GLOSSARY

Glucose–Fructose Blend combines glucose and fructose in the same intake plan. The total amount, ratio, fluid provision and individual tolerance determine practical use.

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.

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.

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.

For example, combining a glucose-yielding source with fructose can use different intestinal pathways during prolonged exercise. Check the whole plan, including the carbohydrate already present in drinks and food. The athlete still needs a tolerated total and appropriate fluid; choosing a blend does not create unlimited absorption or make every ratio equally suitable.

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.

Liquid, solid and semisolid sources can all contribute carbohydrate, with digestion and tolerance influenced by their composition and the exercise context. A drink may help combine fluid and fuel, while solid food can add variety during longer events. A concentrated gel may need to be coordinated with water according to its formulation and the plan. Combining forms should account for the total intake rather than counting each product in isolation or assuming liquid carbohydrate bypasses digestion and absorption limits.

Fluid planning should consider sweat losses, conditions, tolerance and opportunities to drink. Carbohydrate and fluid needs can differ, so a single beverage may not meet both without adjustment. Excessive drinking can also be harmful; more fluid is not always better. Sodium provision may be relevant in selected prolonged or high-loss situations, but it does not make unlimited drinking safe. Practice the combined food-and-fluid plan in training and evaluate actual intake and symptoms rather than relying only on a product label.