Mayo Magazine

Measuring Motion

Kenton R. Kaufman, Ph.D., (left) and Kai-Nan An, Ph.D., co-direct the Biomechanics and Motion Analysis Laboratories at Mayo Clinic Rochester. One visit to their lab demonstrates that movements are unique in ways you probably never dreamed possible.

Steven E. Irby stands in front of the Motion Analysis Lab walkway. The walkway is marked with distinctive prints and hatch marks that serve as starting and stopping points for patients undergoing motion analysis testing.

Using specially designed hand rims, researchers at the Biomechanics and Motion Analysis Laboratories record the propulsion and maneuvering forces of wheelchair users during everyday activities. This information is used to design techniques to reduce upper extremity pain, a common complaint among people who use manual wheelchairs.

In the Biomechanics and Motion Analysis Laboratories at Mayo Clinic, the principles of mathematics, engineering and physics are applied to human movement, a science called biomechanics. Whether the question is about pitching a baseball, replacing a joint or propelling a wheelchair, this is the place where diverse teams of experts collaborate using the tools of biomechanics to solve everyday issues.

Mayo Clinic has been a leader in the study of biomechanics for more than 40 years. And during that time, Mayo has made enormous contributions to the development of technologies that help millions of people around the world. Founded in 1971 by Edmund Y.S. Chao, Ph.D., Mayo Clinic's Orthopedic Biomechanics Laboratory (as it was then called) was created in recognition of the important role engineering plays in the field of biomechanics.

Today, the Biomechanics and Motion Analysis Laboratories are co-directed by Kai-Nan An, Ph.D., and Kenton R. Kaufman, Ph.D. Those in the lab conduct research with a patient-care focus, meaning special emphasis is placed on applying research discoveries to the issues of daily living. About 20 percent of the lab's resources are devoted to helping physicians improve patient-care activities by providing specific evaluations and recommendations for treatment.

Research for everyday solutions

Although the field of biomechanics has a history dating back to Leonardo da Vinci, it's a field that's not widely understood by the general public. Few of us are aware of our individual movements, or the force being exerted by our muscles or gravity until we have difficulty moving. At that point, each of the distinguishing characteristics and individual idiosyncrasies of the way we move becomes crucially important. The technology of biomechanics measures individual movement in order to customize solutions.

"Every research project in this lab begins with an important unanswered clinical problem," says Dr. Kaufman. With 11 fully funded National Institutes of Health (NIH) research projects currently under way, research in the Biomechanics and Motion Analysis Laboratories impacts a wide range of people.

Walking independently: People with significant quadriceps weakness, often as a result of conditions such as polio, stroke or neurological problems, are often prescribed long-leg braces, also known as knee-ankle-foot-orthoses (KAFOs). However, the energy it takes to use the brace results in a rejection rate of between 60 percent and 80 percent, says Steven E. Irby, M.S., a mechanical engineer at the lab. This means many people are forced to give up walking independently and use a wheelchair.

Dr. Kaufman and Mr. Irby have set out to change that. It took more than $1.5 million and 10 years of cumulative research, but they've improved the long-leg knee brace. Their new model is now electronically controlled to allow for knee motion while the foot is in the air and for knee stability when the leg is bearing weight. This enables a person to walk independently with less wasted energy. The two have patented this newly designed brace, which soon will go to market.

Wheelchair mobility: People who use manual wheelchairs often experience upper-extremity pain. Mayo Clinic's Biomechanics and Motion Analysis Laboratories currently have an NIH-funded project to analyze wheelchair propulsion in order to reduce the musculoskeletal problems associated with wheelchair use. Using specially designed hand rims, researchers record the propulsion and maneuvering forces of wheelchair users during everyday activities.

Exercising with osteoarthritis: Osteoarthritis causes people to limit their movement and activity, because restricting joint motion decreases their symptoms and reduces pain. Researchers in the Biomechanics and Motion Analysis Laboratories are studying the effects of aerobic exercise in people who have early osteoarthritis. In this study, researchers measure forces generated around the knee when walking to see if exercise restores a more normal gait. The goal of the research is to determine if people with osteoarthritis can follow the surgeon general's recommendations of exercising three times a week or if modifications are necessary.

Partnering for advancement

One visit to Mayo's Biomechanics and Motion Analysis Laboratories demonstrates that movements are unique in ways you probably never dreamed possible. For most of us, this becomes important only when our ability to move is impaired due to an injury, accident, aging or illness. Thanks to the dynamic group of researchers in the Biomechanics and Motion Analysis Laboratories who are passionately committed to developing state-of the-art technologies, patients are able to move and live more independently. With partnership and support, these researchers can continue to forge new frontiers in the prevention and cause of injuries and to increase the quality of life for all of us.

Technologies commonly used at Mayo Clinic's Biomechanics and Motion Analysis Laboratories:

1. Measuring motion
   In the lab, whole-body motion measurements are made using a computerized camera-based system. "These are the same devices used by companies to study golf swings or baseball pitches," says Mr. Irby. "At Mayo we have a 10-camera digital system that we use to study people while they walk, climb stairs, step over obstacles, use a wheelchair or throw a ball." For more limited-range studies, a more finite system is used to measure the motions of the fingers and wrists.

2. Measuring force
   Force platforms look something like built-in bathroom floor scales. They measure not only standing weight, but also the sliding, pivoting or twisting forces created when you move. "As an engineer, if we know position and force, we can make all sorts of engineering calculations," says Mr. Irby. "We can calculate the forces around the hip joint, even though the hip joint isn't touching the ground." Measurements such as these might be used to measure the differences in forces around the joint before and after a total hip or a total knee replacement.

3. Measuring muscle movement
   Dynamic electromyography allows researchers to examine muscle activity when you walk, for example. "We literally listen to the muscle trying to move," says Mr. Irby. "It is the synchronicity of muscle firing patterns that we are really interested in. For example, it's OK if the quadriceps (the big muscle in the front of your thigh) is firing when you're standing on that leg. But, if that muscle is firing when you're trying to swing that leg forward, it might be the reason you drag your toe. Normal muscle-firing patterns can then be compared to a person's walking pattern to help understand the underlying causes for unusual limb motions."

4. Measuring pressure
   Pressure measurement technology uses a paper-thin wafer in the shape of a foot to provide a map to show the pressure between your foot and shoe. "This lets us see pressure in real time as you walk," explains Mr. Irby. These sensors are used to measure foot pressure on people with diabetes. Researchers also use a square pressure map, which, when placed on the seat of a wheelchair, can measure a person's seating pressure. Appropriate seating is important to help those who are wheelchair-bound avoid pressure sores.