How about a lesson on common exercise/gym terminology?
Talking about working out, treadmills, exercise bikes, weights, jogging, push ups, sit ups, crunches, cardio, aerobics.
Just today I was thinking about how to say "work out" - I have an amiga in a cardio kickboxing class and I wanted to ask her "are you ready to work out today" or "how was your workout" - but I had no idea how to.