## 4 Discussion
The differences from our findings may be because the authors analyzed all the teams in the J-League without considering the percentage of ball possession, which can influence running performance, whereas our study focused on a single team compared in two situations where there were no differences in the percentage of ball possession that could influence running performance or differences in the schedule and level of our studied league. The present study showed statistically higher running activity by players during the first half compared to the second half, except DC \(>\) 25.2 km\(\cdot\)h\({}^{-1}\). These findings are consistent with previous research, which has demonstrated a reduction in overall distance covered during the second half compared to the first half ([PERSON] et al., 2019; [PERSON] et al., 2019; [PERSON] et al., 2019). [PERSON] et al. (2020) found that when players exerted more physical effort in the first half, there was a subsequent decrease in physical performance indicators such as total distance covered, high-intensity running distance (\(>\)14.4 km\(\cdot\)h\({}^{-1}\)), and very high-intensity running distance (\(>\)19.8 km\(\cdot\)h\({}^{-1}\)) in the second half. Conversely, when the physical exertion in the first half was lower, total distance covered and high-intensity running distance (\(>\)14.4 km\(\cdot\)h\({}^{-1}\)) remained stable, and very high-intensity running distance (\(>\)19.8 km\(\cdot\)h\({}^{-1}\)) even increased during the second half ([PERSON] et al., 2019). Our data showed that players did not show a decrease in DC \(>\) 25.2 km\(\cdot\)h\({}^{-1}\) during the second half, but they decreased the sprint distance covered (DC \(>\) 25.2 km\(\cdot\)h\({}^{-1}\) maintained for at least 1 s) and the number of sprints \(>\) 25.2 km\(\cdot\)h\({}^{-1}\). In some cases, the substituted players did not manage to cover the distance at this speed, which may have contributed to the lack of difference between the three and five substitutions. Previous research revealed that running distances between \(>\)19.8 km\(\cdot\)h\({}^{-1}\) and \(>\)21.1 km\(\cdot\)h\({}^{-1}\) remained unchanged between the first and second halves of a reserve team from the Premier League and teams from the Spanish first division, respectively ([PERSON] et al., 2012; [PERSON] et al., 2012) found, in semi-professional English football players during the 2009/2010 season, no significant differences in the number of sprints \(>\)21 km\(\cdot\)h\({}^{-1}\) performed by players between the first and second halves and concluded that players were able to maintain their sprinting efforts throughout the game ([PERSON] et al., 2019). These discrepancies in findings could be attributed to the match-to-match variability during official games for professional soccer players. Variability in running activity is high for some variables, particularly high-speed running and sprinting, suggesting that players do not consistently produce maximal efforts in official games. Therefore, these parameters might not be a good indicator of players' physical performance and possible accumulated fatigue ([PERSON] et al., 2019). In our study, the numbers of accelerations and decelerations by full-time players were substantially reduced between the first and second half. These outcomes are in line with a previously published systematic review and meta-analysis that asserted that there is a small decrease in the frequency of high- and very high-intensity accelerations and decelerations from the first to the second half periods of match play, with the limitations that the meta-analysis included different sports teams and its conclusions were not based solely on football articles [1]. For A-League professional soccer players in Australia, [PERSON] et al. [39] identified a substantial reduction in the number of medium accelerations and decelerations (2.5-4.0 m\(\cdot\)s\({}^{-2}\)) and a reduction in the number of rapid decelerations (>4.0 m\(\cdot\)s\({}^{-2}\)) between the first and second halves of the game.