Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance

by Alex Hutchinson

It wasn’t until 2009 that researchers at the University of Birmingham settled the debate, with a study that confirmed the performance benefits of swishing and spitting a carbohydrate drink—and used functional magnetic resonance imaging to show that brain areas associated with reward were lighting up as soon as the subjects had carbohydrate in their mouth.30 Crucially, neither the brain scan nor cycling performance showed any effects when the drink was artificially sweetened, but the benefits returned when maltodextrine, a tasteless and undetectable carbohydrate, was added to the artificially sweetened drink. The sweet taste of sugar, in other words, is not enough to trigger the benefits. Instead, the mouth appears to contain previously unknown (and as yet unidentified) sensors that relay the presence of carbohydrate directly to the brain. In Tim Noakes’s central governor framework, it’s as if the brain relaxes its safety margin when it knows (or is tricked into believing) that more fuel is on the way.