Increased fatigue of isovelocity vs. isometric contractions of canine diaphragm

Bill Ameredes, T. L. Clanton

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

A comparison of fatigue as a loss of force with repeated contractions over time was performed in canine respiratory muscle by isometric (nonshortening) and isovelocity (shortening) contractions. In situ diaphragm muscle strips were attached to a linear ergometer and electrically stimulated (30 or 40 Hz) via the left phrenic nerve to produce either isometric (n = 12) or isovelocity (n = 12) contractions (1.5 s) from optimal muscle length (L(o) = 8.8 cm). Similar velocities of shortening between isovelocity experiments [0.19 ± 0.02 (SD) L(o)/s] were produced by maximizing the mean power output (Ẇ(max) = 210 ± 27 mW/cm2) that could be developed over 1.5 s when displacement was ~0.30 L(o). Initial peak isometric tension was 1.98 kg/cm2, whereas initial peak isovelocity tension was 1.84 kg/cm2 (P < 0.01) or 93% of initial isometric tension. Fatigue trials of 5 min were conducted on muscles contracting at a constant duty cycle (0.43). At the end of the trials, peak isovelocity tension had fallen to 50% of initial isometric tension (P < 0.01), whereas peak isometric tension had only fallen by 27%. These results indicate that muscle shortening during force production has a significant influence on diaphragm muscle fatigue. We conclude that the effects of shortening on fatigue must be considered in models of respiratory muscle function, because these muscles typically shorten during breathing.

Original languageEnglish (US)
Pages (from-to)740-746
Number of pages7
JournalJournal of Applied Physiology
Volume69
Issue number2
StatePublished - 1990
Externally publishedYes

Fingerprint

Isometric Contraction
Diaphragm
Fatigue
Canidae
Muscles
Respiratory Muscles
Muscle Fatigue
Phrenic Nerve
Respiration

Keywords

  • energetics
  • in situ muscle
  • isokinetic
  • muscle mechanics
  • muscle shortening
  • power
  • respiratory muscle fatigue

ASJC Scopus subject areas

  • Endocrinology
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Increased fatigue of isovelocity vs. isometric contractions of canine diaphragm. / Ameredes, Bill; Clanton, T. L.

In: Journal of Applied Physiology, Vol. 69, No. 2, 1990, p. 740-746.

Research output: Contribution to journalArticle

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