Kim Kardashian does squats and lunges to keep her famous butt in shape.

The reality TV star's derriere is the envy of women all over the world but Kim's trainer Jennifer Galardi revealed she works hard to keep it in shape.

She told Britain's Glamour magazine: "Squats and lungs are very effective. They are very effective. Kim wanted to tone and tighten her bum without losing its shape - squats and lunges are perfect. We alternate the two, doing three sets of 12 reps each per session."

Kim, 31, also keeps her abs toned with a series of different exercises for maximum effect even though she doesn't always enjoy it.

Jennifer added: "Kim hates the plank position but I make her do it because it tones the abs so well. She bends one knee and crosses it underneath her, then stretches it back out. We also do 'stair climbers' where you drive your knee forwards instead of inwards and 'side planks' where you turn on one side and hold yourself up for 30 seconds before changing and then doing the same on The Other Side."