# Measurement of the Impact Loads to Reduce Injuries in
## 4 Discussion  
The purpose of this study was to build a platform with a similar surface to that used in training practice to allow measuring the forces performed in a high jump. This way, all the results could be compared with the results obtained on the commercial platform to validate the new platform. By comparing Figures 10 and 11, it can be observed that the curves show the same behavior, the maximum vertical loads are very similar, and the contact times are almost the same. From Table 2, it is possible to verify that the maximum vertical loads obtained with the specific platform are always higher than those evaluated with the commercial one. Also, the standard deviation of the maximum load value obtained for the new platform is much lower than the corresponding load for the commercial force platform. As can be seen in Figure 12, 60% of the athletes land with the midfoot and the other 40% with the forefoot. Comparing the maximum load transmitted in both cases, it can be seen that the load transmitted when athletes land with the midfoot is around 33.5% higher than that evaluated when the landing is performed with the forefoot. From Figure 13, it can be observed that there is a linear relationship between the loads obtained for both platforms. Also, the scatter of the maximum force values assessed with the new platform is much lower than the values measured with the commercial system. In \begin{table}
\begin{tabular}{c c c} \hline \hline
**Gymnast** & **Ratio CP** & **Ratio NP** \\ \hline
1 & 11.99 & 13.46 \\ \hline
2 & 10.85 & 13.08 \\ \hline
3 & 13.31 & 16.09 \\ \hline
4 & 18.26 & 20.45 \\ \hline
5 & 13.68 & 15.87 \\ \hline
6 & 16.38 & 19.17 \\ \hline
7 & 15.43 & 17.59 \\ \hline
8 & 11.53 & 13.72 \\ \hline
9 & 14.63 & 16.68 \\ \hline
10 & 10.73 & 12.16 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Ratio (Equation (1)) for both platforms. Figure 13: Linear relationship between the two platforms. fact, the dispersion is 10.6% for the new platform and 15.5% for the commercial one. This can be justified by the fact that the piezoelectric platform can induce some errors in the evaluation of static loads. In the case of a jump, as the contact time is very small, the load can be considered almost static. However, the biggest difference between the platforms, around 21%, was determined for gymnast number 2, and the smallest, around 12%, for gymnast number 4. These differences can be justified by the building principles associated with each platform. In the case of the commercial platform, the force is applied to a piezoelectric crystal, and the electric charge is captured at the crystal surface and converted into a voltage signal by a charge amplifier. The new in-house-built platform is strain gauge-based, in which the load is applied to a spring body, capturing changes in electrical resistance, and causing compression or stretching of the attached strain gauges and, therefore, a change in their electrical resistance. Also, the contact surface is different. The commercial one is metallic, and the new one is made of plywood, meaning the rigidity of the platforms is quite different, which explains the different forces exerted on the platforms. As previously mentioned, the new platform has a surface close to the practicable surface normally used by acrobatic gymnasts and is, therefore, more suitable for this study and analysis in these sports. According to Table 3, it is possible to verify that only four gymnasts performed the landing with the forefoot. Observing Figure 12, it can be concluded that gymnasts who initiate the jump landing on the forefoot exert significantly lower maximum loads (\(p<0.05\)) than those in the group performing the landing on the midfoot, regardless of body weight. No statistical correlation was observed between the maximum load and the maximum height (\(p=0.442\)), the maximum load and the contact time (\(p=0.060\)), and the maximum load and the distance from the greater trochanter to the ground (\(p=0.683\)).