If you're doing the plank properly, you'll be struggling to hold the position much sooner than you'd expect. This could mean that you only hold a plank for 10 seconds, or that you last all the way to ...

Brace the core as you lift the knees just an inch or two off the ground and hold. Take a deep breath as you draw your navel into your spine. Begin in a forearm plank position with elbows under ...