Mandatory Monday Move: Plank

Stop what you're doing and get up...or actually, get down on the ground.  No matter what you have going on today, at some point you need to do the Mandatory Monday Move: the plank.  Maybe see how long you can hold it, or see how many times you can do it until you just can't do it anymore.  Try it, decide you hate it, maybe try it one more time for good measure.  Just do it because it's mandatory!

There are various versions of the plank, but I think the starter version is with your arms fully extended and your hands located directly below your shoulders.  Keep your tummy tight and your butt down.  I've read that this move is good for your core and shoulders.

How long can you hold the plank?