Dual Energy X-ray Absorptiometry (DEXA)

• Equipment:  Hologic QDR-4500™ bone densitometer, Hologic Inc, Bedford, MA.

• Technique:  DEXA is based on the three component model of body composition.  DEXA uses two X-ray energies to measure body fat, muscle, and bone mineral.  When having the scan done, one must lay still in the supine position on what looks like an x-ray table.  It takes approximately 15 minutes for the computer software to produce an image of the tissues.  The results may be viewed as whole body estimates of body fat, muscle, and bone mineral.  Separate films may be viewed for bone density only for the lumbar spine, hip, and forearm.  DEXA takes bone mineral content into consideration when estimating body fat and muscle, therefore it is considered to be more accurate and valid than a two component model of body composition such as underwater weighing.

Bioelectrical Impedance

• Equipment:  Multiple-frequency bioelectrical impedance device, model 4000B, Xitron Technologies, San Diego, CA.

• Techniques:  The bioelectrical impedance system allows for the in vivo prediction of total body water, extracellular water and intracellular water.

Whole Body Plethysmography

• Equipment:  The BOD POD Body Composition System®, Life Measurement Instruments, Concord, CA.

• Technique:  This system measures whole body mass and volume, which are then used to estimate whole body density.  Once whole body density is measured, the relative proportions of body fat and lean body mass can be calculated using population-specific equations which relate body density to body fat and lean tissue masses.

Anthropometrics

• Techniques:  Standardized techniques are available for the measurements of whole body mass, height, various skinfold thicknesses and body circumferences.