## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Landing (\%)**} & \multicolumn{2}{c}{**Pre-Fatigue**} & \multicolumn{2}{c}{**Post-Fatigue**} & \multicolumn{2}{c}{**Mean Difference**} & \multicolumn{1}{c}{**95\%CI**} \\  & \multicolumn{1}{c}{**B**} & \multicolumn{1}{c}{**J**} & \multicolumn{1}{c}{**B**} & \multicolumn{1}{c}{**J**} & & & \\ \hline \multirow{3}{*}{RA} & CMJ & 26.31 \(\pm\) 36.32 & 19.64 \(\pm\) 26.22 & 9.73 \(\pm\) 5.33 & 8.69 \(\pm\) 5.29 & B:–16.58 & B:20.53 \\  & SPJ & 46.17 \(\pm\) 72.95 & 19.75 \(\pm\) 16.32 & 22.74 \(\pm\) 14.93 & 15.55 \(\pm\) 11.84 & J:–10.95 & J:13.97 \\  & & & & & & B:–23.44 & B:41.08 \\  & & & & & & & J:–4.20 & J:6.65 \\ \hline \multirow{3}{*}{ES} & CMJ & 54.38 \(\pm\) 23.47 & 55.94 \(\pm\) 42.32 & 52.69 \(\pm\) 28.54 & 45.22 \(\pm\) 24.15 & B:–16.69 & B:14.28 \\  & SPJ & 58.70 \(\pm\) 35.35 & 67.63 \(\pm\) 41.26 & 45.33 \(\pm\) 35.03 & 50.00 \(\pm\) 32.12 & J:–10.72 & J:19.74 \\  & & & & & & B:–17.63 & B:25.67 \\  & & & & & & J:–13.37 & J:20.30 \\ \hline \multirow{3}{*}{RF} & CMJ & 105.77 \(\pm\) 39.25 & 94.60 \(\pm\) 36.56 & 86.04 \(\pm\) 32.11 * & 85.02 \(\pm\) 36.31 & B:–19.74 & B:15.70 \\  & SPJ & 113.06 \(\pm\) 46.76 & 108.68 \(\pm\) 32.99 & 113.65 \(\pm\) 65.23 & 122.99 \(\pm\) 45.08 & B:–0.59 & B:18.58 \\  & & & & & & J:–14.31 & J:21.71 \\ \hline \multirow{3}{*}{BF} & CMJ & 59.42 \(\pm\) 89.38 & 56.65 \(\pm\) 38.79 & 26.44 \(\pm\) 12.97 & 39.09 \(\pm\) 20.44 & B:–32.98 & B:54.94 \\  & SPJ & 79.32 \(\pm\) 73.37 & 93.34 \(\pm\) 138.19 & 71.70 \(\pm\) 56.57 & 56.17 \(\pm\) 47.27 * & B:–37.17 & B:85.99 \\  & & & & & & J:–7.62 & J:20.73 \\ \hline \multirow{3}{*}{TA} & CMJ & 128.30 \(\pm\) 48.54 & 101.26 \(\pm\) 41.47 & 85.25 \(\pm\) 49.08 * & 90.98 \(\pm\) 48.30 & B:–43.05 & B:30.49 \\  & SPJ & 86.95 \(\pm\) 21.64 & 92.19 \(\pm\) 26.84 & 105.18 \(\pm\) 34.75 & 103.96 \(\pm\) 41.72 & B:18.23 & B:18.32 \\  & & & & & & J:11.78 & J:14.69 \\ \hline \multirow{3}{*}{GN} & CMJ & 164.21 \(\pm\) 123.81 & 169.51 \(\pm\) 108.71 & 169.85 \(\pm\) 52.22 & 175.74 \(\pm\) 74.63 & B:5.64 & B:64.10 \\  & SPJ & 171.75 \(\pm\) 75.01 & 201.36 \(\pm\) 129.18 & 166.86 \(\pm\) 91.63 & 192.08 \(\pm\) 79.28 & B:–9.28 & B:33.06 \\ \cline{1-1}  & & & & & & J:–4.89 & J:24.25 \\ \hline \hline \end{tabular} Asterisks (*) indicate a significant difference (\(p<0.05\)); CMJ: counter-movement jump; SPJ: spike jump; B: braking leg J: jumping leg; RA: rectus abdomis; ES: erector spinae; RF: rectus femoris; BF: biceps femoris muscle; TA: anterior tibialis; GN: gastrocnemius; CI: confidence interval.  
\end{table} 
Table 5: Muscle activation at touchdown (%). height [34]. This corresponds with our finding of significantly reduced maximum jump heights. After fatigue, during CMJs, the athletes had a significant decrease in the knee joint angle at take-off, which means that they used stiff motions to take off [35] and that they reduced knee flexion to complete the jump action. During the SPJ, there were no significant differences in the joint angles of the jumping leg. Additionally, during both SPJs and CMJs, after RA fatigue, there was a significant decrease in the activation of the RA, and there was no significant change in the myoelectric signals of the ES and lower extremity muscles; thus, there was no improvement in the degree of activation of the muscle groups of the lower limbs. The RA is considered to be a globally stabilizing muscle group. Its main function is to generate a large moment to balance the impact of external forces [13]. The take-off is an active movement, and the abdomen does not bear a large external force. Therefore, it may be directly affected by fatigue exercise, which reduces the activation of the RA. However, other muscles that were not affected by the fatigue exercise didn't exhibit significant changes. During the SPJ, after the RA fatigue, when the athlete landed, the plantar-flexor moments of the ankle joint of the jumping leg were significantly reduced.