Caffeine has a number of effects that will make a difference during your workout, so much so that it was once on the Olympics’ list of forbidden substances, with the blood-level equivalent of 8 cups of coffee enough to get an athlete banned from the Games. Caffeine is found naturally in coffee beans, tea leaves, and chocolate, and is a popular added ingredient in carbonated beverages and some over-the-counter medications such as cold remedies, diuretics, aspirin, and weight control aids. Though caffeine is no longer banned, the IOC still tests for its presence, reserving the right to re-ban caffeine if it starts finding elevated levels in a large number of competitors.