Hi Anna
Part of the confusion in this whole area is an imprecision that us yoga teachers use in our vocabulary when we teach: we say “stretch” a lot, just as you did in your question. “ Are we stretching connective tissue?" A better term to adopt is “stress”. In our yoga asana practice we create stresses within the body: sometimes these stresses result in a stretch, but not always. While we do want to generate stresses, we do not necessarily always want to generate a stretch. Muscles can be stressed with 3 consequences: they elongate (called eccentric lengthening…they are trying to contract but they get longer); they shorten (called concentric contraction); or they stay the same length (called isometric contraction). In all 3 cases, the muscles are being stressed, but they are not always stretching.
A similar thing happens in our connective tissues: we stress them in yoga. That is good! (Although, of course, you can do too much stressing and that would be bad.) Every material has an initial state where with the first signs of stress, they have a little give and lengthen a tiny bit, but then any slack is quickly used up and they may not stretch at all, until the stress levels become much higher. If the stress remains below that critical threshold, but is maintained for time, something called creep can start to occur. (I have written about stress and creep
here.) If the stress exceeds this threshold, the material will become plastic and will stretch, but it may not return to its original length…but it might! It depends upon the material, the level of stress and the time the stress was held for.
So, you can see that saying “stretch” is not a great word: let’s say we create a
stress in a yang practice—which is true. Are we stressing connective tissues? Definitely, and this can be good. Tendons need stress!Whenever you stress a muscles, you can’t help but also stress the tendon. Do you intend to stretch the tendon. No. Nor do we intend to stretch other connective tissues. We do intend to stress them, however. In time, they may become longer as the body remodels the tissues to accommodate the ongoing stresses we create. That is a healthy adaptation response. But in any one yoga session, we are not trying to stretch the connective tissues…we are trying to stress them.
[Technical note: there are some connective tissues, like our ligament flavum in the spine, that are quite elastic. These will stretch with any stress, but they don't stretch as much as our muscles. So, we can't always say we never want our connective tissues to stretch under a stress...always is always wrong, and never is never right!]
I hope this helps! I do encourage you to read the article on creep: it talks to this question more deeply.
Cheers
Bernie
