"Okay, so it appears that a warm-up can improve performance and minimize tissue stress, but is it absolutely necessary? No! Simply going through the motions of any exercise is sufficient to supply blood to the appropriate working muscles. Just a few reps is all you need to really warm-up the muscles. Aerobic activity isn't necessary and may in fact zap some valuable energy as well as time."
http://www.t-nation.com/readTopic.do;jsessionid=DEA1316F7A69B853FE73E07C91E6A932.hydra?id=804576
http://www.t-nation.com/readTopic.do;jsessionid=DEA1316F7A69B853FE73E07C91E6A932.hydra?id=804576