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Clinical Scenario: Orthopedic knee conditions are regularly treated in sports-medicine clinics. Rehabilitation protocols for these conditions are often designed to address the associated quadriceps strength deficits. Despite these efforts, patients with orthopedic knee conditions often fail to completely regain their quadriceps strength. Disinhibitory modalities have recently been suggested as a clinical tool that can be used to counteract the negative effects of arthrogenic muscle inhibition, which is believed to limit the effectiveness of therapeutic exercise. Neuromuscular electrical stimulation (NMES) is commonly accepted as a strengthening modality, but its ability to simultaneously serve as a disinhibitory treatment is not as well established. Clinical Question: Does NMES effectively enhance quadriceps voluntary activation in patients with orthopedic knee conditions? Summary of Key Findings: Four randomized controlled trials (RCTs) met the inclusion criteria and were included. Of those, 1 reported statistically significant improvements in quadriceps voluntary activation in the intervention group relative to a comparison group, but the statistical significance was not true for another study consisting of the same sample of participants with a different follow-up period. One study reported a trend in the NMES group, but the between-groups differences were not statistically significant in 3 of the 4 RCTs. Clinical Bottom Line: Current evidence does not support the use of NMES for the purpose of enhancing quadriceps voluntary activation in patients with orthopedic knee conditions. Strength of Recommendation: There is level B evidence that the use of NMES alone or in conjunction with therapeutic exercise does not enhance quadriceps voluntary activation in patients with orthopedic knee conditions (eg, anterior cruciate ligament injuries, osteoarthritis, total knee arthroplasty).

Neuromuscular electrical stimulation (NMES) is often used by clinicians as a therapeutic adjunct to improve quadriceps strength deficits following orthopedic knee conditions. The efficacy of NMES treatments is primarily dependent on the NMES training intensity, which is a direct result of NMES-induced torque production. The importance of NMES training intensity is well known, yet adequate NMES training intensities are often difficult to achieve due to a variety of limitations associated with NMES (eg, fatigue and patient discomfort). This article provides recommendations that a clinician can use to increase NMES training intensity when strengthening the quadriceps with NMES for orthopedic knee conditions. These recommendations should allow forceful contractions that can be sustained over a treatment with multiple repetitions without the rapid decline in force that is typically seen when NMES is used.

Neuromuscular electrical stimulation (NMES) is the use of an electrical current for the purpose of eliciting a muscular response, and these treatments are most often used clinically for the specific purpose of increasing quadriceps strength. It is commonly accepted that the effectiveness of NMES for this purpose is primarily determined by the NMES training intensity. However, spatially limited motor unit recruitment, fatigue and discomfort negatively impact NMES-induced torque, which subsequently reduces NMES training intensities. Due to the importance of NMES training intensity, a substantial amount of research has focused on strategies designed to increase NMES-induced torque production, as well as to reduce NMES-induced fatigue and discomfort. However, authors have indicated that additional strategies are needed, as many of the strategies supported by empirical evidence cannot be easily applied in clinical settings. The Kneehab® XP (Theragen LLC, Leesburg, VA) is an electrical stimulator that incorporates a novel multipath current distribution strategy (m-NMES) marketed to address the primary factors limiting NMES training intensity, and as such it has gained a significant amount of attention in the literature. Relative to conventional NMES (c-NMES), authors have reported improved outcomes while using the novel m-NMES but due to a series of methodological limitations the influence of the multipath current distribution strategy on these outcomes remains unclear. Therefore, the purpose of this iii project was to further investigate the influence that m-NMES has on NMES related outcomes. A convenience sample of 21 participants completed two basic studies designed to compare the influence of m-NMES and c-NMES on maximum comfortable stimulus intensity and NMES-induced peak torque, as well as fatigue and discomfort related outcomes. The statistical analyses of each study did not reveal any significant differences across the two conditions deemed to be clinically relevant. Therefore, it does not appear that the novel multipath current distribution method influences the outcomes included during this project in a clinically meaningful manner. The large declines in NMESinduced torque that occurred, irrespective of the NMES condition, suggest the need for the development of additional strategies. iv ACKNOWLEDGMENTS I would like to recognize the following individuals for their support; without each of their individual contributions this project would not have been possible. My Committee Chair and advisor Dr. Bill Holcomb. Thank you for the countless hours you spent patiently teaching and guiding me throughout my entire collegiate experience. I chose to attend USM for the opportunity to learn from you, and you exceeded my expectations. I will be forever indebted to your mentorship.