RESUMO
Background While severe obesity in childhood poses the greatest long-term health risks, access to treatment is a common barrier. The present pilot study examined the effect of a 7-week low-dose physical activity (PA) intervention on PA and body mass index (BMI) in severe obese adolescents delivered via telephone and mail. Methods Adolescents (n = 64) receiving care from a pediatric obesity medical clinic were randomized to a control (n = 30) or intervention (n = 34) group. Height and weight were measured and BMI z-scores were calculated. PA was assessed by a pedometer. All measurements were completed pre- and post-intervention. The intervention group received weekly newsletters and telephone calls discussing various PA topics based on motivational interviewing for 7 weeks. The control group received no contact. A series of 2 × 2 (group by time) repeated measures analysis of covariances (ANCOVAs) adjusting for length of time between visits were performed to examine the effect of the intervention on PA and BMI z-scores. Results The majority of adolescents were severely obese (77%, BMI: > 99th percentile). Intention-to-treat analysis revealed intervention effects were not observed for either pedometer steps or BMI z-score (p > 0.05). Among those with complete data, adolescents who successfully changed their BMI z-score had larger BMI z-score changes than those who did not change their BMI z-score (p = 0.0001). This improvement was due to something other than PA as the change in BMI z-score was similar among those who did and did not successfully increase PA levels (p > 0.05). Conclusions More intensive, comprehensive, and longer-term treatment is needed in this high risk population.
RESUMO
BACKGROUND: Aerobic fitness (VO(2)max) is a key component of youth fitness testing. Criterion-referenced (CR) assessments are used in FITNESSGRAM(®) to assess health risk. PURPOSE: The purpose of this study was to develop and cross-validate regression models to estimate VO(2)max from Progressive Aerobic Cardiovascular Endurance Run (PACER) 20-m shuttle run performance in boys and girls aged 10-16 years. Several previously published PACER models were also cross-validated. A secondary purpose was to examine the CR validity of the models. METHODS: PACER performance and VO(2)max were assessed in a sample of 244 participants. The sample was randomly split into validation (n=174) and cross-validation (n=70) samples. The validation sample was used to develop the regression models to estimate VO(2)max from PACER, BMI, gender, and age. CR validity was evaluated by comparing classification of the prediction models with classification by the criterion of measured VO(2)max. RESULTS: For the Quadratic Model, the multiple correlation between measured and estimated VO(2)max was 0.75, and the SE of estimate (SEE) was 6.17 mL/kg/min. Similar accuracy was found for Linear Model 2 (R=0.74; SEE=6.29 mL/kg/min). Accuracy of these models was confirmed on the cross-validation and total samples. Cross-validation demonstrated that the Quadratic Model and Linear Model 2 were slightly more accurate than previous PACER models. Evidence of CR validity for the newly developed models was of moderate levels. CONCLUSIONS: The Quadratic Model and Linear Model 2 provide valid estimates of VO(2)max and compare favorably to previous models. The CR validity evidence for the Quadratic Model and Linear Models developed in this study was slightly better than for the other models examined.
