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Columns: A Nutritionist's View

Carbohydrate and Caffeine Mouth Rinsing and Exercise Performance

Volpe, Stella Lucia Ph.D., R.D., L.D.N., FACSM

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doi: 10.1249/FIT.0000000000000320
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Most research in nutrition and exercise performance focuses on the effects of food or supplements on exercise performance. However, some researchers have assessed the effect of simply asking athletes to use a mouth rinse of either carbohydrates or caffeine, or a combination of both, to evaluate if the mouth rinse would improve exercise performance. This may seem ineffective; however, the mouth rinse is thought to regulate brain activity (1). In this Nutritionist’s View column, I will review some of the research conducted on carbohydrate and caffeine mouth rinses and exercise performance.

CARBOHYDRATE AND CAFFEINE MOUTH RINSES AND EXERCISE PERFORMANCE

Beaven et al. (1) evaluated the effect of carbohydrate and caffeine mouth rinses on improving intermittent sprinting performance in 12 men. The men performed five sprints on a cycle ergometer, for 6 seconds each, with 24 seconds of active recovery. The men were required to rinse their mouth for 5 seconds before the intermittent sprinting with either a placebo (without any calories), a 6% glucose solution, or a 1.2% caffeine solution. These were all mouth rinses; therefore, the men did not ingest any of the solutions. Because this was a double-blind, crossover design study, none of the men knew which mouth rinse they were receiving. In addition, they all acted as their own control, because each participant received each one of the mouth rinses. In addition to comparing the three aforementioned mouth rinses, the researchers assessed the combination of the carbohydrate and caffeine solution with the carbohydrate solution alone.

Beaven et al. (1) reported that the carbohydrate mouth rinse improved peak power in the cycling sprint performance. They also reported that both the carbohydrate and the caffeine mouth rinses increased mean power in the cycling sprint performance. In addition, the combination of the carbohydrate and caffeine solutions augmented mean cycling sprinting power compared with carbohydrate alone. The researchers concluded that carbohydrate and/or caffeine mouth rinses can quickly improve power production during sprint cycling. The quick improvement in exercise demonstrates that there might be a more central mechanism for the ergogenic (performance enhancing) effect.

The “central mechanism” described by Beaven et al. (1) may be a result of a stimulation of the oral receptors, and subsequently, stimulation of the brain regions involved with reward (3). De Ataide e Silva et al. (3) state that the effect of mouth rinses might be heightened when muscle and liver glycogen stores are low.

Doering et al. (4) conducted a study to examine if a caffeine mouth rinse would improve a trial performance in 10 well-trained male cyclists (32.9 ± 7.5 years of age). The cyclists completed two 60-minute time trials after 24 hours of a standardized diet and exercise protocol. Standardizing dietary intake and exercise before the time trial for data collection strengthens the study, because the researchers were able to control what the athletes ate and how much they exercised the day before data collection. Like Beaven et al.’s (1) study, this was a double-blind, crossover design. In this study, the male cyclists were administered a 25-ml mouth rinse, to rinse for 10 seconds. They received either a placebo or 35 mg of caffeine, eight times throughout the 60-minute time trial. In contrast to Beaven et al. (1), the caffeine mouth rinse did not improve time trial performance or physiological variables measured (e.g., heart rate, blood lactate concentrations) compared with the placebo.

Clarke et al. (2) assessed the effect of carbohydrate and caffeine mouth rinses on resistance exercise. They researched the effects of carbohydrate and caffeine mouth rinses on maximum strength and muscular endurance in 15 resistance-trained men.

The weight training protocol used was a one-repetition maximum (1-RM) bench press (muscular strength assessment), which was followed by 60% of 1-RM for the bench press (number of bench presses until failure) (muscular endurance assessment). This, again, was a double-blind, randomized crossover design. Before each exercise, the participants were administered 25 ml of a placebo (water), a 6% carbohydrate solution, a 1.2% caffeine solution, or a combination of the carbohydrate and caffeine solutions. To ensure the participants could not distinguish among the solutions, all of the solutions were flavored with sucralose (a nonnutritive sweetener). The researchers also used the final training session to assess if no mouth rinse had an effect on the participants. There were no significant differences among the trials, regardless of the solution used as a mouth rinse. Therefore, these researchers concluded that a carbohydrate, caffeine, or a combination of carbohydrate and caffeine solution did not improve muscular strength or muscular endurance in these male participants.

In a systematic review, de Ataide e Silva et al. (3) examined previous research that assessed the effect of carbohydrate mouth rinses on exercise performance. The researchers deemed that 11 studies were suitable to use in their review. In 9 of the 11 research studies, a carbohydrate mouth rinse improved exercise performance during moderate- to high-intensity exercise (the exercise performed was generally an hour in length, at 75% of maximal oxygen consumption). Although they reported that, in general, the carbohydrate mouth rinses significantly improved exercise performance, there were many differences among the study designs that limit the generalizability of the findings.

SUMMARY

Carbohydrate, caffeine, or a combination of carbohydrate and caffeine mouth rinses may result in improved exercise performance. However, the research conducted thus far has demonstrated equivocal results. The reason for these differences may be due to the fact that the trials have been conducted primarily in trained men. In addition, the length of fasting before data collection differed among studies. Furthermore, the type of exercise, the exercise procedures, and sample sizes may provide some explanation for the differing results (3).

References

1. Beaven CM, Maulder P, Pooley A, Kilduff L, Cook C. Effects of caffeine and carbohydrate mouth rinses on repeated sprint performance. Appl Physiol Nutr Metab. 2013;38(6):633–7.
2. Clarke ND, Kornilios E, Richardson DL. Carbohydrate and caffeine mouth rinses do not affect maximum strength and muscular endurance performance. J Strength Cond Res. 2015;29(10):2926–31.
3. de Ataide e Silva T, Di Cavalcanti Alves de Souza ME, de Amorim JF, Stathis CG, Leandro CG, Lima-Silva AE. Can carbohydrate mouth rinse improve performance during exercise? A systematic review. Nutrients. 2013;6(1):1–10.
4. Doering TM, Fell JW, Leveritt MD, Desbrow B, Shing CM. The effect of a caffeinated mouth-rinse on endurance cycling time-trial performance. Int J Sport Nutr Exerc Metab. 2014;24(1):90–7.

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