Cross-Validation of Single-Stage Treadmill Tests for Predicting Aerobic Fitness in Adolescents with Type I Diabetes.

PURPOSE: Determining fitness is important when assessing adolescents with type 1 diabetes mellitus (T1DM). Submaximal tests estimate fitness, but none have been validated in this population. This study cross-validates the Ebbeling and Nemeth equations to predict fitness (VO2max (ml/kg/min)) in adolescents with T1DM. METHODS: Adolescents with T1DM (n = 20) completed a maximal treadmill test using indirect calorimetry. Participants completed one 4-min stage between 2.0 and 4.5 mph and 5% grade (Ebbeling/Nemeth protocol). Speed and grade were then increased until exhaustion. Predicted VO2max was calculated using the Ebbeling and Nemeth equations and compared with observed VO2max using paired t tests. Pearson correlation coefficients, 95% confidence intervals, coefficients of determination (R²), and total error (TE) were calculated. RESULTS: The mean observed VO2max was 47.0 ml/kg/min (SD = 6.9); the Ebbeling and Nemeth mean predictions were 42.4 (SD = 9.4) and 43.5 ml/kg/min (SD = 6.9), respectively. Paired t tests resulted in statistically significant (p < .01) mean differences between observed and predicted VO2max for both predictions. The association between the Ebbeling prediction and observed VO2max was r = .90 (95% CI = 0.76, 0.96), R² = .81, and TE = 6.5 ml/kg/ min. The association between the Nemeth prediction and observed VO2max was r = .81 (95% CI = 0.57, 0.92), R² = .66, and TE = 5.6 ml/kg/min. CONCLUSION: The Nemeth submaximal treadmill protocol provides a better estimate of fitness than the Ebbeling in adolescents with T1DM.

Ten-year objective physical activity tracking: Iowa Bone Development Study.

PURPOSE: This study aimed to examine the tracking of physical activity (PA) during a 10-yr period and to investigate whether sex differences in PA trajectories are altered after aligning by maturity instead of age. METHODS: The Iowa Bone Development Study collected accelerometer data on a cohort of 140 girls and 128 boys at ages 5, 9, 11, 13, and 15 yr. Logistic regression determined the odds ratio of being in lowest PA tertile at 15 yr if in lowest tertile at age 5 yr. Spearman correlation coefficients examined PA tracking from age 5 to 15 yr. Using additional Iowa Bone Development participants at ages 9, 11, 13, and 15 yr (N = 482, 457, 416, and 316, respectively), we examined the stability of PA for chronological and biological age in 2-yr intervals surrounding peak height velocity (PHV) age. Year from PHV was estimated using the Mirwald prediction equation. RESULTS: Girls had significant 10-yr correlations (r = 0.27); boys did not. Girls, not boys, were more likely to be in the lowest tertile for PA at age 15 yr if in the lowest tertile at age 5 yr (moderate to vigorous PA: odds ratio = 3.1, 95% confidence interval = 1.4-6.9; vigorous PA: odds ratio = 2.8, 95% confidence interval = 1.2-6.1). Girls' 2-yr intervals for PA showed moderate associations (r = 0.31-0.56) when aligned chronologically but were moderate to high (r = 0.41-0.63) when aligned biologically. Boys' associations were low to moderate (r = 0.26-0.56) chronologically. When aligned biologically, the associations were low for the -1- to 1-yr interval (1 yr before the 1-yr post-PHV) but moderate to high for the -2- to 0-yr and 0- to 2-yr intervals (r = 0.50-0.61). CONCLUSIONS: Physical activity tracking from childhood to adolescence is stronger in girls than that in boys. Intervention programs targeting boys should focus on time surrounding puberty in boys during which activity patterns change.