I think maybe I was wrong - you don't need to be physically fit do teach aikido. However I do believe that students need to be confident of its effectiveness and in the dedication of the instructor. I think you can learn some things, even from relatively poor instructors. However until you are in the position to critically evaluate the martial art, we initially have to take a lot on trust when we train under an instructor. Dedication can be inferred through physical conidtioning but also by training after a stroke, or whilst having a physical difficulty.