Environmental influences, physical activity, and weight status in 8- to 16-year-olds.

OBJECTIVE: To assess the association between vigorous physical activity, participation on sport teams and in exercise programs, television watching, family environment, and weight status in youth. DESIGN: Cross-sectional data from the Third National Health and Nutrition Examination Survey. PARTICIPANTS: A group of 2791 youth between the ages of 8 and 16 years who were enrolled in the Third National Health and Nutrition Examination Survey. MAIN OUTCOME MEASURES: Overweight was defined using age- and sex-specific 85th percentile of body mass index using Center for Disease Control and Prevention growth charts. RESULTS: Both males and females who had an overweight mother and or father were more likely to be overweight compared with youth who did not have an overweight parent. Females who watched 4 or more hours of television were more likely to be overweight than those who watched less than 4 hours. Males and 14- to 16-year-old females who participated in sport team and exercise programs were less likely to be overweight than their counterparts who did not participate. Also, females with larger families and males from families with higher family incomes were less likely to be overweight. CONCLUSIONS: These results suggest that family environment is associated with overweight in youth and that sport and exercise program participants are less like to be overweight and that, for females, increased television watching is related to overweight.

Correlates of objectively measured physical activity in preadolescent youth.

OBJECTIVE: The purpose of this study was to identify the psychosocial and environmental correlates of objectively measured physical activity behavior in a diverse sample of sixth-grade students. DESIGN: Cross-sectional. PARTICIPANTS AND SETTINGS: One hundred ninety-eight sixth-grade students from 4 public middle schools in Columbia, South Carolina. The study group was 52.0% female, 55.1% African-American, with a mean age of 11.4 +/- 0.6 years. MAIN OUTCOME MEASURES: Time spent in moderate physical activity (MPA) and vigorous physical activity (VPA) was assessed using a uniaxial accelerometer (CSA WAM 7164) (Computer Science and Applications Inc., Shalimar, FL). Determinant variables included: age, gender, race/ethnicity (demographic); physical activity self-efficacy, social norms related to physical activity, and beliefs regarding physical activity outcomes (psychosocial); and perceived physical activity habits of parents and peers, involvement in community physical activity organizations, involvement in community-based sports programs, access to fitness/sporting equipment at home, and self-reported hours spent watching television or playing video games (environmental). RESULTS: For boys, physical activity self-efficacy, social norms related to physical activity, and involvement in community physical activity organizations were salient predictors of MPA and VPA. Among girls, only physical activity self-efficacy emerged as a clear predictor of objectively measured physical activity. CONCLUSIONS: These findings are consistent with previous studies using self-reported physical activity and suggest that interventions to increase physical activity in preadolescent youth should endeavor to boost physical activity self-efficacy by offering a wide selection of enjoyable, developmentally-appropriate physical activity options.

Determinants of physical activity in active and low-active, sixth grade African-American youth.

This study compared the determinants of physical activity in active and low-active African-American sixth grade students (N = 108, 57 F, 51 M). Objective assessments of physical activity over a seven-day period were obtained using the CSA 7164 accelerometer. Students were classified as active if they exhibited three or more 20-minute bouts of moderate to vigorous physical activity over the seven-day period. Relative to low-actives, active boys reported significantly higher levels of self-efficacy, greater involvement in community physical activity organizations, and were significantly more likely to perceive their mother as active. Relative to low-actives, active girls reported significantly higher levels of physical activity self-efficacy, greater positive beliefs regarding physical activity outcomes, and were significantly less likely to watch television or play video games for > or = 3 hrs/day. These observations provide preliminary guidance as to the design of physical activity interventions targeted at African-American youth.

Validity of the computer science and applications (CSA) activity monitor in children.

PURPOSE: The purpose of this study was to evaluate the validity of the CSA activity monitor as a measure of children's physical activity using energy expenditure (EE) as a criterion measure. METHODS: Thirty subjects aged 10 to 14 performed three 5-min treadmill bouts at 3, 4, and 6 mph, respectively. While on the treadmill, subjects wore CSA (WAM 7164) activity monitors on the right and left hips. VO2 was monitored continuously by an automated system. EE was determined by multiplying the average VO2 by the caloric equivalent of the mean respiratory exchange ratio. RESULTS: Repeated measures ANOVA indicated that both CSA monitors were sensitive to changes in treadmill speed. Mean activity counts from each CSA unit were not significantly different and the intraclass reliability coefficient for the two CSA units across all speeds was 0.87. Activity counts from both CSA units were strongly correlated with EE (r = 0.86 and 0.87, P < 0.001). An EE prediction equation was developed from 20 randomly selected subjects and cross-validated on the remaining 10. The equation predicted mean EE within 0.01 kcal.min-1. The correlation between actual and predicted values was 0.93 (P < 0.01) and the SEE was 0.93 kcal.min-1. CONCLUSION: These data indicate that the CSA monitor is a valid and reliable tool for quantifying treadmill walking and running in children.

Physiological characteristics of elite middle and long distance runners.

The purpose of this study was to compare the physiological responses of highly trained middle (MD) and long distance (LD) runners during treadmill running. The oxygen uptake (VO2) of 74 elite runners (42 MD and 32 LD) was measured during treadmill running at several speeds (201, 241, 282, and 322 m/min at 0% grade) and at maximal effort. The mean VO2max (ml/kg X min) of the LD runners (76.9) was significantly higher (p less than 0.01) than the value for the MD group (68.9). At each running speed, the relative oxygen costs (%VO2) was lower (p less than 0.01) for the LD group averaging 8% less across the four running speeds. The slopes of the relationship between submaximal VO2 (ml/kg X min) and running speed of 0.183 and 0.216 for the MD and LD groups, respectively, were not significantly different. The relationship between running performance, maximal treadmill running time (TRT), and VO2 was studied for each group. VO2max was more highly correlated with running performance in the MD group (r = 0.70) than in the LD group (r = 0.32) although the standard errors of estimate were similar for both groups. Results of this investigation demonstrate that there are differences in the metabolic characteristics of the MD and LD runners as classified in this study.