Step by step instructions
Stand with feet hip-width apart next to a sturdy box (you'll eventually work your way up to 2 feet-tall). Keep hands in front to mimic Julia Mancuso's skiing posture and to maximize the use of your butt and hamstrings.
Bend both knees and jump up on top of the box, landing with both feet at once. Land with bent knees to absorb any impact. At the top, stand up straight to open hips and either step off or jump down with bent knees. Do as many reps as possible in the suggested time.