Thursday, February 3, 2011

Bike fitting and the body.

A friend of mine has purchased a new bike and was concerned about handling on descents as this is sometimes a problem for him. In part related to bike geometry but also likely related to riding style and posture.

This spurred an online discussion about getting lower on the bike to allow for better handling. The comment also included advice on using your core to support your trunk so that the rider could let his arms relax while riding. Not unlike this:

I agree that the changes suggested would improve handling on descents. But sometimes a body just can't do it.

I did a bike fit for the rider in question with the focus on trying to relieve any pain issues while riding. We did that successfully. While the lower position described may help with handling on descents and other technical riding, the rider has to have a body that will accept that position as well which requires sufficient core strength, hip and hamstring flexibility. *IF* the rider can get into the position, maintain a good low back and pelvic alignment, the neck might be able to take the posture. If the low back and pelvic position and stability aren't there, neck posture will be crap and there will be huge compressive forces through that part of the spine. Even with perfect low back/pelvic positioning, the neck will take more strain due to the way the head has to be lifted to look forward with the lower stem/handlebars. A younger spine can take that strain fairly easily. Older spines (greater than 35 years old) start having bone spurs and things that complicate the issue.

The comments made by others in the discussion about riding posture were absolutely correct, not just about the position but also about having to use your core to support your trunk instead of having a lot of weight on the hands. Unfortunately, a lot of riders do not have sufficient core strength to do so, or insufficient muscle endurance to maintain that core support over longer rides.

So this is perfect example of fitting a bike for performance versus ergonomics. In some cases, you have no choice but to give up one for the other. Finding the right bike fit is a balancing act. It's not black and white.

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