Talking for 90 minutes at a time through a mask is absolutely exhausting, for me at least. I don’t feel light-headed, as some people claim to do, and maybe there’s no diminishment of oxygen uptake – studies seem to vary about that – but I just get worn out from the extra effort of breathing through the damn thing. At the end of a class I’m sweating like mad (even in Texas A/C!) and feel like I’ve just run a 5K.