Swimmer Michael Phelps is the most decorated Olympian of all time. He has won 28 medals total, and 23 of them are gold. No big deal or anything. He's annihilated world records left and right, retired and then come back stronger than ever, and even married the former Miss California on the D.L. So it's no wonder that when he walked into a Starbucks with his wife and pal (likely Australian swimmer Grant Hackett, if Instagram stalking is any indication), the barista behind the counter scrawled a different name on his cup: "The GOAT" (greatest of all time). (His wife, Nicole, and friend got "Wife of GOAT" and "Friend of GOAT" respectively on their own cups.) 

In an Instagram post, Phelps wrote, "Interesting names on our Starbucks cups today... Made us all laugh." It's probably the one time a Starbucks' name "misspelling" has been appreciated, but there was something even more interesting marked on the cups: the number of espresso shots. Mr. and Mrs. Phelps seem to have a truly amazing tolerance for caffeine. Michael's medium—ahem, Venti—drink contains four shots of espresso, while Nicole's tall coffee has three. That's a lot of caffeine to consume in one day, let alone one sitting. 

So let's do some math. The Mayo Clinic says that 400 milligrams of caffeine a day is safe for most people. One "venti" cup of Starbucks Pike Place roast has 310 milligrams of caffeine. Starbucks says that one shot of their espresso contains about 75 milligrams of caffeine. All told, then, Michael is drinking about 610 milligrams of caffeine. 

So yes, it's a lot. However, "most people" aren't 6-foot-4 Olympic champions with insane, energy-depleting workout regimens and a history of 12,000-calorie diets. And it also takes a lot to actually, fatally overdose on caffeine. So as long as Phelps isn't downing, like, 70 Venti coffees with four shots of espresso, he should be just fine.