Mouth Rinsing With Carbohydrate Solutions at the Postprandial State Fail to Improve Performance During Simulated Cycling Time Trials

Abstract

Mouth-rinsing with carbohydrate solutions during cycling time trials results in performance enhancements, however the majority of studies have utilised ~6% carbohydrate solutions.Therefore, the purpose of this study was to compare the effectiveness of mouth-rinsing with 4%, 6%, and 8% carbohydrate (CHO) solutions on 1-h simulated cycling time trial performance. On four occasions, seven trained male cyclists completed at the postprandial period, a set amount of work as fast as possible in a randomised, counterbalanced order. The subjects mouth rinsed for 5-s, upon completion of each 12.5% of the trial, with 25 mL of a non-CHO placebo, 4%, 6%, and 8% CHO solutions. No additional fluids were consumed during the time trial. Heart rate (HR), ratings of perceived exertion (RPE), thirst (TH) and subjective feelings (SF) were recorded after each rinse. Further, blood samples were drawn every 25% of the trial to measure blood glucose (BG) and blood lactate (BG) concentrations, whilst whole body carbohydrate oxidation was monitored continuously. Time to completion was not significant between conditions with the placebo, 4%, 6%, and 8% conditions completing the trials in 62.0 ± 3.0, 62.8 ± 4.0, 63.4 ± 3.4, and 63 ±4.0 minutes respectively. There were no significant differences between conditions in any of the variables mentioned above however significant time effects were observed for HR, RPE, TH, and SF. Post-hoc analysis showed that TH and SF of subjects in the CHO conditions but not in the placebo were significantly increased by completion of the time trial. In conclusion, mouth-rinsing with CHO solutions did not impact 1-h cycling performance in the postprandial period and in the absence of fluid intake. Our findings suggest that there is scope for further research to explore the activation regions of the brain and whether they are receptive to CHO dose, before specific recommendations for athletic populations are established. Consequently mouth-rinsing as a practical strategy for coaches and athletes is questionable under specific 3 conditions and should be carefully considered before its inclusion. The emphasis should be focused on appropriate dietary and fluid strategies during training and competition.

The Effects of Carbohydrate Mouth Rinse Concentration on Cycling Time Trial Performance

“…Blood glucose, blood lactate, HR, RER, CHO oxidation, or RPE were also not different between trials (Ispoglou et al, 2015). During each trial, participants rinsed 25ml of the experimental solution for 5sec every 12.5% of the trial.…”

“…To date, three studies Ispoglou et al, 2015;Wright & Davison, 2013) have investigated whether there is an improvement in performance with higher CHO concentration mouth rinses. The varied exercise protocols, specifically the 30min protocol of Bottoms et al (2014) which may be too short of a duration and the small sample sizes of these studies limit the conclusions that can be drawn regarding a dose-response effect to CHO mouth rinse concentration and warrants the need for more research on the topic.…”

“…While performance was not different, cadence, speed, and power differed between trials suggesting that the rinse concentration affected participant pacing strategy but the abstract does not describe how ). Ispoglou et al (2015) found that following a 3h fast, 1h cycling time trial performance was not improved compared to a placebo (251 ± 28W) with a 4% (248 ± 28W), 6% (246 ± 31W), or 8% (247 ± 33W) CHO mouth rinse (Ispoglou et al, 2015).…”

“…During each trial, participants rinsed 25ml of the experimental solution for 5sec every 12.5% of the trial. The authors suggested that the increased perceived thirst during CHO trials and the lack of fluid intake may have influenced the results even though no relation between thirst and power was found (Ispoglou et al, 2015). Because of the protocol differences of rinse duration, concentration and frequency and small sample size it is difficult to draw conclusions regarding the effects of CHO mouth rinse concentration on exercise performance.…”

“…This duration may be too short to see any differences. As well, Ispoglou et al (2015) showed no cycling time trial performance differences when rinsing with a 4%, 6%, and 8% CHO solution.…”