Swishing a sports drink around in your mouth and then spitting it out might sound like a nonsensical way to boost performance, but it's been nearly a decade since research first suggested that rinsing improves your workout. A study by sports scientists at University of Central Lancashire this April found that during an hour-long workout, cyclists who swished carbohydrate-rich sports drinks for longer covered more distance and felt less tired than after a five-second rinse or rinsing with water.
How the trick works may surprise you. Brain scans show that specific regions light up when carbs are in your mouth. The longer you rinse, the more time the carbs have to stimulate sensors in your brain, says study author Lindsay Bottoms. "The concept of mouth rinse supports the idea that the brain is very much playing a key role in fatigue," says Bottoms.
Swishing is most beneficial during relatively short, intense workouts. Not only can the rinse give you a performance boost of about 2 percent, but it also helps avoid indigestion from swallowing carbs during workouts. "When performing high-intensity exercise lasting less than 60 minutes, using a carbohydrate rinse for 5-10 seconds can improve performance," says Bottoms. "It could potentially allow you to train harder." If you're doing a couple hours of exercise, however, rinsing will start to lose its effect since your muscles really do need more carbs.