Friday, October 19, 2018

Using Dartfish to Help Determine Cause of Knee Pain During Bike Fit

Recently, I had a client come in for a new bike fit. He said he copied his old bike’s dimensions to his new bike but things didn’t quite feel the same or feel right. He said he felt awkward on the bike and most importantly saying “I’m slower on my new aero bike!”
I went to the computer and looked up the manufacturers geometry charts for each bike. As I guessed, they had a different stack & reach – the best way to compare modern day frame sizes. Since the frames are a little different, the angles were a little different as well. Being that he put the same size components on the new bike (stem, saddle, crank arms) he placed these into what he thought was the same position.
He was close, but far enough off that there would be a difference.
For my bike fits, I start with the cleats, move to the saddle then finally the cockpit. Double-checking his cleats, they looked perfect. Watching him pedal, I noticed that he was struggling a little, well, really a lot. Moving my camera to the rear of the bicycle, I noticed he had a lot of movement with his left heel. Note: on his old bike, he didn’t have this movement. I started capturing his motion and the fed the video into Dartfish.