Predicting Noncontact Lower Limb Injury Using Lumbar Morphology in Professional Australian Football and Rugby League Players

INTRODUCTION: Non-contact lower limb injuries are common within the Australian Football League (AFL) and National Rugby League (NRL). Smaller (<8.5 cm2) lumbar multifidus at the fifth vertebra (LM L5) and larger (>8.2 cm2) quadratus lumborum (QL) cross-sectional area (CSA) have been associated with increased non-contact lower limb injury risk in AFL players. These associations have not been explored in an NRL cohort. This study will attempt to replicate previous research findings by confirming that muscle morphology is associated with non-contact lower limb injury.

METHODS: AFL (n = 87) and NRL (n = 151) players underwent LM L2-L5 and QL CSA ultrasound measures during preseason. Each club's medical staff reported all non-contact lower limb injuries sustained in the subsequent regular season. LM and QL CSA, age, body mass index and non-contact lower limb injuries were analysed using multivariable logistic regression.

RESULTS: Seventy-two players sustained a non-contact lower limb injury in the 2020 regular season (AFL = 21, NRL = 51). The multivariable logistic regression (OR: 1.36, 95%CI: 1.02-1.85, p = 0.038) identified AFL players with larger QL CSA at increased risk of sustaining a non-contact lower limb injury during the regular season but no relationship was found for LM CSA and non-contact lower limb injuries in the AFL (OR: 1.01, 95%CI: 0.36-2.78, p = 0.591) or NRL (OR: 0.63, 95%CI: 0.29-1.33, p = 0.149).

CONCLUSIONS: AFL players who sustained regular season non-contact lower limb injuries had larger QL CSAs in pre-season tests. no significant associations between either LM L5 CSA or LM L5 to QL ratio and regular season non-contact lower limb injuries were found.