Muscle proton T2 relaxation times and work during repetitive maximal voluntary exercise

J. L. Fleckenstein, D. Watumull, Donald D McIntire, L. A. Bertocci, David P Chason, Ronald M Peshock

Research output: Contribution to journalArticle

48 Scopus citations

Abstract

We studied the effects of progressive maximal voluntary handgrip contractions (MVCs) on muscle proton spin-spin (T2) relaxation times and work, measured as the integrated force vs. time curve (FTI). Six healthy volunteers performed 10, 20, 40, and 80 MVCs in a 0.35-T magnet on four separate occasions. Repeated measures analyses of variance of increases in T2 and FTI during successive bouts were significant (P < 0.005 and P < 0.001, respectively). FTI increased with successive bouts to a greater extent than did muscle T2 (P < 0.05). For T2, the Helmert contrast judged the 10- MVC response lower than the mean of the remaining responses (P < 0.005), and the differences between all others compared with the means of subsequent responses were not significant, indicating a 'flattening' of the T2 response after the increase from 10 to 20 repetitions. For FTI, all the single degree of freedom Helmert contrasts were significant (P < 0.001), indicating a continual increase in response over increased MVCs. The curved nature of the T2 response conformed best to a hyperbolic function, suggesting that a limit of ~32% exists for the change in T2 during progressively longer bouts of MVCs. A limit in the T2 response is consistent with the existence of a limit in the amount of water that muscle can take up from the vasculature during exertion.

Original languageEnglish (US)
Pages (from-to)2855-2859
Number of pages5
JournalJournal of applied physiology
Volume74
Issue number6
StatePublished - Jan 1 1993

Keywords

  • force
  • magnetic resonance imaging
  • muscle contraction
  • muscles

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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