## 2 Materials and Methods
### Statistical Analysis  
The statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS), v.21.0 for Windows. (IBM Corp. Released 2012. IBM SPSS Statistics for Windows, Version 21.0. IBM Corp.: Armonk, NY, USA). The normality of each variable was initially tested using the Kolmogorov-Smirnov test. Descriptive statistics were calculated for each genotype. The genotype frequencies of all polymorphisms were compared between non-injured and injured football players and injury aetiologies, using a \(\chi^{2}\) test. The disequilibria of SNPs were estimated using the Hardy-Weinberg Equilibrium (HWE). The characteristics of the injuries were recorded, and the genotype characteristics were analysed using the \(\chi^{2}\) test. To determine what genotype was associated with an unexpected distribution, the standardised residuals were calculated based on the difference between the observed and the expected values. Briefly, within each injury variable, a genotype was considered to have a statistically different distribution from the expected value when its distribution was > or < the critical \(Z\)-score value (i.e., 1.96). The significance level was set at \(p\) < 0.050. **3. Results**  
All the polymorphisms analysed met the HWE (all \(p\) > 0.05). The genotype frequencies for the six polymorphisms in the women's amateur football players are shown in Table 2.  
In total, 93 (55.4%) women's amateur football players suffered a non-contact injury during the season, for a total of 169. The remaining 75 players (44.6%) had no injuries during the season. The characteristics of the injuries recorded and analysed during the season are presented in Table 3. \begin{table}
\begin{tabular}{c c c c c c} \hline  & **Gene** & **Polymorphism** & **dbSNP** & **Genotype** &
\begin{tabular}{c} **Women Football** \\ **Players, n (\%)** \\ \end{tabular} \\ \hline \multirow{3}{*}{_ACE_} & Angiotensin-converting enzyme & \multirow{3}{*}{I/D} & \multirow{3}{*}{rs4646994} & DD & 86 (51.2) \\  & & & & ID & 57 (33.9) \\  & & & & II & 25 (14.9) \\ \hline \multirow{3}{*}{_ACTN3_} & \multirow{3}{*}{alpha-actinin-3} & \multirow{3}{*}{c.1729C\textgreater{}T} & \multirow{3}{*}{rs1815739} & CC & 47 (27.9) \\  & & & & CT & 96 (57.2) \\  & & & & TT & 25 (14.9) \\ \hline \multirow{3}{*}{_AMPD1_} & Adenosine monophosphate deaminase 1 & \multirow{3}{*}{c.34C\textgreater{}T} & \multirow{3}{*}{rs17602729} & CC & 125 (74.4) \\  & & & & CT & 29 (17.2) \\  & & & & TT & 14 (8.4) \\ \hline \multirow{3}{*}{_CKM_} & Muscle-specific creatine kinase & \multirow{3}{*}{c.*800A\textgreater{}G} & \multirow{3}{*}{rs8111989} & GG & 22 (13.1) \\  & & & & GA & 75 (44.6) \\  & & & & AA & 71 (42.3) \\ \hline \multirow{3}{*}{_MLCK_} & Myosin light-chain kinase & \multirow{3}{*}{c.49C\textgreater{}T} & \multirow{3}{*}{rs2700352} & CC & 111 (66.1) \\  & & & & CT & 50 (29.7) \\ \cline{1-1}  & & & & TT & 7 (4.2) \\ \cline{1-1} \cline{2-6}  & & & & AA & 7 (4.2) \\ \cline{1-1}  & & & & CA & 18 (10.7) \\ \cline{1-1}  & & & & CC & 143 (85.1) \\ \hline \end{tabular}
\end{table} 
Table 2: Genotype frequencies in women ’s amateur football players. The genotypic distribution in the epidemiology of injured women's amateur football players compared to the non-injured players showed no statistical differences in any polymorphism (all \(p>0.050\)) (Table 4).