Statistical analysis
A sample size of 20 adolescents per group was estimated to be needed to
detect a difference of 6 ml/kg/min with a standard deviation of 6
ml/kg/min in the VO2peak (22). The final sample size was
22 adolescents per group, assuming a loss of up to 10%. The sample size
was calculated to provide 80% power and an alpha level of 0.05. The
normality of the data was evaluated using the Kolmogorov-Smirnov test.
The between-group comparisons of the categorical variables and the
analysis of the differences in the proportions of adolescents across
groups were performed using the chi-square test or Fisher’s test. For
the between-group comparisons of the continuous variables, the t-test or
Mann-Whitney test was used. The data were analyzed using the Statistical
Package for Social Science (SPSS) software, version 22.0 (Chicago, IL,
USA).