GLOSSARY

Body Mass Index (BMI) Classification Table

Adult BMI categories are screening descriptors; they do not measure fat mass or establish an athlete body-composition target.

Body Mass Index (BMI) Body mass divided by squared height, used as a screening index whose interpretation depends on age and context.

Growth assessment compares accurate serial measurements with an age- and sex-appropriate standard or reference. Confirm exact age, measurement technique and the chosen chart. A percentile describes relative position; a z-score describes distance from the reference distribution under that chart's model. A change in trajectory can warrant assessment without establishing one nutritional cause. Adult body-mass categories do not transfer directly to children. For young athletes, interpret growth together with maturation, health and intake rather than treating a low body mass as evidence of superior fitness.

Repeated measurements become more informative when timing, clothing, scale, hydration and recent intake are comparable. An average can reduce random daily noise, but it can also conceal rapid changes that need attention. Keep individual values available and relate the trend to symptoms, food and training. Monitoring should have a clear purpose and appropriate frequency. More frequent weighing or scanning is not inherently better, especially if it increases distress or encourages restrictive eating without improving decisions.

Validity concerns whether a method estimates the intended quantity accurately, while reliability concerns consistency on repetition. A method can repeat well while remaining biased. Technical error and prediction error also describe different sources of uncertainty. Small changes should be interpreted relative to relevant measurement error, with the same protocol used over time. Agreement at group level does not guarantee close agreement for every individual athlete, and switching instruments can create an apparent change that is methodological rather than biological.