Target your glutes and hamstrings with hip thrusts.

How to

1.    Lie on your back on the floor with your hands at your sides, your knees bent, and your heels on a small medicine ball.
2.    Tighten your abs and glutes, and thrust your hips upward off the ground towards the ceiling. Hold for a count, then lower yourself three-quarters of the way back to the floor, keeping your abs contracted, and repeat for the recommended number of repetitions.

How many sets & reps?

Week 1–2    5 sets    20–25 reps
Week 3–4    4 sets   15–18 reps
Week 5–6    3 sets   10–12 reps

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Workout from Nichelle Laus (pictured); photo credit: Dave Laus