Nov. 15, 1999 (New York) -- Achilles tendinitis, or inflammation of the Achilles tendon, is a common lower-leg injury in long-distance runners. Runners who land hard on the outer part of the foot and twist their heel and those who do not have good muscle strength are those most likely to suffer such an injury, according to research presented in the journal Medicine & Science in Sports & Exercise. Runners with a high arch, faster runners, and those who were either new to the sport or had been running for a number of years also were found to be more susceptible to the injury.
"Strength training and changing your running shoes every 300 miles" could help prevent Achilles tendinitis, according to lead study author Stephen P. Messier, PhD. He also finds that good stretching habits were effective in preventing this injury. Messier is a professor in the department of health and exercise science at Wake Forest University in Winston-Salem, N.C.
In the study, researchers evaluated 31 runners who sustained an Achilles tendinitis injury against 58 runners who did not. All runners in the study ran at least 10 miles each week for a minimum of one year. The researchers measured the strength and physical characteristics of the athletes' legs, made high-speed video to analyze their running motion, and studied the interactions of their feet and the ground as the athletes ran.
"From a mechanical standpoint, we found injured runners ran faster, which can put your foot through microtears," says Messier. "Another thing is that people who were either new at running or had been running for a large number of years" were more likely to be injured. A high arch also increased the risk for sustaining the injury, according to Messier. "What frequently happens with a high arch is that people hit the ground with the same force but over a smaller surface area," he says, which may lead to the development of rigid feet."
Another risk factor for Achilles tendinitis is "excessive motion in the rear foot, where you strike the ground at a more extreme angle on the edge of your heel, which can then force you to turn your foot inward," Messier tells WebMD. "When there is excessive motion in the rear foot, the tendon gets whipped like a bowstring."
In an interview seeking objective commentary, John Cianca, MD, tells WebMD that the study shows that "people ought to understand where they are starting from when they begin running." He suggests that novice runners begin slowly, gradually increasing their distance and speed. "If you go too far, too fast, you are going to be more prone to these kinds of injuries," says Cianca, who is assistant professor of physical medicine and rehabilitation at Baylor College of Medicine in Houston. Cianca also has co-authored a screening study on marathon runners.
Building "strength and flexibility are absolutely critical" in training, according to Cianca. "Most runners think that running makes them strong, but it doesn't. Separate weight-training conditioning is necessary to best prevent injury." He advises working on "your own intrinsic strength" and recommends using the right shoes for your foot, something he says few people know how to do.
"Once you have a problem, don't wait and ignore it," says Cianca. "Chronic tightness over time can lead to microtears in your tendons." He advises beginning conditioning early in a running season, not after problems develop. Strengthening the outside of the leg below the knee and the inside of the shin can prove particularly helpful.