Hmm. 9S doesn't really understand it as a point of shared experience; as androids, they don't really tire so easily. Really, their biggest concern is physical breakdown from repeated and frequent over exertion. Do the combat androids even need to practice? And, well, he's not even supposed to be able to fight, so running through drills is a moot point.

But he understands it, in a way. Magic is a drain on Strange's energy source and he just needs to replenish it.

"If that's the case, you really should rest. Sit down or something. You look beat." A glance away. "You shouldn't have gone so far if it was going to do a number on you."