Unaccustomed eccentric contractions impair plasma K+ regulation in the absence of changes in muscle Na+,K+-ATPase content
Article
Article Title | Unaccustomed eccentric contractions impair plasma K+ regulation in the absence of changes in muscle Na+,K+-ATPase content |
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ERA Journal ID | 39745 |
Article Category | Article |
Authors | Goodman, Craig A. (Author), Bennie, Jason A. (Author), Leikis, Murray J. (Author) and McKenna, Michael J. (Author) |
Journal Title | PLoS One |
Journal Citation | 9 (6), pp. e101039-1 |
Number of Pages | 7 |
Year | 2014 |
Publisher | Public Library of Science (PLoS) |
Place of Publication | United States |
ISSN | 1932-6203 |
Digital Object Identifier (DOI) | https://doi.org/10.1371/journal.pone.0101039 |
Web Address (URL) | http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0101039 |
Abstract | The Na+,K+-ATPase (NKA) plays a fundamental role in the regulation of skeletal muscle membrane Na+ and K+ gradients, excitability and fatigue during repeated intense contractions. Many studies have investigated the effects of acute concentric exercise on K+ regulation and skeletal muscle NKA, but almost nothing is known about the effects of repeated eccentric contractions. We therefore investigated the effects of unaccustomed maximal eccentric knee extensor contractions on K+ regulation during exercise, peak knee extensor muscle torque, and vastus lateralis muscle NKA content and 3-O-MFPase activity. Torque measurements, muscle biopsies, and venous blood samples were taken before, during and up to 7 days following the contractions in six healthy adults. Eccentric contractions reduced peak isometric muscle torque immediately post-exercise by 26±11% and serum creatine kinase concentration peaked 24 h post-exercise at 339±90 IU/L. During eccentric contractions, plasma [K+] rose during Set 1 and remained elevated at ∼4.9 mM during sets 4–10; this was despite a decline in work output by Set 4, which fell by 18.9% at set 10. The rise in plasma [K+].work−1 ratio was elevated over Set 2 from Set 4– Set 10. Eccentric contractions had no effect on muscle NKA content or maximal in-vitro 3-O-MFPase activity immediately post- or up to 7 d post-exercise. The sustained elevation in plasma [K+] despite a decrease in work performed by the knee extensor muscles suggests an impairment in K+ regulation during maximal eccentric contractions, possibly due to increased plasma membrane permeability or to excitation-contraction uncoupling. |
Keywords | muscle contraction; skeletal muscles; torque; knees; muscle analysis; exercise; strength training; biopsy |
ANZSRC Field of Research 2020 | 420702. Exercise physiology |
Byline Affiliations | Victoria University |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q47q1/unaccustomed-eccentric-contractions-impair-plasma-k-regulation-in-the-absence-of-changes-in-muscle-na-k-atpase-content
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