Power fatigue of the rat diaphragm muscle

Bill Ameredes, Wen Zhi Zhan, Y. S. Prakash, Rene Vandenboom, Gary C. Sieck

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

We hypothesized that decrements in maximum power output (W(max)) of the rat diaphragm (Dia) muscle with repetitive activation are due to a disproportionate reduction in force (force fatigue) compared with a slowing of shortening velocity (velocity fatigue). Segments of midcostal Dia muscle were mounted in vitro (26°C) and stimulated directly at 75 Hz in 400-ms-duration trains repeated each second (duty cycle = 0.4) for 120 s. A novel technique was used to monitor instantaneous reductions in maximum specific force (P(o)) and W(max) during fatigue. During each stimulus train, activation was isometric for the initial 360 ms during which P(o) was measured; the muscle was then allowed to shorten at a constant velocity (30% V(max)) for the final 40 ms, and W(max) was determined. Compared with initial values, after 120 s of repetitive activation, P(o) and W(max) decreased by 75 and 73%, respectively. Maximum shortening velocity was measured in two ways: by extrapolation of the force-velocity relationship (V(max)) and using the slack test [maximum unloaded shortening velocity (V(o))]. After 120 s of repetitive activation, V(max) slowed by 44%, whereas V(o) slowed by 22%. Thus the decrease in W(max) with repetitive activation was dominated by force fatigue, with velocity fatigue playing a secondary role. On the basis of a greater slowing of V(max) vs. V(o), we also conclude that force and power fatigue cannot be attributed simply to the total inactivation of the most fatigable fiber types.

Original languageEnglish (US)
Pages (from-to)2215-2219
Number of pages5
JournalJournal of Applied Physiology
Volume89
Issue number6
StatePublished - 2000
Externally publishedYes

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Diaphragm
Fatigue
Muscles

Keywords

  • Fatigability
  • Isometric
  • Isovelocity
  • Slack test

ASJC Scopus subject areas

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

Cite this

Ameredes, B., Zhan, W. Z., Prakash, Y. S., Vandenboom, R., & Sieck, G. C. (2000). Power fatigue of the rat diaphragm muscle. Journal of Applied Physiology, 89(6), 2215-2219.

Power fatigue of the rat diaphragm muscle. / Ameredes, Bill; Zhan, Wen Zhi; Prakash, Y. S.; Vandenboom, Rene; Sieck, Gary C.

In: Journal of Applied Physiology, Vol. 89, No. 6, 2000, p. 2215-2219.

Research output: Contribution to journalArticle

Ameredes, B, Zhan, WZ, Prakash, YS, Vandenboom, R & Sieck, GC 2000, 'Power fatigue of the rat diaphragm muscle', Journal of Applied Physiology, vol. 89, no. 6, pp. 2215-2219.
Ameredes B, Zhan WZ, Prakash YS, Vandenboom R, Sieck GC. Power fatigue of the rat diaphragm muscle. Journal of Applied Physiology. 2000;89(6):2215-2219.
Ameredes, Bill ; Zhan, Wen Zhi ; Prakash, Y. S. ; Vandenboom, Rene ; Sieck, Gary C. / Power fatigue of the rat diaphragm muscle. In: Journal of Applied Physiology. 2000 ; Vol. 89, No. 6. pp. 2215-2219.
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