During the 2018 World Cup, viewers and readers of the New York Times took notice of athletes performing carb rinsing. This is the act of irrigating their mouths, without ingesting the fluid. It is assumed that the players were rinsing with carbohydrate solutions.
Reported mechanisms for why carb rinsing improves performance:
- trick the brain into believe nutrients are coming, and so it allows the muscles to work harder
- boost energy levels for up to 15 minutes
- avoid cramps and bloating that arise from ingested carbohydrates
We know that the circuits that relay taste information are capable of activating dopamine circuits in the brain. There are also anecdotal observations in humans: the simple act of snacking reduces feelings of fatigue faster than it takes for ingested sugars to enter the bloodstream.
What about the scientific record? Below is a snapshot compiled from Andrew Hamilton at peakendurancesport:
While in summary, there does appear to be a positive performance benefit, there are also appear to be conditions / activities where carb-rinsing would not provide benefit.
It will be interesting in the future, if guidelines can be established by athletic trainers for productive carb rinsing.