Relationship between training load and injury risk in elite young male football players: a systematic review

Objective This study aimed to systematically review the relationship between training load and injury risk in elite football players and propose an evidence-based training load management strategy for promoting their sustainable development. Methods This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines, with literature searches performed using the PubMed, Web of Science, SPORTDiscus, and MEDLINE databases. Study quality was assessed using the Newcastle–Ottawa Scale, levels of evidence were classified using the Oxford Centre for Evidence-Based Medicine (OCEBM) model, and the certainty of evidence was summarized using the Grading of Recommendations Assessment, Development and Evaluation framework. Results A total of nine studies met the inclusion criteria. For internal loads, psychosocial factors were not clearly associated with injury risk. Higher injury risk was observed in association with abrupt increases in session rating of perceived exertion (sRPE) and high monotony or strain, whereas stable moderate loads were associated with protective effects. For external loads, high or rapidly increasing volumes of distance, high-speed running, and accelerations were associated with an increased risk of injury, whereas lower or moderate loads were associated with protective effects. Acute–chronic workload ratio (ACWR) analysis indicated that very high ratios, particularly under low chronic loads, were associated with increased injury risk, whereas low ratios were associated with protective effects. Conclusion Abrupt increases in training load, rather than total load volume, were consistently associated with a higher incidence of injuries.