Apologies for the delay. Two words: Finals week.
Now bend at the waist and touch your toes! If you can't touch your toes, you're not flexible enough! Heard that before? Turns out, it's probably not true, at least if your passion is distance running. Following is a discussion on the current scientific evidence relating to stretching and 3 myths about stretching that I for years thought were the gospel truth.
1. Stretching or high flexibility improves performance in distance runners
2. Stretching increases flexibility (i.e. makes muscles longer, loosens tendons, etc.), and increases range of motion.
3. Stretching prevents injury
Now before all the yogis in the world conspire to offer a sizeable reward for my head, let me state that I think that stretching can be beneficial in certain applications. In my experience, with proper application and technique, a little light stretching can be a very helpful part of injury rehab and will sometimes help little "niggles" feel better. If yoga, weightlifting, soccer, rock climbing, or gymnastics are your passion, it is conceivable that stretching may range from important to an absolute must in those activities. I am not any kind expert in those fields (nor am I REALLY an expert in any field, though I would like to think I am), so I will leave that discussion for others.
With that said, lets get on to Myth #1.
A cursory Google search of flexibility and distance running performance revealed a couple of articles and four independently conducted, peer reviewed studies dealing with the problem of flexibility and its effect on distance running performance. Out of those four studies, three found a significant inverse relationship between flexibility in relevant muscle groups (usually tested using the sit-and-reach measurement) and running economy. One of those three, conducted on collegiate distance runners, found that those who were the least flexible not only had the highest efficiency, but also had the best 10k performances. The fourth study, which was conducted on collegiate women only, found no correlation. By simple democratic process, it appears that, in general, the less flexible you are, the higher your running efficiency will be, and consequently the better your performance will be (especially if you happen to be male). Although none of the studies formally proposed a theory as to why this is the case, most surmised that the gains in efficiency and performance of being somewhat inflexible are likely due to the increased ability of the muscle to efficiently store and release mechanical energy in an elastic fashion--much like a spring or a rubber band. And, just like a spring or rubber band, if you stretch it beyond a certain point, it loses its ability to rebound as effectively, although the unstretched size and shape may remain the same. Increased "flexibility" does not improve performance. Indeed, it looks as if stretching probably inhibits performance in distance runners.
Myth #2
One of the main reasons that stretching was touted as essential before and after exercise was that it would "lengthen muscles," "loosen tendons," and "improve range of motion." Long, loose muscles have been viewed as a sign of good fitness for years. As it turns out, this Junior High P. E. assumption is false (don't worry, this one surprised me, too). In a
New York Times article on the subject, Dr. Malachy McHugh, research director at the Nicholas Institute of Sports Medicine and Athletic Trauma at Lenox Hill Hospital, NY, is quoted asserting that almost all flexibility is determined by genetics. We may make small increases in our natural flexibility, but this takes months of concerted daily effort. Now, someone will say that this is a bunch of nonsense, because "of course if you stretch consistently you will perform better on flexibility tests." On the contrary, the "improvements" we see are only due to the fact that by stretching we are simply training our brain to accept the pain of the stretch as normal. We are not actually increasing our muscle length or the ability of our muscles to stretch to a given point. Indeed, by hard static stretching, it is conceivable that we are bypassing the safety net provided by the pain reflex to greatly lessen the margin between what our brain allows us to do with a muscle and what will ultimately cause that muscle to reach its breaking point. Moreover, according to Dr. McHugh and others, the feeling of looseness, along with the tolerance we build to the stretch, are only short lived. Some of the effects, such as the feeling of "looseness" last only minutes, while others, such as the tolerance to the stretch, may last a few days or weeks, but are ultimately short lived. In other words, in order to effect an actual structural change in a muscle and supporting tissues, it takes weeks or months of stretching for hours to facilitate what little gain in actual flexibility can be had. To put it bluntly, a stretching routine does not actually increase flexibility, nor does it increase range of motion.
Myth #3
There is one remaining myth remaining in our trifecta of misconception. Does increased flexibility reduce injury? To address this question, I again turned to the more trustworthy source of published studies on the subject. Unfortunately, it appears that this area of research is much more clouded with many conflicting results. One review stated that "good flexibility reduces the risk for injury" but provided no evidence to support the statement. Another researcher concluded that the effectiveness of stretching in injury prevention depended upon the sport in question. Most other studies were inconclusive at best. Taking the available research as a body, it appears that there is little evidence to suggest a correlation between stretching or flexibility and injury avoidance in distance runners. According to the evidence presented, participants in high intensity sports that involve a large amount of jumping and bouncing, such as football, basketball, and soccer, tended to experience fewer injuries with increased flexibility. Conversely, participants in low-intensity, repetitive motion activities, such as distance running, cycling, and swimming, did not in general see a reduction in injury. However, for participants in all sports, the evidence suggests that warming up or "dynamic stretching" (i.e. lightly exerting the muscles through the natural range of motion prior to the intended activity--especially those muscles which will be used extensively) is effective at reducing injury. This type of activity does not, however, improve performance in flexibility tests. To sum it up, if we can draw any conclusion from the evidence, it is that increased flexibility has not been conclusively shown to reduce injury in distance runners.
This little study on stretching was really interesting to me. I've never been much into stretching. I never really felt it was that necessary to me, but I was surprised to find that there was a reason for that. What are your thoughts? Have you experienced a reduction or increase in injury after implementing or discontinuing a stretching routine? Have you observed any increases in performance either way? Personally, I have noticed a slight decrease in both rate and severity of injuries (mostly small "niggles") since I started running marathons, a period in which I also have abandoned stretching. I am a much better runner as well. But it is hard to positively attribute any of these improvements to my stretching habits, or lack thereof, since I believe it has much more to do with my increased training volume compared to my high school career (in which I did stretch). Anyway, interesting stuff. Let me know your thoughts.
Here are links to the studies I mentioned for your perusal:
http://www.ncbi.nlm.nih.gov/pubmed/19050648,
http://www.ncbi.nlm.nih.gov/pubmed/11774065,
http://www.ncbi.nlm.nih.gov/pubmed/16230980,
http://www.ncbi.nlm.nih.gov/pubmed/8784761
