09.10.08
Identifying Reasons for Hamstring Pulls
In today’s show, adapted from an article written for the U.Va. Engineer , the Alumni Magazine of the UVA School of Egineering and Applied Science, by freelance writer Charlie Feigenoff, we discuss the research of Silvia Salinas Blemker, an assistant professor of mechanical and aerospace engineering, who is trying to identify reasons and mechanics of hamstring pulls.
When the world’s best sprinters stepped up to the mark at the 100 meter final during this summer’s Olympic Games in Peking, they were moments away from subjecting their leg muscles to thousands of pounds of force as they fought to be first across the finish line less than 10 seconds later. By and large, their leg muscles handled the strain well, but inevitably one or more of these elite runners, despite intense conditioning, will suffer a hamstring pull during the track and field season.
As Silvia Salinas Blemker, an assistant professor of mechanical and aerospace engineering at the University of Virginia’s School of Engineering and Applied Science has said, “Of all the muscles that work together when we run quickly, the muscles in the hamstring group are most subject to injury, and one particular hamstrings muscle, the biceps femoris long head, is most commonly injured.”
Blemker has the expertise in three-dimensional muscle modeling to find out why this muscle is so susceptible to pulls. Collaborating with Darryl Thelen, an associate professor of mechanical engineeering at the University of Wisconsin, she has embarked on a project to identify the points of strain as the biceps femoris moves dynamically and compare it to the other two hamstring muscles. Their research is supported by a four-year, $1.2 million grant from the National Institutes of Health.
The hamstrings run along the back of the thigh and attach on both sides of the knee joint. They are responsible for pulling the foot from the ground with each stride. In the past, researchers treated these muscles like anatomical rubber bands, uniformly elastic along their length.
Blemker said, “This simplistic view made it difficult to understand why one muscle is prone to injury while another isn’t.”
Blemker’s approach is more detailed. She has developed models that incorporate the muscle’s intricate internal geometry, which she is combining with a model of the whole-body dynamics of sprinting, developed by Thelen. By combining the model of the hamstrings with the framework provided by Thelen, Blemker will be able to predict how the muscle behaves in the course of real movement.
Blemker and Thelen face a number of challenges. The first is to merge these two models. Second, they then have to validate their new model by comparing predictions with MRI-imaging techniques that measure muscle strain distribution.
Blemker said, “Ultimately, we hope to learn how the internal structure of muscle changes when it is injured, which will help us suggest more effective rehabilitation strategies.”
As director of the U.Va. Multiscale Muscle Mechanics Laboratory, Blemker is also developing computational models that connect the properties of muscle fibers and the extracellular matrix that binds them together with the properties of the muscle as a whole. This line of research will help us understand how aging and diseases such as cerebral palsy and muscular dystrophy affect muscles.
Blemker’s work straddles several fields. She has appointments in biomedical engineering and orthopedic surgery as well as mechanical and aerospace engineering, but muscles have always been her focus. “I’ve been fascinated by the fact that muscles, which are so strong, are so easily injured,” she said. “Now I am finding out why.”
You’ve been listening to the Oscar Show, I’m Jacob Canon. Join us for our next show, when we will well discuss the research of a multi-institutional team of scientists, including Bob Hirosky, a University of Virginia associate professor of physics, and there attempt to verify or refute the existence of the Higgs boson, which is theorized to be the essence of all matter, and the ultimate basis of everything in the universe.