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The Female Athlete Triad: What It Is and Why It Matters

Left unrecognized or untreated, the female athlete triad will eventually claim your attention. It has the potential to spell the end of an athlete’s career. Its health consequences include debilitating stress fractures that may not be reversible, infertility, and disorders affecting an athlete’s weight and performance, heart, kidneys, digestive and nervous systems, and more.

“Any female athlete can potentially be at risk for the female athlete triad,” says Dr. Elizabeth Joy, a family physician at Intermountain Healthcare in Salt Lake City and past president of the American College of Sports Medicine.

Here is a brief summary of the triad and why it matters. In a companion piece, learn who is at risk, and how to combat it.

What is the triad?

The female athlete triad is a condition consisting of one or more of the following three parts. The parts often interact with one another.

  1. Low energy availability. Also referred to as low energy stores, this is the underpinning of the triad, and increases the chance of developing the other two parts. Low energy availability develops when an athlete is not consuming enough food to replace energy she is burning in training and competition.

“It can be defined pretty simply,” says Joy. Doctors start with how many calories you eat per day. They subtract from that the number of calories you burn when you exercise. Then they factor in the percent of an athlete’s body weight that isn’t fat, known as fat-free mass; athletes who are very lean have a greater risk of developing the other two parts of the triad. The final calculation helps show how much more an athlete needs to eat to be healthy or how much to cut back on exercise.

  1. Menstrual dysfunction. This term refers to menstrual periods that are delayed or less frequent than normal. It can be defined in a few ways: a delay in a girl’s first period after age 15 (on average the first period is around age 13); irregular periods—one every two or three months, instead of every month; or complete loss of menstrual bleeding for three months in a row or longer.

“The loss of menstrual bleeding is not a positive adaptation to sport,” says Joy. “It is a negative health consequence, and it implies that there is low energy availability. One of the most profound consequences is… low estrogen.”

  1. Low bone mass. Women build most of the bone they will have as adults during their adolescence and young adulthood. Genetic factors have a major impact on bone health, as do the energy and nutrients in food. But many girls and women don’t realize that estrogen levels are critical as well. “Most females are estrogen-dependent for bone health,” notes Joy.

Why does the triad matter?

The interactions among the different parts of the triad are complex. In brief:

  • Low energy availability can lead to missed or absent menstrual cycles.
  • Menstrual dysfunction and low energy availability contribute to low bone mass.
  • Low bone mass can result in painful bone stress injuries, including stress fractures that sideline an athlete.

Any single element of the triad increases the chance that a woman will suffer a bone stress injury or stress fracture. If two elements are present, the risk is greater. The presence of all three factors increases the risk of stress fracture still more.

Experts recommend that if one part of the triad is present, an athlete should be evaluated for the other parts.

How the triad causes bone problems

“Low energy availability creates a physiologic state in the body that says, ‘If there’s not enough energy in the body to protect the self, then we need to do things to conserve energy,’” explains Joy.

The menstrual dysfunction that results is referred to as “functional.” Its function is to prevent pregnancy, because pregnancy would consume energy a woman needs for basic survival. “Historically… during times of great famine, the birth rate goes down,” says Joy. Menstrual dysfunction “serves the purpose of trying to prevent pregnancy and preserve energy for the self.”

With fewer menstrual periods and less estrogen, the bones of female athletes may not withstand the rigors of running or repetitive jumps and landings that are routine in many sports. Bone stress injuries typically occur when the bone can’t repair itself fast enough during periods of repetitive loading.

“If you combine less bone health with impact-loading exercise, you increase the likelihood of stress fractures,” explains Joy. Low bone mass can also cause the bones to weaken to the point where they break (early osteoporosis).

“Some people think of stress fractures as these nuisance injuries. [They say] ‘You just get them in your feet, how bad can it be?’ But stress fractures can certainly be season-ending injuries,” says Joy. “They can be a career-ending injury… They are serious injuries that affect the careers and life and quality of life for many female athletes.”

Factors that increase the chance of stress fractures

Joy collaborated with Dr. Aurelia Nattiv, a team physician and director of the UCLA Metabolic Bone and Osteoporosis Center, to develop a tool that helps doctors assess the risk of developing stress fractures and advise athletes on whether it is safe to train and compete.

Their research suggests that the leading risks for stress fractures are the following:

  • First menstrual period at age 16 or later
  • Fewer than six periods in the past 12 months
  • A confirmed eating disorder such as anorexia nervosa
  • A body mass index (BMI) of 17.5 or less, or a weight loss of 10% or more; BMI measures whether a person’s weight is low, normal or high after taking into account a person’s height
  • A previous bone stress injury or stress fracture
  • A “Z score” of minus 2 or less; the Z score compares a woman’s bone health to that of average women her age