I was at a karate cl last night and I want to ask a question about their warm-up?

Last night I went to a small karate dojo and I've got a few questions about it. First of all, during their warm-ups they got down on their knees and bowed to something, like a worship, what was that, and second of all, during their warm-up they got criss-cross and sat quietly for about 30 seconds, it looked like meditation, but how can it be meditation if it was on for 30 seconds, how is it done and what is it for. And finally, the karate dojo is very small and there is a back room known as the "dressing room" or "closet", but how can the whole cl change in there, why not have a locker room.