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Whats the Best Type of Bike Fit?

2016/7/25 10:00:18

If you ride your bike long enough, chances are you'll want to get a bike fit. A properly fitting bike can help to prevent injury, promote pedaling efficiency and increase comfort.

But with all of the different bike fitting options available, how are we to know which one is best? Is the simple, more traditional approach better than using the latest and greatest technology?

Determining the correct approach towards blending modern technology, the expert eye and experience to get the best fit for the customer can be a difficult task. To help us out, let's look at the different types of bike fits and get some advice from one of the industry's best, Stu Waring.

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Bike Fit Setups

First, here's a brief overview of two bike fit approaches and tools:

Standard Fitting/Studio Set-Up: Today, almost every bike store has a spot in the back with a trainer and a wheel block where a client's bike can be set up for a fitting. Hanging on the wall is a goniometer, a plumb bob and a few tools that help to measure inseam and torso length. The client mounts their bike, pedals it and has to stop several times to have the position measured. This is called a static fit.

High Tech Fitting/Studio Set-Up: In addition to what an "old school" studio has, the high tech fit studio consists of a dynamic fit bike or a motion capture system.

Tools of the Trade

SpinScan is part of the CompuTrainer system, which is an electronic Pedal Stroke Analyzer that can help increase power and efficiency. The software is able to show the left and right leg power splits and gives the rider feedback necessary to practice pedaling in "circles." It identifies "flat" or "dead" spots in the pedal stroke where power is not being transferred to the drivetrain and is a great tool during the fitting process.

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Motion Capture Systems: Retul is the most popular 3D motion capture system that uses a marker-based optical tracking system. It tracks infrared light (IR) emitted by an eight-point body harness worn by the rider that is equipped with light-emitting diodes (LEDs). This cycling-specific 3D motion capture system reads a rider's movements (knee angle, back angle etc.) while pedaling and records all three planes of movement (3D) in real-time. Retul's dynamic fit tools allow a bike fitter to make fast and easy adjustments to a rider's position using objective and highly accurate fit measurements to guide the changes.

Dynamic Fit Bike: The "fit bike" or "fitting machine" is the evolution of mechanical fit bikes (Waterford, Serotta) and replaces the need for a stationary trainer and client's bike. Instead of being fit on your own bike, we install your saddle, a similar sized bar and pedals directly onto the fit bike, which you then ride during the fitting process.

The beauty of these fitting machines is that they allow a rider's position to be changed while pedaling (dynamic state) with accurate adjustments (up/down, forward/backward) of the saddle and handlebar. Some examples of these are DFU, Retul MOVE and Guru Fit Bike. While they essentially do the same thing, the way they operate can differ. Most fitting machines have the option to be equipped with a power meter. The addition of SpinScan used during a dynamic bike fit provides methods to remove guesswork from the bike fit process that were not previously available.

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Debating Approaches

To accurately capture what all of this means to you, the reader, I've asked Stu Waring, a Master Retul fitter and instructor, his thoughts on the advantages and disadvantages of old-school methods versus high-tech methods. I trained Stu years ago using the PowerFiTTE methodology, but he currently uses the more tech savvy Guru Dynamic Fit Bike and Retul for all of his fittings. I consider him the person most knowledgeable to discuss the merits of both approaches.

JH: Hey Stu, hand fitters appear to have been unceremoniously swept to the curb by a tech savvy, effectively marketed array of glitzy technology. Have the "hands-on" fitters become anachronisms of a dying culture? Or just in need of better tools like the CompuTrainer SpinScan that essentially measure the fluid dynamics of the pedal stroke? Share some of your thoughts on the pros and cons of "Tech vs Hand."

SW: Well John, the main advantage in using a Fit Bike is that we can make adjustments to the rider's position in a dynamic state. Traditionally, adjustments using the client's bike can only be made in a static state. The rider had to stop pedaling, lift off the saddle or get off the bike while adjustments were made.

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The DFU that I use allows me to save multiple positions and quickly revert back and forth with a click of the mouse. With a hand fit, it's impossible to go back to another position without tearing the bike apart, which takes time. In regards to measuring the rider's position, the biggest variable with static fitting is that the fitter is required to stop the rider and position the foot at the bottom of the stroke to measure the knee angle.

The hand fitter has to set the foot, and therefore is putting the rider in a position that the fitter perceives as the most desirable and not how the rider actually pedals. This leaves the door wide open for inaccuracies. Retul measures the ankle angle and knee angle at the same time dynamically, which allows for the best position to be attained for the rider.

JH: OK, but with a good eye, an experienced hand fitter can watch the pedal stroke and do the same thing, right?

SW: I would have agreed until I saw how Retul works. Now I feel it is at best a good guess and not accurate.

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JH: I agree that replication of foot angles are important. We use a separate goniometer just to check the angle and a laser to measure the consistency of the angle. I believe my method is also accurate. I train my cyclists to pedal at 17 to 20 degrees of plantar flexion for maximum, consistent output. Another strong point concerns sacral alignment, which we check before measuring the leg angle.

SW: Like you, we are constantly looking and communicating with the rider during the entire process. This is something that you instilled in me years ago and is still a big part of my process.

JH: OK, we agree on visual observation. With the simplicity of a telescopic goniometer, I can check the body's trigger-point markers to get it right quickly, then back test the results with Computrainer's SpinScan (SS) technology.

SW: Yes, it's hard to argue the cost and simplicity of the goniometer. It's a classic tool and every fitter will always have one. A point on SS, it does not capture the entire stroke—it measures the torque output and calculates the information it provides on the first 180 degrees (down stroke) for each side.

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JH: You are right it's a calculated representation, but it reads directly off the tire edge and the physics are spot on. Actually nothing is better, with load being calculated at 100 times per second.

SW: The Computrainer and SpinScan are great tools and I use both too, and most fit bikes come standard with one. Retul adds the ability of literally drawing the path of the knee during the entire pedal stroke.

JH: It appears we both use similar methods to accomplish the same end result. Certainly Retul offers the data as back up, but essentially it does not change the output of the fit. As for other elements of the positioning, it's important to take notes and use body markers. We're both looking for one position, and that's the right one for the customer.

SW: The downside of any Fit Bike/motion capture combination is that it's expensive to purchase and is permanently installed. The Computrainer is very inexpensive by comparison. It can be stored in a closet and is mobile. The Fit Bike is time consuming to use because the final position has to be transferred from the fit bike back to the owner's bike. However this is only done once and can save time when dealing with multiple bar and stem changes. The Computrainer saves time since all of the changes are made directly to the owner's bike. However, this can backfire when working on the cockpit or when more than one stem and bar change is required.

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JH: Agreed on all points.

SW: With our system, we're able to provide accurate electronic data capture throughout the fitting that can be e-filed for each customer. The final position can be used to help determine the correct size and set up for a new bike purchase. With the Computrainer the position capture is made by hand, is time consuming and might not be as accurate.

JH: I'm mesmerized by the amount of data produced by the Retul system.

SW: If and when there's a problem or imbalance, the data is there to determine the cause. Most of the time we only use a small amount of the data, but when there's a red flag, we have options and plenty of data to fall back on.

JH: I'm not sure if all of that information is necessary. I'm skeptical on its value to the athlete, who really just needs to know a few documented position markers for replication, and whether or not the cyclists has improved power and comfort.

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SW: Truthfully I was skeptical too, until I started to use it. Now I find it invaluable. I've seen the technology in action and the benefits the data can provide, make it hard to use anything else.

It boils down to this: dynamic vs. static data capture. Do you want to measure the rider while they're pedaling or stationary? The answer is obvious. Retul is simply a better tool because it allows motion-based rider data capture. I call it a "liquid tape measure" because it provides the ability to capture data accurately and quickly while the rider is pedaling. Hand tools cannot do this. They require the rider to be in a motionless state. The addition of a Fit Bike provides the opportunity to increase accuracy of bike data capture by being able to adjust the position in a dynamic state. The bike on a trainer requires the rider to stop for an adjustment.

What you do with the data is completely dependent on your ability and experience as a fitter. Neither of these tools creates a position for you, they only capture data and allow easy adjustment. You still have to know how to fit someone.

When it comes to the determining the correct position, Retul and Fit Bike don't do it for you. You have to spend time with the client to determine their physical constraints and limitations, so "Hands-on" fitting is still a major part of determining the fitting solution. Personal interaction develops trust and confidence between fitter and the client. No amount of technology will ever replace the human aspect of a fitting.

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JH: Bike fitting is a SERVICE, not a technology or a product. While technology can potentially make bike fits more accurate, we both agree that it is still up to the fitter and his or her experience level to determine what to do with the data. This has been a good exchange of thoughts, ideas and views. You have done a great job of expressing your position and you're right—technology is here to stay, but from this exchange I think we're achieving similar results, but taking a slightly different approach to get there.

SW: I would hope that you agree John that looking at this from a broader perspective, that these tools allow fitters to see things they might otherwise miss or take years to spot.

JH: I would acknowledge that it's not realistic to expect everyone to have the depth of experience that we have cultivated. New fitters and those with experience need to understand the importance of accuracy and repeatability, developing a quick diagnostic eye rather than missing details.

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