Tuesday, February 23, 2010

Retül fitment at Bicycle Trip

Most of us know how important it is to have our bicycles fit our bodies as closely as possible. Poor bike fit is not only slower, but can lead to repetitive stress injuries over time... especially for old guys who are trying to "get back in shape" after years of couch-potato drills. I've been professionally fitted to my bikes three times over the years, and also done it myself using various established methods (Colorado Cyclist has a nice online fitment tool). But when Bicycle Trip bought a full-on Retül Fit Studio I knew it was time to reevaluate my bike's adjustments.

Retül uses sophisticated motion capture to dynamically analyze the motion of your body's joints in 3D, using a special sensor and adhesive markers attached at key body joints (feet, ankles, knees, hips, shoulders, elbows and wrists). You then pedal your own bike at power on a trainer placed in front of the sensor which records the position of each marker in 3D space over time. From this any wobbles and inefficient joint angles can be precisely defined and eliminated through the usual bike adjustments. I'd seen similar technology covered on TV before... but only for pro golfers and baseball players.

After I was all plugged in and on my bike in front of the sensor, Aaron had me pedal at my "7 out of 10" power for 15 seconds. My motion was played back as a moving stick figure on the PC's screen. Everything was defined numerically too. We could instantly see how my position on my bike compared with typical ranges. Awesome!

From the graphical display we could see that my knees wobbled a bit laterally, but not enough to require adjustment.

But my back angle and arm reach were rather aggressive and probably hampered my power a bit. That might suit time-trialing, due to better aerodynamics, but that's not my goal. So we installed a shorter bar stem (80mm vs. 100mm) to reduce my hip angle while raising my back a bit.

I was fairly sure we'd raise my saddle too, for better use of my leg muscles, and we did. But my reach was still far so we shifted the saddle forward some. This effectively lowers the saddle in the process, so Aaron ended up raising the saddle even more, by a full inch from its original height. I couldn't believe it! Moving the saddle forward minimized the effect, but that was still a huge change.

When everything was done Aaron saved the results in PDF files saved out of Retül. He e-mailed them to me and now I have them available for future reference.

So, what's the net effect?

I've been riding on the adjusted bike for several weeks now, and so far it seems good. My bike now feels faster on climbs, thanks to better use of the leg muscles no doubt (I'd always felt it was too low while climbing but just figured it was my imagination). Sometimes I become very aware of the higher saddle, mostly on level roads. My hips stay level while pedaling though, so it's still within traditional parameters. And my power seems higher for the perceived exertion. I'd say thumbs up for sure!

Interesting, and very cool! Let's hope this keeps my aging body healthy... and faster!

1 comment:

Geoff Drake said...

Great writeup, thanks!