I’m a big fan of the plank exercise for core strenthening and include it in almost all of my sessions. But I’m not in favor of holding it for too long. Why spending 5 min doing nothing while you can challenge your plank position in so many ways. Drop your knees to the floor, lift your butt, lift up a leg or shift back and forth a while keeping your core thight and braced. Get more bang for your buck with these challenging variations.