If you're looking for a challenging way to strengthen and tone your quads and hamstrings, you're going to love doing single leg lifts on a exercise ball. All at once, you'll be working the quad and hip flexors of the lifting leg, but you'll also feel an incredible burn in the hamstring and glutes of the leg remaining on the ball. That's because it takes a tremendous amount of down pressure to keep the ball in place as you do your leg lifts.

To find out how to do this dynamic move read more.

• Lie on your back and place an exercise ball under your calves. Place your hands on the floor for stability as you lift your bum off the ground.
• Hold the ball steady with your left leg as you lift your right leg off the ball. Then lower it towards the ball, but don't let it touch, then lift your leg again. Keep both legs straight as you repeat lifting and lower 10 to 15 times.
• Then lower your right leg to the ball and do the leg lifts with your left leg. Repeat again for a total of three sets.

If this is too challenging for you, build up to the exercise by bridging on the ball. Or you can put the ball in a corner so it is considerably more stable. The exercise will still be challenging for your legs.