STRAIGHT-ARM plank or FOREARM plank: Which plank is more for the core?
BOTH are great to challenge your core but the Forearm plank is the way to go. The closer you are to the ground, the harder the position is to maintain. You're fighting gravity. The F-plank will target those abs more effectively.
The Straight-arm plank recruits shoulders and triceps instead of straight focus on the core. SA-planks can be a great full body workout… that is why some believe that a SA-plank is harder because it gets your shoulders and arms burning. But if your main focus when you plank is abs, then take the burn out of the arms and Forearm plank to target abs.
Regardless of how you plank, keep it up! Planks can be done anywhere and they're so good for strengthening your core without having to do a single sit-up and they are safer. Always keep a straight line b/w your shoulders and ankles, don't stick your butt in the air and don't collapse the lower back.
And is this not INSANE?!? the World Record Plank Hold is: 4 hrs 26 mins. Thats like watching Titanic AND THEN listening to the entire Soundtrack…. sounds like a BLAST! NOT!