You will need to have your idea legally protected by getting a patent and trademark it. Then you can start promoting it to the rest of the world.
Once you have done this, then some ways of promoting it are:
-Create a video
-Write an article
-Present at various fitness workshops, seminars and conventions (you can do it also as a vendor)
-If you think your idea/workout routine/equipment is great and unique then have some research study/studies back it up in order to give you even stronger credibility. This will help you with the promotion and acceptance of your idea by the rest of the fitness industry.
I hope this helps. Good luck!