January 27, 2011 
- Not yoga class
In a previous post I argued that flexibility is often massively overrated as a desirable physical quality for sports performance. Nowhere is this point more clear than in the case of running economy, as shown by a few recent studies.
Running economy basically means efficiency – a runner with better economy uses less energy to go the same speed and distance as a runner with poor economy. Running economy can vary between runners as much as 30%. Not surprisingly, studies have shown that running economy is an excellent predictor of successful performance, even among elite runners.
Many runners believe they can increase their running economy by becoming more flexible. At first glance, this theory appears plausible. As runners age, they typically lose efficiency and flexibility. Perhaps there is a connection there. Further, one might imagine that better flexibility would allow greater stride length or perhaps reduce muscular resistance to movement at the end ranges of motion. However, research on this issue does not support this theory. In fact, many studies have found that running economy actually correlates with less flexibility, not more.
In one representative study on distance runners, researchers asked subjects to perform the sit and reach test, which is basically a hamstring stretch. The runners who reached further were found to have poorer running economy. Several other studies have reached similar conclusions, including a recent study measuring flexibility at the ankle.
Why would less flexible runners be more efficient? One reason is that elastic recoil of muscle and tendon is an important contributor to running power, accounting for as much as 25-40% of the necessary energy. Stiff calves and hamstrings may enhance the storage and return of elastic energy, just as a tightly inflated ball will bounce higher and longer than a deflated one.
Based on these facts, you might guess that stretching before running would be detrimental to efficiency. One recent study found exactly that. Researchers from the University of Florida had ten extremely fit runners either stretch for sixteen minutes or do nothing immediately prior to a one hour run. The runners who did not stretch on average covered more ground and burned less calories. It should be noted that several previous studies have reached different conclusions, finding that either acute or chronic stretching, including stretching that increases flexibility as measured by the sit and reach test, did not affect running economy one way or the other.
Based on this evidence, I think the best that could be said for stretching is that it might not make you slower. (This assumes you are not sprinting, in which case it will definitely make you slower.) By the way, another thing we can definitely say about stretching is that it won’t help prevent injuries.
For some ideas on how to be more efficient in your running or anything else, see here.
For an excellent way to avoid “pulling a hammy” without stretching, see here.
Better Movement 
What about stretching after running? Is that any good? I think everyone I know does it after a run…
Alfredo! Great to hear from you on the blog!
Why do you ask? Your running career is over! You’re a father now. Maybe you are asking so you can coach Emilio.
I think bottom line is that if it feels good do it. However, I wouldn’t expect it to help prevent injury. if there was any way that stretching could help prevent injury, it would have shown up in the many studies where they had people stretch and then measured injuries.
Everytime that I took my “stretching” seriously…I got slightly injured. Then I would stop my stretching activities.
My legs and hips are pretty tight (ankles too) from all the years of soccer and tennis…but with the exception of a too quick a transition to running barefoot (VFF) I NEVER pulled a muscle in my life. I’m 43.
stretching on an intuitive level, never really felt “right”.
Maybe for others it’s a different experience…perhaps whenever they DON’T stretch they pull something.
Good read this morning Todd, Thank you.
Marc
Marc,
Thanks for stopping by. We have a lot in common – soccer, tennis, hatred of stretching, 43 years old, and injuries caused by overeagerness to use the vibrams.
The important notion is functional flexibility – developing a range of motion appropriate to your sport.
Richard,
I agree. In my opinion most sports do not require much range of motion at all. The exceptions are diving, martial arts, dance, and gymnastics. It is interesting to note that in each case the flexibility is often used for aesthetic not functional purposes.
Mobility vs. Flexibility and injuries.
As we all know, flexibly at the joint doesn’t equate mobility. Just because you are flexible doesn’t mean you have good mobility. Mobility is active range of motion. Flexibility is more about putting the joint to rest, good for recovery.
Explaining possible reasons for injuries for static stretching, the nervous system. I would imagine that static stretching provides little in the way of actually lengthening soft tissue and more to do with decoupling, relaxing the nervous system. This isn’t idea for avoiding injury while doing any activity. Asleep at the wheel if you will.
Mobility exercises on the other hand wakes up the brain and mechano/sensory-receptors in soft tissues at joint level. This coupling or turning on the joints intelligence provides feedback and proper response to terrain and environment pressures so that the body/joint makes appropriate changes, avoiding injuries.
Last year running the NYC Marathon, I was unfortunately able to predict who would be getting injured and when in my large running group by who stretched before their run and for how long.
Not that you shouldn’t stretch, just don’t static stretch before loading your ligament and tendons.
Very interesting!
I would imagine that there is a U-shaped relation: Too much stiffness and too few stiffness both hinder efficient movement. (A ball without air doesnt bounce. But a ball made of stone doesnt bounce either…)
Thus young athletes probably dont need more flexibility and exessive stretching might actually decrease their efficiency. Meanwhile older athletes might have too stiff muscles and joints, so that the CNS feels threatened by movement and blocks mobility. But that’s just my guess.
I do some sort of stretching after running, but it’s a slow wave-like movement without strain (from the book “stretch to win”). This helps me to open up my muscles or joints. And it’s coordinated with my breath (out-breath = exploring my range of motion; in-breath = moving back an relaxing). So far this has helped me to restore mobility.
BG,
Good point – I would definitely imagine there is a U shaped relationship between running economy and flexibility. Great analogy with the rock. But as a practical mater I would also guess that most people who are healthy enough to run at all do not need more flexibility to do so. I agree with your statement about the old athletes having brain’s that are threatened by movement and therefore get stiff. I distinguish flexibility from stiffness. Flex means ROM while stiffness means a subjective sense that the ROM is not smooth or easily attained.
Good idea with the waves and breathing. I always prefer movement to static holds, especially when it is mindful.
I think not warming up properly is the real culprit behind many of the injuries often attributed to not stretching. We like to get straight to the main workout and our muscles will complain if they have to immediately go from a standstill into high-intensity movement. Especially in colder weather, I think proper warm-up is much more crucial than an extended stretching session.
Jon,
Exactly. Warming up is a proven way to reduce injury before athletic activity. https://toddhargrove.wordpress.com/2010/11/24/quite-a-stretch-guest-post-from-paul-ingraham/
Light static stretching afterwards could aid after-workout recovery, and I do dynamic stretches for a warmup. However, why would I want an increased range of motion? For running? Biking? Swimming? Not likely. Seems like a waste of energy.