Injury incidence and burden in a youth elite football academy: a four-season prospective study of 551 players aged from under 9 to under 19 years - Materne, O.; Chamari, K.; Farooq, A.; Weir, A.; Hölmich, P.; Bahr, R.; Greig, M.; McNaughton, L. R. (British Journal of Sports Medicine, 2021)