Hello, for you don't have a website, neither a ready app, the best way I suggest for the video is to concentrate on the final benefits that user could have applying to your services. Practically I'd like to edit a video with stock footage showing real people. They can make fitness work out and else and feauture a call to action to the website.
I'm an advertising designer with professional background in broadcasting TV as audio/video editor, author, post producer and commercial creative/maker.
Please, take a look at my portfolio for some video samples.
Feel free to contcat me for further details and information.
Best regards.
A. I.