Carbohydrate mouth rinsing has no effect on power output during cycling in a glycogen-reduced state.
BACKGROUND
The effect of mouth rinsing with a carbohydrate (CHO) solution on exercise performance is inconclusive with no benefits observed in the fed state. This study examined the effect of CHO mouth rinse or CHO ingestion on performance in 9 moderately trained male cyclists.


METHODS
Four trials were undertaken, separated by 7 days, in a randomized, counterbalanced design. Each trial included a 90-min glycogen-reducing exercise protocol, immediately followed by a low CHO meal and subsequent overnight fast; the following morning a 1-h cycling time trial was conducted. The trials included 15 % CHO mouth rinse (CHOR), 7.5 % CHO ingestion (CHOI), placebo mouth rinse and placebo ingestion. Solutions were provided after every 12.5 % of completed exercise: 1.5 mL · kg(-1) and 0.33 mL · kg(-1) body mass during ingestion and rinse trials, respectively. During rinse trials participants swirled the solution for 8 s before expectorating. Blood samples were taken at regular intervals before and during exercise.


RESULTS
Performance time was not different between trials (P = 0.21) but the 4.5-5.2 % difference between CHOI and other trials showed moderate practical significance (Cohen's d 0.57-0.65). Power output was higher in CHOI relative to other trials (P < 0.01). There were no differences between CHOR and placebo groups for any performance variables. Plasma glucose, insulin and lactate concentrations were higher in CHOI relative to other groups (P < 0.05).


CONCLUSIONS
In a fasted and glycogen-reduced state ingestion of a CHO solution during high-intensity exercise enhanced performance through stimulation of insulin-mediated glucose uptake. The CHO mouth rinsing had neither ergogenic effects nor changes in endocrine or metabolic responses relative to placebo.
School of Sport and Exercise, Massey University, Auckland, New Zealand.
Ajmol
A
Ali
School of Applied Sciences, Auckland University of Technology, Auckland, New Zealand.
Michelle Ji Yeon
MJ
Yoo
School of Sport and Exercise, Massey University, Auckland, New Zealand.
Catherine
C
Moss
School of Food and Nutrition, Massey University, Auckland, New Zealand.
Bernhard H
BH
Breier
D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling / Q000502:physiology; D001786:Blood Glucose; D004040:Dietary Carbohydrates / Q000378:metabolism; D004435:Eating; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D008297:Male; D009067:Mouthwashes / Q000378:metabolism; D058573:Performance-Enhancing Substances / Q000378:metabolism*; D013997:Time Factors; D016896:Treatment Outcome
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D009067:Mouthwashes; D058573:Performance-Enhancing Substances
Ergogenic aid; Fluid ingestion; Mouthwash; Sports drink; Supplementation; Time trial