This is one of the reasons we have steps outside the dojo. Sometimes you have to test yourself in different ways, walking up steps on your hands or seiken is just one way to do that. We took advantage of the nice weather to do some outside training on a Friday night. There was also the usual hopping up the stairs, running etc hopefully this helps strengthen the legs. You just have to be careful when doing such training in fact you should always be careful.
As in instructor you should always be aware if any of your students have any injuries that might prevent them from performing a particular movement safely if that is the case give them an alternative.