This discussion on 'muscle testing' from another group may be of interest

Someone asked:

This elicited the following response:


Mel Siff:

***All of the tests involve plantarflexion of the ankle with a fully extended
knee, a movement that does not simply involve gastrocnemius action, but also
action of soleus, tibialis posterior, flexor hallucis longus, flexor
digitorum longus, plantaris (w), peroneus longus (w), and peroneus brevis
(w), where (w) refers to weak action of these muscles.

In other words, it appears to be impossible to directly measure strength or
torque produced by gastrocnemius alone, so at best we could use the above
tests to assess torque or strength produced by ankle plantarflexion.

This suggests another "Puzzle & Paradox (P&P)".

In fact, is it not generally more appropriate to measure the torque produced
by a given joint action, rather than the 'strength' of one of a group of
muscles which may be responsible for producing that joint action? When
various authorities presume to accurately and non-invasively assess strength
of individual muscles either manually or by machines, are they not measuring
the compound action of several muscles.

Therefore, is it not somewhat of a misnomer to refer to "muscle testing",
when the popular clinical tests really are tests of specific joint actions?

What are the implications for some very popular testing of muscles such as
the individual muscles of the rotator cuff? Can we justifiably carry out one
of those internal or external rotation flexed elbow tests of the shoulder and
state that we are isolating, for example, only scapularis (which
collaborates with teres minor) or infraspinatus (which collaborates with
teres major, pecs and latissimus)? What about the popular tests for isolated
testing of piriformis or transversus?

Can anyone think of any joint actions, especially of the major joints, that
rely on contraction of only one muscle? Could we justifiably state that one
example is biceps femoris which appears to be the only muscle involved with
lateral rotation of the flexed knee?

Does this mean that the concept of non-invasive "muscle testing" should
rather be replaced by the testing of specific joint actions in the sagittal,
longitudinal and transverse planes and/or in other planes oriented at other
angles to the standard reference planes?

Would certain superpositions of torques obtained with joints being tested in
several different standard and non-standard planes enable one to
mathematically derive a better picture of individual muscle contributions?
Has there been any work done along these lines to make the concept of
isolated non-invasive muscle testing more valid, especially in the clinical

Dr Mel C Siff
Denver, USA

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