Jim Smith aka Smitty posted a guest blog over on Ask Joe on DeFranco's Training about a plank variation. It's very detailed as to why to use it and how to use it. Short version? Actively-band resisted planks on a glute-ham raise!
Here it is:
Real "Core Strength" for Athletes
Very cool! I hope I get to try it soon...
Where Athletic Power Really Comes From
2 hours ago