July 11, 2016
Robert Jeffers1, Robert Shave2, Emma Ross3, Emma Stevenson4 & Stuart Goodall4
1 School of Sport & Education, Brunel University, Uxbridge, UK.
2 Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, UK.
3 Physiology, English Institute of Sport, UK.
4 Faculty of Health and Life Sciences, Northumbria University, Newcastle, UK.
It is well known that carbohydrate (CHO) is of particular importance to an athlete’s diet and this is emphasised by a joint position stand from the American College of Sports Medicine and the American Dietetic Association and Dietitians of Canada on nutrition for athletic performance. It is accepted that CHO supplementation during prolonged exercise (>2 h) can delay fatigue and improve performance. The primary mechanisms responsible for improvements in performance have been linked to maintenance of blood glucose concentrations. However, improvements in performance have been absent when CHO is directly infused into the circulation, highlighting how important the mouth is for effective CHO supplementation. In the first study of its kind Carter and colleagues (2004) examined the effect of a CHO mouth-rinse on 1 hour cycling time-trial performance. At regular intervals throughout the task participants rinsed a 6.4% tasteless CHO solution or water around their mouth for 5 seconds and it was found that the CHO mouth-rinse improved performance by 3% (1 min and 48 seconds). Following this study, several others have also reported that mouth rinsing with a CHO solution can improve cycling and running performance when compared to a similar tasting CHO-free placebo.
Part of the benefit that a CHO mouth-rinse has is presumed to result from the stimulation of CHO taste receptors within the mouth which activate areas of the brain associated with reward and activity. Ultimately, stimulation of these areas can lead to an increased central drive to exercising muscles. We investigated whether an increased central drive during exercise could reduce the amount of fatigue in the working muscles. On two separate occasions a group of well-trained male cyclists completed 45 min at 70% peak power followed by a 15 min time-trial whereby they were instructed to complete as much work as possible. At 7.5 min intervals participants were given either a tasteless 6.4% maltodextrin mouth-rinse (CHO) or water in a double-blind fashion. We measured the maximum voluntary force of the quadriceps as an index of muscle fatigue pre and post the cycling task. There were significantly greater losses in maximal strength following the time-trial using water (20 ± 10%) compared to the CHO (12 ± 8%) mouth-rinse, however, the attenuation in strength loss did not translate into a time-trial improvement.
Our study was the first to examine the effects of a CHO mouth-rinse on time-trial performance and fatigue. No performance improvement was observed however; our results suggest that a CHO mouth-rinse can attenuate the reductions in maximal strength that occur during cycling. Despite the reduced fatigue, it is likely that the pre-exercise fasting period and duration of the exercise task influenced the performance effect. It would be anticipated that a CHO mouth-rinse will continue to have a pronounced effect on markers of fatigue and performance as the exercise duration exceeds 2 h and glycogen depletion becomes prominent. Moreover, the use of such a nutritional strategy might offset fatigue in moderate duration high intensity exercise, without the added gastrointestinal burden of CHO ingestion in the form of gels, liquid or food.
References:
Robert Jeffers, Robert Shave, Emma Ross, Emma J. Stevenson and Stuart Goodall. The effect of a carbohydrate mouth-rinse on neuromuscular fatigue following cycling exercise. Applied Physiology, Nutrition and Metabolism, 2015, 40(6): 557-564. dx.doi.org/10.1139/apnm-2014-0393
Carter, J.M., Jeukendrup, A.E., and Jones, D.A. 2004. The effect of carbohydrate mouth rinse on 1-h cycle time-trial performance. Med Sci Sports Exerc 36: 2107-11.
This article is a summary of an article published in Applied Physiology, Nutrition & Metabolism. If you intend citing any information in this article, please consult the original article and cite that source.