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Synchronous oscillations of length and stiffness during loaded shortening of frog muscle fibres

Edman, Paul LU and Curtin, N A (2001) In Journal of Physiology 534(2). p.553-563
Abstract
A study was made of the damped oscillations in fibre length that are observed when isolated muscle fibres from the frog are released during the plateau of an isometric tetanus to shorten against a constant load (force clamp recording) near the isometric level (temperature, 1.0-11.0 C; initial sarcomere length, 2.25 m). 2. The oscillatory length changes of the whole fibre were associated with similar length changes of marked consecutive segments along the fibre. The segmental length changes were initially in synchrony with the whole-fibre movements but became gradually more disordered. At the same time the length oscillation of the whole fibre was progressively damped. 3. The fast length step that normally occurs at the outset of the... (More)
A study was made of the damped oscillations in fibre length that are observed when isolated muscle fibres from the frog are released during the plateau of an isometric tetanus to shorten against a constant load (force clamp recording) near the isometric level (temperature, 1.0-11.0 C; initial sarcomere length, 2.25 m). 2. The oscillatory length changes of the whole fibre were associated with similar length changes of marked consecutive segments along the fibre. The segmental length changes were initially in synchrony with the whole-fibre movements but became gradually more disordered. At the same time the length oscillation of the whole fibre was progressively damped. 3. The fast length step that normally occurs at the outset of the load-clamp manoeuvre was essential for initiating the oscillatory behaviour. Accordingly, no length oscillation occurred when the load clamp was arranged to start as soon as the selected tension level was reached during the rising phase of the tetanus. 4. The instantaneous stiffness was measured as the change in force that occurred in response to a high-frequency (2-4 kHz) length oscillation of the fibre. During the load-clamp manoeuvre, when the tension was kept constant, the stiffness underwent periodic changes that correlated well in time with the damped oscillatory changes in fibre length. However, there was a phase shift between the stiffness oscillation and the oscillation of shortening velocity, the latter being in the lead of the stiffness response by 21.4 0.8 ms (n = 19) at 1.8 0.1 C . 5. A mechanism is proposed to explain the oscillatory behaviour of the muscle fibre based on the idea that the quick length step at the outset of the load clamp leads to synchronous activity of the myosin cross-bridges along the length of the fibre. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physiology
volume
534
issue
2
pages
553 - 563
publisher
The Physiological Society
external identifiers
  • wos:000170110100020
  • scopus:0035878803
ISSN
1469-7793
DOI
10.1111/j.1469-7793.2001.t01-2-00553.x
language
English
LU publication?
yes
id
9430ec36-efdd-492d-b03a-bfada276c109 (old id 131809)
date added to LUP
2007-07-11 14:17:41
date last changed
2018-10-07 04:19:07
@article{9430ec36-efdd-492d-b03a-bfada276c109,
  abstract     = {A study was made of the damped oscillations in fibre length that are observed when isolated muscle fibres from the frog are released during the plateau of an isometric tetanus to shorten against a constant load (force clamp recording) near the isometric level (temperature, 1.0-11.0 C; initial sarcomere length, 2.25 m). 2. The oscillatory length changes of the whole fibre were associated with similar length changes of marked consecutive segments along the fibre. The segmental length changes were initially in synchrony with the whole-fibre movements but became gradually more disordered. At the same time the length oscillation of the whole fibre was progressively damped. 3. The fast length step that normally occurs at the outset of the load-clamp manoeuvre was essential for initiating the oscillatory behaviour. Accordingly, no length oscillation occurred when the load clamp was arranged to start as soon as the selected tension level was reached during the rising phase of the tetanus. 4. The instantaneous stiffness was measured as the change in force that occurred in response to a high-frequency (2-4 kHz) length oscillation of the fibre. During the load-clamp manoeuvre, when the tension was kept constant, the stiffness underwent periodic changes that correlated well in time with the damped oscillatory changes in fibre length. However, there was a phase shift between the stiffness oscillation and the oscillation of shortening velocity, the latter being in the lead of the stiffness response by 21.4 0.8 ms (n = 19) at 1.8 0.1 C . 5. A mechanism is proposed to explain the oscillatory behaviour of the muscle fibre based on the idea that the quick length step at the outset of the load clamp leads to synchronous activity of the myosin cross-bridges along the length of the fibre.},
  author       = {Edman, Paul and Curtin, N A},
  issn         = {1469-7793},
  language     = {eng},
  number       = {2},
  pages        = {553--563},
  publisher    = {The Physiological Society},
  series       = {Journal of Physiology},
  title        = {Synchronous oscillations of length and stiffness during loaded shortening of frog muscle fibres},
  url          = {http://dx.doi.org/10.1111/j.1469-7793.2001.t01-2-00553.x},
  volume       = {534},
  year         = {2001},
}