GLOSSARY

Maximal Exogenous Carbohydrate Oxidation is the highest measured exogenous carbohydrate oxidation under a specified protocol; it is not a universal personal intake target.

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.

Glucose and galactose use intestinal SGLT1 transport, while fructose uses GLUT5. Combining suitable carbohydrate sources can engage different absorption pathways and increase exogenous carbohydrate availability under relevant conditions. Maltodextrin yields glucose units during digestion rather than creating a separate fructose transport pathway. The blend, total intake, fluid provision, exercise and tolerance all matter. No single glucose-to-fructose ratio or hourly intake is a universally optimal prescription for every athlete and event.

For example, a tracer study may show a different oxidation rate after two carbohydrate drinks. Before translating that finding into a race plan, check the amount consumed, exercise duration, fluid provision and the performance outcome. A larger intake or oxidation value is informative without independently proving that the same strategy will suit every athlete.

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.

Glycogen use depends on exercise intensity, duration, recruited muscles, training status and starting availability. A decline in one sampled muscle or fiber population should not be assumed to represent all stores throughout the body. Carbohydrate feeding can support blood glucose and performance during suitable exercise, but it does not guarantee uniform sparing of muscle glycogen. Depletion is a change in a finite pool, whereas depletion rate specifies the speed over an observation interval.

Gut training means practicing the intended food and fluid strategy during suitable training sessions and progressing according to tolerance. Repeated exposure may improve comfort or handling, but symptom improvement does not directly prove increased transporter expression in an individual. Glucose and fructose transport involve different proteins and their adaptation is a specific research question. Record actual intake, conditions and symptoms. A very high intake used successfully by one athlete should not be treated as the starting requirement for everyone.

A nutritional strategy should be evaluated by the quality and relevance of evidence, the athlete's response and the feasibility of implementation. Molecular signaling, a substrate-oxidation change, a laboratory capacity test and race performance are different outcomes. Association does not establish cause, and a response in one small study need not generalize to all athletes. Define the intended benefit before changing the plan, then evaluate training quality, recovery and performance under comparable circumstances rather than judging success by novelty.