Yoga practitioners know the classic posture called The Cat.
It feels good to stretch.
“Bad things happen when we don’t stretch enough,” said Dr. Hélène Langevin of the University of Vermont College of Medicine in a recent lecture here. “Or when we can’t stretch some part of our body for some reason.”
Principal investigator of 3 NIH-funded studies, Langevin presented “The Effect of Stretching on Connective Tissue: From Yoga to Acupuncture.” Part of NCCAM’s Integrative Medicine Research Lecture series, the talk was held in Lipsett Amphitheater.
Dr. Hélène M. Langevin
Professional sports teams have long been interested in whether stretching can improve performance and reduce injuries.
Langevin discussed findings based largely on animal models; before these can be translated into therapies for humans, further studies are needed. Yet this crucial stage in her own research has already yielded a new concept in how connective tissue regulates its own tension level.
Athletes, physical therapists and the millions of folks with low back pain will want to stay tuned.
So do we know if stretching is good for you?
Langevin, who is professor of neurology, orthopedics and rehabilitation and director of UVM’s Program in Integrative Health, began with an overview: How scientists first focused on static stretching, which pulls and holds the tissue beyond the range of motion (ROM is the full movement potential of a joint, usually its range of flexion and extension).
Studies in athletes over the last 10 to 20 years have shown that static stretching before competitive sports, in fact, does not help. In fact, it increases the number of injuries.
Researchers then turned to dynamic stretching (for example, t’ai chi). This ancient practice could be a better way to warm up and increase ROM without injury.
As for yoga, which Langevin called “stretching while paying attention to your body and your breathing,” she reported a study that found it effective, when compared to controls, in reducing back pain.
What’s going on in there?
NCCAM director Dr. Josephine Briggs (r) observed that Langevin’s studies showed “an interesting use of ultrasound as an objective measure. And it’s cheap, portable and noninvasive.”
Photos: Michael Spencer
When we stretch, we’re stretching not only muscle, but also our connective tissue, which forms a dynamic, body-wide, mechanically responsive network. Connective tissue acts like cellular glue. It includes specialized forms (such as tendons, ligaments and joint capsules) and non-specialized forms (both “dense” and “loose,” which go around and through everything else). Visualize it as a tissue matrix that supports, ensheathes and binds together other tissues.
Interestingly, Langevin described how loose connective tissue layers allow the dense connective tissue planes to glide past one another. In cross section, these look like miniature geologic strata, or complicated cake layers with colorized frostings.
The looser layers allow range of motion, while the denser stuff keeps us glued together inside. The different layers correspond to muscles with different directions of pull.
How does the sustained stretching of loose connective tissue work on a cellular level? Using in vivo experiments, Langevin and her team stretched a mouse at a 20 percent strain—a modest stretch typical in daily activities.
“You’re all sitting down,” she said, “so the tissues of the back are all stretched relative to the tissues of the front…at the end of the hour you’re going to get up, and the relationship between the front of your body and the back of your body will change.”
In the fibroblast cells within connective tissue, she and her team found changes that influenced the tension within the tissue itself.
“This is a new concept,” Langevin said, “because connective tissue is not supposed to regulate its own level of tension.”
The rotation of acupuncture needles also produced these dynamic fibroblast responses as collagen fibers wrapped around the needle “like winding spaghetti around a fork.” (Collagen is the main component of connective tissue.) “This suggests that acupuncture can have the function of producing some static stretching of connective tissue.”
Langevin hypothesizes that such changes at the cellular level of loose connective tissue may not only help the tissue to relax, but also create the pleasant sensations we feel when we stretch.
Langevin, of the University of Vermont College of Medicine, discussed the effect of stretching on connective tissue.
On the other hand, what happens in dense connective tissue cells is different.
Injury increases the thickness of the dense connective tissue, causes adhesions and scarring and decreases the mobility of those layers.
Folks with low back pain tend to have these anatomical changes, but it’s still unclear whether this is a cause or an effect.
What’s known is that connective tissue can become abnormal both in the presence of movement restriction in pig and rat models and in the presence of chronic pain in humans.
And in the rat model, active stretching can improve gait, pain sensitivity and connective tissue inflammation.
In the Q&A, Langevin noted: “The physical therapy (PT) world has really woken up to connective tissue in concert with muscles. There’s some creative research with direct clinical applications in terms of the different amounts of stretching. PT already has a whole vocabulary and method.”
NCCAM director Dr. Josephine Briggs observed that Langevin’s studies showed “an interesting use of ultrasound as an objective measure. And it’s cheap, portable and noninvasive.”
Promising news for folks with tender backs.