Caffeine is a proven performance enhancer, and it's legal, too. Doping agencies don't mind it showing up in a urinalysis at all. But how exactly does caffeine work?

New research reports that caffeine operates by upping the power output of muscles through a release of muscle-stored calcium. You can go farther and faster, and it can also help alleviate the brain's sense of exhaustion. A mind-body cuppa whammo. But should you be drinking a pot of coffee before the big race, a Big Gulp soda or just a tiny European-sized cup, no refills included? Previously, experts thought five to six milligrams of whammo per kilogram of body weight was the right stuff, but one expert newly reports just one milligram works. That ratchets down the 20 ounces of coffee a 176-pound man should drink at the five-to-six milligram level, to just four ounces of coffee or around two 12-ounce Cokes.

Too much is not a good thing -- one study found nine milligrams per kilogram resulted in a drop in performance. Perhaps that's why I can't tolerate caffeine before a workout to realize any of its reported benefits -- I get shaky and feel sorta icky. That Starbucks grande is simply way too much. Let's not forget caffeine's third pre-fitness benefit for many: "Runners World" reminds us it cleans out the poop pipes. Do you lean on caffeine before approaching the fitness starting line? Let us know below.

Do you caffeinate before fitness?

Yes, but only because I'm a chronic user, fitness or not.Yes, for better performance.Yes, for performance and a pipe cleanse.No, it hurts my performance.No, I'm not a caffeine drinker.SometimesVote