[Much like a dog, he perks up, brightening as he nods.] Um, the hard part is creating resistance in space. So you have to use something heavy that won't move. Like the walls!

[He pushes himself forward and knocks on the wall.]

So, just push your hand against it, hard as you can. Um, not so hard that you hurt yourself! But a solid push. And then move your arm around at different angles, stretching it. So it'll move all the bones around and stress them a little. It's not much but even a little bit counts!