Lc. Rome, SOME ADVANCES IN INTEGRATIVE MUSCLE PHYSIOLOGY, Comparative biochemistry and physiology. B. Comparative biochemistry, 120(1), 1998, pp. 51-72
Integrative muscle physiology has evolved from black box correlations
to an understanding of how muscular systems are designed at the molecu
lar level. This paper traces some of the obstacles facing integrative
muscle physiology and some of the intellectual and technological break
throughs which led to the field's development. The ability to determin
e (1) which fiber types are active, (2) over what sarcomere lengths an
d velocities they shorten during locomotion and (3) their respective f
orce-velocity relationships, enabled us to show that many muscular sys
tems are designed so that muscles operate at optimal myofilament overl
ap and at optimal V/V-max (where maximum power is generated). The abil
ity to impose the in vivo length change and stimulation pattern on iso
lated muscle has further showed that fish muscle has a relatively slow
relaxation rate, and thus rather than generating maximum power during
swimming, the muscle appears designed to generate power efficiently.
By contrast, during the single shot jump, frog muscle remains maximall
y activated during shortening and generates maximum power. Recently bi
ophysical techniques have shown that relaxation rate can be altered du
ring evolution by changing (1) Ca2+ transient duration; (2) Ca2+ -trop
onin kinetics, and (3) crossbridge kinetics. New technologies will soo
n enable us to better appreciate how different animal designs evolved.
(C) 1998 Published by Elsevier Science Inc. All rights reserved.