Exploring The Physiological and Physical Basis of RPE Responses in Soccer: A Comparative Analysis of Internal and External Load Determinants Across Different Training Drills.

This study investigated the relationships between Rate of Perceived Exertion (RPE) and various objective internal and external training load measures across multiple drill types in youth academy soccer players, a comparative approach that has been rarely examined. Forty-six male outfield soccer players (16.3 ± 0.4 years) from two under-17 academy-level teams competing in a city-level league, training three times per week with weekend matches, were monitored over two weeks during regular training. Data included RPE (CR-10 scale), heart rate responses (HRaverage, HRmax), and external load variables (total distance per minute, average speed, distance in Z4 [15-19 km/h], and Z5 [>19 km/h]) via Polar Team Pro, measured across all drills (3v3, 6v6, 9v9, 11v11, 10x5 positional game, repeated sprint training, muscular endurance circuit training, and slalom exercise). Aerobic capacity (VIFT) was assessed separately using the 30-15 IFT. Results indicated that RPE consistently showed large positive correlations with HRaverage (e.g., 3v3: r = 0.977) and HRmax (e.g., 3v3: r = 0.778) across most drills, Conversely, relationships between RPE and the VIFT were varied, showing large negative correlations in larger-sided games (e.g., 11v11: r = -0.446; 9v9: r = -0.585), suggesting fitter players perceived less effort. Correlations between RPE and general distance/speed metrics were inconsistent, while distances covered in high-intensity speed zones (Z4, Z5) showed large positive correlations with RPE (e.g., 3v3 Z4: r = 0.830; 3v3 Z5: r = 0.710), particularly in drills like 3v3, 6v6, repeated sprint training, and slalom. In conclusion, RPE's relationship with training load is drill-specific. It possibly reflects physiological strain in small-sided games and conditioning drills, but shows more variable associations with external load and fitness in large-sided or tactical formats. Coaches should therefore combine RPE with objective metrics and interpret it in light of drill characteristics. These findings should be viewed cautiously given the short two-week monitoring period and absence of additional physiological markers.