The One Lower-Body Exercise From Blake Lively’s Trainer You Should Add to Your Routine

by Jenny McCoy

"Though sliding leg curls are a hamstring-dominant move, “as your hamstrings fatigue, you will feel it in your glutes too," James Brewer, NYC-based certified personal trainer and certified Spin and TRX instructor, tells SELF.

That’s because the glutes—specifically the gluteus maximus (the biggest muscle in your butt) and gluteus medius (a smaller butt muscle that muscle supports the hip and rotational movement of the thigh)—serve as stabilizers during the move, says Brewer. “If your butt drops as your legs extend forward, that defeats the whole movement,” he adds.”