An innovative concept for an old therapy

© Annals of Joint. All rights reserved. Ann Joint 2017;2:23 aoj.amegroups.com Muscle weakness and decreased functional capacity are common after knee surgery. Recovery duration and success strongly depend on post-surgery rehabilitation. Although neuromuscular electrical stimulation (NMES) therapy has been used for more than 30 years for muscle rehabilitation and strengthening after orthopedic surgery, there is no consensus on the optimal application of this therapy. Several studies have investigated the NMES effectiveness for different orthopedic surgeries but the present literature remains equivocal; various approaches to NMES application have been taken and only two studies have met consistent criteria for Cochrane meta-analysis (1). In this issue of Annals of Joint, Spector et al. proposed a new approach to NMES application after orthopedic surgery that combines previous evidence-based recommendations. The authors focused on two main goals: gains in muscle strength and increases in voluntary activation. Their approach is both prospective and comprehensive, the authors suggest that the medical team and the patient participate in NMES therapy both preand post-surgery and that both muscle strength and voluntary activation be regularly evaluated. The mechanisms of NMES have been previously investigated but remain incompletely understood. This may account for some reluctance of the physicians to employ NMES therapy. Indeed, NMES therapy is often considered inferior to voluntary contraction for therapy. However, NMES can result in equivalent improvements and may actually offer particular advantages. For example, NMES stimulates protein synthesis to the same extent as voluntary contraction (2). Furthermore, despite the fact that NMES is applied peripherally, central adaptations have been reported in cortical and subcortical areas due to activation of cutaneous afferents during NMES stimulation. In addition, the local muscle metabolic demand during NMES training is at least comparable, and potentially higher than during volitional muscle contraction. One important drawback of NMES is that only one muscle group is trained per session, hence it cannot improve muscle coordination as with voluntary activation. Yet, a key advantage is that NMES can be initiated soon after surgery, notably when voluntary activation is very low. Perhaps the best approach would be to combine NMES and voluntary strength training rather than employing only one, since they have complementary effects that may reduce recovery duration and improve outcomes. Indeed, the algorithm proposed is a good example of a complementary approach wherein NMES therapy is performed directly after surgery and is progressively replaced by volitional muscle contractions. The primary point of this review is that NMES therapy should be performed at high intensity and volume. Indeed, high levels of NMES-induced contraction with a high volume of training seem to be required for significant gains in muscle strength after knee surgery (3). It is also known that a current intensity threshold must be exceeded during NMES training session for both structural (muscle mass) and functional (walking distance) changes (2). This is the rationale for regular supervision of this therapy to ensure adequate NMES-induced force during training. However, Editorial