Alpha Progression
DEXA scan
A DEXA scan, also abbreviated DXA, uses two X-ray energy levels to estimate bone mineral content, fat mass, and lean soft tissue. "DEXA" and "DXA" both refer to dual-energy X-ray absorptiometry. A whole-body scan can report total and regional body-composition estimates, while clinical bone-density examinations have a different primary purpose.
During the scan, a person lies still while a scanning arm passes over the body. The system models how the two X-ray beams are attenuated by different tissues and assigns the result to bone mineral, fat, and lean-soft-tissue compartments. DXA does not directly measure individual muscles. Lean soft tissue includes water and non-bone, non-fat tissues, so a change in that compartment should not automatically be called new muscle.
DXA is often more informative than a household bioimpedance measurement, but it remains an estimate rather than an error-free reference. Hardware, calibration, analysis software, positioning, food and fluid intake, recent exercise, glycogen, and hydration can affect results. IOC-associated recommendations on body composition describe DXA as reliable for estimating fat and lean masses when standardized protocols are used, not as a universally exact test.
For progress tracking, compare scans from the same machine and facility under similar preparation conditions. Look at changes larger than the facility’s expected measurement variation and avoid overinterpreting small differences between body regions. Apparent left–right differences do not by themselves diagnose a muscular asymmetry, because positioning and compartment assumptions also influence the image.
DXA uses a low dose of ionizing radiation, but the dose is not zero. The facility should determine whether a scan is appropriate and how often it should be repeated, particularly when pregnancy may be relevant or when the scan has a medical purpose. A 2023 systematic comparison of DXA and BIA in athletes also cautioned against treating the two methods as interchangeable and emphasized medical justification for DXA exposure.
Use a DEXA result as one part of a wider picture. For body recomposition, body weight, circumferences, training performance, and standardized observations can help distinguish a meaningful trend from measurement noise.
