Newswise — The margin in winning a medal in the 100-meter sprint at the Rio Olympics was a mere two-tenths of one percent of the winning time! With such small differences separating levels of athletic success, competitors often resort to sport supplements to improve their chances of winning. Research suggests that a sport supplement may improve performance purely because of the belief it will work. This is often termed a placebo effect. In this study, scientists aimed to discover if the placebo effect influences sprint performance. Over 700 athletes ran five sprints before taking a placebo they believed was a supplement. Athletes then ran another five sprints. Results indicated that no placebo effect was shown in the second five sprints compared to the first five. However, further analysis revealed that athletes who intended to use sport supplements ran 1.3% faster compared to those not intending. Given that 0.2 percent in sprint time could be the difference in winning a medal or not, a sport supplement may improve performance only when athletes intend to use it.