GLOSSARY

Under-Fueling Eating insufficient food or fuel for the person's activity and physiological needs, whether occasional or persistent.

Energy availability describes dietary energy remaining after exercise expenditure, expressed relative to fat-free mass over a defined period. It differs from whole-day energy balance and from body-fat percentage. Calculations are sensitive to errors in food records, exercise expenditure and body-composition estimates. No single threshold or short observation establishes a diagnosis for every athlete. Persistent fatigue, impaired recovery or other concerning changes warrant assessment in the broader health and training context rather than a conclusion from one calculated value.

Relative energy deficiency in sport describes impaired health or function associated with problematic low energy availability and can affect female and male athletes. The duration, severity and individual context matter. No isolated body weight, symptom, hormone value or calculated energy-availability threshold can diagnose every case. Clinical assessment integrates history, signs, measurements and alternative explanations. The IOC assessment framework supports trained clinicians; it is not a self-scoring clearance tool. Management addresses energy supply and training while considering psychological support and the athlete's overall safety.

External training load describes the work performed, such as distance, power or repetitions. Internal load describes the athlete's response, such as heart rate or perceived exertion. Volume, intensity and duration contribute differently, so one summary number does not reveal all nutritional demands. Two sessions with similar duration can differ greatly in carbohydrate use and recovery needs. Food planning should reflect the actual work and subsequent schedule, while persistent mismatch between intake and load deserves review.