I've have taken pre-workout drinks in the past. All of them have contained NO and caffeine to various degrees. Maybe I am hypersensitive to any one of these two ingredients or both, but after about a wk of taking the recommended dosage I start to get heart palpitions. I've asked around and others have experienced this as well. Don't think I have a bad ticker and I do follow the suggested serving size. Anyone have any ideas on pre workout drinks that may not lead me down this path??? Thanks!