Add difficulty to the plank exercise for elite core strength and rotational control. Try the “toe tap” when you're ready for a real challenge. Be sure to master the standard plank before you attempt ...

One trainer shares what a simple plank challenge did for his mental and physical strength.

Stand in front of a step or bench. Alternate toe taps onto step or bench. This can be done in a marching motion for lower intensity or a jog tap while moving arms for a higher intensity. Rachael Hofer ...