This exercise focuses on the extensor muscles along the entire length of the back.  It is a great postural exercise.

To perform the bird dog exercise:

1. Start out on your hands and knees.  Pick a stable, yet comfortable surface (e.g., carpeted floor, yoga mat, etc.).
2. Hollow your abdominal muscles by sucking in your belly button towards your spine.
3. Slowly and simultaneously raise your straightened right arm and your straightened left leg until they are parallel to the ground.
4. Hold this position for 10 seconds.
5. Slowly return your right arm and left leg to the starting position.
6. Repeat steps 2-4 with your left arm and right leg.

Repeat steps 1-6 for a total of 5-10 repetitions.

Variations

• Once this exercise becomes easy, you can add weight to your legs by using weighted ankle straps or heavy boots.  Likewise, you can hold small hand weights to increase resistance on your upper body.
• If you want to focus more on core stability, perform the above exercise using the arm and leg on the same side of your body instead of alternate sides (e.g., raise your right arm and your right leg simultaneously).