Fatiguing Arm Exercise Following Stroke

Study Overview
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Brief Summary
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This study investigates the effects of sub-maximal exercise to task-failure (e.g., fatigue) with the less involved, or so-called non-paretic hand, in people who have experienced a stroke. In previous work the investigators found that non-paretic hand exercise to task-failure increased excitability of the motor cortex in the more involved hemisphere and produced behavioral improvements in the unexercised paretic hand. Importantly, the magnitude of increased brain excitability is greater than what has been observed following brain stimulation with either repetitive transcranial magnetic stimulation (TMS) or transcranial direct current stimulation (tDCS) and lasts longer. This approach could be implemented in the clinical setting and could be accessible to a greater number of people than brain stimulation. The investigators' goals in the current study are to: repeat previous findings in a different group of participants and investigate the neural mechanisms that produce brain and behavioral facilitation in order to inform development of this approach for clinical implementation.

Detailed Description
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The long-term goal is to restore upper extremity (UE) motor function following stroke. The overall objective of this proposal is to improve the investigators' understanding of neural mechanisms contributing to inter-limb and inter-hemispheric transfer following non-paretic limb exercise to task failure. The investigators will use transcranial magnetic stimulation to probe acute adaptations in cortical excitability, intracortical and inter-hemispheric circuits that accompany behavioral facilitation of the paretic hand. The work proposed in this two year project will enable the investigators to obtain three data elements critical to complete the working hypothesis: . Changes in intracortical and interhemispheric inhibition in both hemispheres following non-paretic limb exercise to task-failure. . Behavioral effects using a motor task involving manipulation and dexterity. . Determine the persistence and consistency of neural and behavioral facilitation.

Official Title
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Neural Mechanisms Mediating Interlimb Transfer Following Stroke

Conditions
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Stroke

Intervention / Treatment
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* Other: submaximal exercise (grip)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: individuals at least 6 months post-stroke in the cortical or sub-cortical distribution with residual upper-extremity hemiparesis Non-Veteran Participants are eligible Exclusion Criteria: multiple strokes strokes in both hemispheres brainstem/medullary/cerebellar stroke seizure disorder metal implants in head or neck pacemaker or other implanted device inability to produce any measurable grip force

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Interventional Model Description: Prospective, repeated measures
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Task-failure, Extended Session<br>Repeated sub-maximal gripping exercise with the less affected hand to task-failure - followed by repeated measurements (5) during recovery period | Other: submaximal exercise (grip)<br>* participants perform repeated gripping with visual feedback to task failure<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Short Intracortical Inhibition (SICI) | SICI is a neurophysiologic measure of intra-cortical inhibition, obtained using transcranial magnetic stimulation (TMS) measured here in the ipsilesional hemisphere (IH) at each point to determine how it is modulated in response to task-failure. SICI is quantified as a ratio where values <1 reflect inhibition and >1 disinhibition or relative excitation. In health, SICI is  0.5. Thus if SICI = 0.8, while <1 it would indicate less inhibition than expected in health. Transient change in SICI from 0.8 to 1.1 over the course of this experimental paradigm would reflect a period of relative excitation in response to the exercise paradigm. | baseline, post task-failure (minutes to an hour), every 45 min up to 3.5 hours post-task-failure (7 points total) | 
| SICI Ratio | SICI is a neurophysiologic measure of intra-cortical inhibition, obtained using transcranial magnetic stimulation (TMS) measured here in the ipsilesional hemisphere (IH) at each point to determine how it is modulated in response to task-failure. SICI is quantified as a ratio where values <1 reflect inhibition and >1 disinhibition or relative excitation. In health, SICI is  0.5. Thus if SICI = 0.8, while <1 it would indicate less inhibition than expected in health. Transient change in SICI from 0.8 to 1.1 over the course of this experimental paradigm would reflect a period of relative excitation in response to the exercise paradigm. | Baseline, pre-exercise of 8 repeated sessions | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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hemiparesis