Position
Get on your hands and knees with a natural arch in your lower back. Align your arms straight down from your shoulders, with your elbows slightly bent and your knees directly under your hips. Keep your head and neck in a neutral position.

Technique
Begin with one arm and opposite leg straight out and slightly off the floor, with tension on your deltoids, gluteus, and lower back. Continue to raise your arm and leg to a level position or to the point where your back is challenged to hold a natural arch. Hold, continue to contract your muscles, then slowly lower your arm and leg to the starting position. Repeat.