Determining the relationship between internal load markers and non-contact injuries in young elite soccer players

PURPOSE: To examine the association and predictive ability of internal load markers with regards to non-contact injuries in young elite soccer players. METHODS: Twenty-two soccer players (18.6 ± .6 years) who competed in the Spanish U19 League participated in the study. During a full season, non-contact injuries were recorded and, using session rating of perceived exertion (s-RPE), internal weekly load (sum of load of all training sessions and matches for each week) and acute:chronic workload ratio (typically, acute = current week and chronic = rolling 4 week average) were calculated. A Generalized Estimating Equation analysis was used to examine association of weekly and acute:chronic load ratio markers with a non-contact injury in the subsequent week. Load variables were also analyzed for predictive ability with Receiver Operating Characteristic (ROC) curve and area under the curve (AUC). RESULTS: No association was found for weekly load (CI 1.00, .99 to 1.00) and acute:chronic load ratio (CI .16, .01 to 1.84) with respect to injury occurrence. In addition, the analyzed load markers showed poor ability to predict injury occurrence (AUC<.50). CONCLUSIONS: The results of this study suggest that internal load markers are not associated with non-contact injuries in young soccer players and present poor predictive capacity with regards to the latter.