The domain ranking will not pass to the subdomain. The subdomain is treated like a separate website. This means that if you get ten backlinks to your main site. The subdomain will still have zero backlinks. I would not create a different website either for your trainers. Your new trainers would start with a domain and page rank of zero. I suggest that you add your trainers to the following:

website.com/trainer/trainersite

This way, the trainers will be able to get the domain rank of the main website since it is a subfolder.

Domain advantage will not be passed on to the subdomain. Google will treat the subdomain as a different website.
If you want to pass site juice to the trainer pages, then set it up as normal pages, like:
domainname.com/trainername
domainname.com/trainername

Buying new sites for all trainers will not pass domain juice. I hope this helps. In case of further help with SEO, email me at varun@upreports.com

Hi there,

I recommend to use sub directory if you want to take the SEO advantage.

In sub domain, authority & link juice will not pass and Google treat every sub domain as a separate entity.

I hope this helps.

Thanks,
Hiren

A subdomain will be seen as a separate website by Google, so you might as well create a different website for every trainer and link to it from the main website to give them a DA boost.

Best choice is create a subdomain, because each trainer Will have a different content and layout. But for Google each subdomain is a new website, no share relevance between them. If you can use a page model for each trainer, you can use directory structure such as domain.com/trainers/name, so you will distribue link juice across pages, improving website architecture.

Hey,

I've been working with web designers and developers to help with SEO for over decade now. Your question is common.

The short answer is... Google treats sub-domains as separate sites. So, if you go with a sub-domain for each trainer it will be like a fresh new site with no authority, which is not very good for the trainers. Nor will it bring authority to the root domain because these are fresh sites. Having trainers as sub-domains will be the same as having them on a separate domain.

My recommendation is to keep your trainer profiles as sub-directories if it's at all possible.

I hope this is still relevant and the above input helps a little. Feel free to book a call if you need to discuss more this or other cases.

Thanks!
Alex.