Quote Originally Posted by KnottedYet
When I want to really make myself tired I do bridges with my feet on a physioball. Straight leg, bent leg, and curling-toward-you. I can only do 5 or 10 of each. I aspire to 20 of each. My abs and hamstrings cry out for mercy.

And I aspire to the next step in the plank progression: side planks where you lift and lower the top leg. I can't do that yet at all.
So true. How about planks on your whole forearm? (i.e elbows bent). Killer!