage agreement between the CSA and the activity diary was 68.4% (Kappa = 0.53, P < 0.01). The number of minutes spent in the various activity categories were compared between instruments using an ANOVA model. The results of these analyses suggest that the CSA overestimated light activity and underestimated vigorous activity compared with the diary. CONCLUSION: In conclusion, the CSA monitor may be useful in a field situation where total physical activity and patterns of physical activity are the desired outcomes.