Give yourself a reward before you hit the gym: Dark chocolate might increase your exercise performance.

University of California researchers gave mice a dose of epicatechin, a purified form of cacao’s most prevalent flavonoid and had them hit the treadmill. The mice ran 50 percent farther and faster than the control mice who received water. The experts predict similar results in humans, but don’t go celebrating with a king-size candy bar.

You need only five grams (about the size of one Hershey’s Kiss) to reap the benefit.

Don’t you just hate the fine print?