This bird dog exercise is for the small intrinsic muscles of the spine. This exercise will not fatigue the large muscles as a plank exercise does. The bird dog is mainly to train the posture muscles.
Begin while on your hands and knees with your hands directly under the shoulders and the knees directly under the hips. Relax the low back to a neutral position.
It is important to keep the body in a straight line while lifting the arms and legs.
Start out by lifting one arm slowly and holding the position of the low back (top, left image).
Once this is mastered, lift one leg slowly while holding the position of the low back (top, right image).
Finally, lift one arm and the opposite leg slowly while holding the position of the low back (bottom image).
Repeat this exercise 10 times for each side.
This exercise should be done at least 3-4 times per week.