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Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives
Human muscle fibers are generally classified by myosin heavy chain (MHC) isoforms characterized by slow to fast contractile speeds. Type I, or slow-twitch fibers, are seen in high abundance in elite endurance athletes, such as long-distance runners and cyclists. Alternatively, fast-twitch IIa and II...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2021
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8473039/ https://www.ncbi.nlm.nih.gov/pubmed/34564332 http://dx.doi.org/10.3390/sports9090127 |
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author | Plotkin, Daniel L. Roberts, Michael D. Haun, Cody T. Schoenfeld, Brad J. |
author_facet | Plotkin, Daniel L. Roberts, Michael D. Haun, Cody T. Schoenfeld, Brad J. |
author_sort | Plotkin, Daniel L. |
collection | PubMed |
description | Human muscle fibers are generally classified by myosin heavy chain (MHC) isoforms characterized by slow to fast contractile speeds. Type I, or slow-twitch fibers, are seen in high abundance in elite endurance athletes, such as long-distance runners and cyclists. Alternatively, fast-twitch IIa and IIx fibers are abundant in elite power athletes, such as weightlifters and sprinters. While cross-sectional comparisons have shown marked differences between athletes, longitudinal data have not clearly converged on patterns in fiber type shifts over time, particularly between slow and fast fibers. However, not all fiber type identification techniques are created equal and, thus, may limit interpretation. Hybrid fibers, which express more than one MHC type (I/IIa, IIa/IIx, I/IIa/IIx), may make up a significant proportion of fibers. The measurement of the distribution of fibers would necessitate the ability to identify hybrid fibers, which is best done through single fiber analysis. Current evidence using the most appropriate techniques suggests a clear ability of fibers to shift between hybrid and pure fibers as well as between slow and fast fiber types. The context and extent to which this occurs, along with the limitations of current evidence, are discussed herein. |
format | Online Article Text |
id | pubmed-8473039 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2021 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-84730392021-09-28 Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives Plotkin, Daniel L. Roberts, Michael D. Haun, Cody T. Schoenfeld, Brad J. Sports (Basel) Review Human muscle fibers are generally classified by myosin heavy chain (MHC) isoforms characterized by slow to fast contractile speeds. Type I, or slow-twitch fibers, are seen in high abundance in elite endurance athletes, such as long-distance runners and cyclists. Alternatively, fast-twitch IIa and IIx fibers are abundant in elite power athletes, such as weightlifters and sprinters. While cross-sectional comparisons have shown marked differences between athletes, longitudinal data have not clearly converged on patterns in fiber type shifts over time, particularly between slow and fast fibers. However, not all fiber type identification techniques are created equal and, thus, may limit interpretation. Hybrid fibers, which express more than one MHC type (I/IIa, IIa/IIx, I/IIa/IIx), may make up a significant proportion of fibers. The measurement of the distribution of fibers would necessitate the ability to identify hybrid fibers, which is best done through single fiber analysis. Current evidence using the most appropriate techniques suggests a clear ability of fibers to shift between hybrid and pure fibers as well as between slow and fast fiber types. The context and extent to which this occurs, along with the limitations of current evidence, are discussed herein. MDPI 2021-09-10 /pmc/articles/PMC8473039/ /pubmed/34564332 http://dx.doi.org/10.3390/sports9090127 Text en © 2021 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Review Plotkin, Daniel L. Roberts, Michael D. Haun, Cody T. Schoenfeld, Brad J. Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives |
title | Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives |
title_full | Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives |
title_fullStr | Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives |
title_full_unstemmed | Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives |
title_short | Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives |
title_sort | muscle fiber type transitions with exercise training: shifting perspectives |
topic | Review |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8473039/ https://www.ncbi.nlm.nih.gov/pubmed/34564332 http://dx.doi.org/10.3390/sports9090127 |
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