Quadriceps muscle size changes following exercise in anterior cruciate ligament reconstructed limbs: A systematic review

Anterior cruciate ligament (ACL) injury and reconstructive surgery is known to cause long‐term negative impacts on quadriceps muscle size. With the known link between reduced muscle size and the health and functioning of the knee joint, it is important rehabilitation programs aim to restore quadriceps mass as safely and quickly as possible. However, a comprehensive review of interventions investigating the impact of training interventions on quadriceps muscle size in ACL‐reconstructed individuals has yet to be undertaken. Therefore, this article systematically reviews the evidence investigating training interventions that aim to improve quadriceps size in ACL‐reconstructed individuals. A literature search was performed in MEDLINE, SPORTDiscus, CINAHL, and Web of Science. Observational and experimental studies investigating training interventions impact on quadriceps muscle size in ACL‐reconstructed individuals were included. Risk‐of‐bias assessment (Downs and Black) was completed on included studies, data was extracted, and a best evidence synthesis was undertaken. 718 articles were returned in the initial search; following screening, six articles were included in this review. Results from the best evidence synthesis suggest there is moderate evidence for eccentrically biased training to increase quadriceps size. Both traditional resistance training and blood flow restriction training showed conflicting results for improving quadriceps size. However, the results for traditional resistance training and blood flow restriction training may have been limited by differing imaging methods across included studies. This review highlights the positive changes in quadriceps size seen following traditional, eccentrically biased and blood flow restriction exercise interventions in ACL‐reconstructed limbs, despite the limited number of studies. Further work is needed to identify and optimize the best practice for hypertrophic training in these individuals.