Quadriceps Strength and Functional Performance After Anterior Cruciate Ligament Reconstruction in Professional Soccer players at Time of Return to Sport

Herrington, L, Ghulam, H, and Comfort, P. Quadriceps strength and functional performance after anterior cruciate ligament reconstruction in professional soccer players, at time of return to sport. J Strength Cond Res 35(3): 769-775, 2021-Poor quadriceps strength has been associated with poor outcome after anterior cruciate ligament (ACL) reconstruction (ACLR). This study aims to assess quadriceps strength, muscle inhibition, and hop test performance in professional soccer players after ACLR. Fifteen professional soccer players (age 22.3 +/- 3.1 years, body mass 81.0 +/- 11.5 kg, and height 1.75 +/- 0.1 m) who had undergone ACLR participated. Isometric, eccentric, and concentric quadriceps strength was assessed, along with quadriceps inhibition and single and cross-over hop performance, at the time of return to full-time unrestricted play. In comparison with the uninjured leg, the ACLR leg demonstrated large significant (d >= 0.84, p < 0.01) deficits in isometric, eccentric, and concentric quadriceps strength, quadriceps inhibition, and hop distance. Over 80% of the players failed to exceed the limb symmetry criteria of >= 90% for strength tests, although 75% of the cohort passed the >= 90% criteria for hop tests. The outcome from ACLR in professional soccer players who received full-time intensive rehabilitation has not previously been reported in detail. There were significant deficits in quadriceps strength at the time of return to sport, whereas hop testing, a commonly used outcome measure, failed to show the same levels of deficit. These deficits in quadriceps function may have implications for the development of ongoing knee symptoms and risk of future ACL injury. If this proves to be the case, then it would seem that greater attention should be paid to re-establishing full quadriceps strength before returning to unrestricted sporting activity.