## 3 Results
### 3.2 Shear Modulus and Mechanical Parameters
#### 3.2.3 Previously Hamstring Injured Limbs vs. Contralateral Limb  
With respect to the comparison involving previously hamstring injury limbs vs. the contralateral limb (Table 3), for the active shear modulus, only a significant interaction between sprint instants and limbs with or without injury history was seen for ST (\(p\) = 0.003; \(\eta^{2}_{\rm p}\) = 0.241). For neuromuscular parameters, significant differences were seen for PT (pre: 138.7 \(\pm\) 43.6 Nm; post: 126.7 \(\pm\) 42.0 Nm; \(p\) < 0.001; \(\eta^{2}_{\rm p}\) = 0.548) and RTD 50-100 ms (pre: 807.8 \(\pm\) 224.7 Nm/s; post: 725.4 \(\pm\) 208.1 Nm/s; \(p\) = 0.002; \(\eta^{2}_{\rm p}\) = 0.258) between instants.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**Pre Sprint**} & \multicolumn{2}{c}{**Post Sprint**} & \multicolumn{2}{c}{**Instant**} & \multicolumn{2}{c}{**In Injury**} & \multicolumn{2}{c}{**In injury \(\times\) Instant**} \\  & & **Injured** & **Control** & **Injured** & **Control** & **\(p\)** & **\(\eta^{2}\)**p** & **\(p\)** & **\(\eta^{2}\)**p** & **\(p\)** & **\(\eta^{2}\)**p** \\ \hline \multirow{4}{*}{**Active** (kPa)} & **BFih** & 30.94 \(\pm\) 9.85 & 32.52 \(\pm\) 10.01 & 30.75 \(\pm\) 11.60 & 33.24 \(\pm\) 11.80 & 0.012 & 0.064 & 0.368 & 0.008 & 0.574 & 0.003 \\  & **BFsh** & 48.11 \(\pm\) 16.61 & 52.23 \(\pm\) 16.37 & 53.11 \(\pm\) 16.08 & 54.82 \(\pm\) 15.83 & 0.775 & 0.001 & 0.354 & 0.009 & 0.472 & 0.005 \\  & **SM** & 35.19 \(\pm\) 10.84 & 36.05 \(\pm\) 10.67 & 34.82 \(\pm\) 11.06 & 36.31 \(\pm\) 10.89 & 0.050 & 0.040 & 0.605 & 0.003 & 0.650 & 0.002 \\  & **ST** & 61.27 \(\pm\) 17.33 & 59.39 \(\pm\) 17.83 & 58.48 \(\pm\) 16.52 & 58.96 \(\pm\) 16.30 & 0.330 & 0.010 & 0.841 & -0.001 & 0.330 & 0.010 \\
**Ratio** & **BFihST** & 0.53 \(\pm\) 2.07 & 0.65 \(\pm\) 0.99 & 0.55 \(\pm\) 0.26 & 0.62 \(\pm\) 0.34 & 0.853 & -0.001 & 0.261 & 0.013 & 0.421 & 0.007 \\ \hline
**Peak Torque** (N-m) & 139.09 \(\pm\) 33.45 & 141.45 \(\pm\) 25.84 & 127.27 \(\pm\) 32.95 & 130.79 \(\pm\) 25.16 & 0.055 & 0.038 & 0.660 & 0.002 & 0.571 & 0.003 \\
**RTD 0-50** (N-m/s) & 514.57 \(\pm\) 194.54 & 479.81 \(\pm\) 193.93 & 484.47 \(\pm\) 196.11 & 448.18 \(\pm\) 178.15 & 0.870 & -0.001 & 0.286 & 0.012 & 0.885 & \(<\)0.001 \\
**RTD 50-100** (N-m/s) & 807.81 \(\pm\) 222.87 & 816.87 \(\pm\) 209.56 & 730.42 \(\pm\) 224.07 & 735.79 \(\pm\) 197.19 & 0.259 & 0.013 & 0.981 & 0.001 & 0.996 & \(<\)0.001 \\
**RTD 150-200** (N-m/s) & 343.68 \(\pm\) 41.67 & 366.06 \(\pm\) 212.88 & 310.92 \(\pm\) 94.95 & 344.10 \(\pm\) 102.96 & 0.209 & 0.016 & 0.220 & 0.015 & 0.474 & 0.005 \\
**TU-RTDmax** (s) & 0.073 \(\pm\) 0.022 & 0.080 \(\pm\) 0.023 & 0.074 \(\pm\) 0.023 & 0.076 \(\pm\) 0.021 & 0.031 & 0.048 & 0.200 & 0.017 & 0.835 & \(<\)0.001 \\ \hline \multicolumn{10}{c}{Abbreviations: BFih, biopsy femoris long head; BFsh, biceps femoris short head; SM, semimembranosus; ST, semitembranosus; BFH,ST ratio, biceps femoris long head ratio; RTD 0-50, rate torque development between 0–50 ms; RTD 50–100, rate torque development between 50–100 ms; RTD 150–200, rate torque development between 150–200 ms; TU-RTDmax, time until reach the maximum value of rate torque development (ms); \(p\), \(p\) value; \(\eta^{2}_{\rm p}\), eta squared. Data are presented as mean \(\pm\) standard deviation.} \\ \end{tabular}
\end{table}
Table 1: Acute effects of a sprint protocol in limbs with previous hamstring injury history (n = 34) vs. healthy control players (n = 65) using age as a covariate on the active shear modulus and neuromuscular parameters.  
Figure 2: Average sprint speed values in the sprint performance of 10 sets \(\times\) 30 m in players with no injury history (black) and players with injury history (red). Data are presented as mean \(\pm\) standard deviation. * A significant difference between the current sprint and each subsequent sprint is indicated (\(p\) < 0.05).  
Furthermore, a significant injury and instant interaction was seen for RTD 150-200 ms (\(p=0.045;\eta^{2}_{\rm P}=0.116\)).