The Female Athlete Triad expert panel (1) recommends that BMD testing should be performed in athletes that have the following:

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1. One or more «high risk» risk factors for the Female Athlete Triad

• Current or history of a clinical eating disorder

• BMI equal to or lower than 17.5, or less than 85 % of estimated weight, or recent weight loss of 10 % or more in one month

• Menarche at age 16 or later

• Current or history of less than 6 menses over 12 months

• Two prior bone stress reactions or stress fractures, or one high-risk stress reaction/fracture, or a low-energy non-traumatic fracture

• Low score on a previous DXA-scan (Z-score less than –2.0)

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2. Two or more «moderate risk» risk factors for the Female Athlete Triad

• Current or history of disordered eating for 6 months or more

• BMI between 17.5 and 18.5 (athletes aged 20 or more), or less than 90% estimated weight (athletes aged 19 or less), or recent weight loss of 5–10 % in 1 month

• Menarche between age 15-16

• Current or history of 6–8 menses over 12 months

• One prior bone stress reaction or stress fracture

• Low score on a previous DXA-scan (Z-score between –1.0 and –2.0)

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3. One or more «moderate risk» risk factors

+ two or more long bone traumatic fractures (non-stress), or

+ one or more traumatic fractures in other parts of the body than arms and legs (non-peripheral)

 

Energy availability

 

There is no accurate method to measure energy availability (9). Food logs are often used to estimate caloric intake, but are often inaccurate (9). Also, the only way to accurately measure exercise energy expenditure is to measure how much carbon dioxide is exhaled during exercise, which is not feasible outside of a laboratory setting (10). This means that all calculations of energy intake and expenditure are dependent on less accurate estimates.

 

The ACSM recommends using the method described in the 2011 Compendium of Physical Activities (11) to calculate exercise energy expenditure. This method calculates energy expenditure by multiplying what is known as the «metabolic equivalent» for a certain task with the time spent exercising (hours) and the athletes weight (in kilograms) (1). The metabolic equivalent represents the amount of energy spent during a specific activity compared to calories spent during rest.

 

Examples of metabolic equivalents:

Walking: 2.0-9.9 METS, depending on speed and incline

Running: 6.0-23.0 METS, for running between 6-37 km/h (4-23 mph)

Dancing: 3.0-11.3 METS, depending on the type of dance and intensity

Cycling: 3.5-15.8 METS, depending on the intensity/speed

 

You can find the metabolic equivalents for a great number of activities and intensities here: https://sites.google.com/site/compendiumofphysicalactivities

 

Indicators of low energy availability

 

As stated earlier, a stable weight should not be used as an indication of sufficient energy availability, because it is possible to be in a state of low energy availability and a state of energy balance at the same time (9). This might seem as a paradox, however, a body that is energy deficient will will try to save energy by suppressing certain physiologic functions, including slowing down the metabolic rate and increasing growth hormone resistance (1,12). This reduces the daily energy expenditure, and less calories are needed to maintain a stable weight.

 

Low BMI, on the other hand, may be a sign of low energy availability*. BMI between 17.5 and 18.5 may suggest low energy, and female at availability, and athletes with a BMI of less than 17.5 are likely to have low energy availability.

 

*Absolute BMI cutoffs should not be used in athletes under the age of 20. Instead, a cutoff using 85 % of expected body weight for the athletes age should be used instead (1,10).

 

Other indicators of low energy availability exist, including low or reduced resting metabolic rate (which suggests that the body tries to save energy) and low free triiodothyronine (1). Studies are also ongoing on tracking leptin levels (9).

 

Screening for the Female Athlete Triad

 

The Female Athlete Triad Coalition recommends that female athletes undergo annual screening for the Female Athlete Triad, starting from high-school (1). This recommendation is based on the importance of early intervention to prevent bone loss, since peak bone mass is reached by late teenage years or early twenties depending on skeletal site (13).

 

Such screening should include a set of questions that target key risk factors for the Female Athlete Triad (1):

 

• Have you ever had a menstrual period?

• How old were you when you had your first menstrual period?

• When was your most recent menstrual period?

• How many periods have you had in the past 12 months?

• Are you presently taking any female hormones (estrogen, progesterone, birth control pills)?

• Do you worry about your weight?

• Are you trying to or has anyone recommended that you gain or lose weight?

• Are you on a special diet or do you avoid certain types of foods or food groups?

• Have you ever had an eating disorder?

• Have you ever had a stress fracture?

• Have you ever been told you have low bone density (osteopenia or osteoporosis)?

 

In addition, any physical signs of low energy availability or an eating disorder should prompt further investigation, including low BMI, weight loss, orthostatic hypertension (feeling lightheaded or fainting when standing up), lanugo (thin, soft body hairs that grow as a response to severe malnutrition), hypercarotenemia (orange skin tone), or Russel's sign (calluses on the knuckles or back of the hand due to repeated self-induced vomiting) (1).