Just when your brain is about to let you know it’s quitting time, a little self-encouragement can push you to go farther. In a study published in Medicine & Science in Sports & Exercise, researchers had 24 trained cyclists ride to exhaustion. Then half of the group was taught to use positive self-talk when the going got tough. “Popular choices included ‘Drive forward,’ ‘Feeling good,’ ‘I can do this,’ and ‘Go for it,’” says lead researcher Samuele Marcora of the School of Sport and Exercise Sciences, University of Kent. After two weeks, the riders were tested again. Though both groups maintained roughly the same heart rate, those who received instruction pedaled 18 percent longer, and their perceived exertion increased more gradually. Using negative phrases such as, “Man, this is hard,”…