## 2 Materials and Methods
### Data Collection  
#### Anthropometric Parameters and Biological Maturity Status  
The anthropometric characteristics of body height (0.5 cm; portable Stadiometer SECA 217; SECA, Hamburg, Germany), body weight (1N, Kistler force plate; Kistler Instrumente AG, Winterthur, Switzerland; calculated to the nearest 0.1 kg), and sitting height (0.5 cm; portable Stadiometer SECA 217; SECA, Hamburg, Germany; sitting height table) were assessed. Additionally, the leg length as difference between body height and sitting height (0.5 cm) and the body mass index (BMI; 0.1 kg/m\({}^{2}\)) were calculated. The percentiles of body height and body weight were classified according to [PERSON] et al. [14]. Percentiles of body height and body weight were categorized in three groups (0: percentile 25 and below; 1: between percentile 25 and \(<\)75; 2: percentile 75 and above), which was done in accordance with [PERSON] et al. [15].  
The biological maturity status was assessed using the non-invasive method of calculating the age at peak height velocity (APHV) [16]. These sex-specific prediction equations include the aforementioned anthropometric characteristics (except for BMI) as well as the calculated actual chronological age at the time of measurement. Then, based on these values, the maturity offset as the time before or after individual peak height velocity (PHV) was calculated. Then, the difference between the actual chronological age and the maturity offset was defined as APHV. Then, participants were categorized into three maturity groups according to the sex-specific APHV of the present sample [17; 18]: early maturing, defined as APHV below sex-specific mean - standard deviation; normal maturing, defined as sex-specific mean APHV \(\pm\) standard deviation; and late maturing: APHV higher than sex-specific mean + standard deviation. A negative maturity offset indicated that the athlete was pre PHV, whereas a  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{**Sex**} \\ \cline{2-3}
**Anthropometric Characteristics** & **Male** & **Female** \\ \cline{2-3}  & **M \(\pm\) SD** & **M \(\pm\) SD** \\ \hline Age [yrs] & 10.6 \(\pm\) 0.4 & 10.5 \(\pm\) 0.3 \\ Height [cm] & 144.6 \(\pm\) 5.5 & 142.5 \(\pm\) 6.0 \\ Weight [kg] & 35.3 \(\pm\) 5.1 & 34.0 \(\pm\) 4.9 \\ BMI \({}^{1}\) [kg/m\({}^{2}\)] & 16.8 \(\pm\) 1.9 & 16.7 \(\pm\) 1.7 \\ Setting height [cm] & 77.5 \(\pm\) 4.3 & 77.7 \(\pm\) 4.6 \\ APHV \({}^{2}\) [yrs] & 13.5 \(\pm\) 0.4 & 12.0 \(\pm\) 0.4 \\ \hline \hline \end{tabular}  
* BMI: body mass index; \({}^{2}\) APHV: age at peak height velocity.  
\end{table}
Table 1: Anthropometric characteristics of male and female athletes at the start of the study.  
positive maturity offset indicated post PHV [16]. In accordance with [PERSON] et al. [19] and [PERSON] et al. [20], puberty status was classified as pre-pubertal: maturity offset \(-1\) and smaller; pubertal: maturity offset between \(-1\) and \(1\); and post-pubertalal: maturity offset \(1\) and larger. A previous study [18] confirmed the validity of this APHV method for 10- to 13-year-old youth ski racers. The difference between the calculated APHV and the actual age at the day of the occurrence of an injury was defined as maturity offset at time of injury occurrence. The birth months of the athletes were split into relative age quarters; relative age quarter 1 (Q1) included the birth months January, February, and March; Q2 included April, May, and June; Q3 included July, August, and September; and Q4 included October, November, and December.