## 4 Discussion  
The aim of this study was to investigate the internal load of amateur soccer players during official soccer matches played with the 1-4-3-3 formation and to explore possible relationships with external load indicators. The results revealed the following: (1) In all playing positions during the second half, a decrease in %HRmax was observed. (2) In all playing positions during the second half, a decrease in running pace (m/min) was noted. (3) CM exhibited the greatest decline in most indicators in the second half. (4) A reduction in TRIMP\({}_{\text{Edw}}\) was observed only in the CM and F positions. (5) %HRmax was significantly correlated with running pace (m/min), while TRIMP\({}_{\text{Edw}}\) was correlated with TD and distances covered in different speed zones during matches. (6) No differences were observed in the two internal load indicators among different playing positions. In recent years, researchers have been attempting to observe the relationships between the external load experienced by soccer players during matches and internal load indicators. However, studies that utilize heart rate (HR) as an internal load indicator are limited, and most of them employ the rating of perceived exertion (RPE) [5; 26]. They examine the relationship during training sessions or simulated matches and not actual matches [27; 28; 29; 30]. Starting with TRIMP\({}_{\text{Edw}}\) in the present study, it was found to be positively correlated with TD; distance in zones z1, z2, z3, and z4; and the number of Dec2. Additionally, in the first half, it positively correlated with the TD and z2, while in the second half, it showed positive correlations with almost all variables. Positive correlations were also reported in a previous study [31], where TRIMP\({}_{\text{Edw}}\) was positively correlated with total distance (r = 0.72). However, the above study focused on training sessions rather than actual matches. In the same study, a correlation of TRIMP\({}_{\text{Edw}}\) with distance at high intensity and the number of sprints was observed. In the present study, % HRmax correlated with running pace in both halves and throughout the entire match. A recent study [32] observed moderate to large correlations between time spent in low- and moderate-intensity activities and HR zones of low and moderate intensity. No correlations were observed at high intensities. In their study, [PERSON] et al. (2018) [33] noted a correlation between time spent above 80% HRmax and the number of intense accelerations and repeated intense efforts. Both in the present study and in the studies mentioned earlier, either no correlations were found with the covered distance, or the correlations were weak. It is known that during matches, HR does not respond immediately to intense actions, especially when these efforts have very short durations. This may explain the lack of correlations with high-speed zones [32; 34]. From the internal load indicators in the present study, it appears that % HRmax is best estimated by the players' running pace (m/min), while the TRIMP\({}_{\text{Edw}}\) index is best estimated by the total distance (TD) and distances in zones (1,2,3,4) and Dec2. As mentioned in the results, no differences were observed in the two internal load indicators (% HRmax, TRIMP\({}_{\text{Edw}}\)) among different playing positions. This suggests that the external load experienced by the players in the 1-4-3-3 formation forces them to compete under similar internal load. Therefore, although the external load differs, as will be