NEW YORK â€"  Summer is in the air, and with it, resolutions to shape up those problem parts. In the coming weeks, we're going to some of Hollywood's top trainers to get their tips on how you can get the most desired body parts of today's fittest celebs. 

And we're starting with the biggest muscle in the body: The gluteus maximus. Specifically, Pippa Middleton's now world famous royal derriere, and "Inglourious Basterds" star Michael Fassenbender's much-viewed stone-chiseled backside.

Getting glutes like these will take you some work, but you don't need a $400 personal trainer or pricey pilates to get a backside like these stars. In fact, you can get them for free.

We talked to celebrity trainer Robert Brace, creator of the 28 Day Challenge workout DVD, and health consultant on Food Network series "Fat Chef," about how the ladies can get Pippa's pert part and Fassbender's fine backside.

According to Brace, Men and women need different exercise strategies because women naturally carry more body fat than men, due to their hormonal make up and the fact that women need the extra fat during childbirth. So women need exercises that they can do higher repetitions to burn more fat and men generally need higher weights with less repetition to build more muscle mass.

If you have health issues or pre-existing conditions, check with your doctor first. Then try these butt moves. As always, ladies first.

Gals: Closed Feet Squats

Try a traditional squat with your feet together. Stand up straight with your feet together. Hold a medium weighted dumbbell in each hand, if this is too heavy for you, you can start without weight. Then sit back like you're sitting on a chair until your thighs are parallel with the floor. When you place your feet together in this position it forces the gluteal muscles to work harder. Return to a standing position by pushing from the heel of your foot, straightening your legs and propelling your butt upwards and forwards.  

PHOTOS: Pippa Middleton.

Gals: Single Leg Hip Raises

Lie flat with your back on the floor. Bend your knees and place both feet on the floor. Then take one leg and straighten it towards the ceiling. With the foot that is on the floor, rest your weight on your heels so that your toes are off the floor. Then perform 20 single leg hip raises, slowly thrusting your hips to the ceiling. Smile as you feel the burn.

For guys wanting to get Fassenbender's sculpted bum, here are two great exercises.

Guys: Step Ups

Step-ups are a great way to develop the legs and butt. This can be done anywhere that you have a raised platform or step. Step onto the platform with one leg and use your leg and gluteal muscles to propel your body upwards and forward as you stand up straight up on the step. The higher the platform the more your butt has to work.

PHOTOS: Michael Fassbender.

Both the guys and the girls can't forget to add interval training to their routines

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Guys: Lunges

Lunges are also a tried and true method of building an incredible tush. Stand up straight with your hand by your sides and your feet hip width apart. Take one large step forward and bend the front knee until the thigh is parallel with the floor. Your knees should not extend beyond your toes. While taking your front leg forward, drop your back knee towards the floor (don't let your knee hit the floor).  Finish by pushing off your front leg and returning to standing.

Both the guys and the girls can't forget to add interval training to their routines to burn fat and keep your muscles lean and tight. Interval training is short bursts of high intensity activity followed by short periods of rest. It is the fastest way to shred fat and get lean before building that butt.

Next week: How to get the abdominals of Gwen Stefani and Ryan Reynolds.