delayed muscle activation / 'lag'

[Barneyrabbit]

Hi
I am a physio student and am a bit confused by the term 'lag' when used to describe muscle activation. I understand it is delayed activation of a muscle but despite searching cyberspace seem unable to find a comprehensive explanation of what exactly it is, what causes it and how to test for it. I would be really grateful if someone could explain the term to me.
Thank you in advance to anyone who replies. :-)

[jonathan_PTRP]

INTRINSIC FEEDBACK FACTORS
PRODUCING INERTIAL
COMPENSATION IN MUSCLE
LLOYD D. PARTRIDGE
From the Department of Physiology and Biophysics, University of Tennessee,

you can see that also in this page:
www.biophysj.org/cgi/reprint/7/6/853.pdf


Memphis, Tennessee 38103
ABSTRACT An attempt was made to determine the factors causing the load-inertia
compensation that has been observed in skeletal muscle. Cat skeletal muscle force
output was determined as a function of the two variables, length and stimulus pulse
rate. The results were represented in a system diagram from which it becomes ap-
parent that: (a) the length-tension relationship in muscle forms a functional, non-
neural servo feedback; (b) the force-velocity curve appears as an oscillation-damping,
velocity feedback in the muscle servo; (c) the nonlinear action of pulse rate on re-
sponse is, in effect, in the input element to the muscle servo system. For purpose of
analysis of the motor system it appears that these signal handling characteristics of
muscle make it more nearly a "position servo" than a "force motor."