Like everyone is mentioning most clients are okay with it, I’ve never had a client fight me on it. Just state that you are raising your fee for everyone. Especially if you charge higher for newer clients. What I stated last time I raised my rates was I wanted to close the gap between my prices for current and new clients. I did mine the same week, and clients who were with me for over 2+years had no problem with it 🙂 (I regretted not doing it sooner)
If you’re a good trainer they will know that you’re worth it. If you have to explain yourself here’s what I tell people I don’t charge $50 per hour, what you get for $50 for that hour is my knowledge, years of experience and my 4 + years worth of school and unlimited access to me with any questions you have even when you’re not training etc.
Also if it’s a friend and you have to explain to them, ask them have they ever gotten a raise at their job? The answer will be yes they have, well let them know you have been charging the same rates for years etc and ask them wouldn’t they think that you deserve a raise as well? You’ve grown and kept taking classes to become better and better. (You’re a personal trainer/leader/teacher and another very important thing a salesman) And $5 extra per hour is a good start, I’d not recommend any higher than that unless you were really undercharging