The Neuromuscular Effects of the Copenhagen Adductor Exercise: A Systematic Review.

Only five studies met the criteria, and the authors describe the research on this exercise as not robust: three randomised trials and two cohort studies. The samples were small; the authors name small sample sizes in the included articles as a limiting factor. Everyone studied was a male soccer player, so the results may not carry over to women, to other sports, or to athletes of other ages. One study had no control group, so its strength gains could reflect normal training as much as the exercise. Several studies let players continue their usual strength programme, so other training cannot be ruled out as a contributor to the gains. Blinding was not possible or not documented, the reliability of the strength testing was not fully described, and one trial randomised whole teams rather than individuals, which the authors say raises the chance of a false positive result. The studies excluded players with a previous groin strain, so nothing here speaks to athletes being rehabilitated after a groin injury. No included study measured injuries, so this review cannot say whether the exercise prevents groin problems. The participant numbers in the text and in the tables do not always match (one trial is described as randomising 45 players while its table lists 33), so the exact sample sizes are uncertain.

The authors state that they have no conflicts of interest to disclose. The paper does not report who funded the work.

Do not read this as evidence that the Copenhagen Adductor Exercise prevents groin injuries. None of the five included studies measured injuries; the review only shows that adductor strength and muscle activity increase. The injury figures the paper discusses come from a season-long programme trial in 35 teams, not from any comparison of injury rates within this review, and the fall in substantial groin problems there was not statistically significant.