Article about yin yoga's "controversial" claims about targeting the fascia

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toaster
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Article about yin yoga's "controversial" claims about targeting the fascia

Post by toaster »

I follow Jenni Rawlings and admire her efforts to back yoga with science. However, I thought her analysis of yin here was fairly incomplete:
https://jennirawlingsblog.com/blog/3-co ... physiology

I tried to respond as best I could; I would be interested to see Bernie's response (here or on Jenni's blog).
Visit me on Facebook! YogiBethC ~ YogiPhD
Bernie
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Re: Article about yin yoga's "controversial" claims about targeting the fascia

Post by Bernie »

Thanks for letting me know about this post. I have read Andrew and Matthew's book Physiology of Yoga and found it very good, like Jenny did. And like you, I too respect Jenny and her work. However, this does not mean that I agree with everything in their book. I won't comment on the full article, but below I have excepted their first section and added my thoughts in red. I hope this gives you what you requested. Cheers! Bernie

Claim #1: Yin Yoga Targets the Fascia

It is commonly claimed that yin yoga works on the connective tissues of the body, particularly the fascia, the thin casing of connective tissue that surrounds and invests all muscles as well as every other organ, blood vessel, bone, and nerve fiber. Yin teachers might talk about stressing the tissues of the body and distinguish yin yoga from restorative yoga. While restorative yoga is about resting in comfortable positions, yin should have some degree of discomfort or challenge to elicit change in the tissues of the body (Clark, 2012).

But does yin yoga, wherein poses are often held for three to five minutes, really target the fascia?

Participants in a yin class are often asked to release all muscular tension and relax into the pull of gravity, whereas participants in a vinyasa class might be asked to co-contract antagonist muscles or core muscles. No matter what instruction is given, a stretch is a stretch—and a stretch is a tensile force on a muscle. When a tensile force is applied to a muscle, it is also applied to the surrounding fascia and invested muscle fibers and bundles. The muscle and fascia (or myofascial units) are so interwoven that you cannot choose which one you are stretching by contracting or not contracting certain other muscles.

Here I believe the authors are confusing semantics. It certainly is possible to “target” a part of the body, but this does not mean one is “isolating” the effect to that one area. I can target my biceps for building strength through doing curls with weights. But this does not mean I can isolate the exercise to only the biceps. Lots of other tissues will be affected too. Similarly, I can target the fascia surrounding my hamstrings and the hamstring tendons with Dangling. I am not claiming only the hamstring tissues will be affected, however. So, it is certainly possible to target the fascia! No one is claiming we can isolate the fascia and only affect it.

In vinyasa yoga, Standing Forward Fold is called Uttanasana. In yin yoga, it is called Dangling. Biomechanically and physiologically, there is little to no difference between the two as long as the duration of the stretch (or tensile force) is the same between the two poses. Additionally, engaging the antagonist muscle group (the quadriceps) has little to no effect on the hamstrings (Sharman et al., 2006). So, a standing forward fold, by any name, is a static stretch, and all stretching is a tensile force applied to a myofascial unit.

The two photos used to illustrate uttanasana and dangling are not the same: in one the student’s hands are on the floor and thus preventing all the weight of the upper body from being supported by the back tissue’s. But, the really difference between Dangling and Uttanasana would be more obvious if one student had their knees bent and the other with straight legs. With bent knees, the quadriceps have to work a lot more than if the knees were locked straight. In yin yoga, we prefer to reduce muscular effort, so the student may do this pose with legs straight. But, my main critique is where the authors qualify their conclusion by saying there is no difference between the yin yoga stress and the regular version of the pose if the duration of the stretch is the same. That is ignoring the fact that in yin yoga the duration is not the same as other yoga styles. It is much longer and that will make a difference, which they are ignoring.

It should be noted that as tensile force is applied to tissues, they creep. Creep is the biomechanical term for the deformation of viscoelastic tissues. Once the tensile force is removed, tissues then recover and return to their original length, as long as they have not been elongated beyond their elastic capacity.

One study (Ryan et al., 2010) looked at creep in the muscle–tendon unit of living humans during a 30-second stretch, finding that the greatest amount of creep was measured to occur within the first 15 to 20 seconds. Beyond that, to our knowledge, no studies exist on yoga poses and creep, which means we do not know the ideal duration for stretching tissues or how long tissues take to fully recover from their creep.

I have seen the statement that there is no further creep in our tissues beyond ~20 seconds in many place. However, when you look into the studies, they are comparing 20-second holds to 1-minute holds. They do not look at longer periods like 2-minute or 5-minute holds. In this case, the cited study by Ryan et al. only look at holds up to 30 seconds! And they state in their abstract that "position increased over the entire 30-s stretch". They did not say there was no more creep after 20 seconds or after 30 seconds.

Carla Stecco, in her book Functional Atlas of the Human Fascial System (page 85) says “…we can consider that a time range of 240 s [4 minutes] is sufficient to have an almost complete development of the viscous phenomena [creep].” Four minutes is pretty much the average amount of time a student stays in a yin yoga pose.

So, yes, yin yoga does affect the viscoelastic fascia of our bodies – but not in isolation from muscles – and not any more than the same stretch performed in a different way (i.e., a more active way). Yin yoga, or any stretch held for three to five minutes, will affect the fascia, but the ideal frequency and duration remain a mystery.

Here the authors admit that yin yoga will affect the fascia, even though they claimed earlier we cannot target the fascia. I would agree that we can’t isolate the fascia but we can certainly target it! No one claims it will be isolated. While the ideal hold time remains a mystery to them, to many students yin yoga definitely does a better job of affecting the fascia than shorter holds. Carla Stecco talks about time being important for full stress relaxation. Another study by Cao et al definitively finds a difference between different lengths of time that stress is held. See my article Time is the Magic Ingredient for this reference and other examples of why duration is not as mysterious as Andrew and Matthew think.

But again, I must say I did enjoy their book and would recommend it to everyone, with a few caveats about they way they talk about yin yoga ;-)
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Re: Article about yin yoga's "controversial" claims about targeting the fascia

Post by toaster »

Thank you Bernie! I'm glad to see that the comment I made on the article at least slightly encapsulated the points you made - but I always appreciate your wealth of knowledge and ability to convey it in understandable terms.
Visit me on Facebook! YogiBethC ~ YogiPhD
toaster
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Re: Article about yin yoga's "controversial" claims about targeting the fascia

Post by toaster »

Here is a summary of the article on Instagram:
https://www.instagram.com/p/CfIMzusDhyZ/
Visit me on Facebook! YogiBethC ~ YogiPhD
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Re: Article about yin yoga's "controversial" claims about targeting the fascia

Post by Joy&Yin »

Thanks @YogiBethC for asking Bernie's opinion on this and Bernie, thanks so much for your elaborate response! I, too, felt uncomfortable by what Jenni Rawlings put out there about Yin Yoga (even though I do like her work) and replied to her Insta post a couple of days ago because I just felt her post sent the wrong message about Yin and a wholly incomplete picture of its benefits.
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Re: Article about yin yoga's "controversial" claims about targeting the fascia

Post by toaster »

Joy&Yin (love the name!), that's exactly how I was feeling. I love Jenni's work in general, yet I also think she can be a bit too dogmatic in her tone at times.
Visit me on Facebook! YogiBethC ~ YogiPhD
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Re: Article about yin yoga's "controversial" claims about targeting the fascia

Post by Joy&Yin »

@YogiBethC Only saw your reply just now, sorry! And thanks so much :)
I agree, she sometimes makes me feel uncomfortable too in the way she deals with things.
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