Jennifer Aniston's long-time yoga instructor Mandy Ingber swears by something she calls "the boat pose with leg extensions" to keep the star's middle uber-tight.

Step 1: Sit on the floor with you butt on the ground. Extend your arms straight out in front of you parallel to the floor. Lift your chest and sternum upward as you look up. Start with you knees bent, feet in the air, calves are parallel to the floor.

Step 2: Extend your legs straight so that your toes are at eye level. Pull your lower abdominal muscles tight to balance. Slowly lower down and hover your shoulders and feet a few inches off the floor -- arms extended and hovering a few inches from the ground as well -- straight along your sides.

Step 3: Draw your right knee in, extend the leg straight up and then bring it down alongside the left leg. Now do the same with your left leg. Repeat one more time on each side, then sweep back up into Boat Pose with the knees bent. Finally extend the legs straight, coming into Full Boat and hold for two breaths, just once.

Cameron Diaz's trainer Teddy Bass says this reverse curtsey lunge with a front knee pull will "fire the glute and hamstring muscles to help define and build the bum, hamstrings, and quads."

Step 1: Stand straight with feet hip-width apart.

Step 2: Step back with the right leg into a lunge position.

Step 3: Pull the right leg forward -- your right heel should come above opposite knee -- and come to standing with opposite arm drawing the knee to the chest. Repeat on other side. Aim for two sets of 12 with each leg.

Jennifer Lopez has maintained six pack abs into her 40s thanks to trainer Tracy Anderson's "Holding Knees Leg Extend" move.

Step 1: Lay on your back with hands behind your head to support your neck. Your torso should stay tight in a crunch position.

Step 2: Both knees should be bent holding a towel between your knees, so that your knees are pressed together but your feet are open apart from each other.

Step 3: Don't let the towel fall as you extend legs straight up to ceiling and back down into the starting position. Repeat 50 times.

Anderson also relies on what she calls the "butt pretzel and arm reach" to get clients, like Gwyneth Paltrow, toned arms.

Step 1: Kneel on your hands and knees, left leg is bent under right so legs are crossed in a pretzel shape, crossing at the ankles.

Step 2: Lift your right hand up to ceiling as you lift your right leg up and kick it straight back, toes pointed. Extend your arm and leg at the same time. Repeat for 30 to 40 reps.

Celebrity fitness guru Kit Rich says you can rev up your results by adding a little bit of cardio to each workout. Try high-intensity interval training, which is the most effective workout for weight loss.

"Try 1 minute of running at a vigorous pace and then backing off for 1 to 2 minutes and then repeat," she says. "Or walk briskly at a high incline for 2 minutes and then take the incline down and walk for 1 minute before returning back up to the incline. You can also jump rope for 2 minutes straight as hard as you can, stop completely for 30 seconds and then start again." Perform cardio at least 3 to 4 times a week for at least 25 minutes for best results.