Monitoring internal and external training load in male academy football players (<18 years): Methodological inconsistencies and practical implications

Internal load reflects the psychophysiological response to training, whereas external load captures the work performed. In male youth football, diversity in monitoring tools and variable definitions may limit cross-study comparability and applied translation across age categories. This scoping review synthesized evidence on internal and external training load in male youth soccer players under 18 years, mapping commonly used tools, variables, and age-related patterns. A scoping review was conducted in accordance with PRISMA 2020 and PRISMA-ScR. Web of Science, Scopus, PubMed, and SPORTDiscus were searched; formal searches underpinning study selection were run in November 2025. Eligible studies enrolled male soccer players (<18 years), were peer-reviewed original research published in English, and quantified internal and/or external training load using established monitoring tools. Sixty-three studies were included (3666 records identified; 2777 duplicates removed; 889 screened). External load was predominantly quantified using GPS/GNSS-derived metrics (e.g., total distance, high-speed running, sprinting, accelerations/decelerations), but thresholds and processing decisions varied across studies. Internal load monitoring relied primarily on session rating of perceived exertion, whereas heart-rate-derived indices were less frequently reported. Heterogeneity in device settings, signal-quality reporting, and velocity/heart-rate band definitions limited pooling and cross-study comparability. Risk of bias varied across study designs. GPS/GNSS metrics and session rating of perceived exertion dominate training-load monitoring in male youth football. Greater harmonization of reporting practices and integration of maturation status and longitudinal follow-up may strengthen the utility of load monitoring for age-appropriate progression and safer exposure to high-speed running and sprinting. Registered on OSF prior to the formal searches.