The effects of isokinetic training in athletes after knee surgery: a systematic review

To review the effectiveness of isokinetic training as an alternative method to traditional isotonic resistance training. Researchers examined data from PubMed, CENTRAL, MEDLINE COMPLETE, and Web of Science until February 2023. A total of 365 entries were obtained from databases, including studies that analyzed the effects of isokinetic vs. isotonic-based rehabilitation in athletes (16–50 years) after a surgical knee intervention. Return to sport (RTS), strength of the flex/extensor compartment of the thigh, muscle mass of the thigh, and knee function were screened as main outcomes. Two reviewers independently screened the studies for eligibility and assessed the risk of bias of the included ones. Six studies involving 181 athletes were included. Isokinetic training demonstrated significant benefits in peak torque for knee flexor-extensor muscles in four studies. Two studies favored isokinetic training over isotonic for strength. Muscle mass findings were mixed, with one study favoring isokinetic significantly and two showing no significant differences. In terms of returning to sport, the isotonic group displayed slightly better limb symmetry index values, but without significance. Isokinetic training outperformed isotonic in two functionality questionnaire studies, while two others showed no significant differences. Isokinetic training appears equally, if not more effective than isotonic, for restoring strength balance between hamstrings and quadriceps. This could lead to more favorable muscle mass changes. Isokinetic training also parallels isotonic rehabilitation for functional outcomes and meeting return-to-sport criteria. Therefore, isokinetic training should be included as one of the main strength restoration strategies after knee surgery, especially in early and middle rehabilitation stages. The present systematic review was registered on PROSPERO (registration number: CRD42022370398).