A great article from Runners World
Not only can coffee be linked to health benefits, but it’s also a potent source of caffeine. And caffeine is one of the most popular ergogenic aids in the world for good reason—it works.
It can be more than just a morning pick-me-up. Caffeine has a number of physiologic effects that can help improve athletic performance. It is rapidly absorbed in the gastrointestinal tract and is a mild stimulant that affects multiple organ systems.
Caffeine is known to increase circulation of free fatty acids, which means that it’s glycogen sparing. And studies show that supplementation of caffeine (between 3-6mg/kg) is effective in reducing perceived exertion (meaning that six-minute mile feels like a seven-minute mile). In fact, studies have found that swimmers are faster after 6mg/kg body weight administered in a fruit juice drink two- to five hours before the swim and reported lower perceived exertion. And cyclists’ time to exhaustion was nearly 15 minutes longer while caffeinated with 330mg caffeine one hour before exercise.
Many runners rely on caffeine-laced gels, blocks, and beans for a mid-run pick me up. Because there are many levels of caffeine in these products, always be careful to check the label of your favourite flavor to see how much it might contain. In general, if a product contains caffeine, it likely offers somewhere between 25-100mg per serving. Athletes who don’t often use caffeine but want to try out a mid-run fuel with some kick would do well to start with a conservative 25mg dose and see how they respond.
Remember, while you may find that caffeinated fuel is just the kick you need to make it through a long run or race, the effect of this ergogenic aid can be cumulative. So if you consume double-espresso gels every hour of a long run, you should plan on staying up past your bedtime or until the post-run jitters wear off.
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