I can't be certain that Core Zap is what making me push more and do heavier weights since I've only taken it twice and still getting use to the dosage I need. But I do know it doesn't make me feel jittery at all which is good. The last few days I've carefully pushed harder. I was able to do 40 lb cable DB curl. Now I used one hand but my other hand was holding the other cable so I assume taking about 10 lbs of weight off? Not sure how that works. Anyway it was freakin'hard and I did it. Today I pushed 25 lb DB chest press and did that too. I could have done 30 lbs I believe. I will work with 25 until it feels easy though. I have to be really cautious if I feel any pull or pain in my neck to stop. So that means shoulder press no heavy weight I used 10/5 lbs today. But no pain so that is great!