I'm very small, 5'5, 136 pounds. I took two RPMs before doing my back the other day, empty stomach as suggested, didn't feel much after forty five minutes or so, I popped another. After another half an hour or so I felt insane. I was totally zoned out, and focused on working out and only working out. I did notice a bit better "feel" to my pumps, and I got through anworkout sleep deprived, so I'd have to give another thumbs up.