Strengthening of the quadriceps in the early phase of ACL rehabilitation is difficult due to knee pain, effusion, and concerns about graft elongation when loading the quadriceps.
Thus, it is not surprising that quadriceps strength in the reconstructed leg decreases rapidly in the first few months after ACL reconstruction. Cross-education, as adjuvant to standard care, might reduce the amount of muscle weakness in the operated leg.
The cross-education phenomenon is known for over 100 years, but studies in clinical populations are scarce. A recent meta-analysis of cross-education studies in healthy adults showed that the strength increase in the untrained leg is 16% after strengthening the opposite leg muscles. Therefore, cross-education might be beneficial for patients with a unilateral impairment who are unable to train the injured leg.
Cross-education is especially relevant to ACL rehabilitation, because it acts through neural pathways that are involved in the strength loss of the operated leg. There is evidence that cross-education can reduce the amount of quadriceps weakness in the operated leg and improve self-reported knee function in the first 8 weeks after ACL reconstruction. We examined whether these cross-education benefits in the early-phase can accelerate the late-phase recovery after ACL reconstruction.
Forty-three patients were randomly allocated to a standard care or standard care + cross-education group. All participants were adults awaiting ACL surgery at the Martini Hospital in Groningen, the Netherlands. Quadriceps strength and self-reported knee-function were examined 4 weeks prior to surgery and 5, 12, and 26 weeks after surgery. The examiner was unaware of the group allocation. The cross-education training consisted of quadriceps strengthening exercises with the non-injured leg in weeks 1-12 after surgery. Standard care continued until 26 weeks after surgery. Every patient trained twice a week under supervision of a physiotherapist.
Cross-education in the early phase after ACL reconstruction did not improve quadriceps strength and self-reported knee function in the early and late-phase of ACL rehabilitation. The training load of the cross-education program was not high enough as cross-education training did not result in extra strength gains in the quadriceps muscles of the non-injured leg. Cross-education had no negative influence on ACL recovery and could supposedly still accelerate the ACL recovery when the training load of the cross-education protocol is increased.
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> From: Zult et al., Knee Surg Sports Traumatol Arthrosc 27 (2019) 478-490 . All rights reserved to European Society of Sports Traumatology, Knee Surgery, Arthroscopy. Click here for the online summary.
