You don't pedal that much in a bike fit. I think you're making too much of the fitness required to do a bike fit. My bike fits take 2 hours and you probably pedal a total of 30 minutes, broken up in small increments.
When I'm fitting, I'm not interested in testing the rider's fitness or ability to produce power. We are trying to make sure the rider is in an orthodox position so as they improve their fitness, they are doing so effectively and safely.
Tri Shop - Plano, Texas http://www.trishop.com Facebook
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter - Fit Portfolio