Isometric Force and Maximal Shortening Velocity of Single Muscle Fibers from Elite Master Runners

Authors

Jeffrey J. Widrick, Marquette University
Scott W. Trappe, Ball State University
C. A. Blaser, Marquette University
David L. Costill, Ball State University
Robert H. Fitts, Marquette UniversityFollow

Document Type

Article

Language

eng

Format of Original

10 p.

Publication Date

8-1996

Publisher

American Physiological Society

Source Publication

American Journal of Physiology - Cell Physiology

Source ISSN

0002-9513

Original Item ID

DOI: 10.1152/ajpcell.1996.271.2.C666

Abstract

Single chemically permeabilized gastrocnemius fibers from six elite endurance-trained master runners (RUN group) and five age-matched sedentary controls (SED group) were mounted between a force transducer and a position motor, studied under conditions of maximal and submaximal Ca²⁺ activation, and subsequently electrophoresed on 5% polyacrylamide gels to determine myosin heavy chain (MHC) composition. For the SED group, peak isometric tension (P₀) averaged 143 ± 3, 156 ± 4, and 170 ± 4 kN/m2 and maximal shortening velocity (V₀) averaged 0.43 ± 0.01, 1.90 ± 0.08, and 5.59 ± 0.40 fiber lengths/s for fibers expressing type I, IIa, and IIx MHC, respectively (all comparisons, P < 0.05). Hill plot analysis of relative forces during submaximal Ca^2| activation indicated no SED vs. RUN differences in Ca²⁺ sensitivity or in the cooperativity of Ca²⁺ activation. However, at maximal Ca²⁺ activation, RUN type I and IIa fibers produced 15% less peak absolute force than SED fibers (P < 0.05). This reduction in fiber force was a direct result of the smaller diameter of the RUN fibers (P < 0.05), because P₀, peak elastic modulus (E₀), and P₀/E₀ were not different between SED and RUN groups. RUN type I fibers also displayed a mean V₀ that was 19% higher than the average V₀ of the SED type I fibers (P < 0.05). In separate experiments, quantification of relative myosin light chain (MLC) isoform content revealed a 28% greater ratio of MLC₃ to MLC₂ in single type I fibers from the RUN group (P < 0.05), suggesting that the elevated V₀ of the RUN type I fibers was related to a greater expression of MLC₃. In conclusion, the single fibers from the elite master runners displayed specific morphological and contractile properties that may enhance the performance of these athletes during prolonged muscular activity.

Comments

American Journal of Physiology - Cell Physiology, Vol. 271, No. 2 (August 1996): C666-C675. DOI.

Recommended Citation

Widrick, Jeffrey J.; Trappe, Scott W.; Blaser, C. A.; Costill, David L.; and Fitts, Robert H., "Isometric Force and Maximal Shortening Velocity of Single Muscle Fibers from Elite Master Runners" (1996). Biological Sciences Faculty Research and Publications. 453.
https://epublications.marquette.edu/bio_fac/453