You can change the tab names on your Trainerize site within the site designer.
Navigate to Main Menu -> Site Designer -> You will be brought to a new window with the website elements. Within this page, along the top where you see the tabs you will see a "Pages: Add | Manage" button. Click on "Manage", and click on "Rename" beside the tab you wish to change the name for.
Once you change the name, click "Done", and your site will be updated after you exit the site designer.
This is great for adding new tabs for Testimonials, Pricing, or Video.