The popularity of the Copenhagen Adduction Exercise (CAE) has risen in recent years. This review aims to evaluate the available evidence on the isolated use of the CAE for both performance enhancement and injury prevention. This systematic review included prospective interventional studies investigating the effect of the CAE on strength and conditioning and injury prevention outcomes. 15 studies were included, comprising randomized controlled trials (n = 4), cluster-randomized controlled trials (n = 6), and pre-post trials (n = 5). These studies assessed adduction and abduction strength, jump and sprint performance, core endurance, dynamic balance, adductor longus muscle thickness, and the seasonal prevalence of groin injuries. Meta-analyses of within-group changes and between-group comparisons were performed using standardized mean differences (SMDs) and relative risk (RR). The implementation of the CAE yielded large effect sizes for adduction (within-group SMD = 0.72, 95% CI = 0.41 to 1.0; between-group SMD = 0.95, 95% CI = 0.18 to 1.7) and abduction (within-group SMD = 0.92, 95% CI = 0.47 to 1.4; between-group SMD = 0.94, 95% CI = 0.33 to 1.56) strength. Adduction strength adaptations were dependent on the repetitions performed (adherence-adjusted repetitions: p = 0.02; adherence-adjusted weekly repetitions: p = 0.0063). Dynamic balance can also be improved using the CAE (within-group SMD = 3.9). The CAE showed no statistically significant effect on seasonal groin injury prevalence (RR = 0.83, 95% CI = 0.41 to 1.68). There were no additional benefits of the intervention for other performance metrics, and the quality of evidence underpinning all findings was rated as very low. The inclusion of the CAE can be recommended for adductor strength training, although current evidence does not support its use for reducing the risk of sustaining groin injuries. RETRACTION: M. Quintana-Cepedal, O. de la Calle, P. Diez-Solorzano, B. Sanchez-Martinez, I. Crespo, and H. Olmedillas, "The Copenhagen Adduction Exercise Effect on Sport Performance and Injury Prevention: A Systematic Review With Meta-Analysis," Scandinavian Journal of Medicine & Science in Sports 35, no. 8 (2025): e70119, https://doi.org/10.1111/sms.70119. The above article, published online on 19 August 2025 in Wiley Online Library (http://onlinelibrary.wiley.com/), has been retracted by agreement between the authors; the journal Editor-in-Chief, José A. Calbet; and John Wiley & Sons Ltd. Following publication, the journal received concerns from a third party that the article contains an erroneous analysis, which was not detected during peer review. The journal editors investigated and determined that the meta-analysis misrepresents the reported outcomes of two out of the three cited studies, and contains fundamental methodological flaws that invalidate the article's conclusions. The authors resubmitted a revised version of their manuscript, which after peer review and careful evaluation was deemed unsuitable for publication in the journal. The article must therefore be retracted, without the possibility of publishing a correction.
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