# Comparative Study of the Sprint Start Biomechanics of Men's 100 m Athletes of Different Levels
## 4 Discussion
The ankle angle of the swinging leg is significantly larger in high-level sprimters compared to medium-level sprimters at the front block exit. A proficient starting technique involves both feet swiftly pushing the blocks after hearing the gunshot, followed by keeping both feet close to the ground and positively swinging forward [35]. The increased ankle angle of the swinging leg enables the sprinters to avoid prematurely lifting their center of gravity, favoring the generation of horizontal velocity. [PERSON] and [PERSON] defined starting force as the ability to achieve the highest force in a short period of time, which was determined as the force value achieved in the first 50 ms [36]. Studying the starting force of sprinters is crucial for researchers and coaches to recognize the impact of starting force on block velocity. The present study demonstrated that the relevant starting force did not differ significantly between different levels of sprinters. The reason for this result is that the shorter duration and smaller force generated during the first 50 mms (20-25% of the total initiation time), do not yet constitute a significant mechanical factor influencing block velocity. According to sports biomechanics principles, completing the initial phase too rapidly may reduce the ability to apply significant force in the subsequent stages, potentially influencing overall block velocity [37]. Regarding rate of force development (RFD), medium-level athletes generate significantly greater vertical RFD in the rear block during the 50-200 ms time period compared to high-level athletes, indicating that medium-level athletes generate more force vertically during this period, which will be detrimental to the horizontal velocity. The higher RFD of the rear block in medium-level sprinters compared to than in high-level sprinters is due to the fact that medium-level sprinters produce a greater vertical RFD and a greater horizontal RFD. In maximal starting force, high-level sprinters generate a significantly larger maximum horizontal force of the front block compared to the medium-level sprinters. Meanwhile, medium-level sprinters generate a significantly larger maximum vertical force of the rear block compared to the high-level sprinters, as seen in Figure 7. These results are in contrast to the earlier studies according to which rear block force magnitudes are the most predictive external kinetic feature of block power [38]. Proponents of maximum force of the rear block argue for higher forces throughout the entire rear leg push as well as greater pre-tension against the rear block in the set position [39]. In fact, as seen in this study, the medium-level sprinters generate greater maximal horizontal force of rear block than high-level sprinters (1.30 N/Kg vs.1.14 N/Kg) but this does not result in higher block velocity. According to the results of this study, high-level sprinters had 1.64 times longer front block contact time than rear block contact time, and medium-level sprinters also had 1.32 times longer front block contact time than rear block contact time. Previous research supports the results of this study according to which the front leg contributes 66-76% of the total horizontal impulse due to the 1.9-2.4 times longer block contact time than that contributed by the rear leg, and group mean block velocities are significantly greater with the stronger leg on the front block [40; 41; 42]. Figure 6: Change in ankle angle of front support leg and swinging leg during the push phase in high-level (**a**) and medium-level (**b**) sprinters. The limitation of this study are the absence of clear joint kinetics, morphology, strength, and flexibility on block velocity, and future research should explore this further. Another limitation is shown by the small sample size, which may not be completely generalizable to the interpretation of block velocity.