A

> Hold a medicine ball with hands in front of chest, elbows bent and tucked at sides, and stand on a 2-foot-high plyo box with feet together. Bend right knee slightly, dangling toes off the back edge of the box.

B

> Bend left knee and, keeping torso straight and abs tight, lower right foot toward the floor behind you. Straighten left leg to return to starting position and repeat. Switch sides to complete set.