If you are a personal trainer and want to share your knowledge with the world, consider using a common form of technology to do this. You can easily upload all of the information you know onto a flash drive, which can then be arranged according to different sections
For example, you could create one section that is for those who are just starting a workout routine for the first time. In this folder, you can include certain exercise that they can do without hurting themselves, another folder that contains different ways to stretch, ideas on how those people can modify the exercises if they find they can’t keep up, and pictures of the exercises so they are not confused as to how they are done.
You could then share this with everyone by promoting your business on the flash drive and selling them to your customers or on your website.