Fitsician, Fit Thyself

Riders often ask me when to get a bike fit:  clearly, getting a new bike is an important time, plus whenever we undergo a physical change – such as weight loss or gain, surgery, or even an improvement or decrease in our overall fitness – it is important to make sure we are still correctly aligned in all three dimensions on the bicycle.

I recently had an arthroscopic surgery, so as I got off the crutches and back onto the bike, I knew it was time for a fresh fit on my two road bikes. What surprised me was how much the relatively minor surgery affected the fit! It was a great reminder that the proper fit of a few years ago can be the wrong fit for us today, as our bodies change over time for a variety of reasons.

Fitting myself using the Retul 3-D motion capture technology was a new challenge. Fortunately, my wife was happy to help out, and “takes direction well” (her words!), so I was able to direct her while I was on the bike generating my motion-capture fit data.

A good fit results from a combination of the Retul measurement data, the bike fitter’s observations and experience, and the cyclist’s sense of what feels best. In this session, I was both bike fitter and cyclist – with the Retul system to give me objective information about what my body was doing in motion on the bike.

I had been professionally fit a few years ago on both bikes, and I felt comfortable and confident on both pre-surgery. Both bikes had similar equipment (same saddle and pedals, similar bars); the major difference being that the BH had 170mm cranks and the Focus had 172.5mm cranks. They do, however, have different geometries and tube sizes. I was very curious to see whether and what types of changes might be needed post-surgery.

We started with the BH, which I’d been riding exclusively since the surgery because the slightly shorter cranks were less stressful on my recovering body. The most noticeable change to my fit was in saddle fore/aft measurement. My previous fit placed me significantly farther behind the bottom bracket than where my body wanted to be post-surgery. So, we moved the saddle forward almost to the maximum amount possible, and measured the change. It now showed that I was closer to where I needed to be fore/aft, but needed to change the saddle height a little bit. After these changes were made, I saw that I wasn’t quite as far forward as the reference ranges were suggesting; based on my experience I decided to try a different saddle (Specialized Power – 155 width). Different saddles can cause cyclists to sit differently on the bike, potentially changing the orientation of both the upper and lower body. With this one change, several things happened simultaneously: the saddle fore/aft came into range, various other measurements became more symmetrical (comparing right-to-left side of the body measurements), and my cadence went up about 5 rpm – it just became easier to pedal.

With these major changes completed, I went about testing various smaller details: removing a pedal washer, slightly changing cleat position (and then moving it back), removing an “in the shoe” wedge (and then putting it back), and making another slight (3mm) change in saddle height. With all of these changes, I was done with my first bike: the data was in the desired ranges, and it felt great.

We then switched to the Focus. The Focus has a much longer wheelbase (about 2 cm) than the BH, so I suspected that changes would be needed here too. Very similar changes were indeed necessary: saddle change to the Power, move the saddle closer to the front of the bike, slightly adjust the saddle height, and then this one was done too!

I measured both bikes using the Retul Zinn measuring tool after completing the fit, and then compared these measurements side by side.  The goal of a proper bike fit fit is to “fit the bike to the body.” This would argue that, on different bikes, the major contact points would be in similar relationships. Specifically, the saddle height and handlebar stack/reach (a measure of where the handlebars are relative to the bottom bracket) should be pretty close to each other. And, in fact, that’s pretty much what happened (handlebar reach was different because of the different wheelbases). Between the Retul motion-capture data and my body’s sense of good position, I got the bikes to “feel” as much like each other as possible given their differences. The fit had essentially duplicated my body’s position on two very different machines.

It was illuminating to experience personally the importance of a fresh fit after undergoing a physical change such as surgery: as our bodies change, so does our orientation to our bicycles.

I’ll report back again in a couple of weeks after I’ve ridden the bikes a while and let you know how my new position feels.