DENVER -- With runners, one injury often leads to another. Anecdotal evidence of this experience abounds.
Now for the first time, researchers at the University at Buffalo are attempting to document the relationship between initial and secondary injuries in runners, using a force-measuring treadmill developed in UB's biomechanics laboratory in conjunction with Kistler Instrument Corp.
The researchers have been able to show that runners who develop a muscle injury in the lower extremities alter their running patterns unconsciously after an injury. This change in running mechanics causes a deviation in the foot's normal impact and push-off force, which can be measured on the treadmill.
Harold Burton, Ph.D., UB associate professor of physical therapy and nutrition and exercise science, one of the researchers on the study, said a change in running mechanics may affect the way that force is dissipated. As a result, the added or altered forces are absorbed by joints and/or muscles unaccustomed to this stress, which may lead to a secondary injury in areas such as the knee, hip or lower back.
"Having an idea how a person with a particular problem changes running strategy, we hope to eventually identify a pattern and predict the risk and location of a secondary injury," Burton said. "If we can predict what's going to happen, intervention with corrective measures, such as an orthotic, can prevent the secondary injury from occurring."
Burton and co-investigator John Leddy, M.D., associate director of the UB Sports Medicine Institute, present results of the research here today (Thursday, May 29) at the annual meeting of the American College of Sports Medicine.
The study examined the effect of injury to the thigh muscles, and involved 10 male recreational runners. After collecting baseline measurements during level treadmill running, researchers had the participants induce muscle "injury" by running downhill for two 20-minute sessions. Downhill running can cause microscopic muscle-fiber tears.
For four consecutive days following the injury session, researchers recorded the vertical foot-ground reaction force generated by each runner during level treadmill running. Results showed that the runners who got sore, or "injured," after running downhill produced altered forces during the next running session, indicating alterations in running mechanics. The soreness peaked during the first and second day, and coincided with the largest strength deficit -- 22 percent at day one and 20 percent at day two.
"These altered mechanics may predispose the individual to secondary injuries of other structures, such as joints, ligaments and tendons," Burton said.
Among runners, this is no small problem. Burton said that 50 percent of the people who run regularly experience some type of injury during any one year, and need more education about what can happen as a result. He recommended that runners who experience lingering soreness consult a sports medicine specialist, such as those at UB's Sports Medicine Institute, for a gait assessment.
Using results of the study, Leddy and Scott White, Ph.D., UB associate professor of physical therapy and nutrition and exercise science, are tracking the incidence of secondary injuries in finishers in the Ford Buffalo Marathon held in early May. Results of this and further studies may lay the groundwork for developing "prescriptions" for preventing those injuries, Leddy said.
The concept for the initial study originated in a master's thesis by Heather Collins, a graduate student in the UB Department of Physical Therapy and Nutrition and Exercise Science.