In professional football (soccer), injury rate and burden have risen over the last few years due to the ever increasing physical demands during matches and the packed competitive schedules with short recovery periods between matches. Frequently and objectively monitoring the internal load could identify players at risk of fatigue accumulation and injury. Current internal load monitoring methods have several limitations, but urinary biomarker analysis shows great potential as it is a non-invasive, objective sensitive and practical method. The aim of this project is to discover a URINARY BIOMARKER PANEL that can identify at-risk players by an UNTARGETED METABOLOMICS approach. Concentrations of the biomarkers from the panel will be weighed and converted to develop an internal load score. High internal load scores indicate an elevated injury risk. During this project urine analyses will be executed to MONITOR THE INTERNAL LOAD SCORE in football teams throughout a season. Subsequently INDIVIDUALIZING TRAINING by reducing the external training load for at-risk players, could PREVENT FATIGUE ACCUMULATION AND INJURY. This would be the first study that establishes a urinary analysis biomarker panel that can monitor internal load in a lab-based setting and validates it in a real life football context.