Lots and lots of studies are coming out now, talking about how static stretching is actually NOT good for you. The super-short version is that it actually weakens muscles temporarily, not the net effect people are generally going for.

Here is a Q&A from Dr. Cobb from the November Z-Health newsletter:

Q: Traditional training methods have emphasized stretching prior to and after exercise, and many people stretch as a form of exercise itself. Most of this stretching involves holding a position for a particular length of time, and then deepening into it as the body will allow. Some say that this type of stretching is absolutely necessary, others say that it is not needed, and still others that it can be damaging. I would like your thoughts on stretching, about warming up in general, and how Z-Health relates or compares to them. Thank you.

A: Ahhhh… One of my favorite topics to discuss: stretching! Stretching has probably been the subject of more controversy and misinformation than any other aspect of health and fitness. Because this can be a very lengthy topic, I am going to confine my discussion to only one type of stretching protocol, called static stretching, as this is the method you referred to in your question.

As a method, static stretching involves placing a muscle or group of muscles into a lengthened position and then holding that stretched position for a period of time. In most cases this ranges from 15 seconds to several minutes, depending upon the method of choice.

The stated goal of static stretching is to passively lengthen the connective tissues that cover the muscle fibers and most people use stretching for two primary reasons:

Injury Prevention
Enhanced Performance

Unfortunately, the vast majority of research does not support using static stretching for EITHER of these reasons. Here are a few examples:

One of the largest studies yet conducted looked at 2,600 Australian soldiers — half stretched while the others did not prior to physical training. There was no difference in the injury rates.
Another recent study demonstrated that static stretching decreases eccentric muscular strength up to 9% for an hour or more after the stretching session. This is very bad news if you are using stretching as a part of your pre-exercise routine.
Multiple additional studies have shown that static stretching decreases maximal force output from the involved muscles. You are never going to be able to lift as much or punch/kick as hard if you pre-stretch the related muscles.
Other studies indicate that static stretching decreases coordination during explosive movements when tested immediately after the stretch. This means that your roundhouse kick will be much stronger if you don’t stretch first.
Finally, several interesting studies have shown that there is virtually no relationship between static and dynamic flexibility. In other words, increasing static flexibility does not automatically mean you will be more flexible in your sport.
As you can see, the evidence is strongly AGAINST using static stretching as a primary component of your training programs. With that said, however, understand that in Z-Health we never completely disregard any tool. We simply try to understand how to best utilize that tool. There are very specific occasions post-injury where we may use static stretching in combination with mobility work and other techniques.

If you have been a dedicated “stretcher” for years, consider changing your pre-training focus to more active mobility drills like those found in our R-Phase program or Neural Warm-Ups. These types of drills have shown a direct carryover to both injury prevention and performance enhancement, making mobility drills the warm-up of choice. Thanks again for the question. Have a great month.