Muscle function during jumping in frogs (i): the influence of
temperature on sarcomere length change, emg activity pattern and
jumping performance.
Lutz, Gordon J., and Lawrence C. Rome.
Department of Biology, University of Pennsylvania, Philadelphia PA
19104, (215) 898-9915, (215) 898-8780 (fax)
APStracts 3:0059C, 1996.
We determined the influence of temperature on muscle function during
jumping to better understand how the frog muscular system is designed
to generate a high level of mechanical power. Maximal jumping
performance and the in vivo operating conditions of the
semimembranosus muscle (SM), a hip extensor, were measured and
related to the mechanical properties of the isolated SM in the
following paper. Reducing temperature from 25 to 15oC caused a 1.75
-fold decline in peak mechanical power generation and a proportional
decline in aerial jump distance. The hip and knee joint excursions
were nearly the same at both temperatures. Accordingly, sarcomeres
shortened over the same range (2.4 to 1.9 [mu]m) at both
temperatures, corresponding to myofilament overlap at least 90% of
maximal. At the low temperature, however, movements were made more
slowly. Angular velocities were 1.4-fold lower and ground contact
time was increased by 1.33-fold at 15oC. Average shortening velocity
of the SM was only 1.2-fold lower at 15oC than at 25oC. The low Q10
of velocity is in agreement with that predicted for muscles
shortening against an inertial load.
Received 21 September 1995; accepted in final form 7 February
1996.
APS Manuscript Number C570-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 24 February 96