Objective To investigate the heading demands of elite footballers during training sessions using instrumented mouthguards (iMGs). Methods Methods followed the Consensus Head Acceleration Measure Practices guidelines. This prospective observational cohort study involved 52 elite male players from four clubs in the first and third tiers of English football, and 20 elite female football players from two clubs in the first tier. Players wore iMGs during outfield training sessions to collect data. A linear mixed model was used to identify differences in heading metrics based on sex, age and header situations, analysing 13 distinct metrics related to heading frequency and intensity. Results The study recorded 1496 heading impacts across 63 training sessions. The mean peak (SD) heading intensity was 18.1 (8.5) g and 1068 (776) rad/s2, with a mean impact duration of 10.4 (8.9) ms. Male players had a mean peak linear acceleration (PLA) of 17.8 (8.2) g and a mean peak rotational acceleration (PRA) of 1025 (741) rad/s2. Females had a PLA of 20.1 (9.7) g and a PRA of 1374 (934) rad/s2. Significant sex differences were found for rotational acceleration, with female players showing higher values (p=0.015, np2=0.004), but not for linear acceleration (p=0.152, np2=0.001). Significant differences in PLA and PRA were also observed between different header situations, with the lowest values recorded for headers from throws. Conclusions This understanding of heading demands has important implications for player health and safety. The information can be used to inform training practices and quantification of heading loads.
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