Tone your arms, and work your core too, with this double-duty move.
Credit: David Martinez

You’ll need: One pair of 5- to 15-pound dumbbells

Do it: Stand with feet shoulder-width apart, holding a dumbbell in each hand, palms facing forward, arms at sides. Bend arms at elbows, and curl weights straight up in front of shoulders, then lower.

Learn: Standing curls benefit more than your arms; they also help tighten your core. “Each time you curl the weights, your body has to use core stabilizing muscles to prevent you from tipping forward,” says Jeff Bell, CSCS, owner of Bell Fitness Company in New York City.