Yes. Ten minutes is my record. (That was the target, didn't aim for longer). The point is that static exercise only builds strength at the particular muscular

Yes. Ten minutes is my record. (That was the target, didn't aim for longer). The point is that static exercise only builds strength at the particular muscular extension tested by the exercise. With planks your core remains weak for anything that doesn't resemble a plank, just as standing doesn't meaningfully improve your running.