Purpose and method: To investigate the possible role of carbohydrate (CHO) receptors in the mouth in influencing exercise performance, seven male and two female endurance cyclists (VO(2max) 63.2 +/- 2.7 (mean +/- SE) mL.kg*(-1).min(-1)) completed two performance trials in which they had to accomplish a set amount of work as quickly as possible (914 +/- 40 kJ). On one occasion a 6.4% maltodextrin solution (CHO) was rinsed around the mouth for every 12.5% of the trial completed. On the other occasion, water (PLA) was rinsed. Subjects were not allowed to swallow either the CHO solution or water, and each mouthful was spat out after a 5-s rinse.
Results: Performance time was significantly improved with CHO compared with PLA (59.57 +/- 1.50 min vs 61.37 +/- 1.56 min, respectively, P = 0.011). This improvement resulted in a significantly higher average power output during the CHO compared with the PLA trial (259 +/- 16 W and 252 +/- 16 W, respectively, P = 0.003). There were no differences in heart rate or rating of perceived exertion (RPE) between the two trials (P > 0.05).
Conclusion: The results demonstrate that carbohydrate mouth rinse has a positive effect on 1-h time trial performance. The mechanism responsible for the improvement in high-intensity exercise performance with exogenous carbohydrate appears to involve an increase in central drive or motivation rather than having any metabolic cause. The nature and role of putative CHO receptors in the mouth warrants further investigation.