The impact of a sucrose mouth-rinse in the fasted and fed-state on time trial performance

Several studies have reported that carbohydrate (CHO) ingestion can improve
performance during exercise of short duration (less than 60 min) (4, 7, 10,
11). However, there is no apparent metabolic explanation for this observation
because endogenous carbohydrate stores should not be a limiting factor during
short duration exercise (11). Nonetheless, several groups have attempted to
investigate CHO administration during short duration exercise with varying
results. When CHO was administered intravenously, no performance effect was
observed despite greater plasma glucose availability (5). Therefore, it was
suggested that during exercise of short duration, exogenous CHO ingestion may
exert its ergogenic effect by action through the central nervous system,
possibly mediated by glucose receptors in the mouth. The latter has been
investigated using a CHO-mouth rinse, whereby the CHO solution is spat out to
remove any influence of the gut on exogenous carbohydrate oxidation or
performance. Using this rinse, studies have demonstrated results both for (5,
18), and against (1, 21) any improvement in short duration exercise performance
when compared with a placebo. The discrepancy in the findings may be due to
testing subjects in the fed (1) or fasted-state (5), when liver glycogen stores
may be compromised. However, no study has tested subjects in both the fasted
and fed-state. It remains to be determined whether CHO-mouth rinse is only
effective at improving short duration exercise performance when subjects are in
the fasted, compared with the fed-state.

To assess time trial performance in the fasted and fed state while
mouth-rinsing with a carbohydrate solution and/or a placebo.

Double-blind, randomized cross-over placebo controlled study.

carbohydrate

Exercise has minimal risk.
The minimal risk outweighs the total time involved (17 h).