Caffeine stalls fatigue so you can exercise longer and harder.
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While caffeine can do wonders to improve your mood and alertness, it offers an even bigger benefit to your workout by making you last longer. "The most sustained and valuable feature of caffeine is that it reduces our perception of fatigue, effort, or pain," says Burke. In other words, you'll feel less tired and more energized to run, swim, lift weights, or whack tennis balls after a cup of coffee, Red Bull, or energy gel.