I get asked this one nearly every bike fit I do. I can't believe I haven't just written it down -- maybe it would save me from repeating it 200-300 times a year. Not that I mind terribly; after 14 years of doing 1-on-1 client interaction you get pretty good at talking while you work.
So here it goes:
I have been into bikes since I was about 5. I can remember my first bike -- it was a hand-me-down (of course, in a family of 7 kids) that was rattle-canned copper by my Dad. My Dad and my older brother, Mike, taught me to ride and for the next 8 years or so that is all I did; how I got around the neighborhood; how we played in the "court" (the cul de sac, for you non-Mid Westerners) up the street.
On through high school and then into college where I used my bike to commute to class and eventually got into triathlons.
I graduated from Physical Therapy school and advanced into longer distance triathlons (up to Ironman) and then quickly into mountain biking as well and eventually 24-hour racing in my early 20's.
As you can imagine, I attracted a lot of training partners who thought as I did, that long races were fun -- especially when you weren't gifted with natural speed. When you are a physical therapist, family and friends frequently pick your brain about aches and pains they have, and I was happy to help, since turnabout is fair play -- free investing, home buying, and tax advice easily offsets the time spent on PT stuff.
Often, a quick test or two will reveal the problem with some joint or muscle, but with my cycling friends, they often only had the problem when they were riding. The next logical step? Well, we need to see you on your bike!
There is started, and stayed, for a couple years -- I would just help out a friend or 10 with biomechanical issues on the bike.
Of course, I went searching for help, and any existing information on bike fitting. I read everything I could get my hands on -- some of it made sense, most of it didn't ("So if I'm sitting on the bike and look down, my front hub should be obscured by my handlebar? Why?").
I quickly realized that most of the "rules" were arbitrarily set, and very little research had actually been done to back any of it up. When I first started, the static bike fit system were popular -- Fit Kit, Wobblenaught and the like. In these systems you take measurements of your body, like arm, leg, torso measurements, and plug them into an equation which spits out your fit parameters. You input you body's measurements and the "system" tells you how far to place your bars from your seat, how far behind the bottom bracket your seat ought to be, etc. etc. etc.
As a PT, where we consider pain patterns, strength, flexibility, age, level of activity, and about 50 other factors, this was distinctly unsatisfying -- and as it turns out, mostly useless in actual bike fitting. This became glaringly obvious when my first commercial (non-friend helping) bike fits were from Wobblenaught and Fit Kit clients who came in wondering why they hurt so much when they rode. I then realized that there was a gap in the market -- there were people that had many troubles with their bike fit and wanted help, and it was clear that the static systems weren't going to help and therefore couldn't fill this niche.
I said, why couldn't I fill it? I started off slow, and part-time, doing perhaps 20-30 fits that first year. I kept growing each year, though, and it became more and more of my business. About 9 years later, I bought my Retul system which helped growth further, as I began to get many more clients from around the state and from out of state, since people were looking for someone that had a way to measure their mechanics dynamically and accurately, paired with having the knowledge and experience to apply all this information.
And so here I am. I'm doing anywhere from 200-250 bike fits a year, building custom bikes:
Oh yeah, forgot to include that - I saw about 5 or 6 years ago that some of the custom bikes my clients had were not made for them very well. Not very custom, which is a crime when you're paying $8000. There were aspects I certainly would have designed differently to tailor the bike to them better and their riding style -- so I did! It is truly a pleasure to build a machine that is meant for that one individual to ride comfortably, powerfully, and efficiently for hours and enjoy it.
So that's it; how I got started. It was a fairly organic and seamless process. I would bet there are maybe a dozen or so people in the U.S. that have the background I have, have been doing it for as long and have the equipment available to them that's necessary for the accuracy desired, and I bet every one of them shed the same amount of blood to get to where they are -- and that's the point. You can't short-cut this trade -- there is too much to know and (still) too little good information out there.