What does stretching do for you?

Is there any reason to stretch? And is there such a thing as too much stretching? I’ve been thinking about these questions lately, after starting to lift weights again following a hiatus of 20-some years.

My motivation when I began weight lifting in my twenties was basically cosmetic; I wanted to get bigger, which I failed at doing completely. These days I’m more concerned with my health (and with having fun).

I saw how quickly my already thin father wasted away with illness before he died last year, and I was determined to have more reserves available when I reached his age. People lose muscle as they grow older, a condition called sarcopenia, and, unfortunately, muscle mass is a predictor of longevity. We don’t store protein as we store glycogen and fat; protein gets put to use. Thus, the only significant source that the protein-hungry immune system can call upon to resupply amino acids during severe illness is working muscle. Fortunately, sarcopenia can be slowed with activity, particularly with resistance training.

Also, as thin as I am, I’m more at risk of osteoporosis than other males. I’ve been practicing yoga for long enough that it no longer presents much of a physical challenge for me, or for my bones. There is a minimal essential stress necessary to stimulate bone growth. Of course, there are asanas that remain difficult for me, but overall I doubt that my yoga practice still stresses my bones as it did when I began. Heavy deadlifts certainly do.

And an unexpected benefit of weight lifting is that it’s turned out to be fun. It’s a challenge, especially Olympic lifting, which I’ve been learning lately. I get to feel like a beginner–clumsy, weak and uncoordinated–which I don’t get in my yoga practice, as much as I may try to approach it with a beginner’s mind. So when I actually manage to hoist a heavy barbell up, it’s a thrill.

However, the primary reason I started lifting was that I felt my body had become unbalanced from asana practice. I had become hypermobile, overflexible, at the expense of strength. This was an interesting shift for me. One of the reasons I started practicing yoga seriously in the first place was to restore flexibility that I had lost with weight training back in my twenties. The situation was now reversed. I needed to tighten up to return to balance.

And now, in another interesting shift, as my muscles feel tighter, stretching feels good again. I took a yoga class the other day focusing on deep, slow stretches for the gluteal muscles and hamstrings. Mine felt like they sorely (and I mean sorely) needed the attention after a session of heavy deadlifts the day before. I had forgotten that feeling of tight hamstrings. It felt good to stretch them out, and by the end of class uttanasana wasn’t quite so much the exercise in humility it had been at the beginning of class. The stretching felt like a necessary corrective, rather than over-pulling already loose muscles.

Which brings me to the question I began with. As good as it may feel, is it in fact beneficial to stretch? Is there evidence that it actually does anything for you?

Perhaps surprisingly, in recent years exercise physiologists studying this question have largely come to the conclusion that there isn’t much evidence that it does.

It’s long been assumed that stretching could help prevent injuries among athletes. While that might be true for some specific individuals with some specific injuries, there’s little evidence that it prevents injuries overall. Athletes who don’t stretch are no more (or less) likely to be injured than athletes who do. And, although the evidence is also equivocal, some studies suggest that being hypermobile can increase your risk of injury.

Likewise, in general, stretching doesn’t seem to enhance athletic performance. In fact, stretching immediately before an athletic event probably actually decreases performance.

However, a recent study in the Journal of Strength and Conditioning Research suggests another reason stretching may be beneficial: it may help you relax.

The researchers gave 10 young men with low flexibility a short routine of three stretches, held for 30 seconds and repeated three times. The subjects’ heart rate variability was measured for 30 minutes before stretching, while stretching, and for 30 minutes afterwards.

In simple terms, heart rate variability is an indicator of the state of an individual’s autonomic nervous system. The results of the study indicated that in the period following the stretching routine the subjects had enhanced parasympathetic tone. In other words, they were less stressed and more relaxed than when the test began.

There are reasons to take these results with a grain of salt, or at least to be cautious about how generally applicable they are. For one thing, there was no control group, so we don’t know whether, if the subjects had just sat and relaxed for the same period of time, they would have seen the same results.

In addition, the men were selected for low flexibility, so we don’t know if the results would have been similar for those with more flexibility. (In fact, it’s not even clear that they were generally inflexible. They were tested with the sit-and-reach test, which is considered a standard measure of flexibility—basically, they sat in paschimottanasana, and researchers measured how far they could reach with their hands. Does this test indicate overall flexibility? It might for some individuals, but it only measures hip and spinal flexion and says nothing about other joints or other ranges of motion. However, since the stretching routine the subjects practiced was focused on the hamstrings and trunk, it was probably a valid measure for this study).

Despite the unanswered questions, this study is still intriguing. Perhaps most researchers studying stretching have been barking up the wrong tree. Maybe its benefits have less to do with effects on specific muscles, and more to do with the nervous system as a whole through inducing the relaxation response—which probably comes as no surprise to many yogis.