Sibylla, I have the same problem with my feet as you have described, in fact I was going to post the same question today. I have only been training for a few months and I get what I can only describe as cramp in my feet. I have a few blisters etc. these I can deal with but during every class I get this camp type feeling in both my feet that's very painful. I have asked my instructor about it and he's response was that it may be due to me using parts of my feet that I have not exercised before, and that the cramp type feeling is my body's way of telling my to slow down. We also train with bare feet in a sport hall. I used to train with the same instructor over 10 years ago and never had this problem then (I trained for 5 years but had to stop due to family issues) but obviously I was alot younger and fitter then. If you find an answer I would be grateful if you let me know. I have the feeling that it's just something that will pass with time, more training and conditioning. As for your question about water breaks, I always make sure that I've drank lots of water before training, I always have a water bottle in my kit bag and take a few mouthfuls of water when putting pads on etc. We also have a break session after 1 1/2 hours.