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Michael G. Dolan, Brian G. Pietrosimone, J. Ty Hopkins and Christopher D. Ingersoll

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Kyung-Min Kim, Christopher D. Ingersoll and Jay Hertel

Context:

Focal ankle-joint cooling (FAJC) has been shown to increase Hoffmann (H) reflex amplitudes of select leg muscles while subjects lie prone, but it is unknown whether the neurophysiological cooling effects persist in standing.

Objective:

To assess the effects of FAJC on H-reflexes of the soleus and fibularis longus during 3 body positions (prone, bipedal, and unipedal stances) in individuals with and without chronic ankle instability (CAI).

Design:

Crossover.

Setting:

Laboratory.

Participants:

15 young adults with CAI (9 male, 6 female) and 15 healthy controls.

Intervention:

All subjects received both FAJC and sham treatments on separate days in a randomized order. FAJC was accomplished by applying a 1.5-L plastic bag filled with crushed ice to the ankle for 20 min. Sham treatment involved room-temperature candy corn.

Main Outcome Measures:

Maximum amplitudes of H-reflexes and motor (M) waves were recorded while subjects lay prone and then stood in quiet bipedal and unipedal stances before and immediately after each treatment. Primary outcome measures were Hmax:Mmax ratios for the soleus and fibularis longus. Three-factor (group × treatment condition × time) repeated-measures ANOVAs and Fisher LSD tests were performed for statistical analyses.

Results:

Significant interactions of treatment condition by time for prone Hmax:Mmax ratios were found in the soleus (P = .001) and fibularis longus (P = .003). In both muscles, prone Hmax:Mmax ratios moderately increased after FAJC but not after sham treatment. The CAI and healthy groups responded similarly to FAJC. In contrast, there were no significant interactions or main effects in the bipedal and unipedal stances in either muscle (P > .05).

Conclusions:

FAJC moderately increased H-reflex amplitudes of the soleus and fibularis longus while subjects were prone but not during bipedal or unipedal standing. These results were not different between groups with and without CAI.

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Conrad M. Gabler, Adam S. Lepley, Tim L. Uhl and Carl G. Mattacola

Clinical Scenario:

Proper neuromuscular activation of the quadriceps muscle is essential for maintaining quadriceps (quad) strength and lower-extremity function. Quad activation (QA) failure is a common characteristic observed in patients with knee pathologies, defined as an inability to voluntarily activate the entire alpha-motor-neuron pool innervating the quad. One of the more popular techniques used to assess QA is the superimposed burst (SIB) technique, a force-based technique that uses a supramaximal, percutaneous electrical stimulation to activate all of the motor units in the quad during a maximal, voluntary isometric contraction. Central activation ratio (CAR) is the formula used to calculate QA level (CAR = voluntary force/SIB force) with the SIB technique. People who can voluntarily activate 95% or more (CAR = 0.95–1.0) of their motor units are defined as being fully activated. Therapeutic exercises aimed at improving quad strength in patients with knee pathologies are limited in their effectiveness due to a failure to fully activate the muscle. Within the past decade, several disinhibitory interventions have been introduced to treat QA failure in patients with knee pathologies. Transcutaneous electrical nerve stimulation (TENS) and cryotherapy are sensory-targeted modalities traditionally used to treat pain, but they have been shown to be 2 of the most successful treatments for increasing QA levels in patients with QA failure. Both modalities are hypothesized to positively affect voluntary QA by disinhibiting the motor-neuron pool of the quad. In essence, these modalities provide excitatory afferent stimuli to the spinal cord, which thereby overrides the inhibitory afferent signaling that arises from the involved joint. However, it remains unknown whether 1 is more effective than the other for restoring QA levels in patients with knee pathologies. By knowing the capabilities of each disinhibitory modality, clinicians can tailor treatments based on the rehabilitation goals of their patients.

Focused Clinical Question:

Is TENS or cryotherapy the more effective disinhibitory modality for treating QA failure (quantified via CAR) in patients with knee pathologies?

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Cody B. Bremner, William R. Holcomb, Christopher D. Brown and Melanie E. Perreault

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).