Repeated force production and metabolites in two medial
gastrocnemius muscle compartments of the rat.
Ruiter, C. J. De, A. De Haan, and A. J. Sargeant.
Department of Muscle and Exercise Physiology, Faculty of Human
Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands
APStracts 2:0299A, 1995.
The most proximal and distal motor nerve branches in rat medial
gastrocnemius innervate discrete muscle compartments dominated by
fast twitch oxidative.and fast twitch glycolytic fibers respectively.
The functional consequences of the difference in oxidative capacity
between these compartments were investigated. Wistar rats were
anaesthetized with pentobarbitone (90 mg.kg-1; i.p.). Changes in
force of both compartments during 21 isometric contractions (train
duration 200 ms, stimulation frequency 120 Hz, 3 s between
contractions) were studied in situ, with and without blood flow.
Without blood flow, force and PCr declined to a greater extent in the
proximal than the distal compartment, when compared to the run with
intact flow. After the protocol without blood flow, when flow was
restored, the time constants for force recovery (which were closely
associated to the recovery of PCr) were (means +/- sd): 37+/- 7 s
(proximal) and 148+/- 20 s (distal). It was concluded that the
proximal compartment had a four times higher oxidative capacity and
therefore a superior ability for repeated force production.
Received 10 February 1995; accepted in final form 30 June 1995.
APS Manuscript Number A158-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.