While you can do this move seated or standing, Mark Nutting, CSCS, fitness director of SACO Sport & Fitness in Saco, Maine, recommends that you stay on your feet. “It’s a more functional movement, because it more closely resembles activities you’ll do in real life, such as lifting luggage into an overhead compartment,” says Nutting. MORE: Stronger Arms And A Firmer Butt In One Move Like any move, form counts here. Make sure to keep your knees slightly bent, not locked, and core engaged. You want to avoid the common mistake of arching your back in order to hoist the weights overhead, which puts stress on the lower back. Instead, keep your back neutral—neither flat nor arched—and engage your core by contracting your abdominals. One word of caution: this move isn’t for everyone. “Some people don’t have enough shoulder flexibility to bring the weights overhead vertically,” Nutting says. If this is you, modify the exercise by doing it seated on an incline bench. Tilt the bench back slightly—about one notch, so you’re still nearly vertical—and then perform the move with the dumbbells just in front of your shoulders (instead of right next to your shoulders). “It’s a lot easier on the shoulder joint,” says Nutting. Whether you’re doing the full move or the modification, aim to do 2 or 3 sets of 12 to 15 reps twice a week for best results—and another great excuse to stock up on more summer tank tops. Those end-of-season sales make it okay, right?  MORE: 10 New Moves That Target Cellulite