I am going to preface this article by saying I am not anti-stretching. If you know me, have seen me at a H+P practice, or have seen me as a patient, you will know that there are times where I recommend stretching.
That being said, this whole idea of “stretching is good” – an idea we were taught in elementary school and has now self-perpetuated to the exercise groups we attend in adulthood – is definitely misleading. Stretching is good in some situations and stretching has no impact in other situations; I will deal with these scenarios in a future article. This article will deal with a third situation: how stretching has a detrimental impact on us.
How can stretching be bad you ask? Well, there are a few reasons, but I’ll focus on running: static stretching makes you slower.
How does acute stretching impact performance?
It is widely accepted that stretching decreases performance in power or strength oriented events (like jumping, shot put, power lifting, sprinting).
That being said, how many of you still stretch prior to participating in endurance events? If you do, and you want to be fast, the truth is you should stop. Take for instance this 2010 study looking at the impact of static stretching on endurance running.
In the study, collegiate runners were put through 2 separate 60 minute time trials; 1 with stretching before, and 1 without stretching. The 60 minutes were separated into two components:
–The first 30mins: the runner ran at a constant pace (65% of their VO2 max)
–The second 30mins: the runners were told to hammer and go as hard as they could
The study showed very clearly that the non-stretching trials out performed the stretching trials. Here are the results:
First 30 mins: the non stretchers burned significantly fewer calories than the stretchers (425 vs. 405 kcals)
Second 30 mins: during an all out effort, the runners went 3.4% further when they did not stretch
In other words, when the subjects stretched, they required MORE energy to go the same pace in the first 30 minutes, and they went 3.4% slower at a max effort in the second 30 minutes.
So how does this apply to you? Again, if your goal is to run fast, do not conduct static stretching before hand.
The mechanism
Aswith many things in the scientific community, researchers still are not 100% certain why acute static stretching decreases subsequent running performance. One idea is rooted in a neurological mechanism- this school of thought basically suggests that the stretch triggers a reflex that has an inhibitory impact on muscle contraction. Another school of thought lies in the musculature itself. Here, experts believe the elastic potential energy stored within a non-stretched muscle gives us free energy as the “spring” recoils and launches us forward. However, if we stretch that spring out, then the force available to launch us forward dissipates.
How does chronic stretching impact performance?
This question is a little more complicated. Acute stretching will have a detrimental impact on performance, but what about if we stretch the night before running on a regular basis? Researchers do know that a more flexible runner tends to be less economical than a stiff runner.
Knowing this, one would think that chronic stretching would make us less economical. However, there are studies, like this one, which show chronic stretching having a negligible impact on running economy despite increasing range of motion.
That being said, I think there are a few flaws with these types of studies. For instance, if the stretching is done by athletes who were already sufficiently flexible (to the point where they do not receive the noticeable benefits a stiff muscle), then stretching that muscle would not decrease their performance.
These are my thoughts on chronic stretching: You are likely to get away with more of this type of stretching than the acute stretching. However, we do know that stretching induces an increase in range of motion over time, and we also know that more flexible runners tend to be less economical. So, while you can get away with some chronic stretching, if you do it enough, it’s only a matter of time before it slows you down.
Applying this to your warm up
The good news is that all of this research casting doubt on the role of stretching is strictly looking at static stretching (i.e. sitting there and holding the stretch). The researchers have shown that dynamic stretching, like hip swings, does not have the same detrimental impact on performance.
It is also important to keep in mind that the best way to warm up, by far, is a light jog of about 15-30 minutes in duration depending on your fitness, the race distance, and a few other factors. This helps to dilate the blood vessels so more blood is directed to your running muscles. It also helps to mobilize sugars stored in your body so that they are ready to be converted into running energy. The best part: this is all done while completely preserving any running-boosting muscular stiffness.
When is stretching good?
I will definitely address this in a future article in more detail. The bottom line is that in order to stretch, you should have a specific reason to do so. There must be a specific area of inflexibility that is causing an issue. It may be causing an injury, or it may be that you are unable to complete some of your normal daily tasks because you simply can’t move enough. Whatever the reason is, you should put a plan together to stretch and regain sufficient range of motion without going overboard. If your goal is to be a faster runner, acute and long-term stretching for no particular reason will, without a doubt, prove to be counterproductive and slow you down.
Dr. Sean Delanghe, BSc. (Hons), DC is a regular contributor to the RunWaterloo blog.
