Working out and breast milk

So I am a first time mom and before getting pregnant I was super into working out, I was a sprinter. I was told to stop during my pregnancy because of minor complications, but now that I am 10 weeks pp I want to start back up. I want to do Insanity again and for those of you know know it's a really intense cardiovascular program. I heard rumors tho that working out can negatively affect your breast milk supply :( ... is there any truth to this because I already kind of struggle with supply.