Well-being indicators modulate perceived but not physiological internal load across small-sided games and high-intensity interval training in male soccer players

The aim was to examine whether pre-session well-being indicators differentially predict physiological (% heart-rate [HR] reserve; %HRreserve) versus perceived (rating of perceived exertion; RPE) internal load across soccer training formats. Seventy-seven male soccer players (20.6 ± 1.6 y) completed four monitored sessions over two weeks: 1v1 small-sided games, 5v5 small-sided games, long high-intensity interval training (HIIT), and short HIIT. Mean %HRreserve was obtained from heart-rate monitoring, and RPE was collected immediately post-session. Linear mixed-effects models estimated associations of well-being, training format, and well-being and format interactions with each internal-load outcome. No well-being indicator showed a clear association with %HRreserve. For RPE, longer sleep duration was associated with lower perceived exertion (B = −0.42, p = 0.007), whereas greater musculoskeletal pain was associated with higher perceived exertion (B = 0.47, p = 0.012). A significant sleep and short-HIIT interaction (B = 0.79, p = 0.012) indicated that the sleep-RPE association differed between short HIIT and the reference format (1v1). In this sample, sleep duration and musculoskeletal pain were associated with perceived, but not HR. These findings support interpreting RPE, HR-derived measures, and brief well-being monitoring as complementary tools in soccer training contexts, while causal inference and broader generalisation remain limited.