## 4 Discussion  
This study aimed to investigate the reliability and validity of the CS and LS performance when used for measuring MSS and split times. We observed high intrasession  
Figure 4: Bland–Altman plot showing differences between the GPEXE It and timing gates in split times of short distance (t\({}_{0-10}\)), intermediate distance (t\({}_{0-20}\)), long distance (t\({}_{0-30}\)), and maximum sprinting speed (MSS) for right curvilinear sprint. Each plot depicts absolute systematic bias, 95% limits of agreement (\(\pm\)1.96 standard deviation; dashed), and the regression line (solid). The strength of relationship (R\({}^{2}\)) is also presented in each plot. Figure 3: [PERSON]–[PERSON] plot showing differences between the GPEXE It and timing gates in split times of short distance (t\({}_{0-10}\)), intermediate distance (t\({}_{0-20}\)), long distance (t\({}_{0-30}\)), and maximum sprinting speed (MSS) for left curvilinear sprint. Each plot depicts absolute systematic bias, 95% limits of agreement (\(\pm\)1.96 standard deviation; dashed), and the regression line (solid). The strength of relationship (R\({}^{2}\)) is also presented in each plot. reliability of GPEX It for assessing MSS and split times at intermediate and long distances, whereas lower reliability for split times at short distances was observed. The GPEXE It systematically underestimated MSS and split times of CS and LS, and at the same time showed substantial agreement with TG. Such results are in line with previous indications about the GPS systems, and hold potential for application of the GPEXE It in practice. The previously established high intrasession reliability of the GPEX It for assessing LS MSS align with findings from prior studies [8]. However, its reliability for assessing MSS of CS has been relatively unexplored. The study that investigated intrasession reliability of 10 Hz GPS for measuring MSS during curvilinear sprints (9.15 m radius) reported comparable ICC (\(>\)0.92) to those in our study [24]. Thus, we can confirm good intrasession reliability of GPEXE It for measuring MSS within a session. In contrast, the reliability of GPEXE It for measuring intermediate and longer distances split times was lower than for MSS. The observed CVs (95% CI upper limits \(\leq\) 2.8%) and ICCs (95% CI lower limits \(\geq\) 0.81) are comparable to highly reliable TG systems [25]. A preliminary study introducing a CS test has demonstrated an ICC \(\sim\) 0.90 and CV \(\sim\) 1% for the measurement of a 17 m split time using the TG [4]. This level of reliability closely aligns with the intrasession reliability of 20 m split times of CS to the left measured using GPEXE It in our study (ICC = 0.93; CV = 1.8%). However, the GPEXE It exhibited slightly poor reliability for measuring CS split times at a short distance. Because our results do not allow us to conclude if the lower reliability for assessment of 10 m split times was due to higher sprint acceleration at that particular distance [5], a low, 18 Hz, sampling frequency (random error of \(\pm\)0.055 s or 0.11 s in total), or other technical aspects of the device [9], future study should explore these factors. Moreover, GPEXE It demonstrated a substantial overestimation over TG when measuring CS and LS split times. This discrepancy may arise from split times being potentially obtained from a greater distance than actuality, as suggested by previous research [13], from differences in sprint start initiation between TG and GPEXE It, or both. To address these issues, the models for correcting GPS-measured split times might be used. Employing these in further studies could enhance the usability of the device. Despite good overall agreement between GPEXE It and TG, the Bland-Altman 95% LoA intervals were approximately 0.7 to 0.8 s for CS and 0.5 s for LS split times.