## 4 Discussion
Another interesting finding was that in moderate and high HR% the GK participation in SSGs was associated with an increase in mean values, contrary to what occurred in very high and maximal HR%. This evidence revealed that five SSGs with professional and sub-elite soccer players composed by 3 min performance and 3 min rest interval is a task that is very relevant from the physiological perspective, but can be accomplished with internal load steady state, aiming to develop the aerobic pathway. Notably, in the lower HR zone percentages, the HR mean values tended to decrease or stabilize from SSG1 to SSG5, which reveals a physiological adaptation to the tasks, a condition that we attribute to the level of the soccer players, who are familiar with daily routines of intense training and competition in a very demanding level. Previous studies showed that rule modifications could influence physical responses during SSGs. For example, [PERSON] et al. [31] examined the physical responses of youth players in three different SSG formats (2-a-side, 4-a-side, and 6-a-side) with a constant pitch area and reported that SSGs rule modifications can affect physical responses. Additionally, comparing the internal and external load variations between training regimens it was observed that shorter sets elicited a lower HRmax, a shorter distance covered at low running speed and contributed to an increase in the distances covered at both medium and high speeds running. Additionally, a study was developed with elite soccer players (English Premier League and UEFA Champions League level players), with different formats (SSG-P and SSG-G), the same number of outfield soccer players (5 vs. 5/7 vs. 7/10 vs. 10) and different pitch sizes (SSG-G vs. 5 = 30 \(\times\) 30 m/7 vs. 7 = 45 \(\times\) 35 m/10 vs. 10 66 \(\times\) 45 m and SSG-P 5 vs. 5 = 27 \(\times\) 27 m/7 vs. 7 = 37 \(\times\) 37 m/10 vs. 10 52 \(\times\) 52 m), each drill by this sequence in a continuous regime and all variables were normalized by time (4 min) for data analysis [32]. The main findings of this research were that the total distance, distances run at high speed as well as absolute maximum velocity, accelerations and decelerations increased with large pitch dimensions (10 vs. 10 \(>\) 7 vs. 7 \(>\) 5 vs. 5). Furthermore, the total distance, very high and maximal speed distances, absolute velocity and absolute maximum acceleration and deceleration were higher in SSG-G compared to SSG-P. The authors explained their results by an increase in linear behaviors in games with a defined offensive side (GK conditions). In our study, total distance covered concomitantly increased with the rise in pitch size independent of the condition (SSG-P or SSG-G), but significant statistical differences were only observed in SSGs with GK participation, the distance covered in SSGs-G was significantly lower compared to the same pitch dimension SSG-P. Comparing our results with [PERSON] et al. [32] we can speculate that the participation of GK and goal objective is a main factor for significant differences in the performance of soccer players during SSGs. This is supported in our study by the decreasing values in distance covered, HRmax, HRmean, speed 6-12 and 12-18, PL volume and intensity between the SSGs with the same pitch size, but different condition (ball possession or goal), findings that highlight that manipulating the pitch size by itself may not be the best strategy for soccer coaches aiming to modulate the exercise intensity. Regarding this topic, previous comparison between 4 vs. 4 and 6 vs. 6 SSG formats suggested that exercise intensity decreases as the pitch size increases, and a similar suggestion has resulted from a comparison between 7 vs. 7 and 10 vs. 10 SSG formats [33].