Menstruation and injury occurrence; a four season observational study in elite female football players

Eva Ferrer^1,2,3*Nicola Keay⁴Laura Balagué-Dobón⁵Alejandro Caceres⁵Priscilla Jarrin⁶Gil Rodas^2,3,5,6Juan R Gonzalez Ruiz⁵

• ¹Sant Joan de Déu Hospital, Barcelona, Spain
• ²Barca Innovation Hub, Barcelona, Spain
• ³Universitat de Barcelona, Barcelona, Spain
• ⁴University College London Division of Medicine, London, United Kingdom
• ⁵Instituto de Salud Global de Barcelona, Barcelona, Spain
• ⁶FC Barcelona Servicios Medicos, Barcelona, Spain

BACKGROUD The menstrual cycle (MC) has been proposed as a factor influencing injury risk in female athletes due to hormonal effects on musculoskeletal, metabolic, and neuromuscular systems. However, inconsistencies in study methods and variability in defining menstrual phases have produced conflicting findings. The absence of biological hormone measurements often forces reliance on estimations, limiting data accuracy. Each menstrual phase has distinct hormonal profiles, yet menstruation remains the only stage where hormone status can be inferred with certainty, as it is characterized by low ovarian hormone levels. Understanding this relationship in elite female football players is important for optimizing training load, recovery, health management, and injury prevention. OBJECTIVE To examine whether the early follicular phase (menstruation) is associated with musculoskeletal time-loss injuries in elite female football players across four competitive seasons. STUDY DESIGN Descriptive epidemiological study. METHODS Thirty-three elite female football players were prospectively monitored between the 2019/20 and 2022/23 seasons. Menstrual cycle data were tracked using a calendar-based digital tool, while injuries were classified using the OSICS-10 coding system. Incidence rates per 1,000 hours of exposure were compared between menstruation (bleeding) and non-bleeding phases. In this study, “bleeding,” “menstruation,” “phase 1,” and “early follicular phase” are used interchangeably. RESULTS A total of 852 menstrual cycles and 80 injuries were recorded. 77.5%, occurred in training while 22.5% were during matches. Muscle injuries accounted for 57.5% of cases, ligament injuries 30%, and tendon injuries 12.5%. Injuries during menstruation represented 13.7% of all cases. The overall injury incidence was 6.42 per 1,000 hours (95% CI: 5.09–7.99), with 5.46 during menstruation and 6.60 during non-bleeding phases (p = 0.55). Although rates did not differ significantly, the injury burden was markedly higher during menstruation (684 vs. 206 days lost per 1,000 hours; p = 0.0027), indicating greater severity. CONCLUSIONS Injury incidence did not differ significantly between menstrual phases; however, injuries sustained during menstruation were more severe, resulting in a substantially higher burden. These findings underscore the value of individualized menstrual tracking to support injury prevention and athlete health strategies. Further studies using direct hormonal measurements are warranted to validate and extend these results.