Bigger glutes are in — but so are perkier derrières. For that goal, you need to focus on the “underbutt,” aka “where the lower section of the glutes joins with the upper section of the hamstrings,” says personal trainer Rachel Butler-Green, CSCS. Commonly called “the glute-ham tie-in,” she adds, it’s “really the muscular development of … Continue reading 10 “Underbutt” Exercises for a Perkier Derriere