Clinical trial NCT01688570: Mechanisms of Neuromuscular Fatigue Post Stroke
Official title: Mechanisms of Neuromuscular Fatigue Post Stroke
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: EARLY_PHASE1
Conditions: Stroke
Keywords: neuromuscular fatigue
motor impairment
Lead sponsor: Medical College of Wisconsin
Sponsor class: OTHER
First posted: 2012-09-20
Enrollment: 27
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: BASIC_SCIENCE

Brief summary: While baseline weakness is clearly an important factor that contributes to disability post stroke, neuromuscular fatigue (the acute reduction in force production) of the paretic musculature likely compounds strength deficits and further exacerbates disability. The proposed study aims to improve our understanding of the mechanisms of neuromuscular fatigue in people post stroke in order to optimize strength training. In healthy individuals, both central (neural) and peripheral (muscle) factors are determinants of neuromuscular fatigue, but preliminary data from our laboratory suggests a greater contribution of central components to neuromuscular fatigue in the paretic musculature. Although cortical pathways are clearly disrupted post stroke, it is likely that brainstem pathways, known to have neuromodulatory effects on spinal motor circuitry, are more involved in the sustaining of force in the paretic leg, compared to the non-paretic and control legs. Therefore, the purpose of this proposal is to examine the role of descending neuromodulatory pathways of the brainstem in neuromuscular fatigue post stroke (Aim 1) and to correlate brainstem-related changes in neuromuscular fatigue to walking function (Aim 2). The investigators propose that stroke survivors' decreased capability to sustain force overtime results from the diminished ability of spinal motoneurons to respond to brainstem neuromodulatory inputs (serotonin (5-HT) and norepinephrine (NE)). Aim 1 will quantify stroke-related decreases in motor output sensitivity to a 5-HT and NE reuptake inhibitor (SNRI), serotonin antagonist, or placebo during sub-maximal intermittent fatiguing knee extension contractions. If motoneurons are desensitized to descending monoamines in chronic stroke patients, then they will be less sensitive to the effects of drugs that increase monoamine levels. The investigators predict that in response to the SNRI or serotonin antagonist, the paretic leg will show less change in time to task failure and a smaller reduction in strength as compared to the non-paretic and control legs. For Aim 2, the investigators predict that stroke subjects with the highest walking function will demonstrate the greatest fatigue-related changes in response to the SNRI. This proposal adopts an innovative model of motor impairment post stroke by including the role of subcortical structures in neuromuscular fatigue.


Eligibility criteria: Inclusion Criteria:

General

* be at least 18 years of age
* Cognitively able to give informed consent Stroke

  -≥ 6 months post diagnosis of unilateral cortical stroke
* residual leg paresis

Exclusion Criteria:

General

* chronic low back or hip pain
* major psychiatric disorders (e.g. depression
* substance abuse
* head trauma
* neurodegenerative disorder
* any uncontrolled medical disorder (e.g. hypertension)
* taking any medication or supplement (e.g. St. John's Wort) that has 5-HT or NE mechanisms of action(including Monoamine oxidase inhibitors (MAO) inhibitors)
* narrow angle glaucoma
* chronic liver or kidney disorders Stroke
* history of multiple strokes
* people who are unable to follow 2 step commands
* people who cannot walk ≥ 10 ft without physical assistance.

Primary outcomes:
measure: Force generation
timeFrame: At time of each of 4 testing sessions (all sessions within a 2 year period).
Secondary outcomes:
measure: Surface electromyography (EMG)of lower leg muscles.
timeFrame: EMG measurements will be made during each of the four sessions.
Other outcomes:
Locations:
city: Milwaukee
country: United States
facility: Medical College of Wisconsin
state: Wisconsin
Study officials:
affiliation: Medical College of Wisconsin
name: Philip A. Nelson, MD
role: PRINCIPAL_INVESTIGATOR
References: