In a previous blog we discussed the effect of a simple mouth rinse with a carbohydrate solution on exercise performance. Carbohydrate mouth rinses have received quite a lot of attention (in fact this field seems to have exploded) and many studies have explored the effects of this mouth rinse on different modalities of exercise. However, it appears that the mouth rinse is most potent during exercise that is all out and lasts roughly one hour. The graph here focuses on that type of exercise. I have updated the graph from a previous article with a few new studies. The conclusion hasn't changed: there is a consistent effect of a mouth rinse on this type of performance. This effect is greater when the test is performed in the fasted state. The effects also seem exaggerated when tests are used that measure time to exhaustion rather than time trials.
Not all studies were included. I took the liberty to exclude 2 studies that had extremely low statistical power and therefore never had a chance of finding any effect (and indeed they did not find an effect). Power calculations should be part of an ethics application and low statistical power should also be picked up by reviewers! I may also have left out studies with positive effects.
Another interesting study is a study by Jensen et al that is in press at Medicine and Science ins Sprot and Exercise. This study showed improved time trial performance after 120 min of cycling. The authors reported significant changes in muscle recruitment and time over the last 20% of the TT, along with an average 1.7% improvement in TT time, suggest CHO mouth rinse helps maintain power output late in TT's compared to placebo.
References (newer studies)
James RM, Ritchie S, Rollo I, James LJ. No Dose Response Effect of Carbohydrate Mouth Rinse on Cycling Time-Trial Performance. Int J Sport Nutr Exerc Metab. 2017 Feb;27(1):25-31.
Jensen M, Klimstra M, Sporer B, Stellingwerff T. Effect of Carbohydrate Mouth Rinse on Performance after Prolonged Submaximal Cycling. Med Sci Sports Exerc. 2017 Dec.
Murray KO, Paris HL, Fly AD, Chapman RF, Mickleborough TD. Carbohydrate Mouth Rinse Improves Cycling Time-Trial Performance without Altering Plasma Insulin Concentration. J Sports Sci Med. 2018 Mar 1;17(1):145-152.