David Kirsch shares the inside scoop about celebrity workout routines, including his effective butt workout routines.

When Anne Hathaway, Heidi Klum and Liv Tyler need to get fit fast, they go to David Kirsch. Find out how the stars shape up and what you can do to see A-list results.

Q: What butt workout tips can you offer from your booty-sculpting manual, Butt Book?

Q: Here's another butt workout question. How do you work the backside without building up the quadriceps?

A: If someone is worried about bulking up their quads, they're not going to do a traditional squat. They're going to do a wide-stance squat or a plie squat, which is second position dance, opening up your legs and bringing the focus to the inner thighs and not to the quads. Don't use excessive weight and keep repetitions high. I use body weight or a medicine ball or light hand weights.

[header = Celebrity workout routines: more about trainer of the stars, David Kirsch.]

Q: You're known for whipping celebs into shape in record time. What advice about workout routines do you have for those of us gearing up for bathing-suit season at the last minute?

A: It's going to be a combination of diet and exercise. You're going to clean up your diet. You're going to stay away from processed carbs and sugars. You want to increase your cardio. If you're doing 30 minutes a day, you want to do at least 45 minutes a day. You want to vary your cardio. If you do the treadmill or elliptical all the time, try adding the rowing machine or stair climber, maybe get a new bicycle. You want to keep it fresh.

Q: You helped Heidi Klum get back on the runway soon after giving birth. What workout routines and slim-down suggestions do you have for new moms?

A: Try to get into the best shape you can prior to getting pregnant. It really will help you during and after the pregnancy. Being pregnant is not license to forget all the rules that you abide by when you're not pregnant. Moving your body, getting enough sleep, staying hydrated and eating proper foods throughout the day are even more important when you're pregnant.

Q: Can you share any secrets about celebrity workout routines?

A: It's about doing the work. Each one of them comes and works up a good sweat. They want to work out. They want to work hard. They're focused. Their livelihood is their motivation. My job is to guide them and make it exciting, sexy and fun.

Check out more of David's summer shape-up tips at