Friday, 15 June 2012

Forget the pre-game stretch

Another example of something that sounds good, but isn’t. How many people in the world swear by their pre-game stretches? Or post-game stretches? Especially when there is so much evidence to the contrary.

A Cochrane review on the subject looked at four randomised trials and found virtually no difference in muscle soreness after exercise associated with pre-exercise stretches. Well they actually found that muscle soreness was reduced the day after, by about half a point on a 100 point scale, with a wide margin of error of about 10 points either way. Stretching after exercise did much better, with a whole 1 point difference in muscle soreness (again with a wide margin of error). Even if it were true, it is hardly worth the stretching in the first place.

Regarding injury prevention, a systematic review from 2004 showed that pre-game stretching was ineffective. This review found mixed evidence, and this review came up with nothing.

I haven’t analysed the individual studies for this topic, but I know that the outcomes are subjective and therefore open to bias, and that blinding in such studies is difficult. Therefore, I would expect these studies to have enough methodological weaknesses to allow investigator bias to show a positive result. The fact that they haven’t been able to do this in any consistent way means that it is very unlikely that stretching does anything of any benefit at all; it just sounds good.


  1. Thanks for another great article Dr Skeptic.

    Hmm I wonder whether there are any long term effects (on ligamentous/tendon or cartilage injury) of stretching either prior or post exercise? There does not seem to be any evidence on the topic, but I suppose it would be difficult to design studies to answer that question.

    1. Thanks AA, I am not sure how long the longest follow up is, but the idea of the stretch is to reduce injuries in the game immediately following the stretch. It would take another stretch (one of the imagination) to think that a pre-game stretch could influence injuries further in the future.

  2. I have particular issue with your generalisation of the findings in these studies, to the effectiveness of stretching per se.

    Firstly, let me qualify my statements by asserting that my clinical experience confirms that, in all probability for the average weekend warrior, a significant reduction in injury risk is not envisaged with a single session of unspecific stretching immediately prior to sport. Given that stretching’s so technique specific, with needs varying from individual to individual, sport to sport, I think its ineffectiveness if applied incorrectly or in a misunderstood way may be partially reflected in some of these studies.

    Your quote " is very unlikely that stretching does anything of any benefit at all; it just sounds good" is interesting. It functions well as a piece of journalistic rhetoric, the likes of which I see all too often. Science magazines and the media are quick to glorify some new treatment without critically examining it in a broader context. For example, it’s easy to apply a sweeping generalisation of the effectiveness of stretching by having a quick and uncritical look at these studies, without taking into account the appropriateness or accuracy or these generalisations.

    Your suggestion at this juncture was not “more trails need to be done to determine the proper role of stretching in sport”, but:
    - “forget the pre-game stretch”
    - “it is hardly worth the stretching in the first place”
    - “It is very unlikely that stretching does anything of any benefit at all; it just sounds good”

    I find this attitude surprising.

    As you well know, a brief look at the conclusion on an abstract is not tantamount to thorough knowledge on the subject, and an example of illogical bias in EBM.

    Let me break it down for you. The following factors need to be considered when analysing the studies results: What type of stretching was employed? Static, ballistic, PNF? What were the hold times? What were the specific stretches? How long were the overall programs? Were they individualised to the specific needs of the participants?

    Additionally, while not completely relevant to my overall argument, a closer look at the systematic review by Thacker et al (2004), demonstrates how easily we can be distracted, and have our attention diverted from the relevant information.

    Let’s take the results:
    "Stretching was not significantly associated with a reduction in total injuries (OR = 0.93, CI 0.78-1.11) and similar findings were seen in the subgroup analyses."

    One would not expect stretching to be associated with a reduction in total injuries, but a reduction in soft tissue injuries specifically. We should rationally conclude that injuries like, concussion, fracture, and trauma are unlikely to be effected by stretching before analysing the data, and remove these from our analysis. Reductions in injuries that are likely to be affected by stretching become diluted otherwise.

    (see next post)

  3. (from previous post)
    The systematic review by Fradkin (2006) was not an examination of the effectiveness of stretching at all, but of pre-game warm up (which may or may not include stretching). It appears that somehow a non-specific pre-game warm up has been conflated with stretching, and then used by you to establish your intellectual position on stretching more broadly.

    Granted, the findings of the studies are objective, and the studies well conducted. In Thacker’s (2004) review, it is found that 3 high quality studies demonstrated that warm up prior to performance significantly reduced injury risk, and 2 did not. This is how we fall into a trap in interpreting the results from a systematic review. Each study may have examined a completely different stretching regime, with different participants, and different sports. And while some may have involved high quality, biomechanically sound stretching, some may not, and some may not have included stretching at all.

    We then take a brief look at the conclusion of this review, which is of course inconclusive, and make the statement " is very unlikely that stretching does anything of any benefit at all”. How is it very unlikely? If anything, we know absolutely nothing more about the effectiveness of stretching than before the systematic review was published, because the methodology and results are so non-specific.

    These ideas then get bandied around medical circles, and used as justifications for advice against stretching in a broader injury prevention context.

    As a physiotherapist, I find it confounding that this is considered the gold standard of how we examine the effectiveness or merit of certain interventions.

    The Cochrane review, while interesting, does not provide enough information to make any general conclusions about stretching at all, other than “performing one single session of stretching before or after exercise does not produce clinically important reductions in delayed-onset muscle soreness in healthy adults.” That is a very narrow window of variables, and as a physiotherapist, this result is probably expected. One single stretching session, non-personalised, non-specific, before or after exercise could mean anything. 5 minutes of hamstring stretching (of unverified quality) after a squash game is a different beast than a daily committed, 40 minute personalised stretching program, as a generic example.

    I’m not arguing that the scientific literature is inconclusive, because that is clear. Nor am I arguing that we should take anecdotal reports of benefit, and scientific rationalisation as more important than statistical evidence. What I am highlighting is the problematic use of language when assessing these studies.
    You said:
    “Stretching after exercise did much better, with a whole 1 point difference in muscle soreness (again with a wide margin of error). Even if it were true, it is hardly worth the stretching in the first place.”

    It was hardly worth the stretching for the participants in that specific trail, yes!

    But what does this mean though more broadly? Does this mean that performing (for example) 1 hour of daily active, static PNF flexibility exercises have no effect on injury prevention in sport? This hasn’t been examined at all, in any of the studies. Nor have countless other variables.

    (see next post)

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  5. Statements like " is very unlikely that stretching does anything of any benefit at all” are not reflective of the verbal caveats required to precisely convey the specific and limited information presented in the studies, and leave interpretations of stretching’s effectiveness open to misunderstanding.

    The reality is that stretching is a very broad subject; there are many variations in technique, varying ways to administer it, and varying levels of skill in the practitioners administering/advising on it. It is a skill that, if done properly, requires from the patient time, effort and persistence to master, a fact which is completely overlooked by the generalistic nature of the published evidence.

    My personal empirical experience, and clinical experience as an allied health care practitioner has demonstrated the benefit that stretching can potentially have on injury management and prevention, through a variety of mechanisms. These mechanisms have a science base of course, and include increasing proprioceptive awareness, promoting soft tissue and connective tissue lengthening, reducing specific trigger point tenderness, reducing myofacial restriction etc.
    But perhaps there are things we don’t understand about stretching as well, such as the neurophysiological mechanisms in place, the psychological components of a pre-game routine that can increase athletic performance (independent of injury statistics). These haven’t been examined, yet the phrase " is very unlikely that stretching does anything of any benefit at all” persists.

    And this is where the subjective experience of countless people who practice some form of stretching, such as yoga for example, rubs very hard against medicos who cite one study “proving” that their experience is illusory. This situation I find is abrasive and unhelpful. It facilitates the creation of an “Us Vs Them” mentality, and reduces faith in medical practitioners and research in general. The dialogue needs to change to perhaps be more comprehensive and less intellectually egotistical and reductionist (no ad hominem intended!).

    1. Thanks Scott, you raise some very good points and use some arguments that I am very familiar with.

      Your point about the use of language is a good one. Most of us are guilty of using language to make our arguments more persuasive. Politicians are not the only ones guilty of that. I respect scientists that deliberately avoid "colouring" their arguments, by choosing objective words and minimising the adjectives. I have made a conscious effort in this direction more recently (even in the 18 months since writing this post). I accept that criticism.

      One of your points relates to generalising from specific articles or reviews, and not taking into account different methods of stretching. This is a common argument, particularly in a field where many differences in technique exists (unlike drug trials, for example). My counter argument for this is always the same: if a study is rejected because it did not use your particular technique, it should not be assumed that your technique works. You would need to demonstrate that with an appropriate study, and my position in the meantime will be that there is a lack of supporting evidence.

      The argument that there is a biologically plausible mechanism for a particular treatment does not change my opinion one way or the other, as there are biological plausible mechanisms for all of the ineffective treatments mentioned in this blog - they are just to easy to create.

      Your point regarding this that I do accept, is that further research is needed in order to establish any potential benefit. Until that happens, however, I consider it unlikely (based on probability) that any form of stretching is effective.

      I mean this with all personal respect, but I discount your personal experience and that of others. I deal with practitioners on a daily basis who are convinced that their particular technique / procedure / treatment modality works. They are no more or less convinced than the chiropractor or homeopath. And this gets to the point of my blog: there is a pervasive bias (in practice, in the literature, individually and in institutions and professional bodies) that overestimates the effectiveness of our interventions and underestimates the harms. This is the (more general) area that I am currently spending my time on and plan to expand my expand my section of evidence for bias accordingly.

      Thanks for taking the time to comment so thoughtfully.

  6. Hi Dr Skeptic,

    Thanks a lot for your reply, I’m grateful for you having shared your thoughts.

    I think you’ll probably find I agree with a lot of what you said. However, I need to expand on several of your comments to clarify my position.

    When writing my initial post, I should have supplied details of the specific evidence for my intervention. Regarding specific evidence on my form of stretching (yoga), please find below articles below on yoga:

    • One study of 90 people with chronic low-back pain found that participants who practiced Iyengar yoga had significantly less disability, pain, and depression after 6 months.

    Williams K, Abildso C, Steinberg L, et al. Evaluation of the effectiveness and efficacy of Iyengar yoga therapy on chronic low back pain. Spine. 2009;34(19):2066–2076.

    You can find this on Pubmed

    • In a 2011 study researchers compared yoga with conventional stretching exercises or a self-care book in 228 adults with chronic low-back pain. The results showed that both yoga and stretching were more effective than a self-care book for improving function and reducing symptoms due to chronic low-back pain.

    Sherman KJ, Cherkin DC, Wellman RD, et al. A randomized trial comparing yoga, stretching, and a self-care book for chronic low back pain. Archives of Internal Medicine. 2011;171(22):2019–2026.

    You can find this on Pubmed

    • Conclusions from another 2011 study of 313 adults with chronic or recurring low-back pain suggested that 12 weekly yoga classes resulted in better function than usual medical care.

    Tilbrook HE, Cox H, Hewitt CE, et al. Yoga for chronic low back pain: a randomized trial. Annals of Internal Medicine. 2011;155(9):569–578.

    You can find this on Annals

    • This 2012 literature review gives a further overview of the role of yoga in the treatment of back pain

    Groessl EJ (2012) Yoga for Chronic Low Back Pain: New Evidence in 2011. J Yoga Phys Therapy 2:e108. doi:10.4172/2157-7595.1000e108

    You can find this in the journal of Physical Therapy and Yoga:

    • In this study, a yoga-based regimen was more effective than wrist splinting or no treatment in relieving symptoms and objective signs of carpal tunnel syndrome.

    To review the ubiquitous literature of this type, I would consider visiting the online Journal of Physical Therapy and Yoga.

    The reason I emphasised the use of language (which was really the main point of my previous post) is that yoga is equated with stretching in such a pervasive way, that it gets sullied by association with the reductionist and poorly executed stretching techniques and the poor methodology employed in the studies you cited. Global or blanket statements like “I consider it unlikely (based on probability) that ANY form of stretching is effective” creates a barrier to our understanding of the nuances and/or complete differences in exercise techniques that incorporate some form of stretching.

    (see next post)

  7. (from previous post)

    For example, integral to yoga exercise is the practice of cultivating mindfulness in postures. The postures and stretches incorporated in yoga necessitate the adoption of a reflective state of mind, whereby sensations from the afferent nerves are subjectively processed and examined, and balanced with attention to voluntary muscle contractions and movements (from the efferent nerves) . This provides someone with a means of examining their body and increasing their moment to moment attention and awareness. This type of mindfulness is perfect for exportation into the treatment of chronic pain patients, by modulating nervous input, and reducing central sensitisation.

    Please find below some the research on yoga, mindfulness and chronic pain:

    Salmon, Paul; Lush, Elizabeth; Jablonski, Megan; Sephton, Sandra E. (February 2009). "Yoga and Mindfulness: Clinical Aspects of an Ancient Mind/Body". Cognitive and Behavioral Practice 16 (1): 59–72.

    Schütze, R., Rees, C., Preece, M. & Schütze, M (2010). Low mindfulness predicts pain catastrophizing in a fear-avoidance model of chronic pain. Pain, 148, 120-127.

    Ludwig, David S.; Kabat-Zinn, Jon (17). "Mindfulness in Medicine". The Journal of the American Medical Association 300 (11): 1350–1352. Retrieved 27 April 2011.

    Greeson J. M. Mindfulness research update 2008. Complementary Health Practice Review.2009;14:10–18.

    Additionally, much research has been done on the role of yoga in treating psychological disorders including depression, anxiety, PTSD, and improving general wellbeing. In this regard, its relevance for managing chronic pain is implicit, as it functions as a medium to propagate the biopsychosocial model of health, remove the burden of costs from expensive interventionist surgeries and procedures, unnecessary consultations and referrals, scans, injections, electronically implanted invasive nerve stimulators… do you see what I’m getting at?

    The research has been done, and it’s here:

    Brown RP, et al. "Sudarshan Kriya Yogic Breathing in the Treatment of Stress, Anxiety, and Depression: Part I — Neurophysiologic Model," Journal of Alternative and Complementary Medicine (Feb. 2005): Vol. 11, No. 1, pp. 189–201.

    Brown RP, et al. "Sudarshan Kriya Yogic Breathing in the Treatment of Stress, Anxiety, and Depression: Part II — Clinical Applications and Guidelines," Journal of Alternative and Complementary Medicine (Aug. 2005): Vol. 11, No. 4, pp. 711–17.

    Janakiramaiah N, et al. "Antidepressant Efficacy of Sudarshan Kriya Yoga (SKY) in Melancholia: A Randomized Comparison with Electroconvulsive Therapy (ECT) and Imipramine," Journal of Affective Disorders(Jan.–March 2000): Vol. 57, No. 1–3, pp. 255–59.

    Khalsa SB. "Yoga as a Therapeutic Intervention: A Bibliometric Analysis of Published Research Studies,"Indian Journal of Physiology and Pharmacology (July 2004): Vol. 48, No. 3, pp. 269–85.

    Kirkwood G, et al. "Yoga for Anxiety: A Systematic Review of the Research," British Journal of Sports Medicine (Dec. 2005): Vol. 39, No. 12, pp. 884–91.

    Pilkington K, et al. "Yoga for Depression: The Research Evidence," Journal of Affective Disorders (Dec. 2005): Vol. 89, No. 1–3, pp. 13–24.

    Saper RB, et al. "Prevalence and Patterns of Adult Yoga Use in the United States: Results of a National Survey," Alternative Therapies in Health and Medicine (March–April 2004): Vol. 10, No. 2, pp. 44–49.

    You’d probably want to have a look at a summary of the evidence from the Harvard webpage below.

    It outlines, far more comprehensively than I am able to in this post, the evidence in support of yoga.

    (see next post)

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  9. I’d like to make it very clear, that my intent in writing this is not at all to be some vigilante for yoga, or to push any agenda. What I hope to offer is some insight into how we can be guilty of erroneously conflating differing interventions, and then categorising them inappropriately under the same umbrella.

    I’m sure you’d agree that we need to be clear and unequivocal in how we communicate with our patients, to prevent unintentionally withholding potentially beneficial treatment for them. This could occur from errors in interpreting evidence, and selective/incomplete examination of literature. I mean this in a general sense, but I could see how it was specifically evident in your blog on stretching.

    To wrap up, I agree and completely accept that biological plausibility means very little (otherwise, as you point out, knee arthroscopies for OA, epidural cortisones for sciatica, and fusion surgery for back pain would actually have some good evidence for them). However, when you have biological plausibility, combined with good quality evidence, then you can be more certain your treatment is effective. Here is an article regarding yoga’s biological plausibility, which details the physiological mechanisms and the mindfulness aspects, for your perusal:

    McCall MC (2013) How Might Yoga Work? An Overview of Potential Underlying Mechanisms. J Yoga Phys Ther 3:130. doi:10.4172/2157-7595.1000130

    On re-reading my previous entry, it seems my personal anecdote probably shouldn’t have been included. It wasn’t intended to function as evidence, but rather to contextualise my position. However, I can see how any reference to anecdote may serve to only weaken a position, by allowing comparison to a CAM practitioners’ line of arguments, and subsequent smear.

    I could go on, as this is such a vast subject and deserving of more attention. I’m afraid I haven’t done it the justice it deserves here with such a terse reply. I hope, however, that this has at least demystified my previous post a little for you, and offered a different way of examining the evidence in support of yoga and “stretching” in the pain management and injury prevention field.

    I look forward to hearing your comments, and would be happy to elucidate any potential misunderstandings.

    1. Thanks, this helps a lot. It was not my intention to include yoga under the banner of "stretching". I have not reviewed the literature on yoga but will have a look at the summary you sent.

      On first glance, however, it appears that many of the studies show improvement post treatment, and better improvement than less "involved" or passive treatments. Te same can be said for placebo. In trials of placebo physiotherapy (very difficult to do) they have shown little difference. I guess my question would be: if it were possible to properly blind participants and perform placebo yoga (just assume for a minute that it is possible), would the effect of the active group be greater than the placebo group?
      For surgery, it has repeatedly failed that test, despite good evidence from observational studies that the procedure improved outcomes.

  10. I think that relegating or dismissing the importance of observational studies in examining this type of intervention is a big mistake. I concede, however, that higher quality yoga studies need to be done to confer scientific legitimacy on the discipline in the minds of doctors, and policymakers, and the general public.

    You asked, that if it were hypothetically possible to properly blind participants and perform “placebo yoga”, would the effect of the active group be greater than the placebo group? I think you’ll find that using an RCT to study the outcomes of a long-term Yoga practice is like putting a square peg into a round hole. The true effectiveness of Yoga will always be obscured when measured with a pharmaceutical yardstick.

    We therefore need to examine our scientific tools and use the tools that are the best fit for studying what we want to study. We need ways of embracing (or at least understanding and benefiting from) alternative approaches to framing the “real” world, with their own forms of explanation and their own criteria for evidence. It’s probably relevant at this point to highlight that in randomized, controlled trials, inconsistent and contradictory findings have been found in almost all topics studied anyway.

    But, let’s just assume for a minute studying yoga with a clinical trial was possible, and a well conducted study was completed. The problems are as follows:

    1. It is entirely probable that some systems or individuals which lack an interest in conducting research, or the infrastructure to carry it out, may have the techniques that are the most effective.

    2. What an RCT would fail to do is to investigate what happens additively and cumulatively with a committed Yoga practice, when synergistic outcomes begin to emerge (a healthier diet, a simpler lifestyle, more time outdoors, more kindness and compassion, more loving relationships, more bike-riding, a better path to right livelihood for e.g.) —even six months is a drop in the bucket for a Yoga practice.

    3. By privileging short-term studies and standardised protocols, we are forever studying beginners, and thus systematically underestimating the healing potential of Yoga in research, and systematically excluding an understanding of these synergistic and cumulative effects of the practice. In short, an RCT would short change the potential of our scientific inquiries.

    (see next post)

  11. 4. There is immense difficulty in objectively quantifying the enormous variety of individualised approaches. With hundreds of individual practices (postures and posture sequences, breathing techniques, etc.), and the variations on these techniques used with individual students and in different systems, there are simply more combinations of possible treatments than it will ever be possible to sort out experimentally.

    As a result of this incredible complexity, scientists have simplified the yoga by standardising treatments protocols. For e.g. everyone in the experimental group gets exactly the same 11 postures for their carpal tunnel syndrome (see the article on carpal tunnel that I attached previously).

    But here is where the whole concept of a standardised protocol bumps up against a core principle of therapeutic yoga. Most of the experienced therapists I have studied with insist there can be no standardised anything, for each student is unique. Different bodies and minds, with different abilities and weaknesses, require individualised approaches. The reality is, even something that might have worked with a student one day may not work with the same person the next. If the student has just strained her back or had a particularly stressful day at work, the entire program may need to be changed on the fly. The best of the yoga therapy that I have personally experienced appears to be an art as much as a science. Skilled teachers plan a course but often modify it based on the student's progress and on what they observe. In medical class, Indian yoga teacher B.K.S. Iyengar, legendary for his therapeutic prowess, would sometimes put a student in a pose, take one look, and immediately take the person out. Whatever his theory for choosing the posture, as soon as he saw the result, he knew it was not right. Perhaps the student's face had turned a little red or his breathing wasn't as free.
    Standardised protocols do not allow for this kind of improvisation.

    However, for the purpose of science, the researchers have been willing to standardise. While these standardised interventions have demonstrated some very good outcomes, the irony is, that if standardisation does lower the quality of therapeutics, we might end up amassing the most scientific support for methods that are not the best yoga has to offer. This is no trivial matter.

    Differences between what is studied and what people really do illustrate one way that science, for all its ability to illuminate, can also distort. Since studying the way yoga is used in the real world turns out to be too complex, compromises are made. You might say that what the scientists are doing is collecting meticulous information about an artificially stripped-down version of reality.

    (see next post)

  12. 5. Much of what yoga does can never be measured by science. Examining some of yoga’s aims, like transcending the suffering that marks human existence, equanimity and compassion are difficult if not impossible to quantify.

    As with any holistic endeavour, measuring the constituent parts is not the same thing as understanding the sum of those parts. Reductionist science may tell us that yoga decreases systolic blood pressure and cortisol secretion and increases lung capacity, serotonin levels, and baroreceptor sensitivity, but that doesn't begin to capture the sum total of what yoga is.

    So, if we are going to reconcile the science of yoga and the science of medicine, we may need to change the way we think. We may need a new paradigm. We have to acknowledge there are different ways of knowing.

    There may be wisdom in this method, refined over thousands of years by trial and error and deep introspection, that cannot be captured by current science.

    To be fair, however, I understand the need to look seriously at science's critique of yoga. I accept your criticism that the studies that I gave you showing patient improvement post treatment can be misleading. But, while these interventions may be difficult to experimentally quantify, such evidence cannot and should not be ignored.

    Unless the research is planned to separately evaluate the effects of Triangle Pose (in all its variations), left-nostril breathing (with every possible combination of breath ratios), adopting an attitude of nonviolence, and the thousands of other discrete elements that make up the practice of yoga, isolation is an unrealistic goal anyway. Since in the real world these practices are almost never done in isolation, any such studies wouldn't reflect what yoga practitioners actually do. This is part of a bigger problem with the reductionist paradigm of modern science that I alluded to earlier: It tends to ignore the additive effects of different practices that may help explain yoga's effectiveness. And while synergy may possibly be captured in observational studies, as you highlighted, this doesn’t fit the double blind RCT archetype for assuming effectiveness.

    Relying simply on RCT’s as a one-size-fits-all approach to examining evidence is not reflective of how scientists in other disciplines actually practice their science either.

    If we simply rely on reductionism, all that we’ll have left on the table are procedures that fit the reductionist paradigm. Politically, this could be used as a form of manipulation that only serves the few that use these interventions.

    So, to summarise:

    1. Double-blinding a Yoga experiment is not possible.
    2. Experiments are performed with standardised protocols, but Yoga in the real world is not practiced according to standardised protocols.
    3. Experiments are expensive—and the sponsors of experimental studies are often responsible for biasing and corrupting the results.
    4. Yoga studies tend to involve fixed protocols, whereas Yoga instructions are normally based on an interactive response to empirical observation.
    5. Yoga studies tend to involve exclusion criteria, whereas in normal Yoga instruction, every person is welcome to practice, and it is the job of the instructor to adapt the practice so that it is comfortable and safe for the individual.
    6. The evaluation of short-term changes is usually most effectively accomplished by studying beginners. Thus, the research tends systematically to underestimate the long-term potential of Yoga.

    My argument is simply that putting yoga into a short-term RCT has inherent limitations and can therefore give us only one side of the story. I think we need to balance the picture with observational designs (such as the studies I sent you). What I would suggest is that the importance and the legitimacy of the observational design in Yoga research needs greater appreciation, and these sorts of studies need to be put on a par with clinical trials in giving us the type of information we need.

    1. I disagree with your take on RCTs. I usually perform pragmatic RCTs, which are much closer to real life. I have no funding and seem to do them with no problem, including those with long term follow up. RCTs are not reductionist; science is, but we have have to base our knowledge on the rational, reliable and measurable.
      There would be no problem having an RCT with all the treatment you usually perform, being left free to adjust the treatment as you wish. We could compare it to a chiropractor or physio or whatever, also being left free to treat how they think it is best for each patient. The protocol would be for you to perform yoga to your usual standards and techniques.