I have a 1960 house. I did have my basement outlets upgraded to whatever they’re supposed to be so that we aren’t electrocuted if the basement floods, and it was not expensive.
We also have a treadmill, and use it regularly, and it has never tripped the outlet. So I’d guess that the treadmill doesn’t actually suck up that much power. We’re definitely more likely to use the treadmill at home in the winter than go to the gym.
So, I’d suggest calling an electrician and having your outlet upgraded, and getting a treadmill.