Validity and Reproducibility of a New Treadmill Protocol: The Fitkids Treadmill Test

Purpose This study aimed to investigate the validity and reproducibility of a new treadmill protocol in healthy children and adolescents: the Fitkids Treadmill Test (FTT). Methods Sixty-eight healthy children and adolescents (6-18 yr) were randomly divided into a validity group (14 boys and 20 girls; mean SD age, 12.9 3.6 yr) that performed the FTT and Bruce protocol, both with respiratory gas analysis within 2 wk, and a reproducibility group (19 boys and 15 girls; mean +/- SD age, 13.5 +/- 3.5 yr) that performed the FTT twice within 2 wk. A subgroup of 21 participants within the reproducibility group performed both FTT with respiratory gas analysis. Time to exhaustion (TTE) was the main outcome of the FTT. Results VO2peak measured during the FTT showed excellent correlation with VO2peak measured during the Bruce protocol (r = 0.90; P < 0.01). Backward multiple regression analysis provided the following prediction equations for VO2peak (Lmin(-1)) for boys and girls, respectively: VO2peak FTT = -0.748 + (0.117 x TTEFTT) + (0.032 x body mass) + 0.263, and VO2peak FTT = -0.748 + (0.117 x TTEFTT) + (0.032 x body mass) [R-2 = 0.935; SEE = 0.256 Lmin(-1)]. Cross-validation of the regression model showed an R-2 value of 0.76. Reliability statistics for the FTT showed an intraclass correlation coefficient of 0.985 (95% confidence interval, 0.971-0.993; P < 0.001) for TTE. Bland-Altman analysis showed a mean bias of -0.07 min, with limits of agreement between +1.30 and -1.43 min. Conclusions Results suggest that the FTT is a useful treadmill protocol with good validity and reproducibility in healthy children and adolescents. Exercise performance on the FTT and body mass can be used to adequately predict VO2peak when respiratory gas analysis is not available.