Trends in Physical Fitness in Children and Adolescents Within the Past 18 Years (DONALD Study).

Objective: To evaluate the trends in physical fitness in children and adolescents.

Method: The present study focusses on a longitudinal analysis of the single two-legged jump (S2LJ) from children and adolescents, who participated in the DONALD study from 2004 till 2022. P _max/body mass (power, surrogate for muscular performance), V _max (bounce speed, surrogate for coordination), F _max/body mass (force, surrogate for muscular strength) and $\frac{V_{\max }}{F_{\max }/\mathrm{BM}}$ (Nerve-Muscle Index, surrogate for jump efficiency) were examined by linear mixed models and propensity-score(PS)-matching analysis.

Results: Data from 1,485 measurements from males and 1,445 from females were included. Mean age was 10.9 years for males and 11.4 years for females. The range of the number of repeated S2LJ was 1 to 8, the median was 3. In PS-matching analysis, there was a dose-effect relationship between the test date and the S2LJ parameters in such a way that P _max/body mass and F _max/body mass decreased with more recent test dates (effect size at a difference in the test date of 1.7 decades: 0.25 - 0.3) whereby V _max and $\frac{V_{\max }}{F_{\max }/\mathrm{BM}}$ showed no consistent trend.

Conclusion: Motor performance in children, assessed by the S2LJ, has decreased over the last two decades, mainly due to lower muscular strength, while motor efficiency and coordination seemed to be unchanged.