Wednesday, April 20, 2011

Bike fits and weak hips

I was finally able to squeeze into the schedule of one of the most sought-after fit specialists in the industry, Sean Madsen.  He's the head Biomechanist/Fit Expert at the Boulder Center for Sports Medicine, using the Body Geometry fit system that Dr. Pruitt created.  Sean is responsible for the bike fit of over a hundred cyclists in the pro peloton....if you watched them race on tv on a Specialized, he fit them to that bike.

While doing the fit and analysis, it was a lot of fun talking with Sean about the sport and its most famous members.  Hopefully someday he'll be talking to some client about me the same way...but I digress.

First, I will show you the original position:
You can kind of see the little silver globes stuck to me at various key joints/points of interest, to be tracked in 3-dimensions by the infrared cameras at the top of the picture, same as the motion-capture systems used for CG movies.

I'll skip right to the end.  Remember the little "find 5 things different between the pictures" games? Well, let's play.  Drumroll, please, for my post-fit position....

Alright, it was a trick question (sort of).  Those are different pictures, and some things did change (water bottle, the curtain).  But you can overlay the two pictures and I/the bike will stay the same.  He did the analysis and checked all the angles, and decided that nothing needed to be changed with my position from the fit I got from Wenger early last year.

Nothing on the bike changed, but there were issues to work on with me.

In the physical analysis before the fit, Sean found my weakness quite easily.  There are small stability muscles just behind the hip bones on the outside of your leg, and mine are incredibly weak.  It was pretty staggering when he showed me just how weak they were with a simple exercise.  He's prescribed some exercises to strengthen those muscles, and 20 reps under the weight of my own legs has my legs shaking!  It turns out I'm very strong in the up/down/forward/backward plane of motion, but lateral motion...nope.

So why does that matter in cycling?  Well, because those muscles are used to keep my knees going up and down when pedaling and not side-to-side.  Another issue to be sorted is the natural slant of my feet away from my body when relaxed (called the foot varus).  Mine is pretty radical, and needed one varus wedge in the left shoe and 2 in the right shoe (plus the built-in varus in specialized's shoes).

The weak stability muscles and foot varus conspired to make my knees dive inwards during the pedal stroke. Even with just 15 minutes of riding, the system showed some adaptation to the better foot angle in the shoes.  This is the front view of my legs (the dots are the markers on my legs, my feet are the bottom triangle).  You can see pretty clearly that my right knee (left side in the pic) especially had a lot of side-to-side movement, and that it's a much more up-down motion in the 'after' picture.
Here's my legs from above, and again, the right knee shows a lot of improvement immediately:
Given some time, I'll fully adapt to the new position and the pedal stroke will be more consistent.

With my fit done so quickly and easily, we had time to tinker with my time trial position.  I don't have pics of the before and after, but I'll just say I'm lower, further forward, flatter, and generally more aerodynamic without sacrificing power.  Good stuff!

In fact, the next day I won the local Horsetooth Time Trial (for the 3rd week in a row!) by 2.5 minutes with a time of 34:47 on a course that mimics what we'll experience at Tour of the Gila.  I'm excited.  Here I am in action (the camera angle makes my back look arched, but really it's quite flat).