As with many aspects of the didactic process, it's generally effective to explain to students what exactly they are getting out of a given task or activity. There's a big difference between putting students through conditioning hell, and doing the same and explaining to them that we do the anaerobic stuff because it's giving them the "wind" they need to keep up intensive activity longer than their opponent can, that one thing is muscular endurance and another is strength, that this type of stretching is to avoid injury and that the other is to kick higher, etc. That way you give them motivation AND knowledge.
I was struck by this last night when a kid at the gym I go to told me he was working the weights for arms, chest and back, but not legs because he was getting enough leg work from the TKD classes. I had to bite my tongue, because the weights room instructor was present.