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The Science of Stretching: Stretching and Strength, Speed, and Muscle Growth

The Science of Stretching: Stretching and Strength, Speed, and Muscle Growth

Stretching improves flexibility, but does it prevent injury, increase strength, speed, and muscle growth, and accelerate recovery?


The common reasons for doing stretches that involve holding stretched positions for various lengths of time, or static stretches, before exercise are the beliefs that they help prevent injury, make you stronger and faster, reduce muscle soreness, and accelerate recovery.

While anecdotal evidence would seem to support these claims–everyone from peewee soccer players to professional athletes stretch before or after training–what does science have to say about it?

Stretching and Preventing Injury

Many people stretch before aerobic exercise and weightlifting because they believe it will ward off injury. Research says otherwise.

For instance, a paper published in 2004 by the Center for Disease Control reviewed 361 studies on stretching before all kinds of exercise, and concluded that it doesn’t reduce injury rates.

A study published by the SMBD-Jewish General Hospital did an analysis of their own and found the same: “stretching before exercise does not reduce the risk of injury.” A study published by McMaster University agrees.

In fact, according to Dr. Ian Shrier, a McGill University sports medicine specialist, it’s possible that stretching before exercise can increase your chances of injury due to the cellular damage it causes to muscle and its analgesic effect (it’s probably not a good idea to damage a muscle, increase your tolerance of pain, and then strenuously exercise it).

So where did this belief that stretching prevents injury come from, anyway?

Well, the faulty logic hinged on the assumption that improved flexibility (which stretching definitely accomplishes) reduces the risk of injury.

Research has shown that most muscle injuries occur within the normal range of motion, however, and specifically during the “eccentric” portions of movements (the portion of movement wherein the muscle lengthens, such as when you’re lowering  a dumbbell in a curl).

Therefore, improving flexibility doesn’t do anything in terms of preventing injury, unless the activity calls for actions that require great flexibility (such as doing the splits).

Another reason this issue got confused is the fact that stretching is often done as a part of a more comprehensive warm-up routine that raises body temperature and involves repeated movements within the expected range of motion, which does prevent injury, whether you add static stretching or not.

Scientists mistakenly attributed these benefits to stretching without the warm-up, and the myth was born.

Stretching and Strength and Muscle Growth

Many weightlifting routines begin with a series of stretches in the hopes of increased strength and muscle growth.

Is this just another myth?

Well, consider first a study conducted by the University of Milan.

Researchers had 17 young males do a series of jumps from various squat positions, with or without stretching beforehand. Jump height, power, and maximum velocity were all lower in the group that stretched for 10 minutes before the jumps.

Other research indicates that only static stretches of longer duration (over 60 seconds) negatively impact maximal muscle performance, whereas shorter static stretches (under 30 seconds) don’t improve performance, but don’t impair it either.

There are various theories for why stretching can reduce strength and power.

Some researchers believe that loose muscles and tendons can’t contract as forcefully as shorter ones, whereas others point to evidence that stretching interferes with signals from the brain that tell muscles to contract.

And what about stretching and muscle growth?

Well, you’re probably not surprised to learn that research has proven false the claim that stretching helps more deeply activate muscles and stimulate additional growth.

Stretching and Speed

Louisiana State University conducted a study in 2008 to determine how stretching affects the speed of sprinters.

They took 19 of their top sprinters and had them perform three 40-meter sprints in two sessions, separated by a week each. Before each session the runners performed a warm-up routine, and added four static stretches of the calf and thigh before one of the sprint sessions.

The result?

The stretching slowed them down by one-tenth of a second, with most of the loss occurring in the second half of the sprint.

Miami University conducted a similar study with 18 collegiate sprinters, and their research revealed that static stretching resulted in “a significant slowing in performance … in the second 20 (20-40) m of the [100 m] sprint trials.”

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Stretching and Muscle Soreness and Recovery

Next on the chopping block is the myth (sorry for spoiling the surprise) that stretching reduces muscle soreness resulting from exercise and accelerates recovery.

It used to be believed that muscles damaged by exercise would spasm, which then blocked blood flow and caused the pain we know as delayed-onset muscle soreness (DOMS).

As stretching helps alleviate spasm, it was hypothesized that it would alleviate post-workout muscle soreness.

While the spasm theory was debunked in 1986, the stretching advice has lingered to this day.

Well, evidence of its ineffectiveness in reducing DOMS is readily available.

For instance, the University of Sydney published a paper in 2008 involving the review of 10 studies on stretching and muscle soreness. It concluded that “muscle stretching does not reduce delayed-onset muscle soreness in young healthy adults.”

Another study, this time by the University of Western Australia, demonstrated that neither hot/cold therapy nor post-exercise stretching helped elite rowers recover from stair-climb running.

They published another study with football players demonstrating that post-game recovery is not enhanced by stretching, either.

Is Stretching Good For Anything, Then?

While static stretching doesn’t help prevent injury, increase strength, speed, or muscle growth, and doesn’t reduce soreness or accelerate recovery…it does have its uses.

If you’re going to engage in a sport or activity that requires a high amount of flexibility, then static stretching can help. It’s also best to do static stretches when your muscles are warm (like after exercise, for instance).

There is one form of stretching, however, that has actually been shown to improve strength, power, muscular endurance, anaerobic capacity, speed, and agility: dynamic or active stretching.

Unlike static stretching, active stretching involves movements that repeatedly put muscles through the expected ranges of motion, such as air squats, leg kicks, side lunges, arm circles, and so forth.

Active stretching accomplishes several things that improve performance: it increases the suppleness of and blood flow to the muscles, raises body temperature, and enhances free, coordinated movement.

It can and should be done before any type of exercise, and this is why I recommend several warm-up sets when weightlifting that progressively increase blood flow to the muscles that will be trained, before you load your working weight).


What are your thoughts on stretching? Love it? Hate it? Let me know in the comments below!

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  • Artid

    I agree! It has done nothing to me even when I was told by my coaches to stretch for injury or other cause.

    • Yup, static stretching is only good for increasing flexibility.

      • YF

        Mike, is static stretching post workout detrimental to muscle growth? Any data on this? Thanks.

  • Mo

    And that’s why the first thing I said to Mike in my first e-mail to him is how amazing the warm-up routine mentioned in BLS was for me 🙂

  • Quentin

    I do both stretching types. I personally find static stretching vital sometimes before, or usually after workouts. When I go running my left glute and my right calf can get really tight. Static stretching always solves it and gets them back to normal – if I don’t, then it doesn’t just go away. I’m absolutely convinced stretching has prevented me getting sprains in recent years. Before I knew about stretching I would get frequent(ish) sprains. I thought at first it was just ageing until I discovered static stretching!

    I may be an anomaly (one of those people that wrecks the nice graph that scientists hate!) but the research is incomplete in my view.

    • Michael Matthews

      Cool Quentin. Keep doing whatever works best for you! Stretching after lifting is always fine–there’s no reason not to do that. Stretching before isn’t a good idea for most people, but as you said, it may just be different for you!

  • Freddy Nomura

    Thank you for this article, I have definitely learned what stretching is good for which validates my years of “Active Stretching” in order to increase the suppleness of blood flow while enhancing free coordinated movement. Glad to know that taking the time to stretch through out my last 5 years was not lacking substance or worth.

    • Michael Matthews

      Thanks Freddy! I’m glad you liked the article and that’s great you’ve been doing it right. Keep it up. 🙂

  • thedavidshay

    My goal is to have as usable of a body as possible. I don’t stretch for any of the above needs, but it is nice to be able to touch your toes 🙂 It also hurts sooo good.

    • Michael Matthews

      Agreed! 🙂

  • Artid

    Training for two years, never stretched before set, never injured (BLS warm up) But i like the feeling of it immediately after the set.. looks like it sends away the burn…

    • Michael Matthews

      I like stretching after lifting sometimes as well.

  • Alan Cherney

    Though the benefits of stretching may be argued, the benefits of watching one’s wife do yoga can never be disputed.

    • Michael Matthews


    • Jean DeZonia

      SO 100% true.

  • João

    excellent article. took all my doubts. 🙂

    • Michael Matthews


  • Belinda Jane

    I was most interested in reading about stretching to prevent muscle soreness and both studies you’ve quoted are from Australia! The UWA study is in my own home town.
    I don’t think this is going to stop me from stretching after training (I do it more for flexibility or maintaining flexibility than anything else) but it’s certainly given me something to think about.

    • Michael Matthews

      Thanks Belinda! You should definitely continue stretching, just do it after your exercise that’s all. 🙂

  • William Lim Jr

    Hi Mike,

    Very informative article. The way you compile and synthesize different scientific studies is what we really need to know what’s out there and help us get started on this great journey to fitness.

    I just wanted to ask if you’ve ever looked into pre-workout foam-rolling, and if so, what you think about it? Many advocates say that it is a form of self-myofascial release, which supposedly helps improve performance and increase the benefits of exercise. I’ve also seen some detractors saying it doesn’t really do myofascial release as it claims to be.

    I have been foam rolling for more than a month using a foam roller made by Trigger Point Performance. So far I like doing it better than stretching. I’ve been seeing progress with my workout, but whether or not I can attribute any contribution from foam rolling, I can’t really tell.

    I’m just curious about your thoughts.

    More power to you!

    • Michael Matthews

      Thanks William! I’m really glad you liked the article.

      I’ve actually been playing around with foam rolling and really like it. It loosens up my lower back. I haven’t tried it pre-workout though. I don’t see any reason why you couldn’t however.

      Many people like a dynamic mobility type of warm-up including foam rolling, lacrosse ball work, dynamic stretches, etc.

      • William Lim Jr

        Indeed, I love how it loosens up the back in preparation for chin ups and other related exercises. I’ve always found static stretching for warm up as so tedious and futile but was afraid that not doing them would be bad. Thanks to your article, I am assured that my instincts were apparently right.

        • Michael Matthews

          Yeah, that makes sense. I could probably use some before deadlifting myself.

          Keep up the good work. 🙂

  • Pingback: 5 Foam Roller Exercises That Improve Performance | Muscle For Life()

  • Pingback: How to Improve Shoulder Flexibility and Mobility | Muscle For Life()

  • Jorge Valdivia

    Hello Mike I have a question. So I follow your book pretty well and when it comes to warming-up, I always feel the need to do a light run on a treadmill for about 5-6 min and then proceed to a little bit of stretching because it honestly makes my body feel good. Is doing all that really such a bad thing? I prefer warming up by running. Any recommendations?

    • Michael Matthews

      That’s okay. I recommend dynamic stretching though!

  • Pingback: How to Improve Shoulder Flexibility and Mobility | Muscle For Life()

  • Marcus

    Hi. Got a question: does stretching while under DOMS prevent muscle growth?

    • Michael Matthews

      No, it’s fine.

  • Pingback: 5 Foam Roller Exercises That Improve Performance | Muscle For Life()

  • Saslea

    Static Stretching correct. Other forms for all of the above? Absolutely, stretching is very important guys. Don’t be misinformed.

  • Benito

    Thanks for the clarification Mike, I had specific doubts about stretching and weight lifting. In martial arts I opt for static and dynamic stretching exercises, the first one to develop a general flexibility, the second one to emulate specific movements related to the kicks. However, in teaching little children I have noticed that even those kids capable of doing a complete split in static stretching, they struggle in the ballistic version in terms of flexibility, and vice versa.

    • Michael Matthews


      Yeah ideally a stretching routine combines modalities.

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  • Providence

    Thanks Mike for this article. I love your site because it’s full of information that is both science based and concise.

    I’ve read all of your reference studies and researches in this article and a few more about stretching and flexibility. One issue that I find in almost all of the available studies/researches is that the population they used already have at least “normal” ROM and enough strength – mostly athletes, students and others who have been training for a significant amount of time. I am still searching for a research which has a population of people with less than normal ROM and strength. I mean will never push my luck and recommend even light barbell squats to people who lack hip, ankle and wrist flexibility.

    • Thanks!

      There’s nothing wrong with stretching but you just want to save it for after your training.

  • Gustavo Tadeu

    I’ve be doing stretching before weightlifting exercises until now, thinking that is important for the muscle growth. After read this article, I won’t do it anymore! Thanks for all information about it!

  • Max Green

    Hey mike, do you recommend that we do a dynamic stretching routine like: butt kickers, side lundges, air squats, arm circles, etc and also do the normal warm up routine of 1 set 50 percent, 2nd set 50 percent, 3rd set 4 reps of 70 percent etc that is described in the bigger leaner stronger book before every weightlifting workout? So just to clarify do you recommend doing both routines before weightlifting?
    Thank you, Max
    I’m asking this cause I have been doing a dynamic warm routine and doing the normal warm up routine before every weight lifting workout for the last 6 weeks and I’m wondering if it is too much warm up.

    • You don’t have to, but you can if you want!

      Personally, I just start with the warm-up sets and go to the working sets from there.

      I only do certain mobility routines if I have a specific flexibility issue or other issues I need to address to perform the lift properly.

  • Thank you for sharing an informational post with us. I found this article is relevant to the people suffering from pain. They can heal their body pain by doing this.

  • Ransom

    I know this isn’t the thrust of the post, but did you come across anything regarding stretching (in conjunction with other things) for PT? I’ve been through PT a few times for a few things and their plan always includes a healthy does of static stretching and the program overall seems to work. It makes sense why having tight hips, for example, can pull on other things and mess them up, necessitating loosening/relaxing them.

    • Stretching in general is great. It’s just not great to do before heavy weightlifting.

  • Thank you for sharing an informational post with us. I found this article is relevant to the people suffering from pain. They can heal their body pain by doing this.

  • Nice blog. Thank you for informing people about physiotherapy.

  • Bob

    What about deadhangs then and planks are they pointless as I see them as stretches of sort and do em after exercises or just to loosen up a bit.
    Why does stretching feel kinda right then?

    • Lactic acid builds up and feels like your muscles are a little tight. As long as you’re not holding them long, it should be OK.

  • YF

    Thanks for this article, Mike. I see value in static stretching to improve range of motion on certain exercises, though I do them on rest days. I’ve been wondering though: might static stretching of the muscles (let’s say on a rest day after an intense training session) actually be detrimental to muscle growth? Perhaps they would prefer to be ‘left alone’ to allow recovery? Any scientific studies on this?

    • It depends on how you do the stretching. Really intense stretching sessions might not be the best idea, as you can cause further microtears and cellular damage, and delay recovery, but there are very few studies on that. Stretching does seem to increase blood flow, which could help recovery, but there isn’t much research on that, either.

      Overall, I doubt it makes much of a difference. If you like stretching, and you aren’t doing it right before your strength workouts, you should be fine.

      • YF

        Ok, thanks Mike!

  • Wesley L. Riojas

    Hi Mike! I am experiencing muscles siezing up in my lower back and back in general during my normal day when I twist or reach and such. I thought getting consistent in my compound lifts would help with this, but I’m not seeing improvement. I’m 39 and listen to my body pretty well, but finding a solution to this has me stumped so far. Any thoughts on these siezing muscles that feel “injured” yet seem okay the next day?

    • Hey Wesley! I’d recommend implementing some yoga and getting up/moving more during the day. If it doesn’t get any better, I’d see a doctor about it. I hope this helps!

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