I've a friend who went to the 90 minute "power yoga" class this past weekend to check it out, and she does know yoga. She really liked the instructor. He paid close attention to everyone, and he corrected her position a few times. The reason the class is so long as that it also includes meditation (perhaps this is usual?) and apparently they stayed in some of the positions for 10 minutes. Is this common? She really liked the class, but I don't know how to process what I hear because I do not know anything about it...