Thanks Chicky- it just feels instinctively wrong, especially on heavy days. I'm surprised it isn't much mentioned, and i've felt a bit awkward in some classes having to explain why i don't want to do any inversions that day - not because i'm embarrassed about having a period, but because a couple of teachers have looked at me like i'm a nutter for asking.
I suppose it is a reflection of how variable teachers can be when it comes to dealing with the more philosophical and spiritual aspects of yoga. Can i ask, as a teacher trainer, how much emphasis you put on the non-asana/pranayama aspects in terms of that they are expected to pass on to their students? My current teacher does quite a lot, but he has been the exception - i had one (very briefly) who said she wouldn't be teaching any philosophy as she couldn't be doing with all that Hindu stuff!
In her case i think she loved yoga as a physical discipline but clearly felt some conflict with her religious beliefs, and it made me wonder how she dealt with this when she was training - i know it is often said that you don't need any particular beliefs to practice yoga, but if you have particular beliefs i guess they can be a barrier? More generally though i also wondered, from a teachers point of view, if there is a fear that dwelling on the non-physical aspects may put some people off, or is it more a practical problem of what you can fit into a class? As a student i would love to have even five minutes in class to talk about things like ahimsa, kriyas, diet etc, but it doesn't seem to be common practice.
Sorry for all the questions!