This multi-joint move sculpts your shoulders, upper back, and triceps while also activating your abs to maintain your balance.
How to do it: Grab a pair of dumbbells and stand with your elbows bent by your sides. Shift your weight onto your right leg, left foot extended off the floor behind your hip, hinging slightly forward from your hips to make a straight line from your left foot to your head. Extend your right arm up by your ear into a shoulder press, palm facing in, as you extend your left arm back into a triceps extension. Bend both elbows back in by your sides and repeat, switching arms (left arm goes up, right arm back). Continue alternating sides for 30 seconds, then change legs and repeat for 30 more seconds.
Too tough to balance on one leg? Let your back foot lightly touch the ground until you feel ready for the more challenging version.