GLOSSARY

Muscle Energy Supply describes substrates accessible or delivered to muscle for energy production. Local storage, circulating supply and tissue uptake contribute differently.

Sports nutrition connects food and fluid provision with training, competition, adaptation and health. The appropriate plan depends on the sport, event duration, athlete, environment and available eating opportunities. Adequate energy and nutrient intake form the foundation, while timing and specialized products solve particular problems. A strategy supported in one exercise model is not automatically optimal for every sport. The useful outcome is the athlete's ability to train, recover and perform under the actual conditions.

Carbohydrate requirements vary with the intensity, duration and importance of the work. Daily intake relative to body mass describes a different quantity from an intake rate during exercise, which is commonly expressed per hour. A larger daily target does not mean the same amount should be consumed in every session. Match supply to the schedule, starting stores and practical tolerance, and distinguish grams eaten from grams absorbed or oxidized when discussing a fueling plan.

Muscle and liver glycogen have related but different roles. Muscle glycogen supplies the muscle in which it is stored, while liver glycogen helps support blood glucose. An overnight fast can reduce liver carbohydrate availability without producing the same depletion in every muscle. Starting concentration, recruited fibers and exercise demand affect use. An estimate of total stores does not directly describe the availability of every local glycogen pool during a specific movement.

For example, a muscle can use stored glycogen while also receiving blood glucose and fatty acids. Eating carbohydrate supplies an external source that must still be digested and absorbed. Describe which fuel and which process are being discussed instead of assuming that one named source provides all energy throughout the session.

Exogenous carbohydrate comes from food or drink, while endogenous carbohydrate comes from existing body stores. Digestion, intestinal absorption, circulation, muscle uptake and oxidation are separate steps. Tracer studies can estimate oxidation of ingested substrate under defined assumptions. The amount consumed is not the amount oxidized immediately, and a high measured oxidation rate does not alone prove better race performance. Specify the substrate source and the process measured before comparing research or planning intake.

Fat contributes to exercise energy through circulating fatty acids and intramuscular lipid stores. Greater fat availability, uptake or mobilization does not automatically mean a greater oxidation rate. Relative contribution and absolute rate are also different: the percentage can rise while total exercise demand changes. Oxidizing more fat during one session does not by itself establish greater long-term body-fat loss. Interpret the measured process, exercise intensity, diet and overall energy balance together.

Amino acids can contribute to energy metabolism during exercise, with contribution influenced by duration, energy and carbohydrate availability and training context. Oxidation of an amino acid is not identical to the rate of net muscle loss. Carbohydrate provision can reduce some amino-acid use under relevant conditions, while protein has important roles in repair and adaptation. BCAA or leucine oxidation is a specific process and does not establish that isolated amino-acid supplements are a superior exercise fuel.