*2.4. Statistical Analysis*

Statistical analyses were performed using IBM SPSS Statistics 28 (IBM Corporation, Armonk, NY, USA). To obtain an overview of the distribution within the sample, frequency analyses and cross tables were conducted.

Descriptive statistics with mean values and 95% CI were calculated for each test item and cohort overall and separately for boys and girls to reflect the entire measurement period. Missing data were not interpolated. The analysis was controlled for age and BMI. We conducted a univariate analysis of covariance (ANCOVA) to examine the differences between the cohorts PreCOVID and COVID1, and between PreCOVID and COVID2 adjusted for gender. The PreCOVID cohort value was formed using the mean value of individual cohorts from 2012–2019. The level of significance was set at *p* < 0.05. Effects were assessed with partial eta squared (η<sup>p</sup> 2 ). Pairwise comparisons with Bonferroni correction were performed to determine differences between the cohorts.
