This core exercise I recently learned from Fighter Abs.  It’s a pretty cool program that teaches you how get abs like fighter by training like a fighter, without stepping into a boxing ring or the octagon.  This is a variation of the core exercise, the plank. Instead there is a dynamic aspect to it where you touch side to side.  this makes it so one arm has to hold your body up momentarily – which really activates your core and can make you abs stronger.  This will help with weak lower back muscles and can even help heavy lifting like powerlifting.