I went to my swim class yesterday and the instructor has us do the flutter kick with the dog paddle and within a few minutes my right leg cramped and fell asleep. It was so painful and I had to discontinue, get out of the water, and massage my thigh. I am in good shape, lift weights, and run at least three times a week and this has never happened to me. Is there a way to avoid this from happening again? Also I notice I have a hard time creating movement when I swim. I'm moving my arms and legs and I'm not going anywhere. What do you think is causing this to happen? Thanks for your help.