Abstract
PurposeCross-education reduces quadriceps weakness 8 weeks after anterior cruciate ligament (ACL) surgery, but the long-term effects are unknown. We investigated whether cross-education, as an adjuvant to the standard rehabilitation, would accelerate recovery of quadriceps strength and neuromuscular function up to 26 weeks post-surgery.MethodsGroup allocation was randomized. The experimental (n = 22) and control (n = 21) group received standard rehabilitation. In addition, the experimental group strength trained the quadriceps of the non-injured leg in weeks 1–12 post-surgery (i.e., cross-education). Primary and secondary outcomes were measured in both legs 29 ± 23 days prior to surgery and at 5, 12, and 26 weeks post-surgery.ResultsThe primary outcome showed time and cross-education effects. Maximal quadriceps strength in the reconstructed leg decreased 35% and 12% at, respectively, 5 and 12 weeks post-surgery and improved 11% at 26 weeks post-surgery, where strength of the non-injured leg showed a gradual increase post-surgery up to 14% (all p ≤ 0.015). Limb symmetry deteriorated 9–10% more for the experimental than control group at 5 and 12 weeks post-surgery (both p ≤ 0.030). One of 34 secondary outcomes revealed a cross-education effect: Voluntary quadriceps activation of the reconstructed leg was 6% reduced for the experimental vs. control group at 12 weeks post-surgery (p = 0.023). Both legs improved force control (22–34%) and dynamic balance (6–7%) at 26 weeks post-surgery (all p ≤ 0.043). Knee joint proprioception and static balance remained unchanged.ConclusionStandard rehabilitation improved maximal quadriceps strength, force control, and dynamic balance in both legs relative to pre-surgery but adding cross-education did not accelerate recovery following ACL reconstruction.
Highlights
Anterior cruciate ligament (ACL) rupture is the most common knee injury, especially in adults aged 20–29 years with a preference for sports that involve pivoting, jumping, and direct contact between competitors (Majewski et al 2006)
Maladaptive changes in somatosensory areas following ACL injury and reconstruction contribute to decreased knee joint proprioception (Baumeister et al 2008; Valeriani et al 1999), whereas a bilateral decrease in motor cortex excitability likely contributes to quadriceps weakness and activation failure (Lepley et al 2015; Pietrosimone et al 2015)
We examined whether cross-education can accelerate the recovery of neuromuscular function when added to the standard care program in the early phase after ACL surgery
Summary
Anterior cruciate ligament (ACL) rupture is the most common knee injury, especially in adults aged 20–29 years with a preference for sports that involve pivoting, jumping, and direct contact between competitors (Majewski et al 2006). European Journal of Applied Physiology (2018) 118:1609–1623 but deficits in knee extensor strength, neuromuscular control, and proprioception remain up to 2 years after surgery (Nagelli and Hewett 2017). These deficits are present in the contralateral non-injured leg (Chung et al 2015; Lepley et al 2015; Negahban et al 2014; Zult et al 2017), suggesting that rehabilitation following ACL reconstruction should target both legs. Cross-education, which is the increase in muscle force on the untrained side after resistance training of the contralateral homologous limb muscle (Carroll et al 2006), might as an adjuvant to standard therapy, improve muscle function after ACL reconstruction by increasing the neural drive to muscles of the reconstructed and non-injured leg (Hendy and Lamon 2017)
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