https://www.youtube.com/user/trustedancientcoins A Single ‘Ab Test’ for a Stronger Core (and how to do a plank CORRECTLY!) #ancientcoins May 2, 2017 trustedcoins A Single ‘Ab Test’ for a Stronger Core (and how to do a plank CORRECTLY!) https://youtu.be/v8xd_UVpzw4 If you enjoyed this videovisit the ancient Greek and Roman Coin Collecting youtube channel for more great videos. for more