Exogenous substrate oxidation during exercise: studies using isotopic labelling.

This presentation summarizes the experimental data on the oxidation of exogenous substrates using isotopic labelling: glucose, fructose, maltodextrins, glucose polymers, starch and FFA. The two main determining factors for the oxidation of exogenous substrates are in this order: power output and amount of ingested substrates. The largest oxidation of exogenous substrate is observed for glucose, maltodextrins, Polycose, and starch. For exercises of one hour duration or more, the average rate of oxidation of these compounds can reach up to 0.5 g/min, which agrees with the indirect estimation of Coyle et al. Fructose is oxidized at a lower rate, except when it is taken before the exercise period. FFA are only oxidized to a small extent.