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The Relationship Between Blood Flow and Motor Unit Firing Rates in Response to Fatiguing Exercise Post-stroke

We quantified the relationship between the change in post-contraction blood flow with motor unit firing rates and metrics of fatigue during intermittent, sub-maximal fatiguing contractions of the knee extensor muscles after stroke. Ten chronic stroke survivors (>1-year post-stroke) and nine contr...

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Autores principales: Murphy, Spencer, Durand, Matthew, Negro, Francesco, Farina, Dario, Hunter, Sandra, Schmit, Brian, Gutterman, David, Hyngstrom, Allison
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6524339/
https://www.ncbi.nlm.nih.gov/pubmed/31133877
http://dx.doi.org/10.3389/fphys.2019.00545
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author Murphy, Spencer
Durand, Matthew
Negro, Francesco
Farina, Dario
Hunter, Sandra
Schmit, Brian
Gutterman, David
Hyngstrom, Allison
author_facet Murphy, Spencer
Durand, Matthew
Negro, Francesco
Farina, Dario
Hunter, Sandra
Schmit, Brian
Gutterman, David
Hyngstrom, Allison
author_sort Murphy, Spencer
collection PubMed
description We quantified the relationship between the change in post-contraction blood flow with motor unit firing rates and metrics of fatigue during intermittent, sub-maximal fatiguing contractions of the knee extensor muscles after stroke. Ten chronic stroke survivors (>1-year post-stroke) and nine controls participated. Throughout fatiguing contractions, the discharge timings of individual motor units were identified by decomposition of high-density surface EMG signals. After five consecutive contractions, a blood flow measurement through the femoral artery was obtained using an ultrasound machine and probe designed for vascular measurements. There was a greater increase of motor unit firing rates from the beginning of the fatigue protocol to the end of the fatigue protocol for the control group compared to the stroke group (14.97 ± 3.78% vs. 1.99 ± 11.90%, p = 0.023). While blood flow increased with fatigue for both groups (p = 0.003), the magnitude of post-contraction blood flow was significantly greater for the control group compared to the stroke group (p = 0.004). We found that despite the lower magnitude of muscle perfusion through the femoral artery in the stroke group, blood flow has a greater impact on peripheral fatigue for the control group; however, we observed a significant correlation between change in blood flow and motor unit firing rate modulation (r(2) = 0.654, p = 0.004) during fatigue in the stroke group and not the control group (r(2) = 0.024, p < 0.768). Taken together, this data showed a disruption between motor unit firing rates and post-contraction blood flow in the stroke group, suggesting that there may be a disruption to common inputs to both the reticular system and the corticospinal tract. This study provides novel insights in the relationship between the hyperemic response to exercise and motor unit firing behavior for post-stroke force production and may provide new approaches for recovery by improving both blood flow and muscle activation simultaneously.
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spelling pubmed-65243392019-05-27 The Relationship Between Blood Flow and Motor Unit Firing Rates in Response to Fatiguing Exercise Post-stroke Murphy, Spencer Durand, Matthew Negro, Francesco Farina, Dario Hunter, Sandra Schmit, Brian Gutterman, David Hyngstrom, Allison Front Physiol Physiology We quantified the relationship between the change in post-contraction blood flow with motor unit firing rates and metrics of fatigue during intermittent, sub-maximal fatiguing contractions of the knee extensor muscles after stroke. Ten chronic stroke survivors (>1-year post-stroke) and nine controls participated. Throughout fatiguing contractions, the discharge timings of individual motor units were identified by decomposition of high-density surface EMG signals. After five consecutive contractions, a blood flow measurement through the femoral artery was obtained using an ultrasound machine and probe designed for vascular measurements. There was a greater increase of motor unit firing rates from the beginning of the fatigue protocol to the end of the fatigue protocol for the control group compared to the stroke group (14.97 ± 3.78% vs. 1.99 ± 11.90%, p = 0.023). While blood flow increased with fatigue for both groups (p = 0.003), the magnitude of post-contraction blood flow was significantly greater for the control group compared to the stroke group (p = 0.004). We found that despite the lower magnitude of muscle perfusion through the femoral artery in the stroke group, blood flow has a greater impact on peripheral fatigue for the control group; however, we observed a significant correlation between change in blood flow and motor unit firing rate modulation (r(2) = 0.654, p = 0.004) during fatigue in the stroke group and not the control group (r(2) = 0.024, p < 0.768). Taken together, this data showed a disruption between motor unit firing rates and post-contraction blood flow in the stroke group, suggesting that there may be a disruption to common inputs to both the reticular system and the corticospinal tract. This study provides novel insights in the relationship between the hyperemic response to exercise and motor unit firing behavior for post-stroke force production and may provide new approaches for recovery by improving both blood flow and muscle activation simultaneously. Frontiers Media S.A. 2019-05-10 /pmc/articles/PMC6524339/ /pubmed/31133877 http://dx.doi.org/10.3389/fphys.2019.00545 Text en Copyright © 2019 Murphy, Durand, Negro, Farina, Hunter, Schmit, Gutterman and Hyngstrom. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Physiology
Murphy, Spencer
Durand, Matthew
Negro, Francesco
Farina, Dario
Hunter, Sandra
Schmit, Brian
Gutterman, David
Hyngstrom, Allison
The Relationship Between Blood Flow and Motor Unit Firing Rates in Response to Fatiguing Exercise Post-stroke
title The Relationship Between Blood Flow and Motor Unit Firing Rates in Response to Fatiguing Exercise Post-stroke
title_full The Relationship Between Blood Flow and Motor Unit Firing Rates in Response to Fatiguing Exercise Post-stroke
title_fullStr The Relationship Between Blood Flow and Motor Unit Firing Rates in Response to Fatiguing Exercise Post-stroke
title_full_unstemmed The Relationship Between Blood Flow and Motor Unit Firing Rates in Response to Fatiguing Exercise Post-stroke
title_short The Relationship Between Blood Flow and Motor Unit Firing Rates in Response to Fatiguing Exercise Post-stroke
title_sort relationship between blood flow and motor unit firing rates in response to fatiguing exercise post-stroke
topic Physiology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6524339/
https://www.ncbi.nlm.nih.gov/pubmed/31133877
http://dx.doi.org/10.3389/fphys.2019.00545
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