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Yes, it’s true: stretching can make muscles bigger and stronger! Much like pumping iron, but without the pumping, or the iron.
You have to get savage about it, though.
Since its recent discovery, this fun fact about stretching has made the rounds in social media quite a bit. And that resulted in the inevitable dumbing down and exploitation by people with a stake (financial or ideological) in making stretching sound as awesome as possible in every way, no matter what the science actually says. And so this odd little bit of physiology is getting widely used as fresh new justification for stretching as a “pillar of fitness” — like people weren't enthusiastic enough about stretching already!
But this isn’t a pillar that will be holding anything up for actual people, and probably not even elite athletes. Maybe a few obsessive-compulsive masochists?
Let’s dig into the stretching-as-strengthening science a bit…
Warneke et al did indeed show that a large dosage of just stretching induced the same kinds of changes in muscle (hypertrophy) that we normally only expect to see from “lifting heavy things” (resistance training).1 Huh!
Those results certainly are physiologically fascinating. They suggest that muscle adapts in more or less the same way to almost any kind of strong stimulus — not just exhausting it with contraction. Stress a muscle, and it will grow.
Neat, if true. Perhaps not greatly surprising, but neat. (It’s also meta-fascinating that we didn’t already know this: another good reminder that training and rehab science is still quite young in the big picture.)
Could this Shutterstock fitness dude have earned his great bod with stretching alone? Only if he has a full-time job torturing himself with the strongest possible stretch!
How much stretching does it take to make a muscle bigger?
What Warneke et al. found may be neat, but it’s not very practical information, because the stretching protocol they used is just bonkers. For a single muscle, mind you…
- An hour per day?
- For six weeks?!
- At close to maximum stretch discomfort???!!!
Sheesh. Hard pass. Even half that intensity for half as long would still be an extremely impractical way to build any muscle. It would literally be a full-time job to do it for several of your biggest muscles.
Perhaps a more modest dosage of stretch would work? A similar study by Panidi et al showed the same effect with less outrageous durations, but it was still impractical: “only” 9-15 uncomfortable minutes per muscle, per day, for three months.2 We’re down to a part-time job now, but “ain’t nobody got time for that.”
How about even less stretching? That is unlikely to achieve hypertrophy: a 2020 review by Nunes et al concluded, based on review of several other studies, that lower-intensity stretch shows no clear sign of being able to get strengthening’s job done.3 It’s likely that it just requires an uncomfortable regimen.
This is not a reason to stretch
This has been an excerpt from my main stretching article, which all about how stretching is not actually a pillar of fitness, because it doesn’t actually do most of what people think it does, and what it does do (increase flexibility) isn’t as valuable to fitness as people think. What interested me about this topic was how stretching enthusiasts were using it to bolster the case for stretching as a critical part of any fit person’s repertoire. “All the usual mythical benefits and now strengthening too? Wow, stretching is amazing!”
This may be interesting physiology, but it’s a silly way to argue that stretching is healthy. Probably not one person in 10,000 has ever attempted that much stretching, let alone sustained it. And no one has ever taken up stretching because they thought it would build up their muscles, and it would be a fool’s errand if they did it now based on this news.
But now you know! Pull on a muscle hard enough and long enough, and your body will probably say, “Okay, fine, we’ll upgrade that a little.” Yahtzee.
As always, really the only reason to stretch is because it feels good, or as part of some other functional goal or activity that suits you well. For vastly more detail, see that big stretching article.
- Warneke K, Wirth K, Keiner M, et al. Comparison of the effects of long-lasting static stretching and hypertrophy training on maximal strength, muscle thickness and flexibility in the plantar flexors. Eur J Appl Physiol. 2023 Aug;123(8):1773–1787. PubMed 37029826 ❐ PainSci Bibliography 51621 ❐
- Panidi I, Bogdanis GC, Terzis G, et al. Muscle Architectural and Functional Adaptations Following 12-Weeks of Stretching in Adolescent Female Athletes. Front Physiol. 2021;12:701338. PubMed 34335307 ❐ PainSci Bibliography 51449 ❐
- Nunes JP, Schoenfeld BJ, Nakamura M, et al. Does stretch training induce muscle hypertrophy in humans? A review of the literature. Clin Physiol Funct Imaging. 2020 May;40(3):148–156. PubMed 31984621 ❐