# Comparative Study of the Sprint Start Biomechanics of Men's 100 m Athletes of Different Levels
## 4 Discussion  
This study aimed to analyze some kinematic and kinetic variables associated with start block performance that differentiated high-level sprinters from medium-level sprinters. However, no differences between the two groups were found on starting block, reaction time, and push time. In the starting block, both groups of sprinters used the normal style start, suggesting that the normal style may be optimal for sprinter start. Other studies confirmed this finding, showing that the medium style enables the sprinter to be the fastest over the 20-yard and 50-yard sprint [26, 27]. Although a previous study has also shown that sprinters using elongated versus shortened and normal styles at the start increased block velocity, excessive time spent on the push phase resulted in lower 5 m and 10 m performance [10]. Moreover, the medium style allows the sprinter to have a good torso posture as well as to have a greater first step length compared to the shortened style [28]. Thus, the normal style may not produce the fastest block velocity, but it is a great advantage for short-distance speeds. It is commonly recognized that the generation of horizontal force is greater with steeper block plates. When examined cross-sectionally across a broad spectrum of sprinters, habitual foot plate inclination has little effect on block velocity [12, 29]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **High-Level** & **Medium-Level** & **F** & \(\mathbf{p}\) & \(\mathbf{\eta^{2}}\) \\ \hline Horizontal RFD of Rear Block (N/s\(\cdot\)kg) & 15.31 \(\pm\) 7.46 & 21.79 \(\pm\) 10.32 & 2.59 & 0.13 & 0.13 \\ \hline Horizontal RFD of Front Block (N/s\(\cdot\)kg) & 4.10 \(\pm\) 0.55 & 3.90 \(\pm\) 0.72 & 0.45 & 0.51 & 0.02 \\ \hline Vertical RFD of Rear Block (N/s\(\cdot\)kg) & 7.77 \(\pm\) 3.26 & 13.87 \(\pm\) 7.08 & 6.12 & 0.02 \({}^{*}\) & 0.25 \\ \hline Vertical RFD of Front Block (N/s\(\cdot\)kg) & 4.53 \(\pm\) 0.94 & 4.68 \(\pm\) 1.35 & 0.08 & 0.78 & 0.00 \\ \hline RFD of Rear Block (N/s\(\cdot\)kg) & 15.57 \(\pm\) 6.09 & 22.92 \(\pm\) 8.84 & 4.69 & 0.04 \({}^{*}\) & 0.21 \\ \hline RFD of Front Block (N/s\(\cdot\)kg) & 6.03 \(\pm\) 1.03 & 6.04 \(\pm\) 1.46 & 0.00 & 0.98 & 0.00 \\ \hline Maximum Horizontal Force of Rear Block (N/kg) & 1.14 \(\pm\) 0.33 & 1.30 \(\pm\) 0.21 & 1.84 & 0.19 & 0.09 \\ \hline Maximum Horizontal Force of Front Block (N/kg) & 1.18 \(\pm\) 0.09 & 1.03 \(\pm\) 0.16 & 5.90 & 0.03 \({}^{*}\) & 0.25 \\ \hline Maximum Vertical Force of Rear Block (N/kg) & 0.88 \(\pm\) 0.24 & 1.12 \(\pm\) 0.26 & 4.42 & 0.05 \({}^{*}\) & 0.20 \\ \hline Maximum Vertical Force of Front Block (N/kg) & 1.3 5\(\pm\) 0.16 & 1.24 \(\pm\) 0.23 & 1.46 & 0.24 & 0.08 \\ \hline Maximum Total Force of Rear Block (N/kg) & 1.42 \(\pm\) 0.38 & 1.71 \(\pm\) 0.29 & 3.59 & 0.07 & 0.17 \\ \hline Maximum Combined Force of Front Block (N/kg) & 1.78 \(\pm\) 0.17 & 1.61 \(\pm\) 0.27 & 2.98 & 0.10 & 0.14 \\ \hline \hline \end{tabular} \({}^{*}\) Represents significant.  
\end{table} 
Table 2: Comparison of rate of force development and maximum starting force of sprinters at different levels during push phase. Figure 5: (a) Comparison of starting impulse of sprinters at different levels during push phase. (b) Comparison of starting force of sprinters at different levels during push phase. The major limitation of the present study is the lack of sprimters' anthropometrics, strength, and flexibility information, which combine to influence the choice of the sprinter in the block start. Further research is necessary to clarify the mechanism underlying the biomechanical influence of morphology and physical fitness on the block start. The result of this study on the reaction time Is consistent with the result of [PERSON] et al. 's study [PERSON] _et al._ (2018). Contrary to [PERSON]'s finding, improvement in reaction time is significant for overall performance improvement among sprimters with a 100 m performance from 9.94 to 9.87 s [PERSON] _et al._ (2018).