GLOSSARY

Magnetic Resonance Imaging (MRI) uses magnetic fields and radiofrequency signals to generate images and estimate anatomical tissue characteristics or volumes. It does not use ionizing radiation, and acquisition and segmentation determine the quantified result.

Imaging methods answer different anatomical questions. MRI can quantify tissue volumes without ionizing radiation, CT uses X-rays and provides detailed images, and ultrasound assesses local tissue interfaces and thickness with operator-dependent procedures. A local muscle thickness is not automatically whole-body muscle mass. Standardize landmarks, positioning and analysis boundaries for repeat testing. Choice of method should follow the actual question, practical constraints and clinical indication rather than assuming that a technologically complex image is always necessary for sports-nutrition decisions.

Body-composition models divide the body into components according to a defined level. A two-component model often separates fat mass from fat-free mass. Adding measured water or mineral information can reduce some assumptions in more complex models, but no model removes all error. Molecular, cellular and tissue descriptions are different ways of organizing the same body. Before comparing results, identify the model, measured variables and assumptions rather than treating all reported components as directly measured anatomical tissues.

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.