@ludosc I got certified by a small company that has since gone out of business, it was called Synergy Fitness if I recall correctly. I had to take this online course and then an exam.
There were also exams that you had to keep taking to maintain your certification later on but like I said they eventually went bankrupt.
It was cool to learn more about the field and different training and recovery techniques but to be honest I had already known a lot of it from my past personal research.
Many other great companies out there still like ISSA and ACE.
I can't say I would do it again considering it wasn't for a professional reason, but if I was working in the field I'm sure it would've been worth it. There's so much information online now and many great books, so I can't say it's worth it to get certified if you're not planning on being a trainer.
Hope that helps.