QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by MALAMUD, J. G. Articles by JOSEPHSON, R. K. Search for Related Content PubMed Articles by MALAMUD, J. G. Articles by JOSEPHSON, R. K. Social Bookmarking                         What's this?

Journal of Experimental Biology 159,65-87 (1991)
Published by Company of Biologists 1991

Force–Velocity Relationships of a Locust Flight Muscle at Different Times During a Twitch Contraction

JEAN G. MALAMUD ¹ and ROBERT K. JOSEPHSON ¹

¹ Department of Developmental and Cell Biology, University of California, Irvine, CA 92717, USA

The force–velocity relationships during isotonic shortening were determined for the metathoracic second tergocoxal muscle of the locust Schistocerca americana (Drury). This muscle is a synchronous flight muscle. During the plateau of a tetanic contraction, the maximum shortening velocity (V_max) determined from the force–velocity curve was 5.2 muscle lengths s^-1 (25°C) and the curvature (a/P_o) was 0.62. The maximum isometric force (P₀) was 36.3 N cm^-2.

Early in a twitch (at times shorter than the isometric twitch rise time) the values for V_max and curvature were similar to those during the tetanic plateau, but the curves at different times during the twitch intercepted the force axis at values less than P₀. Later in the twitch, V_max declined.

A variable termed degree of activation (DA) is developed as a measure of the force-generating capacity of a muscle when this may be time-varying, as throughout most of a twitch. DA is determined from the shortening velocity at an intermediate load and is the predicted intercept of the force-velocity curve with the force axis relative to the tetanic intercept. In the locust muscle, DA rose to a maximum in 2–3 ms after the end of the latent period. DA reached 80° of the tetanic value during a single twitch; during the second twitch of a pair, the peak DA reached approximately the tetanic value. After a brief plateau, DA declined approximately exponentially. The time constant of DA decay was about 14 ms.

Note:

Present address: Department of Physiology, Emory University, Atlanta, GA30322, USA.

Key words: muscle mechanics, force–velocity, active state, locust, Schistocerca americana

Accepted on May 30, 1991

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				K. A. P. Edman and R. K. Josephson Determinants of force rise time during isometric contraction of frog muscle fibres J. Physiol., May 1, 2007; 580(3): 1007 - 1019. [Abstract] [Full Text] [PDF]

				C. Guschlbauer, H. Scharstein, and A. Buschges The extensor tibiae muscle of the stick insect: biomechanical properties of an insect walking leg muscle J. Exp. Biol., March 15, 2007; 210(6): 1092 - 1108. [Abstract] [Full Text] [PDF]

				S. Medler Comparative trends in shortening velocity and force production in skeletal muscles Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2002; 283(2): R368 - R378. [Abstract] [Full Text] [PDF]

				R. Josephson, J. Malamud, and D. Stokes Asynchronous muscle: a primer J. Exp. Biol., January 9, 2000; 203(18): 2713 - 2722. [Abstract] [PDF]

				R. Josephson Dissecting muscle power output J. Exp. Biol., January 12, 1999; 202(23): 3369 - 3375. [Abstract] [PDF]

				R. Josephson and D. Stokes Work-dependent deactivation of a crustacean muscle J. Exp. Biol., January 9, 1999; 202(18): 2551 - 2565. [Abstract] [PDF]

				R. Josephson and D. Stokes The force-velocity properties of a crustacean muscle during lengthening J. Exp. Biol., January 3, 1999; 202(5): 593 - 607. [Abstract] [PDF]