## 4 Discussion  
The current study aimed to provide an overview of the literature regarding the assessment of changes in spatiotemporal parameters under the influence of different inclinations. The study included downhill as well as uphill runs. The evaluation included studies in which a constant speed was used during the execution of the test. In the analysis of the results, the methods and research tools of the included papers were taken into account. The results of the review suggest that an increase in inclination changes the spatiotemporal structure of running. Parameters such as SL, FT, and SF changed most often and were characterized by exponential increases or decreases for positive inclination values. The results also indicated that the kinematics of running was different for downhill runs compared to uphill runs. Parameter values for negative values changed irregularly. CT was similar in all cases analyzed except for the three included studies [36; 37; 42]. Changes in spatiotemporal parameters were mainly determined by the inclination adopted in each study. Key to the analysis is a separate kinematic analysis for the uphill and downhill runs. All authors noted significant differences between inclinations and measured parameters, with the exception of [PERSON] et al. [38] and [PERSON] et al. [43]. However, studies that included negative inclinations indicated that statistically significant changes most often involved positive values [30; 31; 39]. [PERSON] et al. [32; 33] noted significant differences for FT only for comparisons of running uphill versus running downhill. FT was unchanged for the inclines of \(-8\%\) and \(-5\%\). [PERSON] et al. [37] investigated four parameters, considering only negative inclination values. He noted a significant decrease only for CT with an increase in the inclination from \(-15.8\%\) to \(-10.5\%\). The different patterns of biomechanics for running at negative values may suggest the very direction of changes in the parameters studied. In all studies, the most common change observed was an increase in SF, with an increasing inclination, regardless of whether the studies included negative or only positive gradient values [30; 31; 32; 33; 34; 35; 36; 39; 40; 41]. This development can be effectively used to optimize step frequency in the training process. Previous studies have shown that recreational runners are characterized by a lower cadence compared to athletes by about 10%. What is more, they choose a subjective selection of individual cadences that are lower by nearly 8% than their optimal step frequencies [44]. Properly selected training using inclinations could effectively increase the cadence of recreational runners, optimizing their technique and thus running economy. Figure 4: Bubble chart for contact time and step frequency. Another trend has been presented by the FT. The value of this parameter in the study of [PERSON] et al. [32; 33] significantly decreased during the run at 0% inclination, after which it began to increase once again. Moreover, the study by [PERSON] et al. [31] confirmed the same relationship for StL and RStL, which did not change significantly when the inclination increased from \(-\)17.6% to 0%. Studies for positive inclination values, in some cases, also presented contradictory results. [PERSON] et al. [40] reported significant differences for CT or SA, but the values increased and decreased in a non-monotonic way. On the other hand, [PERSON] et al. [30] described significant differences for SL, SF, CT, ST, and DF concerning the 0% inclination registered only for \(-\)15.8%. In other studies, [PERSON] et al. [34] reported no significant change in StL in one study, and in a second study, on the same gradients, observed a significant decrease in StL for each gradient [35]. It is worth noting that despite the divergence for SL, in both cases, an increase in SF was observed [34; 35]. As for SF, the underruns could effectively optimize StL or SL.