GLOSSARY

Lean Mass Gain is an increase in a specified lean compartment. Water, organs and glycogen-related changes can contribute, so the result should not automatically be called new muscle protein.

Fat loss, muscle gain and scale-weight change are separate outcomes. An athlete can lose fat while body mass remains similar, or gain scale weight through glycogen and water without gaining much muscle. The pattern depends on starting composition, training stimulus, energy intake and protein provision. No fixed surplus or deficit guarantees the same tissue response in everyone. Assess the intended adaptation over time using standardized measurements and performance, rather than judging a nutrition strategy only by the speed of scale change.

Skeletal muscle contributes force and movement, but muscle quantity and performance are not identical. Training quality, neural adaptations, architecture and task specificity matter alongside tissue mass. Resistance exercise and adequate nutrition can support muscle gain or preservation, while energy restriction may make this harder. A larger measured lean compartment does not automatically demonstrate a larger muscle compartment. Interpret body-composition changes alongside strength, function and the demands of the sport rather than using mass alone as the outcome.

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.