every time i go to work out my biceps its like when i finish my two warm up sets they start cramping and shit, for my warm up i'll normaly just two sets of 20 barbell curls with no weight to get blood pumping. but the past few times its like they spend out out before my work out begins. my water intake is sufficaint. i dont overtrain my biceps for sure, and dont do them the day after back workout. any one else have this problem?