GLOSSARY

DXA Reference Table

DXA estimates bone mineral and soft-tissue compartments using an imaging model; lean soft tissue is not identical to muscle protein.

Dual-Energy X-Ray Absorptiometry (DXA/DEXA) uses X-ray attenuation at different energies to estimate fat, lean soft tissue and bone mineral. Whole-body compartments depend on the device, software, positioning and preparation protocol.

DXA estimates fat, lean soft tissue and bone mineral from the attenuation of X-rays at different energies. It is not a direct chemical dissection of the body. Food, hydration, recent exercise, positioning, software and analysis boundaries can affect longitudinal comparisons. The same device and a standardized protocol improve interpretation. A small apparent lean-mass change may fall within normal variation or reflect glycogen and water, so compare it with the method's precision and relevant performance information.

Fat-free mass includes water, protein, minerals and other nonfat constituents. It therefore includes organs and bone as well as skeletal muscle. Lean body mass, fat-free mass and lean soft tissue can have different technical meanings, although terms are sometimes used loosely. A short-term rise in a device's lean-mass estimate can reflect hydration or glycogen rather than new contractile protein. Check the device definition and testing conditions before calling a change muscle growth.

Bone mineral content is an amount of mineral, whereas DXA bone mineral density commonly expresses mineral content relative to projected area. Neither is identical to the total mass of living bone, which also contains organic material and water. Interpretation depends on site, age, reference population and clinical context. Athletes need adequate energy and relevant nutrients as well as suitable loading. A single body-composition scan should not be used to make an independent diagnosis or to prescribe treatment without appropriate assessment.