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Effects of fatigue on the muscle reactions to changes in the external load
Bugaychenko L.A.
A.A.Bogomoletz Institute of Physiology, National Academy ofScience of Ukraine, Kiev
Abstract
Spreading of fatigue-related effects from active to inactive parts
in the cat gastrocnemius muscle was studied. Fatiguing
contractions of a part of gastrocnemius muscle were evoked
through stimulation of the cut ventral root (VR) S1 with rate
50 s-1 during 20 s followed by 10 s of rest, over 10–30 min
(CFS). To test activation of a non-active part of this muscle
the distributed stimulation of dissected VR L7 with rate of 10
s-1 per filament was applied. After achieving by the muscle a
steady-state level of isometric contraction, a quick transition
to isotonic condition was produced. Transient responses of
shortening and lengthening were analyzed in terms of the two-
component model including the fast inertialess and slow ape-
riodic components. Test duration was 12 s, time intervals
between tests consisted of 3 min. CFS reduced isometric force
of the tested part of muscle as well as the velocity of shortening
and lengthening. The muscle lengthening had been slowing
down with development of the fatigue effects; the final steady
value of the muscle length in transients was reduced, while
weight of the inertialess component increased. Slowing of
shortening was accompanied by reduction of the final length
amplitude and the time constants of aperiodic component were
increased. We suppose that diffusion of metabolites from ac-
tive to inactive muscle fibers was the major reason for
contractility deterioration.
This study was supported by the INTAS grant 01-2130.
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© National Academy of Sciences of Ukraine, Bogomoletz Institute of Physiology, 2014-2024.
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