Start lying on your back with knees bent, feet flat on the floor, and arms by your side. Push through your heels to extend your hips and lift your glutes off the ground, squeezing your glutes at the top. Return to start. Lift one foot off the floor and bend your knee. Push up through the heel of the foot that is still on the ground, squeezing your glutes at the top. Return to start. Lift one foot off the floor and straighten your knee. Push up through the heel of the foot that is still on the ground, squeezing your glutes at the top. To progress, get an Exercise Ball and place both calves on the top with your knees bent. Dig your heels into the ball and lift your hips, squeezing your glutes at the top. Return to start. Extend your knees and dig through your heels to lift your hips with straight legs, squeezing your glutes at the top. Return to start. Again, lift your body with extended legs. From the lifted position, bend your knees in to roll the ball closer to your body. Extend your knees again to return to an extended leg bridge to complete a hamstring curl. Return to start. Move one extended leg to the side of the ball. Push up through the leg on top of the ball to extend your hips, while squeezing your glutes.