Injury incidence, severity and type across the menstrual cycle in elite female professional footballers: a prospective three season cohort study

ObjectivesThe aim of the study was to assess the influence of menstrual cycle phase on injury incidence, severity and type in elite female professional footballers over three seasons. MethodsTime-loss injuries and menstrual cycle data were prospectively recorded for 26 elite female football players across three seasons. The menstrual cycle was categorised into four phases using a standardised model: menstruation (phase 1; P1), remainder of follicular phase (phase 2; P2), early luteal (phase 3; P3), and pre-menstrual phase (phase 4; P4). Injury incidence rates (IRR) and ratios (IIRR) were calculated for overall injuries, injury type, contact vs non-contact, game/training and severity of injury. Results593 cycles across 13,390 days were tracked during the study and 74 injuries from 26 players were eligible for analysis. Muscle injuries were the most prevalent sub-type (n=41). When comparing IRR between phases (reference: P1), injury rates were highest in P4 for overall (IIRR: 2.30 [95% CI: 0.99-5.34; p=0.05]), muscle-specific (6.07 [1.34-27.43; p=0.02]), non-contact (3.05 [1.10-8.50; p=0.03]) and [≤]7 days time-loss injuries (4.40 [0.93-20.76; p=0.06]). Muscle-specific (IIRR P3:P1: 5.07 [1.16-22.07; p=0.03]) and [≤]7 days time-loss (4.47 [1.01-19.68; p=0.05]) injury risk were also significantly higher in P3. No anterior cruciate ligament injuries were recorded across the monitoring period. ConclusionInjury risk was significantly elevated during the luteal phase of the menstrual cycle (P3 and P4) among elite female professional footballers. Further research is urgently needed to better understand the influence of the menstrual cycle on injury risk and to develop interventions to mitigate risk. What are the new findings?O_LIInjury risk was lowest in phase 1, during menstruation. C_LIO_LIRate of overall injuries was highest in the luteal phase (phases 3 and 4), specifically for non-contact and lower severity injuries (e.g. 1-7 days missed training). C_LIO_LIMuscle injury risk increased across the menstrual cycle, with a greater incidence in the luteal phase (phases 3 and 4). C_LIO_LIConversely to current perceptions, squad availability is significantly impacted by a wide range of injuries that are related to menstrual cycle phase, not just significant ligament injuries. C_LI How might it impact on clinical practice in the near future?O_LIWhen reviewing injury occurrence, mechanism and prevention guidelines, it is crucial to consider menstrual cycle day and phase. C_LIO_LILongitudinal menstrual cycle monitoring provides an additional, potentially useful factor to support female athletes. C_LIO_LIThe results of this study demonstrate that there is an urgent need to collect menstrual cycle data alongside standardised injury data to allow for further exploration in a larger sample. C_LI