In a study way back in 2004, Dr James Carter had cyclists undertake a water-only 40km time-trial. After a rest period, they repeated the test but this time they rinsed their mouth with a maltodextrin solution for 5secs without swallowing. Remarkably, the cyclists were, on average, one minute faster with the carbohydrate solution.
Numerous studies have since corroborated Carter’s results. Why is yet to be fully explained but there’s a convincing argument that nerves in the mouth send messages to parts of the brain that control motivation, pain tolerance and motor control. So even if the body gets no actual energy boost from the carb water – rather a transient sensation – the rinse may activate the brain, boosting strength and endurance.
Now, further research by Belgian Kevin De Pauw reveals that sniffing a glucose spray could also provide a boost when your ride begins to hurt. De Pauw showed that the nasal spray activates an area of the brain called the anterior cingulate cortex that’s related to how hard or easy you find a particular swim, bike or run session.
Finally, there’s another positive swilling study by Professor Thomas Jensen and his team, currently in press at the journal Medicine and Science in Sport and Exercise, which shows improved time-trial performance after ‘swilling’ during 120mins of cycling. The authors reported significant changes in muscle recruitment and time over the last 20% of the time-trial, suggesting mouth rinsing helps to prevent fatigue.
The research concludes that mouth rinsing is more potent during high-intensity sessions lasting around an hour, with even better results deriving after eating a high-carbohydrate meal around 2-3hrs before your swim, bike or
Carb rinsing’s also a useful nutritional strategy for individuals undertaking exercise for weight management purposes. Such a strategy would likely result in a lower perception of effort and/or higher exercise intensities without the intake of additional calories.