Shouldn't muscle and tendon length be measured and controlled for separately?

Question

Hi! I have yet to find an adequate answer to what seems like an obvious question and was hoping to get some clarification!

Why don't muscle length tests test separately for tendon length vs muscle length when both are stretched? By muscle length tests I mean those done in a doctor or PT's office to test for muscle stiffness or joint hypermobility, like bending forward to touch hands to the ground. It would seem to me these tests measure only the sum total of tendon+muscle from insertion(s) to origin(s) and may overlook shortened, perpetually contracted muscle compensating for overly-stretched tendon for instance and may incorrectly conclude "average muscle length" in such a case due to the two averaging out. Wouldn't a controlled test demand separate measurements from a stretched position of muscle from musculotendinous junction to musculotendinous junction, and tendon from osteotendinous junction to musculotendinous junction? Lumping them all together when assessing for length and hypermobility seems illogical and like very bad science to me. Am I missing something?

Answer 1

That is a great question!

PT's can differentiate between joint hypo/hypermobiliy and muscle tension by looking at a variety of factors including description of symptoms, provoking and alleviating factors, joint play to assess joints, and muscle length testing to assess the musculature. In PT school, we learned muscle length testing (MLT) in order to specify the specific joint positions that bring on the patients complaints, and can even alter those testing positions to target specific fibers of a muscle more than others (for example, clavicular head of pec major versus sternal head of pec major). Therapists can palpate the tendon and muscle whilst performing MLT in order to determine where the tightness/restriction is most likely coming from. Also, by palpating the tendon and musculature separately, the therapist is able to determine if one provokes the patients' symptoms compared to the other. This helps paint a good picture of which is most likely involved.

Answer 2

It depends, bending forward to touch the floor it is more of a functional activity. A true muscle length is the the bicep muscle length, which is done in spine with the shoulder off the table extended, elbow extended and forearm supinate. Also Thomas’s test is another muscle length test. It is helpful because by assessing that PT’s can know whether the muscle is tight which then leads to impairments to the patients