Abstract
BACKGROUND: Collating evidence on the relationship between training load and physical fitness adaptations in team sport players can help refine training plans. OBJECTIVES: This systematic review and meta-analysis aimed to: (i) identify research designs and methods examining the relationship between training load and physical performance in team sport players, and (ii) synthesize key findings, advancing to meta-analysis where correlations could be established. METHODS: Eligible participants were men and women in team sports at least at the trained or developmental level. Studies included had training loads of at least two weeks with pre-post physical performance evaluations. Searches were conducted in PubMed, Scopus, SPORTDiscus, and Web of Science. Study quality was assessed using the Downs and Black scale, and evidence certainty was evaluated with the GRADE framework. RESULTS: Of 29,552 records screened, 40 studies with 726 players were included. Significant correlations were evident between heart rate (HR)-based training impulse (TRIMP) and changes in maximal oxygen uptake (r = 0.63, p < 0.05), velocity at a blood lactate concentration of 2 mmol·L⁻¹ (V(LT)) (r = 0.47, p < 0.05), and velocity at the onset of blood lactate accumulation (r = 0.43, p < 0.01). A significant correlation between session-rating of perceived exertion (sRPE) and changes in V(LT) (r = 0.29, p < 0.05) was found. CONCLUSIONS: HR-based TRIMP methods to quantify internal training load appear to be effective indicators for potential endurance adaptations around training phases in team sport players. In contrast, sRPE and external training load measures demonstrated limited associations with performance adaptations surrounding training.