Medical Research

The Science of Stretch

Kristen Sparrow • August 02, 2014

I saw the abstract of a recent article by Helene Langevin on the physiology of acupuncture stretch and neuro communication, but alarmed at the price of a reprint, so found this one for free. Her research is all about what happens to connective tissue when a needle is inserted and twisted.  It’s interesting stuff and will hopefully lead to better understanding and treatment.

“Fibroblasts also play a major role in the response to acute injury, particularly when they transform into myofibroblasts. Before the availability of surgery and surgical sutures, gaping wounds needed a powerful mechanism in order to pull shut and heal. Myofibroblasts serve this function by secreting large amounts of collagen and expressing α-smooth muscle actin protein, which make the cells contractile.6 Then, by exerting tension on the collagen matrix, these cells pull the edges of the wound together. Myofibroblasts normally die once this job is done and a stable scar has formed. However, during chronic inflammation, myofibroblasts can drive an excessive deposition of collagen, and the increased tissue tension can result in the development of tissue contractures that restrict full range of motion. This response is also thought to play a role in the development of some types of tissue fibroses and cancer. Indeed, fibrotic, or scarred tissues, become stiffer, and cancer cells have been shown to spread more easily on fibrotic matrices.7

Although much of the work in this area to date has been performed in cell culture, rather than in whole tissue, some of this basic research is beginning to inform clinical research and practice, especially in the area of chronic musculoskeletal pain, including low-back pain. One of the reasons that low-back pain is so difficult to manage is that large numbers of patients have no detectable abnormalities of the spine and associated tissues, and the source of their pain is unknown. Some groups have begun to investigate the possibility that the pain is arising from the nonspecialized connective tissues on either side of the spine.
“Indeed, researchers at the University of Heidelberg found in 2008 that connective tissues contain sensory nerve endings that can transmit pain when these tissues are stretched in the presence of inflammation.8 Until then, it had not been clear whether connective tissue had its own sensory nerve supply capable of generating sensations. Subsequently, ultrasound studies in my laboratory demonstrated that the connective tissues that surround the muscles of the back are, on average, thicker in people with chronic low back pain.9 Normally, these connective tissues are composed of alternating layers of tightly woven dense fibers that can bear substantial loads, and loose areolar tissue, which contains large quantities of water and allows the adjacent dense layers to glide past one another. In addition to having thicker connective tissue overall, people with low-back pain show a decreased gliding motion of dense layers, suggesting that a fibrotic process could cause the decreased mobility.”