The adage "what doesn't kill you makes you stronger" doesn't always apply to distance runners.
Promising running careers can be interrupted or cut short -- and training goals derailed -- by overuse injuries known as stress fractures. Repeated pounding causes these tiny breaks in bones in the feet, legs and hips.
Even casual runners aren't immune. Seven-time Tour de France winner Lance Armstrong suffered through a stress fracture when he ran the New York Marathon for the first time after retiring from cycling competition.
Runners, coaches and sports medicine experts alike are trying to figure out how athletes can train hard without risking these painful injuries. At UCLA, researchers are attempting to establish what predisposes runners to stress fractures in order to prevent them.
"Normally, running is good for bones, but more is not always better," says Dr. Aurelia Nattiv, a professor at the David Geffen School of Medicine at UCLA and a physician for the UCLA track and field team.
She and her colleagues studied 167 male and female volunteers from UCLA track and field teams to determine individual risk factors for stress fractures. The athletes received annual physical exams, filled out health questionnaires and food diaries, provided blood samples and had their strength, flexibility and bone density assessed. The study was funded by the UCLA General Clinical Research Center, the U.S. Olympic Committee and USA Track & Field.
During the course of the five-year study, 37 of the athletes suffered more than 60 stress fractures.
The data have not yet been published, but Nattiv has presented preliminary results to the American College of Sports Medicine and the American Medical Society for Sports Medicine, as well as in meetings with UCLA and the U.S. Olympic Committee coaches.
"In the past, studies have focused on [bone density] being a risk factor for female athletes, but we're seeing it in the male athletes as well," says Nattiv. "We're also looking at weight, and it appears that that plays an important role in men as well as women."
The study also confirmed that having a prior stress fracture is an important risk factor for having another and that eating disorders can predispose runners to stress fractures.
Nattiv prefers the term "bone stress injury" to stress fracture because of the continuum from normal bone to bone fatigue and, with more stress, to actual fracture. The injury results when there is a disturbance in the natural equilibrium between bone formation and bone loss, resulting in weakened bone that is unable to withstand repetitive stress.
