The plank is a commonly performed exercise with numerous variations. Many of these variations do activate the core in the most effective manner and actually activate muscles in a way that is not the most beneficial for maintenance of a healthy core.
The following method of performing the plank will increase core stability and avoid less-effective methods.
Start in a prone position with your elbows directly under your shoulders. Your arms should be parallel, and your palms flat on the floor. Your feet should be together.
Engage your shoulders down and back. Press into your elbows. Tighten your quads to lift your knees. Engage your abs to rise into a plank position. Look just past your fingertips. Lightly press into your little fingers.
At this point, you should have a neutral spine. Hold for 8–10 seconds only, then relax for 4 seconds. Repeat for 8–12 repetitions.
Be sure to breathe. Once again, holding your breath will allow you to support your spine with the diaphragm, which betrays the external stabilizing core muscles.
Common faults: Praying hands or hands together. Having a bend in your hips so your hips are raised, or lowering into a plank by releasing rather than engaging into it. Tucking the toes in too far causing a compression and lessening the support required of essential core muscles.