[Studies on kinetic viscoelasticity of slow muscle fibers--2. Dynamic stiffness changes studied by quick release method and frequency response method].
OBJECTIVE
To evaluate the mechanical properties of slow fibers and fast fibers which make up the extraocular muscles in rabbits.


METHODS
I studied the contractile properties and viscoelastic properties of the superior rectus muscle(SR) and the retractor bulbi muscle (RB) of rabbits using the quick release method and the frequency response method.


RESULTS
In the quick release method, isometric tension transients were slower in the SR than in the RB. In the frequency response method, the muscle length is perturbed sinusoidally to measure kinetic viscoelasticity. In resting muscle, dynamic stiffness was not changed with increasing frequency. In contracted muscle, dynamic stiffness was increased with increasing frequency, and the rate of increase was greater in the SR than in the RB.


CONCLUSIONS
It was concluded that the viscoelasticity of the activated cross bridge is greater in slow fibers than in fast fibers.
Hiraki
Y
Y
Department of Ophthalmology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-01, Japan.
Kimura
H
H
Mizukawa
K
K
Tabuchi
A
A
D000818:Animals; D004548:Elasticity; D007537:Isometric Contraction / Q000502:physiology; D007700:Kinetics; D009119:Muscle Contraction / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology*; D009801:Oculomotor Muscles / Q000502:physiology*; D011817:Rabbits