Objectives To determine the rates of muscle strain injury recurrence over time after return to play in Australian football and to quantify risk factors.
Methods We analysed Australian Football League player data from 1992 to 2014 for rates of the four major muscle strain injury types (hamstring, quadriceps, calf and groin) diagnosed by team health professionals. Covariates for analysis were: recent history (≤8 weeks) of each of the four muscle strains; non-recent history (>8 weeks) of each; history of hip, knee anterior cruciate ligament, knee cartilage, ankle sprain, concussion or lumbar injury; age; indigenous race; match level and whether a substitute rule was in place.
Results 3647 (1932 hamstring, 418 quadriceps, 458 calf and 839 groin) muscle strain injuries occurred in 272 759 player matches. For all muscle strains combined, the risk of injury recurrence gradually reduced, with recurrence risks of 9% (hamstring), 5% (quadriceps), 2% (calf) and 6% (groin) in the first match back and remaining elevated for 15 weeks after return to play. The strongest risk factor for each muscle injury type was a recent history of the same injury (hamstring: adjusted OR 13.1, 95% CI 11.5 to 14.9; calf OR 13.3, 95% CI 9.6 to 18.4; quadriceps: OR 25.2, 95% CI 18.8 to 33.8; groin OR 20.6, 95% CI 17.0 to 25.0), followed by non-recent history of the same injury (hamstring: adjusted OR 3.5, 95% CI 3.2 to 3.9; calf OR 4.4, 95% CI 3.6 to 5.4; quadriceps OR 5.2, 95% CI 4.2 to 6.4; groin OR 3.5, 95% CI 3.0 to 4.0). Age was an independent risk factor for calf muscle strains (adjusted OR 1.6, 95% CI 1.3 to 2.0). Recent hamstring injury increased the risk of subsequent quadriceps (adjusted OR 1.8, 95% CI 1.2 to 2.7) and calf strains (OR 1.8, 95% CI 1.2 to 2.6). During the ‘substitute rule’ era (2011–2014), hamstring (adjusted OR 0.76, 95% CI 0.67 to 0.86), groin (OR 0.78, 95% CI 0.65 to 0.93) and quadriceps (OR 0.70, 95% CI 0.53 to 0.92) strains were less likely than outside of that era but calf (OR 1.6, 95% CI 1.3 to 1.9) strains were more likely than before the substitute rule era.
Conclusion Recent injury is the greatest risk factor for the four major muscle strains, with increased risk persisting for 15 weeks after return to play.
- muscle injury
- Australian football
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Presented at Data from this work have previously been presented at the SMA Conference (October 2018), the Sydney Musculoskeletal, Bone and Joint Health Alliance (SydMSK) annual scientific meeting (November 2018) and the ACSEP Conference (February 2019).
Contributors JWO is the first author of this paper. All subsequent authors have made substantial contributions to data analysis and interpretation as well as drafting and critical revision of the work.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests JWO was the AFL injury surveillance coordinator between 1992 and 2014. KR was the GWS Giants AFL team medical officer in the 2018 season.
Patient consent for publication Not required.
Ethics approval The survey methods were approved by the AFL, the AFL Research Board, AFL Players Association and AFL Doctors Association, acting as Institutional Review for the study. The analysis only involved de-identified player data and was of very large groups of injuries (hence with no potential for an individual player to have been re-identified from data analysis), and therefore, did not require full Human Ethics assessment according to Australia’s National Health and Medical Research Council guidelines and the ethics policy of the authors’ institution (University of Sydney, Australia).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data may be obtained from a third party and are not publicly available. Raw data availability would require specific request to the AFL Research Board. Analysed data outputs, (Excel and SPSS outputs) but not raw data, would be available on reasonable request to the authors.
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