Why Fit Formulas Fail

A version of this article was originally
published in Triathlete Magazine

After reading a magazine article about bike fitting that listed out measurements and things to check to see if my bike fits well, I made some changes to my set-up. These changes included lengthening the stem so that the handlebar blocks my view of the hub when riding and placing my heel on the pedal when it is at the bottom of the stroke to set saddle height. I’m pretty sure that I followed the formulas properly, but I feel stretched out in this position and my lower back hurts. Am I doing something wrong?

Keith

Keith,

You are finding out what many before you have discovered – General positioning suggestions and measurement based “fitting” systems and formulas are based almost purely in anecdotal evidence and thus are inconsistent at best. These systems often have little to no scientific basis and often ignore the individual rider’s needs completely by assuming that all riders are alike and have the same capabilities, riding technique and experience. The items you have listed (handlebar blocking the hub axle and placing the heel on the pedal) are some of the many “old wives’” tales of the bicycle fitting world. These formulas are often based in what worked for a successful pro rider instead of being based in individual biomechanical reality. For example, Greg LeMond rode very successfully with his saddle much further back than average. It was soon printed in fitting and coaching manuals that this laid back saddle position was the best place to ride as LeMond’s results were so strong. What often failed to be mentioned was that LeMond had longer than average femurs (upper leg bone) and thus his knee sat further forward in relation to the pedal than average; what was “reasonable” for LeMond was not really the norm. Not surprisingly, many people suffered from knee, hip and back issues when riding this way.

There are always “quick fixes” and “magic formulas” being presented as they try to simplify a complicated subject – the human body in motion. I’ve yet to find a formula that is consistent and accurate enough to be used universally and thus do not recommend using them. Positioning on the bike is a dynamic process that is as individual as the people who ride. Any solid fitting protocol must take this reality into account to provide consistent and reliable results. The best way to take the guesswork out is to work with a qualified professional fitter as it is their job to know what works and why and will be able to explain it in easy to understand terms.

Enjoy the ride and train hard and smart!

Ian

Originally published August 2007/Copyright © 2007