The Effect of Carbohydrate Mouth Rinse on 1-h Cycle Time Trial Performance
JAMES M. CARTER, ASKER E. JEUKENDRUP, and DAVID A. JONES Human Performance Laboratory, School of Sport and Exercise Sciences, The University of Birmingham, Edgbaston, Birmingham, UNITED KINGDOM
ABSTRACT CARTER, J. M., A. E. JEUKENDRUP, and D. A. JONES. The Effect of CarbohydrateMouth Rinse on 1-h Cycle Time Trial Performance. Med. Sci. Sports Exerc., Vol. 36, No. 12, pp. 2107–2111, 2004. 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 ˙ (VO2max 63.2 2.7 (mean SE) mL·kg 1·min 1) completed two performance trials in which they had to accomplish aset 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 withCHO 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 thatcarbohydrate 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. Key Words: EXERCISE,MALTODEXTRIN SUPPLEMENTATION, MOUTHWASH, MOUTH RECEPTORS
arbohydrate (CHO) ingestion immediately before and during exercise of a relatively short ( 1 h) and ˙ intense nature ( 75% VO2max) has been reported to improve exercise performance. These reports include exercise performed in thermo-neutral (1,2,11,14,21) and hot ambient conditions (3,6,20), although there are also a few studies thathave found no such effect (7,17,19). The mechanism responsible for any improvement in highintensity exercise with the ingestion of exogenous CHO is unclear. One possibility is the maintenance of high CHO oxidation rates, as in the case of CHO feeding during prolonged, moderate-intensity exercise (8,10). However, Jeukendrup and colleagues (14) have argued that this is unlikely to be the case inhigh-intensity exercise, as it was estimated that only 5–15 g of exogenous CHO are oxidized in the first
Address for correspondence: A. E. Jeukendrup, Human Performance Laboratory, University of Birmingham, Edgbaston, B15 2TT, Birmingham, United Kingdom; E-mail: firstname.lastname@example.org. Submitted for publication November 2003. Accepted for publication July 2004. 0195-9131/04/3612-2107 MEDICINE& SCIENCE IN SPORTS & EXERCISE® Copyright © 2004 by the American College of Sports Medicine DOI: 10.1249/01.MSS.0000147585.65709.6F
hour of exercise. This relatively small contribution to the total CHO oxidation rate was thought too small to significantly improve exercise performance. Consequently, whereas the balance of opinion is that oral CHO supplementation is effective in improving 1-hhigh-intensity exercise performance, there is no clear metabolic explanation for this effect. Recently, we studied the effects of glucose infusion (as opposed to oral administration) on performance during a simulated 40-km time trial. This mode of administration was used partly to negate interindividual differences in the rate of glucose absorption. Surprisingly, although there was abundant...