Stand in front of a step or plyo box (6 to 18 inches high) with dumbbells in hand. Step up with one leg, keeping foot pointed straight ahead and knee lined up over mid-foot. Push through the heel and stand up straight, balancing on one leg. Flex the other leg at the hip and knee. Once balanced, curl, then press dumbbells overhead. Lower dumbbells, return lifted leg to the ground, step off box to starting position. Switch legs. Repeat.