Like other athletes at risk, female collegiate distance runners are predisposed to develop bone stress injuries from a condition known as the female athletic triad, said Michael Fredericson, MD, a professor of orthopaedic surgery and sports medicine at Stanford, who has worked with Stanford athletes for more than 25 years.
The triad stems from an energy deficiency, he explained:
When your body isn't getting enough food, then you stop producing normal levels of sex hormones, which leads to menstrual dysfunction. Your growth hormones go down, so you lose muscle mass. Your thyroid hormones go down, so your metabolism gets suppressed. And your stress hormones go up, which also leads to menstrual dysfunction and reduced muscle mass. And all of that leads to lower bone density, and eventually osteopenia [low bone strength] or even osteoporosis.
The problem is common. "Based on our historical data, 38 percent of our female runners developed stress fractures over a three-year period from 2010-2013," Fredericson said. "I knew the time had come to do something to prevent this."
He is investigating the effectiveness of a nutritional intervention, in collaboration with Aurelia Nattiv, MD, from the University of California, Los Angeles. They have enrolled about 180 male and female runners from Stanford and UCLA in their study.
"The goal is to have our runners eat 45 kcal/kg/fat free mass per day, which is really just a normal diet -- so their energy input equals their energy output," Fredericson said. "We found a third of the women were getting less than this and half of the men were getting less. So it's fair to say that a significant number of our runners were not getting adequate nutrition or calories."
The runners met individually with a sports dietician and filled out a questionnaire to estimate their food intake, Fredericson told me. A low-dose x-ray machine was also used to measure their bone density and basic blood work measured vitamin D and thyroid levels, he said. Finally, their risk of female athlete triad was assessed using an established point system.
After their health assessment, a dietician helped each runner select individual nutrition goals, like adding a snack or increasing the energy density of a meal, Fredericson said. "We typically want them to eat smaller more frequent meals -- particularly right before and immediately after exercising," he said.
The runners also used an app developed by collaborators at UCLA, which provided an eight-week nutrition education curriculum, including handouts, video clips, recipes and behavior modifying exercises.
Although the researchers have only completed the first year of a three-year study, they have found their intervention is working. "A majority of the runners have increased their bone density over the one year period by 2 to 5 percent," Fredericson said. " Our preliminary findings also show for every one point increase in risk score, there was a 17 percent increase in the time it took to recover after an injury... Anecdotally, we are seeing less injuries and the type of injuries that we are seeing are less severe."
He emphasized the importance of the work:
We have a number of young women that are exercising at levels beyond their ability to support their nutritional requirements. By the time they enter college many of them have osteoporosis... Ours is the first attempt to address these issues in an organized study with elite athletes. We need to turn things around for these young women, and prevent more serious health problems later in life.
Previously: Director of Stanford Runner's Injury Clinic discusses advances in treating six common running injuries, Stanford physician discusses prevalence of overuse injuries among college athletes and 'Eat a bleeping Dorito': An elite runner and Stanford medical student addresses disordered eating
Photo by David Gonzalez