This is a rather involved question. We really have to explore the reasoning behind taking a supplement just as much as the science of it. Many people take supplements as a means to push themselves. The challenge to explore is what do we think it’s doing for our bodies. This is far from a bad question and is probably on a fair amount of runners minds.
But if you have a solid good grasp about how the supplement improves your performance then this question about how really about perceive aid or assistance. A supplement isn’t a tool. A tool is something like a hammer. It lets you do something you cannot do without the tool. A supplement is like oil. It makes the machine do what it can already do, but do it the best it can.
When used correctly, and using one that performs safely and honestly, it is unlikely an exercise supplement will cause any sort of negative impact. You are pushing yourself with it and you are pushing yourself without it. You are improving no matter what as long as you are doing more than you could before with or without a supplement.