muscles

[Orit Yarden]

Several days ago I posted a question about muscle shortening length when
fully activated and under no resistance. Thanks to all of you who took
the time out to reply.
What follows is a summary of all replies.

Orit Yarden

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>From gatesysm@ac.wfunet.wfu.edu Wed Jun 22 09:34:03 1994
Date: Wed, 15 Jun 1994 11:07:04 -0400 (EDT)
From: "Stephen M. Gatesy"
To: Orit YARDEN
Subject: Re: muscles


Are you interested in the final (shortest) muscle length or the
pattern of shortening over time?

At the fiber level you could probably get a good estimate using sarcomere
force-length data, but for whole muscle I would imagine that shortening
stops prior to the point at which sarcomere force reaches zero.

Fiber architecture will play a more significant role when fiber angles
are large and series connective tissue components are substantial.

I'll be interested in hearing the responses you get.

Best,

steve gatesy
wake forest univ.
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>From Rick_Lieber@som-lrc.ucsd.edu Wed Jun 22 09:34:36 1994
Date: Thu, 16 Jun 1994 08:56:00 -0700
From: Rick_Lieber@som-lrc.ucsd.edu
To: yarden@eng.tau.ac.il
Subject: Re: muscles

Dear Dr. Yarden,
The method for calculating muscle shortening would be to determine the
muscle length corresponding to a sarcomere length change down to 1.6 microns,
the length of the thick filament. In order to do this, calculate the fiber
length (using the muscle length and fiber length/muscle length ratio), correct
for pennation angle (if any) and make an estimate of resting sarcomere length
at resting muscle length. Finally, include any species difference in the
length of the actin filament (2.0 microns for frogs, 2.6 microns for humans).
Good Luck!
Rick Lieber
UCSD
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>From pklein@resu1.ulb.ac.be Wed Jun 22 09:34:59 1994
Date: Thu, 16 Jun 1994 21:42:40 +0200
From: Paul Klein
To: Orit YARDEN
Subject: Re: muscles

Dear Orit

Question:
When a human skeletal muscle is fully activated and allowed to contract
freely (without any resistance), how could one estimate the change in
length (shortening length) ?
Is it possible to estimate this value for a specific muscle by some
percent of the muscle length ?
Any comment would be appreciated.

Suggestion
If the instantaneous moment arm (MA) of the muscle is known for and together
with the joint angle (alpha) one gets a nice approximation of the muscle
length by: MA x alpha [alpha in radians].

Other possible parameters may be: - wrapping around other muscles together
with changes due to muscle cross section variations, - changes due to
visco-elasticity of the muscle itself, - ?.

For hamstings length changes see for instance:
P. Klein,Influence of the pelvis tilt angle on the contraction velocity of
the hamstrings during hip and knee extension. Posture and Gait: Control
mechanisms. M. Woollacott, F. Horak (editors). University of Oregon Books,
Eugene, vol.1: 396-399, 1992.

Best regards
Paul


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* Klein Paul Ph.D. *
* Institut for Physical Therapy and *
* Rehabilitation *
* Free University of Brussels *
* CP 168, Avenue P. Heger, 28 *
* 1050 Brussels, Belgium *
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* Phone 32-2-6502470 Fax: 32-2-6502473 *
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