View Full Version : muscle twitch peak time as a function of activation level

01-17-2007, 09:29 AM
In an experiment involving single-pulse TMS of the hand
area when the subject produced various finger forces in
isometric condition, I observed that the peak times of the finger
twitches were shorter for larger initial levels of force. The peak
times did not depend on the intensity of the TMS. Finally,
as expected, peak force depended on both factors.

My guess is that the shorter peak time observed with
an increased initial level of muscle contraction is
essential a mechanical effect due to the increased stiffness
of the muscle (stiffer springs must have a higher-cut off frequency
when viewed as low-pass filters since they transmit better
higher frequencies).

I have done a research in pubmed and I have not found
studies reporting the peak time of the muscle impulse
response for various levels of baseline activation and
impulse intensity. I also don't know if it is a well-known
property of Hill-like models of the muscles.

I would be grateful if somebody could point a reference
to me that shows (theoretically and/or experimentally)
that the peak time of a muscle twitch in isometric conditions
depends primarily on the initial activation level and less
(or not at all) on the impulse intensity.

Gabriel Baud-Bovy
UHSR University