Home Exercises:

Back Extension

Lie face down with your arms by your sides, palms facing up and legs extended and relaxed. Hold your head up slightly or rest your forehead on the floor. Relax your shoulders into the floor, but keep your abdominals tight.

Contract the gluteals and use your lower back muscles to slowly lift your shoulders and chest off the floor.  
Repeat 15 - 30 times, three to five times per week.

For more intensity, do the exercise with arms extended overhead.