[ultrasounder]

Not sure I can add anything more to this discussion than any more that has already been said, but the real problem about validating ones idea is,” you start out with an extreme bias” towards your idea. Conversely, if you are validating an idea, you the only true and tried and tested way is to Mom test it. It’s not enough you run a statistical poll and use that to run a product development program. You have to actually talk to people. In this case, OP needs to actually talk to the people in his demographics and validate the idea that they would like to get a personalized email from his trainer with a custom plan. If not it’s all shadow dancing with no real validation. Mom test is an excellent book to drive this point home.

[ultrasounder]

Was on the phone and am not good with touch typing. But, I actually did what I mentioned above. Being stuck at home like the OP, I actually had a lot of time on hand. So, I started calling Coffee shops that had recently pivoted to Shopify model(that change is happening in a massive scale) to try and see if they would be interested in a subscription model for their coffee beans and grinds. The outcome is for a different day, but the moral is "Always try to Invalidate your idea". Your ideas are innately biased. And that's why Starting with a clearly defined pinpoint is way easier than to apply Lean Startup methodology to Your "ideas". Hope that helps. Cant recommend Ryan Fitzpatrick's Mom Test enough. Guy even has a YT channel where he expands on some of the things he talks about in his book.