The Evidence Against Stretching

Fat guy stretching weird

“…there is no research which proves categorically that there is any need for separate stretching sessions, phases or exercises to be conducted to improve performance or safety….There is no real need to prescribe separate stretching exercises or sessions, since logically structured training should take every joint progressively through its full range of static and dynamic movement” – Dr. Mel Siff

In the field of exercise science there has been a growing chorus questioning the efficacy and safety of stretching. Doubts began mounting in the late 90s in comprehensive scientific reviews. Yet, due in part to the existence of dozens of stretching protocols, a variety of hypothesized outcomes and persistent mysteries in soft-tissue physiology, the evidence against stretching is all over the place.  After reading the peer reviewed literature available today, I’ve distilled the best practices from the evidence based data. What I can confidently claim is that typical stretching does not improve performance (in fact it may diminish it), does not warm you up, does not prevent soreness nor prevent injuries. And no, it will not make you taller or prettier. Stretching may increase joint range of motion, although this may not be a good thing.

Systemic Research Conclusion:  Kay AD, Blazevich AJ looked at over 4500 studies to determine if stretching had any benefit stating, ““overwhelming evidence that stretch durations of 30-45 seconds …imparted no significant effect” and even some evidence of harm.

So why then do so many people stretch?  Perhaps they believe in the old paradigm and think it will prevent injury and help them perform better. One guy actually admitted to me that he’d like to be more flexible in order “to impress the girls in yoga class.” He couldn’t be helped. One given reason I cannot argue with, is that stretching feels good. In fact, at the end of many of my personal training sessions, I stretch my clients. I do this not because it will help them but because it makes them feel better. We learned in Psychology 101 that doing a pleasurable activity at the end of a difficult or strenuous activity changes the perception of the experience into something positive. This is known as the peak-end rule.  This little bit of social engineering goes a long way.

The fitness industry is fraught with many conflicting theories when it comes to stretching (among other things). I remember my high school track coach getting upset that I could not touch my toes during the Sit and Reach Test. How would I ever become a good runner or athlete if I wasn’t flexible?  I may not be a world class Kenyan runner, but from what I gather many of them can’t touch their toes either and most do not participate in any type of flexibility programs. Depending on your goals, and contrary to popular belief, it might not be a problem if you are ‘tight’.  Sometimes tightness actually helps people in sports. Having tight hamstrings can make you a more economical and better runner according to a Nebraska Wesleyan study.  Moreover, inflexibility isn’t always due to simple disuse or a lack of stretching.  There’s often a functional and genetic basis for tightness. In fact, not only may tightness help you run faster it might even help protect against injury.  Stiffness in soft tissues and joints helps store and release more kinetic energy, enabling an enhanced economical gait. So stop stretching before your run. The data has convinced me the costs of participating in a flexibility program outweigh the benefits.

There are many kinds of stretches.  All stretches fall under these two categories:

  1. Static – A stretch which is held in a challenging but comfortable position for a period of time, usually 10-60 seconds. Includes passive, static active and isometric stretches.
  2. Dynamic – A stretch which moves through a challenging but comfortable range of motion, usually repeated 10 to 12 times, held for no longer than 2 seconds and incorporating muscle contractions. Includes active, PNF and ballistic stretches. There may be some more compelling reasons to perform these stretches but the data is unclear.
Side Note:  Self-myofascial release, otherwise known as foam rolling, is also unlikely to increase performance or diminish soreness. The therapeutic significance of this protocol is couched in incomplete science. We do know it will not elongate fascia or any other soft-tissue and it does not rid the body of trigger points. The most popular foam rolling position is on the IT band. Most people don’t realize that direct pressure from the roller will not stretch or rid the IT band of so called ‘knots’. “The poor quality of research into the use of myofascial release for orthopedic conditions precludes any conclusions being drawn about its usefulness for this purpose.” – Mckenney et al.
 

A goal of stretching a tight muscle is to push it into a position it was not capable of achieving before. But why is the muscle tight to begin with?  Are you addressing the symptom and not the cause? All your muscles work in pairs and have opposing/antagonist muscles.  When one muscle is tight, many times it is because the opposite muscle may be overstretched or weak.  By addressing the antagonist muscle you may relieve the tightness without spending one-minute stretching.  Moreover, new research actually shows stretching does not increase the length of muscles. Magnusson et al. illustrated that long term static stretching would not change the stiffness or structural integrity within a muscle or joint. You may see a temporary change in joint range of motion but there will be no accompanying plastic soft tissue change.

The greater degrees of flexibility garnered with stretching are likely the result of boosted tolerance to the pain of stretching, not actual lengthening of tissue.  In other words, you get used to the pain and can go farther in the stretch.

“…researchers…found that when athletes did static stretches, performance often suffered. Many couldn’t jump as high, sprint as fast or swing a tennis racquet or golf club as powerfully as they could before they stretched. Static stretching appeared to cause the nervous system to react and tighten, not loosen, the stretched muscle, the research showed.” -NY Times

Note: There are a few notable therapeutic scenarios where stretching may come in handy: Planter fasciitis, frozen shoulder or after an injury or operation in order to regain range of motion. The bedridden, elderly or handicapped person who moves very little may benefit from a light flexibility program.

Another major concern of flexibility training is stretching past the point of what you can control. If you cannot control the range of motion there is little reason to go there.  Let me show you what I mean.  Take a look at the photo below.  Even though,  I’m not crazy about this ‘quad stretch’ it serves as a good example.  Please stand up and try it. Were you able to get your heel to your butt? Ok, now tighten your hamstring, remove your supporting hand and try to keep your heel up.  Did your foot drop?  This is called your flexibility/strength window: the distance between your passive flexibility and your active range of motion.

overstretch of quad

 

Why would you stretch past the point of where you can control?  Many times the discrepancy in these flexibility/strength windows are so big, it contributes to injury.  It is not uncommon to slip and be flexible enough to fall into a certain position but not strong enough to hold it, resulting in tearing of some soft tissue. Athletes shouldn’t stretch outside of their “working” range. Too much mobility can increase injury potential to ligaments, tendons and muscle. The next time you stretch try powering your limb/joint into the stretch position using only the strength of the opposing muscle. Hold it there for a prescribed amount of time and then attempt to bring it a little farther into the range of motion.  You may find it useful to have a friend or personal trainer act as a barrier to hold your position.  Do not allow the person “push” you into a range of motion you can’t control. I’ve seen people with dislocated joints as a result of this “pushing”.

If you are going to stretch here are some rules:

  1. Get an evaluation and find out what muscles and joints are tight and why.  You may not need to stretch.
  2. Flexibility is largely genetic and increasing your flexibility takes a long time. Re-evaluate why you are stretching and if your time might be better spent elsewhere.
  3. Only static stretch after your warm up, not before. Or don’t do it at all.  Instead of stretching do the activity you are warming up for, but slowly at first.
  4. It may be good to lightly stretch at night before bed if you like the way it feels. Many people report it helps them sleep.
  5. Do not perform static stretching prior to an event or activity. This will inhibit the muscles from contracting fully during your movements.
  6. Don’t over stretch!  At best, you will lose stability in your joints and at worst you will tear a tendon or ligament (which shouldn’t be stretched, to begin with) and forever have a looser joint, opening you up to future injuries.
  7. Don’t stretch loose joints, it will only make them more unstable.
  8. Be very careful when stretching your spine in the morning. While you sleep your disc height increases which stretches the surrounding soft tissue. It is easy to over stretch this tissue.

Instead of stretching simply start a daily movement practice with full range of motion. One of my favorite movement practices that open up the knee, hip, ankle, and spine is the third world squat. Work out with external resistance and focus on the the eccentric part of the lift. Under load lower the weight slowly and move to your end range of motion, making sure you do not pass the point of control or pain. These accentuated eccentric lifts will help keep your soft tissue and joints mobile.

A big bugaboo of mine is watching people stretch all their muscles, including the loose ones.  Think of your body like an out of tune guitar.  When you tune an instrument, would you stretch all the strings the same or just the out of tune ones?  Stretch all the joints and muscles the same and you’ll be a looser and more unstable version of your asymmetrical self.  If you insist on a flexibility program find out what is tight and why and then stretch only those muscles that need an improved range of motion.

The one uncontroversial truth about stretching is that it does increase flexibility…unless you commit to a long and dedicated effort, the result of which will give you brownie points in yoga class, a better shot at joining the circus or more elegant splits. There are some legitimate reasons for increasing flexibility but most come at the high cost of joint instability and potential future injury. I believe flexibility is over-hyped, especially since a lack of flexibility is rarely problematic.  Simply participating in a smart exercise program will actively move all your joints through their normal safe range of motion. This may be enough.  Ask yourself: is independent flexibility training worth the gym time even though most of its benefits are unproven?

Full Disclosure:

Before you discredit this article because you think I have a confirmation bias about stretching please know I used to be a huge advocate of flexibility training.  I even taught other trainers about its efficacy and how to properly integrate it into one’s routine. Many of them are still doing it today. The National Academy of Sports Medicine (NASM) awarded me their top stretching certification: Integrated Flexibility Specialist. Then one day the darn science caught up and got in the way. Since I’m not one of those guys who ignores science, I was forced to reevaluate my flexibility protocols. 

Other Sources
  1. Mel Siff, Facts and Fallacies of Fitness, Denver, M. Siff,  pp 121-122; 2002.
  2. Sit-and-reach flexibility and running economy of men and women collegiate distance runners. Trehearn TL, Buresh RJ. J Strength Cond Res. 2009 Jan;23(1):158-62.
  3. Running economy is negatively related to sit-and-reach test performance in international-standard distance runners. Jones AM. Int J Sports Med. 2002 Jan;23(1):40-3.
  4. The association between flexibility and running economy in sub-elite male distance runners. Craib MW, Mitchell VA, Fields KB, Cooper TR, Hopewell R, Morgan DW. Med Sci Sports Exerc. 1996 Jun;28(6):737-43. 
  5. NY Times: To Stretch or Not to Stretch
  6. Konrad A, Tilp M. Increased range of motion after static stretching is not due to changes in muscle and tendon structures. Clin Biomech (Bristol, Avon). 2014 May 9.
  7. Herbert et al. BMJ “Effects of stretching before and after exercising on muscle soreness and risk of injury: systematic review”. 2002.
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