## 4 Discussion
Due to insufficiently developed musculature and knowledge of the specific movement, the subjects in this research study did not perform unilateral jumps at the level that sprinters would likely perform. To determine the correlation between the kinematic parameters of the UHCJ20m test and success in the M100m, MRLS20m, and MRFS20m tests, multiple regression analysis was performed (Tables 4-6). Due to the direct dependence of movement speed and final score on the set of predictor variables formed by the kinematic parameters, speed was not included in further analysis as it is the only variable that is statistically significantly correlated with success in sprint running. Furthermore, due to the occurrence of multicollinearity, a stepwise multiple regression analysis was performed. A correlation (\(R\) = 0.37) was found between the set of four variables and the M100m test results. Two statistically significant parameters, SL and CT, were highlighted, which carry most of the information about the correlation between predictors and criterion (Table 4). The most important parameter was the average SL, which is important for predicting the results of the M100m test. Many authors investigated the relationship between SL and SF in relation to the achievement of maximal running speed in all phases of sprint running in athletes of different levels, from elite athletes [42; 52; 53; 54; 55; 56; 57] to non-sprinter athletes [38; 58]. [PERSON] et al. [11] state that some research studies have found SL as the most significant parameter for the development of maximal running speed, whereas other research studies state SF as the most significant factor. An application of vertical and horizontal types of jumping exercises could contribute to longer SL [11; 59; 60]. However, [PERSON] et al. [61] claim that CT is the most important kinematic parameter in sprint running that distinguishes better and weaker sprinters. Changes in CT bring changes in SF values, which are also influenced by other parameters. Exercises targeting lower extremity explosive strength, especially horizontal jumps, may influence CT shortening and thus other parameters responsible for achieving higher sprint running speed. Jumps are specific training operators that use the stretch-shortening cycle to develop acceleration [46], and these types of exercises have a similar ground contact time to start acceleration running [11]. Block clearance and start acceleration (Table 5) were correlated with SN in the UHCJ20m test, which can be explained by the specificity of start and acceleration, i.e., the need to generate large muscle force, which also manifests itself in horizontal jumps through explosive strength and the longest possible jump. Subjects who had a lower number of steps/jumps also had a better result in the MRLS20m test. The importance of the number of steps, i.e., optimal stride length, is theoretically calculated using the formula presented by [PERSON] [62], while [PERSON] et al. [61] concluded that better sprinters perform fewer strides than worse sprinters and deviate less from the optimal number of steps calculated by [PERSON] [62]. In the same research study, [PERSON] et al. [61] stated that average ground contact time is an important indicator that differentiates between better and worse sprinters in start acceleration running. In this case, SL, FT, and CT also play an important role in the UHCJ20m test and the prognostic possibility of the results in the start acceleration run represented by the MRLS20m test. The stepwise forward regression analysis (Table 6) identified parameters that carry the most information and implied how SL and CT in the UHCJ20m test are parameters that can be associated with successful running in the MRFS20m test. Running at maximum speed requires the sprinter to have an optimal ratio of SL and SF, which is also influenced by other kinematic parameters; therefore, the UHCJ20m test requires an optimal SL and SF, to achieve the maximum possible movement speed.