This is a great exercise to strengthen the lower back.  Muscles Involved:  Primary lower back with an emphasis on the glutes and transverse abdominals.

Body Alignment:
o  Lie face down on your stomach on either a mat, physioball or bosu ball with your feet approximately shoulder width apart.
o  Your knees are slightly bent and your feet are on the floor.
o  Place your hands behind your head with your elbows out to the side.
o  Brace the transverse abdominals.

Movement:
o  Slowly raise your upper body.
o  Make sure that your head and neck are in proper alignment.
o  Pause at the top of your movement and hold your position for a second or two.
o  Slowly lower your upper body back down to the starting position.
o  Repeat.

Training Tip:

Pay careful attention not to bend your neck.  Keep your head and neck in a straight line.  You can also perform this exercise with your arms either at your sides or you can rest your forehead on your hands with your elbows out.