## 4 Discussion
The major findings associated with 5 SSGs performed with 3 min play and 3 min interval rest were: (i) Total distance covered increases in SSGs-P played between 16 m and 36 m but always decreases with GK participation in different SSG but with the same pitch size; (ii) HR\({}_{\text{max}}\) and HR\({}_{\text{mean}}\) decrease with GK participation but present steady state mean values throughout the SSG framework; (iii) PL volume and intensity decreases and has the lowest values with GK participation, namely in SSG3 and SSG5; (iv) The relative HR percentage in this soccer training task is predominantly high (80; 90%) and very high (90; 95%), mean values increasing in moderate and high relative HR with GK participation, contrarily to the decrease in very high and max relative HR; (v) The five performed SSGs were predominantly associated with distances covered at 0-6, 6-12 and 12-18 km\(\cdot\)h\({}^{-1}\) running speeds with distance covered tendentially decreasing in every running speed interval with GK participation (exception 0.6 km\(\cdot\)h\({}^{-1}\)) and globally the lower values in each running speed occurred in SSG5 (also with the exception of 0.6 km\(\cdot\)h\({}^{-1}\)) and (vi) The performance of five consecutive SSGs with 3 min play and 3 min rest interval with increasing pitch size (16 \(\times\) 24 m SSG1 and SSG2; 20 \(\times\) 30 m SSG3 and SSG4 and 24 \(\times\) 36 m SSG5) and SSG1, SSG2 and SSG4 characterized has ball possession game and SSG3 and SSG5 with goal objective and GK participation, promote different internal and external load responses in sub-elite U-23 soccer players which should be carefully monitored during daily training. Previous research used the 5 vs. 5 plus GK format as a setting for assessing the physical and physiological demands in ten young soccer players in four repetitions of 6 min in a space of 100 m (SSG1) or 200 m (SSG2) and six repetitions of 4 min in 100 m (SSG3) or 200 m (SSG4), the authors suggested increasing pitch size to induce greater physical demands and to use SSGs with smaller pitch size, and independently of the bout duration, to induce neuromuscular fatigue [26]. Additionally, another study conducted with young Italian soccer players, compared the effects of different types of SSGs (3 vs. 3, 4 vs. 4, and 5 vs. 5) with aerobic interval training. Apart from the time spent above 95% HR\({}_{\text{max}}\), the results showed no differences in terms of intensity [27]. Differences in HR response between game formats have also been found in a few studies on amateur [28] and professional elite soccer players [29] and in general, HR increases with increasing area per player [11]. Additionally, the 3 vs. 3 format was previously tested in three regimens and found that long sets (3 \(\times\) 6 min/2 min rest) contributed to a drop in HR responses compared to medium (3 \(\times\) 4 min/2 min rest) and short sets (3 \(\times\) 2 min/2 min rest), although, no significant difference was observed for perceived effort or technical actions [15]. More recently, it was observed in recreationally active male soccer players that HR was above 90% HR\({}_{\text{max}}\) in 45% of the total playing time (2 \(\times\) 20 min SSG with, respectively, 80 and 60 m\({}^{2}\) per player) [30]. In our study, HR\({}_{\text{max}}\) and HR\({}_{\text{mean}}\) presented no significant differences in the outfield players when all the five played SSGs were compared, the lower mean values were always observed in the first SSG (pitch size 16 \(\times\) 24 m) and both HR\({}_{\text{max}}\) and HR\({}_{\text{mean}}\) always increased comparing SSGs with the same pitch area but different objective (SSG-P or SSG-G). When analyzing the relative HR, we could observe that the SSG training framework of this study is physiological demanding, since the majority of HR% was high (80; 90%) and very high (90; 95%) and in very high and maximal HR% the mean values even decreased between SSG4 and SSG5.