A cool thing I learned last Sunday is keeping one foot stationary. You can do it in a very small area. For example, Heian Shodan. first move is step out, downblock. you can't move the left foot, so you step away with your right foot. Hope this makes sense. So the whole time, one foot stays perfectly still. Or, you can have one student do it at a time do it. If there isn't enough space, instead of stepping forward and running into the wall, have them step back and step forward. This works the leg muscles. If the next move is step in punch, have them step back with the front leg and quickly change before they fall down. Okay, hope a made at least a little bit of sense.