You will not open Boeing or Airbus doors in flight!! No matter how strong you are.
While I agree based on the math of a pressurized airplane I'll throw in a technicality... what if you depressurize first and then open it in flight?
On a more serious note I remembered the DB Cooper incident when I was reading through the replies, while the door in the aft bulkhead on a 727 is a plug type door it opens inward only. From my point of view (I go in and out of it often enough) and from a purely functional stanpoint it's near identical to the L-1 door (well duh, it's a door), but I'm wondering how much pressure, if any, DB Cooper was dealing with when he went to do that. I doubt it was 8.6 DPSI, but I bet someone knows the exact figure.