Female college athletes on low-calorie diets could be putting themselves at risk for stress fractures, according to new Saint Louis University research published in this month's The American Journal of Sports Medicine.
Researchers studied risk factors for exercise-related leg pain, including stress fractures in women participating in four popular fall sports - cross-country running, field hockey, soccer and volleyball.
Women with "disordered eating," which includes eating disorders such as bulimia and anorexia but more generally refers to insufficient caloric intake, were more likely to develop stress fractures as a result of decreased estrogen production, says researcher Mark Reinking, PT, Ph.D., chairman of the department of physical therapy at Saint Louis University's Doisy College of Health Sciences.
"When people expend more calories than they consume, they release fewer hormones, which slows down menstrual cycles. This decreases estrogen in the body, which is responsible for bone development," says Reinking, also chairman of the American Board of Physical Therapy Specialties.
Leg pain is one of the most common problems afflicting athletes, Reinking says.
"It causes people to miss practices and competitions, and I wanted to understand if two people were undergoing the same exercise regime, why only one of them would have leg pain," he says. "It's not as simple as 'Run less' or 'Change your shoes every 300 miles.' It's a complex problem, and you can't prevent something if you don't know what causes it."
Risk factors for exercise-related leg pain were a prior history of the condition, disordered eating and excessive pronation (a rolling inwards) of the foot.
"Exercise-related leg pain is often described as common in athletes, but this is only the second study of its kind to quantitatively describe the condition and identify the risk factors for it," Reinking says. "The history and incidence data from this study support the notion that leg pain is common among female athletes."
Exercise-related leg pain is a term used to describe lower extremity overuse conditions in which pain is felt below the knee and above the ankle bone and is associated with exercise. Although it is often thought to be related to external factors such as training volume, playing/training surface or footwear, there is little scientific evidence to support these elements as risk factors for leg pain.
Rather, internal factors such as excessive foot pronation, menstrual function and bone mineral density have been found to be associated with this condition.
Reinking studied 76 female college athletes playing one of four fall sports at a Midwestern NCAA Division I school (29 soccer, 18 field hockey, 18 cross-country and 11 volleyball athletes). Data were collected on the athletes' eating behaviors, years in school sports, menstrual history, bone mineral density, body mass index, incidence of prior leg pain, and the degree of foot pronation.
Three-quarters of the female athletes reported a history of leg pain, with cross-country runners having the highest percentage (94.4 percent) and soccer players the lowest (55.2 percent). All athletes were then monitored for leg pain during one intercollegiate sports season. Of the 76 athletes, 26.3 percent experienced leg pain during the season, all of whom had reported prior leg pain.
Athletes who developed stress fractures had more abnormal scores on the eating behavior questionnaire and also showed decreased bone mineral density, findings suggestive of disordered eating, which is an umbrella term for common eating disorders as well as any other nutritional deficiency.
The type of sport played was not correlated with high scores on the eating behaviors survey.
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