Long, Skinny Muscle Found Crucial to Healthy Spine

The UCSD team found that the multifidus is unique among the body%u2019s muscles. It%u2019s composed of short fibers within rods, with the fibers being stiffer than any others in the body. The researchers used a laser diffraction technique to reveal the extraordinary design of the multifidus and to show how it stabilizes the spine.

"It is important to identify what each individual muscle does, and this is just a start, showing that the multifidus contributes significantly to spinal stabilization,%u201D said Steven R. Garfin, professor and chair of UCSD's Department of Orthopedic Surgery."The more we know about what muscles do, the better we can devise therapeutic interventions, such as physical therapy to target specific muscles."

The new study may have implications for surgery, he said, because many modern surgical techniques actually damage the multifidus muscle, inadvertently contributing to lower back pain. Recently devised, minimally invasive spinal surgery methods that don't disturb the muscle will thus likely come increasingly to the fore. The role of the multifidus in preventing pain in the lower back, which bears most of the body's weight and receives most spinal stress, cannot be overemphasized, according to Lieber. He explained that muscles always get weaker as they are extended.

 But not the multifidus, which actually gets stronger as it lengthens. "The length of the sarcomere - the structure within the muscle cell where filaments overlap to produce the movements required for muscle contraction - is shorter in the multifidus than in any other muscle cell," explained study%u2019s first author, Samuel R. Ward, assistant professor of radiology at UCSD School of Medicine. "But as it gets longer, for instance as a person leans forward, the multifidus actually strengthens."