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Research Questions

  1. How has airman fitness changed over time?
  2. Do different measures result in different assessments of health and fitness?
  3. Which fitness measures can USAF use to ensure a more accurate evaluation of the health and fitness of the force?

Physical fitness is an important element of military readiness and is the responsibility of every airman. U.S. Department of Defense (DoD) and U.S. Air Force (USAF) policies reflect this view. DoD's position is firmly grounded and supported by decades of research that has established clear linkages between physical fitness and a wide variety of health outcomes, such as hypertension and heart disease.

This report focuses on measures used to monitor the general fitness of airmen, which guide personnel actions and reports on the health of the force. To provide a more comprehensive evaluation of USAF fitness and health, the authors compare results from the 2018 DoD Health Related Behaviors Survey with data collected as part of regular USAF fitness assessments from fiscal year (FY) 2005 through FY 2018.

The authors present evidence to suggest that body mass index (BMI), although commonly used as a sole indicator of overweight or obesity status in personnel and media reports, can be misleading when used alone. Specifically, BMI may misclassify service members as overweight or obese when they are not; BMI may be less accurate than other easily obtained measures, such as abdominal circumference (AC) or waist-to-height ratio (WHtR); other fitness metrics suggest that USAF fitness has improved over time; and other USAF measures that assess cardiorespiratory and muscular fitness should also be used in conjunction with body composition measures to provide a more accurate assessment of health risk across subgroups (e.g., gender, race).

Key Findings

Physical fitness is an important element of military readiness and is the responsibility of every airman

  • Physical fitness is linked to a wide variety of health outcomes, such as hypertension and heart disease, improved sleep, cognitive functioning, and mental health.

On average, airman fitness has been improving over time

  • Since 2012, less than 1 percent of airmen have exceeded the USAF AC standards.
  • The average AC has been decreasing over time.
  • The average 1.5-mile run time has steadily decreased through 2016.
  • The average number of push-ups and sit-ups completed during regular USAF fitness assessments has increased.

Conclusions about healthy body composition depend heavily on the specific measure and standard being used

  • BMI classifies 60 percent of airmen as overweight or obese.
  • WHtR indicates that between 14 and 22 percent of airmen have an increased risk of an adverse health condition.
  • AC indicates that less than 1 percent of airmen are at an increased risk of an adverse health condition.
  • It is possible that each fitness measure assesses an independent risk factor, and the metrics should be considered together when evaluating the health and fitness of the force.


  • USAF should continue to use AC in combination with other body composition metrics, such as WHtR and BMI, to assess the general fitness of airmen.
  • BMI should not be used alone as a diagnostic tool to indicate health risk or to report on the health of the force.
  • Future analysis should explore which combination of fitness measures is most predictive of important health outcomes.

Research conducted by

This research was commissioned by the Air Force's Force Management Policy Directorate (AF/A1P) and conducted within the Workforce, Development, and Health Program of RAND Project AIR FORCE.

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