## 4 Discussion  
The aim of this study was to investigate the effect of high temperatures on differently cushioned shoes. We explored how changes in shoe material could alter the kinematics, kinetic, and muscle activity characteristics of the lower leg after prolonged running at high temperatures. We can confirm that there is not much difference between these two shoes, after 5 km of running, NN fluid shoes will be more suitable for extreme weather changes. Our results demonstrated that the RF, MG, and SOL EMG activity after the 5-kilometer trial running were not influenced by the shoe midsole material or the temperature effect (Figure 5). This finding allows us to rule out the fatigue that causes the joints' changes. Figure 4: Depiction of the COP trajectory, as well as the results of the x-axis offset range, y-axis offset range, and envelope area. The upper left and upper right boxes represent the COP variations for different midsole materials at the same temperature. The bottom left and bottom right are the COP variations for the same shoe tool at different temperatures. It is logical to think that as the temperature rises, the change in the material causes a change in the first peak of the ground reaction force. A study by [PERSON] et al. [10] demonstrated that EVA footwear had no effect on lower-limb joint displacement, regardless of midsole stiffness, though the softer midsole substantially decreased the peak vertical loading rate (131.28 to 138.40 and 139.54 BW/s). This observation is reflected in our results-- namely, we found that after the 5-kilometer running trial, the initial peak and loading rate were both higher, likely due to the temperature-induced changes in the midsole in both shoes. [PERSON] et al. [40] found that if the heel protector does not adequately reduce the impact load of running, the injury risk may increase. Consistent with previous reports, the results of our study indicate that high temperatures in the midsole of EVA and NN shoes lead to an increased peak GRF and elevated loading rates. These findings indicated that runners might be subjected to a higher injury risk when running in extremely high temperatures, possibly because the shoe materials' integrity becomes less stable. It has been shown that when footwear midsole EVA foam reaches a temperature of 70 \({}^{\circ}\)C, the material begins to dissolve [12]. The midsole temperature of each shoe worn by the participants exceeded 70 \({}^{\circ}\)C; thus, the cushioning capability of the EVA shoes is degrading. High temperatures cause EVA shoes to lose strength [41]. The applied force will increase and reduce the cushioning capacity. Previous reports have demonstrated that padded footwear effectively decreases the loading rate [42; 43]. This cushioning material can maintain its material properties under high temperatures and reduce the risk of injury. We demonstrated a significant increase in the rate of first peak GRF after the shoes were exposed to prolonged running in a high-temperature condition. This result confirms our initial assumption that the excessive softening of footwear after exposure to high temperatures results in a loss of elastic support during heel landings. After the 5-kilometer running trial, the temperature of the midsole increased similarly in both shoes. The EVA shoes showed a substantially larger displacement range and envelope area than NN shoes, while NN has a significantly smaller envelope area. This outcome is likely attributed to the temperature increase, which differently affected the two shoes. Based on the differences in the GRF characteristics, we can see that NN shoes seem to be more consistent with the trial before the 5-kilometer run and have smaller changes in COP. Thus, we can assume that the cushion material was less affected by the temperature than the EVA shoe. This outcome can be the specific result of the NN material. We thought that there would be some deformation of non-Newtonian  
Figure 5: Comparison between before and after a 5-kilometer running trial in both shoes’ muscle activity.