Abstract

Introduction: Anterior cruciate ligament (ACL) injuries are multifactorial, and recurrence rates after ACL reconstruction (ACLR) remain high, highlighting the need to redefine the criteria for a safe returning to sport (RTS). Fatigue is proposed to negatively impact lower limb biomechanics and task performance, contributing to the risk of re-injury. This systematic review aims to establish how fatigue affects task performance or lower limb kinetics after ACLR, and how these changes contribute to the risk of re-injury. Materials and Methods: A systematic review of the literature was conducted using PubMed and Cochrane databases, including studies published between 2014-2023 in English. Inclusion criteria based on the PICO model involved patients who underwent ACLR (Population), underwent a fatigue protocol (Intervention), and were compared to a non-fatigated state (Comparison). The outcomes were lower limb kinetics / kinematics and task performance (Outcomes). The results were analysed to understand if fatigue increases injury risk. Results: The systematic review included 10 articles, involving 160 participants. Two studies used a peripheral fatigue protocol, while 8 used a central fatigue protocol. Outcome measures are heterogeneous including alterations in kinetics or kinematics, variations in task performance, or specific scores. Conclusion: Fatigue-induced changes generally increase the re-injury risk, but inconsistencies exist due to the heterogeneity of the studies. Therefore, caution is needed when establishing a causal relationship. Future studies with consistent criteria and rigorous methodologies are necessary to determine if ACL rehabilitation programs should consider the impact of fatigue for safer RTS after ACLR