As a member of the yoga community for many years, I have heard numerous claims about how stretching affects the body. These claims vary widely, and I’ve heard everything from “stretching is a magical cure that will heal all of your ailments” to “stretching is damaging for the body, and therefore yoga is bad for us.”
I try to be as evidence-based as possible in my approach to yoga, so I’m naturally skeptical of strong opinions about the body that appear to lack scientific support. In order to help clarify these issues for both myself and the greater yoga community, I decided to consult with an expert who is extremely up-to-date on the most current scientific research on stretching.
Dr. Greg Lehman, BKin, MSc, DC, MScPT, is a Clinical Educator, Physiotherapist, Chiropractor, and Strength and Conditioning Specialist. He travels the world teaching his Reconciling Biomechanics with Pain Science course to health & fitness professionals. He is also the creator of the “Recovery Strategies” pain workbook, which is an amazing, informative, and free resource for anyone in pain. Greg’s work has had a profound impact on the therapeutic, fitness, and yoga/movement worlds, and I am incredibly honored that he said yes to being a part of this Q&A!
YOGA & STRETCHING Q&A W/GREG LEHMAN
QUESTION 1: In the yoga world, there is a widespread claim that stretching can lengthen connective tissues like ligaments & tendons, causing them to become lax and leading to "joint instability". Is this a biologically plausible assertion?
ANSWER: There is no evidence that this actually happens. Pretty unbelievable, eh? There is certainly more evidence that suggests when you pull (apply tension) to connective tissue it responds by getting stiffer, stronger and sometimes thicker. Old research by Dr. Woo has shown this consistently. The only consistent thing that can make connective tissue less stiff is immobilization and injury. So, it is possible that people who gain massive amounts of flexibility may have at some point damaged their tissue.
If people feel “lax” because they stretch I would guess that it would be more of muscle or nervous system change. People may not have the strength in those ranges to control the motion rather than the idea that they lengthened connective tissue constraints.
QUESTION 2: What exactly does "stability" mean when it comes to our joints, and is there evidence to support that a lack of joint stability causes pain and/or dysfunction?
ANSWER: A stable joint system just means when it gets perturbed or jostled it comes back to its resting place. But, people have expanded the definition to mean that a joint just moves a lot when you don’t want it to move. Joint instability is a problem when a joint pops out of place and does not readily go back into place. It certainly does happen but I doubt it’s that common.
QUESTION 3: Can passively stretching a muscle compromise its strength (i.e. decrease its ability to produce force)?
ANSWER: Not significantly, meaning 1-5% of max force production [if stretching immediately before a strength activity]. And since we regularly don’t need to produce max force it’s not really an issue. And you only get this transient force reduction when you hold a static stretch for 45 or more seconds. Some research (Blazevich) even suggests that these max force/power losses are mitigated or completely ameliorated provided you do a warm up.
There is no reason to think that long term stretching will make you weak.
QUESTION 4: Aside from concerns about lengthening ligaments & tendons that we've already covered here, is it inherently injurious or damaging for the body to spend time in passive end range stretches? What about for someone with a connective tissue disorder such as generalized joint hypermobility (GJH) or Ehlers-Danlos Syndrome (EDS)?
ANSWER: I think with EDS it makes sense to limit those movements and get strong instead. That’s one of those conditions where shit really does pop out of place. But for other people, who cares if you hang out at end range. You are just applying tensile load to tissue (pretty much what strength training does but at other ROMs) and the tissue will adapt by getting stronger.
We aren’t made of taffy. We don’t really “stretch” that way with applied loading like end ROM stretching. I don’t think it’s injurious but you could certainly argue that there better options to achieve health and mobility – like adding strength training or even resistance throughout the range of motion.
QUESTION 5: There is a growing dialog in the yoga world about the distinction between active & passive stretching, with a new emphasis being placed on the benefits of training active strength & control through our ranges of motion ("active stretching") and a de-emphasis being placed on passive stretching. The reasoning goes that if we have more passive ROM available at a joint than active ROM, we are more susceptible to injury because we lack "control" in those end ranges. Would you agree with this line of thought?
ANSWER: I think you should do both. I wouldn’t be worried about injury though. I don’t think most people are getting injured because they have lost “control” of the joint. Further, if you get injured because the joint suddenly goes to end ROM, it’s not strength at end ROM that would have helped you - it’s the strength and control that you needed before you went to end ROM.
QUESTION 6: Many long-term yoga practitioners have discovered through imaging that they have a hip labral tear, and yoga is often blamed as the cause of this tear. Given that yoga is a low-load activity and that a majority of people in general will develop an asymptomatic labral tear as they age [Ref, Ref, Ref, Ref], is a long-term yoga practice a likely cause of a hip labral tear?
ANSWER: Labral tears are common. Heck, they might even be beneficial for performance. It’s not unreasonable to think that ANY activity can predispose you to joint changes. They happen and I doubt there is much we can do about it. You will see labral tears and bony changes in most sports.
So should we stop physical activity because of the chance of a labral tear? No. There are way too many benefits from a movement practice that far outweigh the negatives of a potential increase in the chance of having a labral tear.
QUESTION 7: In terms of stretching physiology, I believe that many people conflate the "muscle spindle stretch reflex" (reflexive muscular contraction during a stretch) with "stretch tolerance" (tolerating the discomfort of stretching) in their minds. Could you describe the difference between these two phenomena? Do they both play a role in stopping us at the end range of a stretch?
ANSWER: I’m not sure to be honest. Stretch tolerance definitely plays a role as the stretch is stopped (in the experimental studies) when the participant says its too much. What happens with long term stretching is that you are able to go farther without there being a dramatic change in tissue qualities. Meaning we assume that the changes in ROM are due to your tolerance or perhaps habituation rather than a structural change.
The muscle spindle stretch reflex is assumed to not be occurring during end ROM stretching because in these studies they monitor muscle activity. Meaning, they try to make sure there is no measurable muscle activity that occurs at end ROM. We assume its just a passive resistance to stretch. However, it is plausible that there is minor amount of activity that isn’t being picked up and this could be “putting on the brakes”.
QUESTION 8: Do you believe there are ways in which passive stretching could actually be beneficial for the body on a musculoskeletal level? If so, how?
ANSWER: Yes. I think long term stretching is just passive tensile force and tension has the ability to create positive structural adaptations in tissue. Some (Kubo) have argued that passive stretching can make tendon more efficient. Others suggest that passive stretching influences muscle stiffness which might be good to balance the stiffness changes in a tendon that can occur with injury.
I certainly don’t view stretching as a negative which I once did. I think if you argue against stretching you are really not “against” stretching but more pro some other intervention. So, if you like to stretch and its helpful for you I would encourage you to keep it up.