Injury risk and patterns in newly transferred football players: a case study of 8 seasons from a professional football club

This case study investigated injury risk and patterns in players newly transferred to a professional football club. Time-loss injuries were recorded prospectively over 8 seasons (2008-2015). Injury incidence overall, in match and training, and patterns (contact, non-contact, sprain, strain, overuse and re-injury) were compared in transferred players (n = 25) across their first versus second seasons and with those in players currently at the club at the moment of the transfer (n = 55 individual players, 134 in total). Incidence rate ratios [IRR] in transferred players in their first versus second competitive season ranged from a 0.9 lower risk in training to a 1.5 higher risk of sustaining a contact injury (respectivePvalues: 0.74, 0.19, inferences:unclear, likely harmful) in the first season. IRR for transferred players in their first and second seasons compared to rates in the same seasons in current players ranged from a 0.5 lower risk of incurring an overuse injury to a 1.1 higher risk of match injury (respectivePvalues: 0.18, 0.89, inferences:unclear, possibly harmful), both occurring in season 1. For the between season and group comparisons, effect sizes regarding mean injury layoff time and matches missed ranged fromtrivialtosmall(0.03-0.22). Although limited to one club, these findings are positive as generally there was no meaningful increase in injury risk or burden in newly transferred players. Potential explanations include systematic pre-participation screening and injury prevention protocols and player rotation strategies in place at the club.