Great to see our collective applied research making it into sport! Great article in @nytimes on apparent CHO mouthwashing at the World Cup. Great to also get quoted along with @Jeukendrup & @Rollo_I – https://t.co/D0J8JzTPGG
— Trent Stellingwerff (@TStellingwerff) July 11, 2018
The New York Times was undoubtedly right in speculating that the English World Cup team was practising carb rinsing (also known as mouth washing). Carb rinsing refers to the practice of swishing with sports drinks for five to ten seconds during exertion, but then spitting it out instead of swallowing.
Swishing with a carb-laden drink is refreshing and lets you avoid the feeling of bloating or cramping that may come with swallowing liquid, but carb rinsing has been shown to actually provide an energy boost. And it’s particularly beneficial to runners. (There actually isn’t much research on the benefits for soccer players. It may simply be the players’ belief that it works, rather than any hard evidence, that accounts for the practice.)
It’s believed that the practice works to trick the brain and central nervous system, via pleasure and reward receptors in the mouth, into expecting more energy to be available. It’s not a conscious thing, but it’s been proven to work.
The first study to suggest this, back in 2004, was done on cyclists. The times of cyclists who carb rinsed were a minute faster over a 40K time trial. Another study on fencers showed greater lunging accuracy after carb rinsing.
In 2014 physiologist Trent Stellingwerf of the Canadian Sport Institute Pacific reviewed the literature on carb rinsing, examining 61 studies on a total of 679 people. His review showed that 82 per cent of the studies demonstrated significant benefits to performance, as compared with rinsing with water.
Of course, runners do actually need to ingest the carbs at some point, to maintain glycogen stores for fuelling. The rinsing works best during periods of exertion lasting under an hour. For runs of longer than two hours, it’s best to both swish and swallow.
Recent research indicates the benefits to carb rinsing (increased focus and decreased fatigue) last about 15 minutes.
Best to choose a sports drink that’s not loaded with sugar, since swishing and spitting does nothing to reduce cavities.