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Despite the physical demands of firefighting, several recent studies have reported that greater than 75% of all current and new firefighter recruits are overweight and/or obese. Research also suggests that obesity had a significant impact on lower back muscular endurance.

Eric Ryan, PhD, Assistant Professor of Exercise and Sport Science, and his research team recently completed a feasibility study with the Kannapolis Fire Department using the UNC Nutrition Obesity Research Center’s mobile body composition trailer. The purpose of this study was to assess the test–retest reliability and minimum difference values of air-displacement plethysmography (ADP) and the Siri 3-compartment (3-C) model in a mobile trailer; and to identify any environmental fluctuations in the trailer.

Firefighters were examined on two separate days at the same time of day (±2 hours) following an eight hour fast. Body composition was measured using air-displacement plethysmography and bioelectrical impedance spectroscopy. Muscular strength was also assessed with a portable load-cell testing device.

The findings suggest that ADP can reliably determine percent body fat when transported in a climate-controlled mobile trailer. Additional accuracy is achievable with the Siri 3-C model, providing an attractive and promising method to measure body composition in larger scale community-based settings.

“Given its consistency, ease of use, and ability to accommodate a wide range of populations, the mobile body composition trailer may provide an attractive means to examine percent body fat in many field and community based settings,” Ryan said.

Read the full results from this study in Clinical Physiology and Functional Imaging.


This research is funded by the UNC Nutrition Obesity Research Center and the UNC Nutrition Research Institute. For more information about using the mobile body composition trailer in your research project, please visit the UNC Nutrition Research Institute’s Human Research Core’s web site or contact Jomari Torres.

Research Details

  • Research Center: University of North Carolina at Chapel Hill
  • Featured NORC Member(s): Eric Ryan, PhD, Assistant Professor of Exercise and Sport Science; Abbie Smith-Ryan, PhD, CSCS, CISSN, Assistant Professor of Exercise and Sports Science
  • Center Contribution: The UNC Clinical Research Concierge provided assistance with obtaining initial IRB approval and reviewed all study related forms and documents. The UNC Human Research Core performed all body composition assessments for this study.

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