UPDATE
Stretching vs. Non-Stretching

Dr. Phil Maffetone


For decades, I’ve discussed the dangers of stretching, and why it’s not the best way to warm up. Occasionally, I update this information as more studies show the reasons why stretching not only does not prevent injury, and won’t help endurance performance, but can cause harm. My books and articles outline the details of these issues, and this update, along with just a few references, is an addendum to my other materials.

Runners, cyclists, swimmers, and other athletes use various types of static stretching routines. In addition, sports medicine professionals and coaches often recommend stretching. For many years, those with opposing views—athletes, sports medicine professionals, and coaches—argued that stretching does not reduce the risk of injury or improve athletic performance, the primary reasons given for stretching, and that it can contribute to injury and reduce performance. Those opposed to the use of stretching have relied on two different perspectives in which to make their claims.

The first perspective is a clinical one. This includes physical findings whereby a muscle’s function is shown to diminish after it’s stretched. Other observations are made as well; take a group of athletes divided into stretchers and non-stretchers, and many more injuries will be found in the first group.

I first learned about the dangers of stretching in the mid 1970s, and by the early 1980’s, with more experience treating and training athletes, developed an even better clinical perspective. By that time I had many hundreds of athletes to compare. The results were that in those who were injured a significant number stretched regularly. But in other athletes who did not stretch, injury rates were significantly lower. While these were simply observations, those in sports medicine who recommended stretching often claimed they had the opposite perspective—stretching helped athletes.

Clinicians who evaluated muscle function in athletes observed one outstanding factor—stretching a muscle could make it longer (the reason it increases flexibility), and this resulted in a reduction in function from a loss of power. In other words, stretching caused abnormal inhibition—weakness. There was a consensus on this issue by many, although certainly not all, clinicians.

Despite these notions, the tradition of stretching became a difficult one to break for millions of athletes—performing it was as ritualistic as reading the new running shoe reviews.

Trying to rationalize against strong tradition was not easy. I often used a common example of the increased injury rate in stretchers versus non-stretchers regarding the hamstring muscles. It is both the most frequently injured muscle group and the most stretched. Studies now show that stretching does not make tight hamstrings less stiff.

The decade of the 80s saw a dramatic rise in the number of recreational runners, along with a whole new endurance sport of triathlon. Combined with more athletes on university and college campuses, researchers had what they needed: more subjects for research. Studies began appearing that showed stretching not only did not reduce injuries or improved performance, but it could actually cause injuries and reduce performance.

This was the start of the much-needed second perspective—published research. It continues today. For the most part, these carefully conducted human studies have shown that stretching decreases a muscle’s force production capacity—it causes weakness. This and other unhealthy side effects of stretching were demonstrated in various ways by measuring muscle function using electromyographic, dynamometer, mechanomyographic, and similar devices commonly used in human research.

One particular study, conducted by J. Cramer and colleagues from the Department of Kinesiology at the University of Texas, compared changes in muscles that were stretched and not stretched in the same person. It concluded that, stretching one muscle can also impair another muscle that was not stretched, possibly through a central nervous system inhibitory mechanism. In other words, by weakening a muscle through stretching, the brain and spinal cord may trigger other muscles that are not stretched to become weak as well. This may occur, for example, even in muscles in the left leg when those in the right leg are stretched.

Other studies demonstrated adverse effects on lower limb power, sprinting ability, vertical jump, and aerobic endurance training. Despite these studies, the tradition of stretching continues in power sports, track and field, basketball, and endurance sports.

While the studies show that these abnormal changes induced in a stretched muscle can last for an hour, some clinicians have demonstrated that stretching can cause prolonged muscle problems that can last days and weeks.

As studies on stretching increased over the years, another type of evaluation—one that assesses a large group of studies and the subjects used for them—were performed. Ian Shrier, M.D., a past president of the Canadian Society of Sports Medicine, published such a study in the Clinical Journal of Sports Medicine in 1999 titled "Stretching Before Exercise Does Not Reduce the Risk of Local Muscle Injury.” Among his conclusions were that stretching can produce damage in muscles, and that stretching can mask muscle pain.

An important issue almost got lost in what sometimes became a heated debate. There were few, if any, published studies that consistently demonstrated that stretching reduced injuries or improved endurance performance—the two main reasons given for stretching.

Confusion arises when a study shows that ranges of motion or flexibility improve with stretching. This has been shown by some studies. However, increased range of motion at what cost? These studies don’t address this important question. One problem caused by stretching is that muscles become too loose—weaker—allowing the associated joint to move in a wider range of motion. This increased range of motion/flexibility puts more stress on the joint, which is no longer supported properly by the muscle, increasing the risk of injury.

Damaging a muscle through any means, including stretching, will obviously have an adverse affect on an athlete’s gait. The loss of smooth efficient movement puts stress on virtually all other structures—ligaments, tendons, joints and bones, in addition to many muscles. The body tries to compensate for this irregular movement, and in doing so uses up more energy, taking away from ones performance. A recent study by Jacob Wilson and colleagues from Florida State University showed how stretching can result in poor running economy, increasing energy consumption during an endurance event, and decreasing performance.

My recommendation has always been to include an active, aerobic warm up as part of each workout or race. This can be accomplished through slow running, biking, swimming or any aerobic activity that last at least 12-15 minutes. In addition to improving oxygen utilization, lung capacity, and fat burning, it increases flexibility in a safe way. Stretching cannot do the same.

More athletes, sports medicine professionals and coaches are quietly changing sides in the stretching vs. non-stretching debate. We welcome them.

NOTE: Reader responses and questions about this essay can be found in the Forum in the BIG BOOK OF ENDURANCE TRAINING AND RACING section.

Partial Bibliography

Bacurau RF et al. Acute effect of a ballistic and a static stretching exercise bout on flexibility and maximal strength 2009 J Strength Cond Res 23: 304-8.

Cramer JT et al. The acute effects of static stretching on peak torque, mean power output, electromyography, and mechanomyography. Eur J Appl Phsiol 2005;93(5-6): 530-9.

Kubo, K, Kanehisa, H, and Fukunaga, T. Is passive stiffness in human muscles related to the elasticity of tendon structures? Eur J Appl Physiol 2001;85: 226-32.

Nelson AG et al. Acute effects of passive muscle stretching on sprint performance. J Sports Sci 2005;23: 449-54.

Wilson, Jacob M et al. Effects of Static Stretching on Energy Cost and Running Endurance Performance. J Strength Cond Res 2010;24 (9): 2274-79.

Young, W and Elliott, S. Acute effects of static stretching, proprioceptive neuromuscular facilitation stretching, and maximum voluntary contractions on explosive force production and jumping performance. Res Q Exerc Sport 2001;72: 273-9.