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

Introduction Noncontact lower limb injuries are common within the Australian Football League (AFL) and National Rugby League (NRL). Smaller (<8.5 cm(2)) lumbar multifidus at the fifth vertebra (LM L5) and larger (>8.2 cm(2)) quadratus lumborum (QL) cross-sectional area (CSA) have been associated with increased noncontact 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 noncontact 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 noncontact lower limb injuries sustained in the subsequent regular season. LM and QL CSA, age, body mass index, and noncontact lower limb injuries were analyzed using multivariable logistic regression. Results Seventy-two players sustained a noncontact lower limb injury in the 2020 regular season (AFL = 21, NRL = 51). The multivariable logistic regression (odds ratio (OR) = 1.36; 95% confidence interval (CI), 1.02-1.85; P = 0.038) identified AFL players with larger QL CSA at increased risk of sustaining a noncontact lower limb injury during the regular season, but no relationship was found for LM CSA and noncontact 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 noncontact lower limb injuries had larger QL CSA in preseason tests. No significant associations between either LM L5 CSA or LM L5 to QL ratio and regular season noncontact lower limb injuries were found.

Automated summary

This study found that AFL players with larger QL cross-sectional area (CSA) were at increased risk of sustaining noncontact lower limb injuries during the regular season. However, there was no significant association between LM L5 CSA and noncontact lower limb injuries in both AFL and NRL cohorts.