Dear all,

This is the summary of replies to our question concerning the resting force
or tension in muscles, especially wrist muscles.

Replies were sent by R. Wells (, J.B. Boren
(, R.L. Lieber (, Z. Hasan
(, R. Herbert (, K. Campbell
(, P.W. Johnson (, and A. Hollister
( Thanks to these persons, especially for their
expertise in this field. I learned a lot.

Here are the major contents of these replies:

JB Boren suggested that the parameter we were looking at was the "elastic
component" of the wrist muscles, which is a function of muscle size, in
normal conditions, but he does not have the coefficient.

According to R.L. Lieber, our question is complex and cannot currently be
answered. Resting tension as a function of length, and CSA are highly
variable in both magnitude and shape, so that generalization is difficult.
He suggested several papers (see above).

R. Herbert replied that, although oodles of data on the passive
length-tension curves of muscles exist, there is relatively little on whole
muscle-tendon units and even less relating this to the physiological rangeof
joint motion. He gave some references that suggest that some muscles may
fall slack within their physiological range, that show the resting
length-tension curves of whole muscle-tendon units with reference to
physiological ranges, or resting length-tension properties of muscle
fascicles and various architectural features (including PCSA) in five cat
hindlimb muscles.

K. Campbell replied that the passive stretch of non-crossbridge components
makes a significant contribution to the resting tension of skeletal muscle.
Possible sources of passive resting tension include the sarcoplasmic
reticulum, the sarcolemma and the filament lattice system itself, but their
precise contribution to resting tension in vivo remains unclear. Recent
results suggest that titin is not significantly stretched at normal lengths.
In vivo, actively generated tension increases the tension due to the passive
stretch of non-crossbridge components and is known as the Filamentary
Resting Tension (FRT), but this does of course not interfere in anatomical

A. Hollister replied that the first question to be answered is: what is
resting force? By what factors is that force determined? Moreover, this
resting load varies in different situations (anesthesia, denervation,
spasticity,...). Probably the resting tension of real muscles in real
settings is open to question. Anne sugested moreover that Richard Wells is a
good source of information.

These are the references included:

Keir, P., Wells, R., and Ranney, D. Passive Stiffness Of The Forearm
Musculature and Functional Implications, Clinical Biomechanics,
11(7):401-409, 1996.

Patel, T.J. and R.L. Lieber. (1997) Force transmission in skeletal muscle:
from actomyosin to external tendons. Exercise and Sport Science Reviews

Lieber, R.L., Gelberman, R.H. Kaufman, K.R, Whtney, J., and D. Amiel.(1996)
The relationship between passive or active motion and flexor tendon force in
the canine model. J. Hand Surg. 21A:957-962.

Schuind F, Garcia-Elias M, Cooney WP, and An K-N. (1992) Flexor tendon
forces. In vivo measurements. J. Hand Surg. 17A:291-198.

Hill, DK (1968) Tension due to interaction between the sliding filaments in
resting striated muscle. The effect of stimulation. J. Physiol. 199: 637-684.

Wei-JY; Simon-J; Randic-M; Burgess-PR (1986) Joint angle signaling by muscle
spindle receptors.Brain Research 370, 108-118;

Herbert-RD; Gandevia-SC (1995) Changes in pennation with joint angle and
muscle torque: in vivo measurements in human brachialis muscle. J Physiol
484, 523-532).

Herbert-RD; Balnave-RJ (1993) The effect of position of immobilisation on
resting length, resting stiffness, and weight of the soleus muscle of the
rabbit. J Orthop Res 11, 358-366.

Brown I.E., Liinamaa T.L., Lorb G.E. (1996) Relationships between range of
motion, Lo, and passive force in five strap-like muscles of the feline hind
limb. J Morph 230, 69-77.

Lakie, Walsh & Wright (1983). Resonance at the wrist demonstrated by the use
of a torque motor: an instrumental analysis of muscle tone in man. Journal
of Physiology, 353, 265-285

Tskhovrebova L., Trinick J., Sleep J.A., Simmons R.M. (1997) Elasticity and
unfolding of single molecules of the giant muscle protein titin. Nature,
387, 308-312

Ranney DA, Wells RP, Dowling J (1987) Lumbrical function: the interaction of
lumbrical contraction with the elasticity of finger muscles and its effect
on metacarpophalangeal equilibrium. Journal of Hand Surgery 12A: 566-575.

Thanks again to all those who took time to help us.


Veronique Feipel, Ph.D.
Laboratory for Functional Anatomy
ULB (CP 619)
808, route de Lennik
B-1070 Brussels, Belgium
Tel: ++ 32 2 555 63 29
Fax: ++ 32 2 555 63 78