- I was recently at a weekend workshop with Sarah Powers where I asked her a question about the effects of Yin Yoga on fascial tissues and she suggested I contact you with my question. My question is how does Yin Yoga effect myofascial units that are locked long vs locked short in the body? I have been studying Tom Myer's Anatomy Trains and I'm curious to undertsand the effects a little more deeply. Thank you for your time and consideration in this question.
As you obviously know, the muscle is not just muscle but also fascia (about 30% fascia) and Yin Yoga deliberately targets the fascia. It is not true to say that Yin Yoga doesn't affect our muscles: it does, via the fascial envelopes and networks. Having said that, I know of no studies that have looked at the effects of Yin Yoga on myofascial tissues that are locked long or short: I don't believe any studies have been done. So, all I can do is speculate.
In the locked short situation, Thomas Myer says, "Since what we want to do in a locked-short muscle is break / melt the bonds between these angled fibers to allow the myofascial unit to lengthen, we run along the tissue in the same direction as the muscle fibers, presumably unwinding some of the muscle tension". Well, that is what we do in Yin Yoga as well: if we have a hamstring muscle locked short, we apply a long-held, static stress along the length of the muscle (perhaps via Half-Butterfly or Caterpillar). The stress in the muscle affects the myofascial bonds causing them to lengthen. How they lengthen is not quite understood: it may be due neurological desensitization, or due to the collagen changing orientation, or breaking crosslinks, or it may be due to water being pumped out of the myofascial over time, or maybe all of the above is happening. Over time the muscle should reform at a slightly longer length.
When a muscle is locked long, however, tugging along the axis of the muscle fibers don't seem to work so well: that would lengthen the already too long fibers. In this case Thom suggests, "In a locked long, eccentrically loaded muscle, the major bonding is across the short diameter of the rhombus, ergo at right angles to the muscle fibers, so we go across the myofascial unit." This is a more specialized case and to use Yin Yoga now requires some creativity: how can you apply a stress at right angles to the muscles' orientation? I don't know how this could be done in the legs, but I don't think we come across leg muscles locked long very often. In the upper body it may be possible to work in these other directions but it depends upon the muscles and where the "lockage" is.
If your question is more about how Yin Yoga affects the connective tissue, I have written about that in several places and would invite you to check out these resources:
- A Scientific Basis for Yin Yoga -- a forum thread (which includes some references to Thom)
A Scientific Basis for Yin Yoga -- an article
In Defence of Yin Yoga -- an article