## 4 Discussion  
This study aimed to analyze the differences in workload (i.e., internal, external, and mental load) between training sessions based on players' match participation. This is the first study that compares the load imposed on soccer players, considering their participation in the previous match in a holistic model (i.e., considering internal, external, and mental load). The main findings of this study revealed significant differences in all categories during MD+2, with starter players exhibiting the lowest values. Conversely, starter players presented the highest values on MD in all categories. Regarding MD-4 and MD-3, no differences were found in cognitive, emotional and affective loads, TD \(>\) 25 km\(\cdot\)h\({}^{-1}\), sprint number and PLoad, while significant differences were observed in RPE (i.e., MD-3, G2 vs. G3), motivation (i.e., MD-4, G1 vs. G3; MD-3, G1 vs. G2 and G3), mental fatigue (i.e., MD-4, G1 vs. G2), TD \(>\) 19 km\(\cdot\)h\({}^{-1}\) (i.e., MD-4, G1 vs. G2), max. speed (i.e., MD-3, G1 vs. G2), ACC (i.e., MD-3, G1 vs. G3) and DEC (i.e., MD-3, G3 vs. G1 and G2). Finally, the lowest values in all variables for the starter players were observed on MD-2 and MD-1. Understanding the perceived load by soccer players is essential to check if the scheduled training is being executed as planned [28] or to assess the effort performed during competition [29]. In this regard, starter players showed the lowest RPE values on MD+2 compared to their counterparts. This could be because the aim of this session was to compensate the competition efforts for those players who completed a few minutes in the previous match (i.e., G2 and G3), while starting players (i.e., G1) carried out some recovery strategies [11]. No significant differences were found on MD-4, and only differences between non-starter and non-participant players were observed during MD-3. On MD-2 and MD-1, lower values of RPE were found in starters players, possibly due to the lower accumulation of weekly fatigue since the MD+2 session was softer for starter players compared to non-starter and non-participant players. Finally, the highest RPE values on MD were found in starter players as expected since they played a greater number of minutes during the match than non-starter and non-participant players. In recent years, mental load analyses have increased in team sports [20; 21], since research has reported that mental load is related to mental fatigue, which could impair soccer performance [30]. Although there is scarce literature related to mental load in a soccer microcycle week, these findings provide knowledge about this question in a professional soccer team over a full season. In our study, in MD+2 sessions, the lowest values were observed in starter players, without differences, in MD-4 and MD-3 sessions. On the other hand, starter players presented the lowest values in the sessions prior to the match (i.e., MD-2 and MD-1), possibly because, in these sessions, coaches apply tasks where players could guess their participation in the next match (i.e., tactical or strategic orientation), implying a possible decrease in the mean values of mental load. Conversely, these players presented the highest values on MD, influenced by their match participation. Regarding motivation, non-participant players presented the highest values in the MD+2 session, perhaps influenced by their interest in demonstrating their performance in order to obtain opportunities in the next matches. In MD-4, starter players presented lower values of motivation compared to the other groups, possibly due to the accumulated fatigue from their significant participation in the match. No differences were observed on MD-3 and MD-2, although non-participant players increased their motivation values during MD-1, as they could experience positive expectations about their inclusion in the next match.