Bike fit and performance

[indysteel]

I think it depends in large part on how far off you currently are from your optimal fit. If the fitter just tweaks the current set up of your bike, you might see very slight improvements in terms of speed, comfort or endurance. If, however, the fitter makes more significant changes, then you could possibly see more signficant increases in speed and/or performance. It's also a function of what issues you need to address with a fitting. A fit that optimizes power, for instance, my not be the best fit for you in other respects, e.g., if you have a chronic injury or the like. A good fitter will take all that into account.