In my experience, fitness trainers operating boot camps or classes do better with Groupon type deals. The price point is much lower than a personal training session so appealing to the masses to fill classes is a good idea.
Personal means “one-on-one” and that comes at a premium to the client and the trainer. When you offer “discounts” for mass referrals, it doesn’t allow you to get your ideal type of “client” that work best for your style of training and business.
The service you offer should dictate what type of offers you give, but after 17 years of being in this business, and just RAISING my rates and cutting discounts, I can attest that it will actually grow your business.
I do more personal incentives based on referrals or number of sessions purchased. You get more of a commitment (necessary) from the client when you charge appropriately. There is a perceived value when things are at a premium.