The Prone Leg Raise on the Ball is great for stabilizing the spine and strengthening the lower back, but even more than that it also works your hips and glutes. To do this exercise you'll need an exercise ball. Here's how:

• Lie face-down on a stability ball with your arms bent slightly, abs tight, and legs straight.
• Keep your abs engaged, slowly lift both legs toward the ceiling.
• Pause for three seconds (or at least one second), then lower your legs back to the floor.
• Do two sets of 10 reps.

Fit's Tip: If you're having a hard time doing this (i.e. wobbling off the ball) then start by raising one leg at a time until you get strong enough to do both.