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Background and aims: Previous injury surveillance studies in women’s football have primarily relied on medical staff to record time-loss injuries. However, these methods have been found to underestimate gradual onset injuries, which groin injuries often are. The latest surveillance studies also suggest that muscle injuries are on the rise, groin injuries included, possibly reflecting the soaring physical demands of the game. In men´s football adductor-related groin injuries are the most common type of groin
injury, but in women’s football we do not yet know which type poses the greatest burden. The Adductor Strengthening Programme, based on the Copenhagen Adduction exercise, has been found to reduce the prevalence of groin injuries in men’s football, and increase hip adductor strength in a dose-response manner. The strength effect of this program has not been investigated in women. The overarching aim of this thesis was to lay the foundation for future groin injury prevention in women’s football. This was done in three steps. First, by providing an updated overview of groin injuries as a part of the bigger injury picture, using methods better suited to capture gradual onset
injuries. Second, by describing the clinical and imaging characteristics of the groin injuries reported. Finally, by comparing the strength effects of a low- and high-volume Adductor Strengthening Programme protocol in female players.
Methods: This thesis is based on two research projects. First, we conducted a two-season (2020-2021) prospective cohort study in the Norwegian women’s premier league. In this project 294 players reported all health problems weekly, using the Oslo Sports Trauma Research Centre Questionnaire on Health Problems (OSTRC-H2). We calculated average weekly prevalence, incidence and burden of all health problems and for the groin injuries especially. Team physiotherapists diagnosed reported health problems using the Sport Medicine Diagnostic Coding System and classified the groin injuries based on the Doha classification system using a standardised form. Groin injuries meeting certain criteria were eligible for magnetic resonance imaging (MRI) and findings described using a standardised form. Second, we conducted a randomised trial involving 52 female players from the Norwegian women's 1st and 2nd division. Players were randomised to perform either an 8-week low or high-volume protocol of the Adductor Strengthening Programme, followed by a 10-week maintenance protocol, during which both groups trained alike. We compared the protocols’ effect on isometric hip adductor strength, measured with a long-lever squeeze test in 0° and 15° of hip abduction.
Results: The average weekly prevalence of substantial health problems was high (22%, 95% CI: 21% to 23%), primarily due to injuries. Gradual-onset injuries accounted for 44% of the injuries. The thigh was the most common injury location (26%), including the three most common injury diagnoses: hamstring, quadriceps and adductor injury. In total 124 groin injuries were reported. On average, 3.9% (95% CI: 3.4-4.4) of players reported a groin injury at any time; of which 78% caused time loss. The incidence rate was 1.6 injuries/1000h (95% CI: 1.3-2.0) and their burden was 11 days lost/1000h. The physiotherapists examined 67 (53%) of the reported groin injuries. Adductor-related injury was the most common (55%), followed by hip flexor-related (27%). Pubic-related injuries caused the most time loss (median: 24 days, IQR: 5-133). Of the 42 injuries who were investigated with MRI 32 (76%) showed at least one nonacute finding. In our randomised trial, both groups increased their isometric hip adduction strength over the 8-week period, with no between-group difference in either test position (0°: -0.01 [95% CI: −0.11-0.01] Nm/kg; 15°: 0.10 [95% CI: −0.09-0.29] Nm/kg). Also, both groups maintained their strength throughout the 10-week maintenance period, with no betweengroups difference in either test position (0°: 0.12 [95% CI: −0.01-0.24] Nm/kg; 15°: 0.06 [95% CI: −0.11-0.23] Nm/kg).
Conclusion: At any given time, one in five players reported a health problem that negatively affected their participation or performance. Gradual-onset injuries were more common than previously reported and the incidence and burden of groin injuries were high. Adductor-related injuries were the most common, followed by hip flexor injuries. Pubic-related injuries caused the most time loss. Most MRI investigations revealed non-acute findings. A high-volume protocol of the Adductor Strengthening Programme was not more effective than the original low-volume protocol in increasing isometric adductor strength in female football players. Players in both groups improved their strength during the 8-week training period and maintained it throughout the subsequent 10-week maintenance period.
