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

First published online August 18, 2005
Journal of Experimental Biology 208, 3249-3261 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01770

This Article Figures Only Full Text 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 Similar articles in PubMed 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 Brainerd, E. L. Articles by Azizi, E. Search for Related Content PubMed PubMed Citation Articles by Brainerd, E. L. Articles by Azizi, E. Social Bookmarking                         What's this?

Muscle fiber angle, segment bulging and architectural gear ratio in segmented musculature

Elizabeth L. Brainerd^*, and Emanuel Azizi^*

Department of Biology and Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA

Author for correspondence (e-mail: brainerd{at}brown.edu)

Accepted 29 June 2005

The anatomical complexity of myomeres and myosepta has made it difficult to develop a comprehensive understanding of the relationship between muscle fiber architecture, connective tissue mechanics, and locomotor function of segmented axial musculature in fishes. The lateral hypaxial musculature (LHM) of salamanders is less anatomically complex and therefore a good system for exploring the basic mechanics of segmented musculature. Here, we derive a mathematical model of the LHM and test our model using sonomicrometry and electromyography during steady swimming in an aquatic salamander, Siren lacertina. The model predicts longitudinal segment strain well, with predicted and measured values differing by less than 5% strain over most of the range. Deviations between predicted and measured results are unbiased and probably result from the salamanders performing slight turns with associated body torsion in our unconstrained trackway swimming experiments. Model simulations of muscle fiber contraction and segment shortening indicate that longitudinal segment strain, for a given amount of muscle fiber strain, increases with increasing initial fiber angle. This increase in architectural gear ratio (AGR = longitudinal strain/fiber strain) is mediated by muscle fiber rotation; the higher the initial fiber angle, the more the fibers rotate during contraction and the higher the AGR. Muscle fiber rotation is additionally impacted by bulging in the dorsoventral (DV) and/or mediolateral (ML) dimensions during longitudinal segment shortening. In segments with obliquely oriented muscle fibers, DV bulging increases muscle fiber rotation, thereby increasing the AGR. Extending the model to include force and work indicates that force decreases with increasing initial muscle fiber angle and increasing DV bulging and that both longitudinal shortening and DV bulging must be included for accurate calculation of segment work.

Key words: biomechanics, muscle architecture, segmentation, myomere, myosepta, swimming, sonomicrometry, fish, salamander, Siren, Urodela

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

This article has been cited by other articles:

				M. McNamara, P. J. Orr, S. L. Kearns, L. Alcala, P. Anadon, and E. Penalver-Molla Organic preservation of fossil musculature with ultracellular detail Proc R Soc B, October 14, 2009; (2009) rspb.2009.1378v1. [Abstract] [Full Text] [PDF]

				S. M. Deban and N. Schilling Activity of trunk muscles during aquatic and terrestrial locomotion in Ambystoma maculatum J. Exp. Biol., September 15, 2009; 212(18): 2949 - 2959. [Abstract] [Full Text] [PDF]

				J. T. Thompson, J. A. Szczepanski, and J. Brody Mechanical specialization of the obliquely striated circular mantle muscle fibres of the long-finned squid Doryteuthis pealeii J. Exp. Biol., May 1, 2008; 211(9): 1463 - 1474. [Abstract] [Full Text] [PDF]

				J. L. van Leeuwen, T. van der Meulen, H. Schipper, and S. Kranenbarg A functional analysis of myotomal muscle-fibre reorientation in developing zebrafish Danio rerio J. Exp. Biol., April 15, 2008; 211(8): 1289 - 1304. [Abstract] [Full Text] [PDF]

				E. Azizi, E. L. Brainerd, and T. J. Roberts Variable gearing in pennate muscles PNAS, February 5, 2008; 105(5): 1745 - 1750. [Abstract] [Full Text] [PDF]

				A. M. Gabaldon, F. E. Nelson, and T. J. Roberts Relative shortening velocity in locomotor muscles: turkey ankle extensors operate at low V/Vmax Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2008; 294(1): R200 - R210. [Abstract] [Full Text] [PDF]