Unlike product-based businesses, service-based businesses are generally harder to scale. You've built out your brand and are the only person who can do what you can do. There are also only so many hours in the day you can work. I'll be going through some tactics you can apply to scale and grow your business.
Creating a Team of Employees
A team of people will help everything. Even having one extra person to help can literally double your work output. You can delegate smaller tasks to your employees that will free up even more time for you to do more important tasks. If you trust their work ethic, you can even train an apprentice to coach clients for you. Keep in mind that they represent your brand and anything that they do is a representation of your company. Having extra people will help you scale out and increase your revenue and the amount of time you have.
You could feasibly build out an online roster full of clients and have in-person clients as well. Online clients take half the time to manage and you can still charge the same or slightly less for consultations. They are a great way to increase the number of clients you can take without "working" 40 extra hours.
Just like any product based business, this is easily scalable. Has your brand grown enough? Think about launching your own line of merchandise. With the power of the internet, you can even find suppliers to create your own supplement brand. Maybe you're a bit more creative and want to create a line of fitness accessories that you can use with your clients. The world is your oyster, you can pretty much create anything you want these days. You just need to do a bit of digging on the internet.
Online Programs/E-Books & Audiobooks.
Don't have any money to spend on product development? Use the knowledge inside your head. Sell informational programs that you can easily sell online. These are easy to distribute and cost nothing to create (other than your time). Just make sure these programs actually provide value to your clients. They'll be upset if they paid for junk and it will negatively effect your brand.