This study investigated perceived exertion (RPE) differences among soccer players at two competitive levels - Tier 2 (trained) and Tier 3 (highly trained) - during small-sided games (SSGs) and high-intensity interval training (HIIT), while controlling for internal physiological load using percentage of heart rate reserve (%HRreserve). Seventy-seven male university players from the China University Football Association participated (Tier 2: n = 37; Tier 3: n = 40). Each player underwent a fitness assessment to determine HRmax and HRrest, followed by four randomized training sessions: 5v5 SSGs, 1v1 SSGs, long HIIT, and short HIIT. Heart rate was continuously monitored, and players reported RPE using the Borg CR10 scale immediately post-session. A linear mixed-effects model was used, with competitive level and training format as fixed effects, and %HRreserve included as a statistical covariate. The analysis revealed a significant interaction between training format and competitive level (F(3, 224.761) = 3.20, p = .024), indicating that the influence of training format on RPE varied by competitive level. A significant main effect of training format was also found (F(3, 234.484) = 11.24, p < .001). Specifically, Tier 3 players reported higher RPE during short HIIT than Tier 2 players (p = .002). Both groups reported lower RPE during 5v5 SSGs compared to 1v1 SSGs and HIIT formats (all p ≤ .003). These findings show that training format influences RPE in a format- and tier-specific manner, even when accounting for internal physiological load. For coaches and sports scientists, larger-sided SSGs may be useful to reduce perceived exertion while maintaining cardiovascular demand. Future research should include elite players and assess psychological and physiological mediators to better understand the complex drivers of perceived effort.

• The study found significant differences in Rating of Perceived Exertion (RPE) across training formats, with 5v5 small-sided games (SSGs) eliciting lower RPE compared to 1v1 SSGs and HIIT protocols, even when controlling for physiological load (%HRreserve).

• While no overall RPE difference existed between Tier 2 (developmental) and Tier 3 (national-level) players, a key interaction revealed that Tier 3 players perceived short HIIT as more strenuous than Tier 2 players, suggesting competitive-level nuances in effort perception.

• %HRreserve significantly influenced RPE, confirming its role as a valid internal load metric. However, RPE variations persisted beyond physiological strain, highlighting the multifactorial nature of perceived exertion (e.g., psychological and exercise modality).