I have been taking the Stak 2 since Summer 2006 and with my initial can, I was looking for this warm tingling feeling or something as a sign that it was in my system...but, no such sign. What I did get was aggression and speed of recuperation. I was able to power up more weight and move through sets faster. I did not realize, nor attribute my new found power to the Stak 2 until I was on my second can. Why? Because it felt normal to me...like it was in me all along. It was at the end of the second can (during the one week off period) that I lacked the same tenacity to move my previous weights. That's when I realized Stak 2 is the truth. And, I have been following the recommended cycle ever since.