Abstract
We compared the effectiveness of a home-based neuromuscular electrical stimulation (NMES) program applied to the quadriceps of the nonoperative side against sham-NMES as a complement to standard rehabilitation on knee extensor neuromuscular function in patients following anterior cruciate ligament (ACL) reconstruction. Twenty-four patients completed the 6 week NMES (n = 12) and sham-NMES (n = 12) post-operative interventions and were tested at different time points for neuromuscular function and self-reported knee function. Isometric, concentric, and eccentric strength deficits (muscle weakness) increased significantly from pre-surgery to 24 weeks post-surgery in the sham-NMES group (p < 0.05), while no significant changes were observed in the NMES group. On the stimulated (nonoperative) side, quadriceps voluntary activation and muscle thickness were respectively maintained (p > 0.05) and increased (p < 0.001) as a result of the NMES intervention, contrary to sham-NMES. Self-reported knee function improved progressively during the post-operative phase (p < 0.05), with no difference between the two groups. Compared to a sham-NMES intervention, a 6 week home-based NMES program applied to the quadriceps of the nonoperative side early after ACL reconstruction prevented the occurrence of knee extensor muscle weakness 6 months after surgery. We conclude that nonoperative-side NMES may help counteract muscle weakness after ACL reconstruction.
Highlights
In healthy subjects, unilateral resistance training of a single muscle group results in significant strength gains of the trained muscle and—to a lesser extent—of the nontrained homonymous muscle on the contralateral side [1,2]
Even if this type of training is not considered in anterior cruciate ligament (ACL) rehabilitation guidelines [14], in the last 10 years, four randomized controlled trials have investigated the effectiveness of different contralateral training protocols on knee extensor muscle strength early following ACL reconstruction [10,11,12,13]
These patients underwent arthroscopically-assisted ACL reconstruction surgery using the hamstring or patellar tendon graft [16], completed a 24 week standard rehabilitation program according to the guidelines of our clinic [17], completed a 6 week intervention phase with either neuromuscular electrical stimulation (NMES) or sham-NMES applied to the nonoperative side, and were tested for neuromuscular function and self-reported knee function 2 weeks before surgery and on post-operative week 2, week 8, and week 24 (Figure 2)
Summary
Unilateral resistance training of a single muscle group results in significant strength gains of the trained muscle and—to a lesser extent—of the nontrained homonymous muscle on the contralateral side [1,2]. Because the impossibility to adequately exercise the knee extensor muscles on the operative side early after ACL reconstruction surgery seems to be one of the main contributors to the resulting muscle weakness, contralateral (i.e., nonoperative-side) resistance training has been proposed as a potential countermeasure against muscle weakness [10,11,12,13] Even if this type of training is not considered in ACL rehabilitation guidelines [14], in the last 10 years, four randomized controlled trials have investigated the effectiveness of different contralateral training protocols on knee extensor muscle strength early following ACL reconstruction [10,11,12,13]. It would be extremely relevant to explore the cross-education effect induced by NMES, which has the unique ability to recruit fast (in addition to slow) motor units even at relatively low contraction intensities [15]
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