What’s going on back there? For some, it’s too much fat. For others, it’s the ability to hold a pencil under each cheek (handy, but annoying). And then there are those who complain — try to find pity for them — of having no butt at all.

Valerie Waters, the Los Angeles-based trainer behind Jennifer Garner’s and Jessica Biel’s behinds, prescribes a solution for kicking your own ass. Here are some of the butt workouts she recommends you try.

Abundance. Cardio Rx: Aim to do 45 to 60 minutes of intense cardio, four or more days each week. Try interval training on a treadmill or stationary bike (sprint for one minute, then recover at a reduced speed for two minutes), or run outdoors.

Sculpting Rx: Mini band side step. Place an elastic mini band around your ankles, and separate feet slightly wider than hip-width. Stand tall, knees bent, and step to the left. Bring the right foot in so there is still tension on the band. Take 15 steps, then repeat, leading with the right foot.

Single-leg squat. Stand with feet together. Lift right foot slightly; let it hover next to your left ankle. Press butt back and chest forward, lowering into a deep squat (put a bench behind you and lower down until you hit it). Push up through the heel and rise. Do ten reps. Switch legs and repeat.

Leg lift. Stand in front of a chair, lean over 90 degrees, and place both hands on the seat, forming a straight line from head to hips. Lift the right foot straight back until the leg is parallel to the floor. Hold and lower. Do 20 reps. Switch legs. Repeat the entire circuit three times. [via]