This is not Instagram boxing. At Matt Baiamonte’s, you learn how to throw a proper punch (and, occasionally, take one too). The gym is run by real boxers with the noses and cauliflower ears to prove it. And they’ll put you through the same workouts that they used to go through themselves—which can be quite punishing. Boxers are some of the most well-conditioned athletes on the planet and after one class here, you’ll understand why.