Carbohydrate Mouth-rinse

Several studies have reported that carbohydrate (CHO) ingestion can improve performance during exercise of short duration (less than 60 min). However, there is no apparent metabolic explanation for this observation because endogenous CHO stores should not be a limiting factor during short duration exercise. 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 CHO oxidation or performance. Using this rinse, studies have demonstrated results both for (5, 16), and against (1, 19) 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 using a CHO-mouth rinse. 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. The investigators will test the hypothesis that CHO-mouth rinse improves performance in the fasted-state only compared with a placebo-rinse.