Stretching our thinking about stretching.

like most of you I grew up with the notion that stretching prevents athletic injuries. In the summer of 1972 I went to a camp for student athletic trainers where we were taught many truisms of sports medicine, including the preeminence of stretching. The problem with truisms is that, although they are accepted as fact, they may not be and to challenge them is to risk being branded a heretic. These "facts" are so ingrained in our thinking that often they are never subjected to the same rigorous scientific evaluation that new ideas are.

The truism about stretching is that to prevent athletic injuries one must warm up, stretch, exercise, stretch, and then cool down. Look in most sports medicine books, whether written for the lay person or the health professional, and you will see something that says stretching prevents injury. Likewise, search the Web and the almost universal finding is that stretching prevents athletic injuries. This has appeared in Running & FitNews many times.

For me, the first challenge to the omnipotence of stretching came during a talk Bill Rodgers gave before the New York City Marathon almost 20 years ago. He talked about running with L.A. Olympic Marathon Gold Medalist Carlos Lopes. Rodgers said that he asked Lopes if he stretched before running, and Lopes said yes. Lopes bent over, didn't even touch his toes, and then started to run. I figured if someone could run at that level without stretching maybe my own pain while stretching was in vain. I still told my patients to stretch but the seeds of discontent were sown.

Over the past 20 years sports scientists have conducted research to see if regular stretching really does prevent injury. They most often take a team of runners and randomly assign some members to a group that does regular stretching and the others to a group that does not. Alternatively, they might take a whole team and have it stretch and have another team in the same league avoid stretching. In either case one looks at the injury rate for those who stretch compared to those who do not.

Some of these studies have found that stretching helps and some have found that it does not. This kind of confusion often makes the public throw up their arms and say, "Research is useless." To examine conflicting results among studies, researchers perform a systematic review. This is a rigorous process where someone systematically collects all the research on a topic, both pro and con, and uses a method to compare the studies that is analogous to comparing apples and oranges by calling them all fruit. When the body of research appears equally for or against a given protocol like stretching, the systematic review is the way to tease out of all the divergent data the trend that is hidden there. It should be noted that systematic reviews and meta-analyses are often done over and over to account for the publication of new studies that might shift the balance between support for or against some treatment.

There have been many systematic reviews of the effectiveness of stretching as a way to prevent athletic injuries. All have unequivocally found that stretching does not prevent injuries and might even cause them. There are many reasons why this might be so. Stretching is performed in a way that is very different from how the muscles are actually used, and therefore injured. The actual effect of stretching may be only short-lived. And having tight muscles might not be so bad. A runner with tight hamstrings has more than enough flexibility to move the leg normally during a stride, so the tightness may not be an impediment to running.

One study even found that distance runners with tighter hamstrings and calves are more efficient runners. During certain parts of the running stride, these muscles will absorb some of the energy of the body's movement, like a rubber band stretching. Then, some of this absorbed energy can be given back (as a rubber band snapping back) during another part of the stride. The more energy absorbed, the less wasted. Flexibility, then, may not translate to better running times. Most of the research cited below, however, makes no claims one way or the other about the role of stretching in improving running performance. The question at hand is, How effective is stretching at preventing injury?

One issue that sometimes clouds our judgement of stretching's effectiveness is that stretching is often an effective treatment for various sports injuries. The fact that stretching is a good treatment leads us to believe that it should be a good preventive measure. However logical this is, it does not appear to be true. Warming up is an undoubtedly vital component to injury-free running. Another may be regular strength training--if you want to prevent injuries, make the muscle stronger. But the take-home message on stretching to prevent injury is, If you like to stretch, do so. If you don't like it, don't do it. If stopping regular stretching results in problems, then stretch. If stopping does not result in any injuries, then save the time and don't stretch.

(Clin. J. Sports Med., 1999, Vol. 9, No. 4, pp. 221-227; Phys. & Sportsmed., 2000, Vol. 28, No. 8, pp. 57-63; Br. J. Sports Med., 2000, Vol. 34, No. 5, pp. 324-325; BMJ, 2002, Vol. 325, No. 7362, pp. 468; Evidence-based Sports Medicine, Chapter 7, "Does stretching help prevent injuries?" by lan Shrier, 2002, BMJ Books, Williston, VT, www.bmjpg.com/books/ebsm/ch7.pdf; Man. Ther., 2003, Vol. 8, No. 3, pp. 141-150; Med. Sci. Sports & Exerc., 1996, Vol. 28, No. 6, pp. 737-743)

by Stephen M. Perle, DC, CCSP 

Editorial board member Stephen M. Perle is an Associate Professor of Clinical Sciences at the University of Bridgeport College of Chiropractic.