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.

Monday, October 8, 2018

A Killer Quad Workout to Build Crazy Strong Legs

Bulging, carved quads are like flashing neon signs announcing that you are a cyclist, and you’ve come to kick some ass. And those diamond-cut cannons are more than just aesthetically pleasing in your spandex. The four muscles collectively called the “quads” are the primary movers when you push through the pedal stroke, so stronger quads equals more watts.
“Cycling is a power sport,” says David Ertl, Ph.D., a USA Cycling Level 1 Coach with Peaks Coaching Group. “You need leg strength to crank out power. That means building all the muscle fibers you can. If you can get 10 or 20 percent stronger than the next guy or gal, you won’t fatigue as quickly, and you’ll have that much more in reserve when you need to give a burst up a hill or off the line at the start.”
This size of yours depends on a host of factors including your height—shorter riders’ legs tend be (or appear to be) stockier; your genes—some people, like sprinters, have more fast-twitch “anaerobic” muscle fibers, the ones that really pop, giving track racers those Lycra-busting quads; and how and where you ride—spinning easy at a high cadence develops less muscle than pushing harder on those pedals. Of course, powerful quads come in many shapes and sizes. After all, Chris Froome’s legs are downright willowy compared to the tree trunks on Mark Cavendish, yet both do an admirable job of getting a bike to the line fast and often first.

Tuesday, September 25, 2018

How To Achieve The Perfect Bike Fit

By Rick Schultz

I recently had a great discussion with one of the premier fitters in the U.S. – Happy Freedman.
The original discussion revolved around me asking, “What differences (angles, etc.) are you seeing between fitting someone statically or dynamically?”
We also discussed the state of bike fitting, which will be a separate article.

Quick Definitions

  • Static Bike Fit – All measurements taken in a static / fixed position. For example. the cyclist is placed in a foot down position then measured, foot forward position then measured, etc.
  • Dynamic Bike Fit – All measurements are taken via a motion capture camera while the cyclist is pedaling under a high resistance (i.e., high wattage output). The video is analyzed then changes made to the bike.
Happy replied, “it’s actually more complicated than that.” He went on to explain that there is a greater difference in measured angles depending upon the time of day.

How Tall Are You?

There have been many scientific studies that conclude that people are 1-3cm (0.4”-1.2”) taller when they get out of bed than they are when they go to bed at the end of the day. Why? Gravity. In fact, NASA states that astronauts are 5-7.6cm (2”-3”) taller while in space.
For the bike fitter, during the interview process, there are more questions to ask;
  1. Do you train to race or train to stay in shape?
  2. Do you want your bike to fit you during your races, during your training or doesn’t matter?
    a. What time of day are your races?
    b. What time of day do you train
And, based on the cyclist’s answers to these questions, the bike fitter might opt to do the bike fit at the same time-of-day that the cyclist will be training or racing.


Discussions with other premier bike fitters, most say that there is somewhere between a 4°-6° difference in knee angles between a Static bike fit and a Dynamic bike fit. The reason for this is that cyclists will tend to move either forward or rearward in the saddle when under a heavy load. Moving forward or rearward places the cyclist in a different position than when sitting neutral in the saddle as with a no-load condition.

So, What Is Best?

Most bike fitters, including myself, agree that a dynamic bike fit is best. The drawback is that this is a longer and therefore more expensive process. But the advantage is that the fitter can view and evaluate the cyclist pedaling under real world loads.
The cyclists’ angles are recorded in real-time using a motion-based capture camera running at a high enough frame rate that smooth pedal rotations are seen without any blurring. The cyclists’ motion is recorded to a file which is then opened in a computer analysis program such as Dartfish. Exact angles can be identified under different loads (if taken) and a more precise bike fit can be achieved.
A dynamic bike fit will put the cyclist closer to their optimal position than a static fit. For an even closer and more precise fit, you must also consider the time-of-day of your races and get a bike fit at this exact time.


Does all of this matter? Even with a static bike fit, a good bike fitter will get their client into a better position than by having no bike fit at all. But, the same good bike fitter will get their client into an even better and near perfect position with a dynamic bike fit.
On average, a dynamic bike fit is about $100 more than a static bike fit. This is because with a dynamic bike fit, the fit needs to be accomplished first, then, the bike fitter need to spend extra time copying the dimensions from the fit bike (Guru, Retul, Purely Custom, Shimano) machine onto the cyclists’ bicycle.
Of course, this is assuming that the bike fitter pays attention to detail as well as knows how to correctly and accurately copy measurements from the bike fit machine to the actual bicycle. Another option employed by a good bike fitter is to use the clients bicycle on a Computrainer and motion-based cameras and analysis software. In this example, the bike fit is a little more difficult to perform but once done, all updates have already been made to the clients’ bicycle.
Since there are several items at play here, a good bike fitter will know how to use them to help you with the perfect fit. The only caveat is that you, the client, needs to find that bike fitter.
Bike Fitness Coaching is your one-stop shop for professional bike fitting and coaching. Guru, Trek and BikeFit static and dynamic fit certified, USAC level 2 certified coach with Peaks Coaching Group.