This laptop is showing the effective power output of each leg at various points through the pedalling cycle. Maximum power output is not one of the focus areas of a Precision Fit, but it’s interesting to see the variations from side to side and throughout each revolution.
in

Trek Precision Fit

Attaining your ideal cycling position is important. By ideal I mean a position that will not cause short or long-term discomfort or injury, and will contribute to optimum performance. You can DIY if you have good advice, time on your hands and a scientific mind to assess the incremental changes you make. Steve Hogg’s article on page 68 is the first in series of articles that can help you correct different aspects of your bike fit.

If you don’t have the time or inclination to do it yourself there is an increasing number of positioning options backed by the big names in cycling. Specialized has their Body Geometry system, Shimano has just released their Bikefitting System and Cannondale has the Guru Fit Experience. Then there’s Retul and a number of independent professional bike fitters like our regular contributor, internationally renowned positioning expert Steve Hogg, who have made their careers by providing expert positioning services and advice. Trek has come to the party as well in recent days and is rolling out their Precision Fit system in participating dealers across the country.

I met with Ian Stewart at Simple Cycles in Wollongong to go through Trek’s Precision Fit process myself. Ian has been fully trained by the Precision Fit boffins and appointed to train Australian Trek dealers in the art of bike fitting. The decision to install the Precision Fit system is up to individual dealers, and the expense is significant so you may not see it at your local dealer immediately. (If you can’t wait, you can pick up one of the Fit Bike Pro jigs for the spare room for $10,900 USD from Purely Custom. Trek’s software package would be extra.)

It’s a small room but set out with computer screens, video cameras, tripod mounted lasers and the impressive looking jig.  “This is a pretty elaborate system, Ian. I see you have the machine that goes ‘bing’ here too. What’s the basis and motivation for developing and implementing such a high tech service?”

“The jig is made by Purely Custom in Idaho, USA. It’s the best out there, so the design is not owned by Trek but it’s the best there is. The whole system is based on three key drivers; the knowledge base of our fitting and medical experts, the best hardware and the Trek developed software. These expert staff include long-term and well respected bike fit professionals Mark Timmerman, Phillip Cavell, Julien Wall and Paraic McGlynn.”

Trek see Precision Fit fundamentally as a customer service, and one that meshes with their ‘Cycling Inform’ philosophy of good fit and good performance. Stewart said, “The more you ride the more likely to incur injury due to poor setup. Cycling is low impact but even so, if you are not set up correctly you can see problems arise. If you think about spinning at 90rpm for a couple of hours your legs will turn a lot of (10,800) revolutions, so even if your set up is marginally out, you can incur some level of discomfort or injury.”

“Who is your typical customer?”

“Well I don’t like to generalise but I’d say our typical customers are mostly middle aged men. When you’re young you’re more flexible and you will just do things without thinking of the consequences—and you will get away with it when you are young.  As you get older you lose flexibility. Better fit improves recovery. For people who are after performance, better fit leads to more efficiency and that will usually lead to more power. We don’t focus on increased power during the fit, though the system does show left and right-side power output, and the early changes that occur during the changes of the Precision Fit process.”

“How do you draw the line between setting up for comfort and speed?”

“One of the most important things in this process is to find out what the person being fitted actually wants, be it a better crit racing position, or to alleviate the sore back that sets in for them after an hour and a half of riding.

“We ask questions to see if you have any restrictions physical issues, run some flexibility tests, strength tests. Then we set up the jig, shoot some video make some adjustments go around a few iterations to get the best fit.

“One of the really nice things about Trek owning the pro team is that they can actually build stuff around the team, there’s continuity; they can get the team together and they have got this whole structure. I think in the last six months they’ve had three camps where they get them (the pro riders) together, get them on the jigs, analyse position and make some adjustments. Some of them don’t want to change things, but some are quite open to it. Bike fit is not an event; it’s a process that is constantly ongoing. Your body changes, you increase strength, lose flexibility, put on weight or lose weight.”

My time in the Precision Fit resulted in minimal but worthwhile changes. It turns out that I am relatively flexible and have minimal physical asymmetry, so there were no really dramatic changes.  According to the system I could do with a longer stem, and a different saddle that will allow me to roll my hips forward and straighten my back a little to enhance aero positioning. So this could amount to a shopping list of $300 or so on top of the fit session cost. It’s one of the unspoken factors that bike position providers from any of the big brands would have in mind.

Ian moved my cleats back marginally to bring my quads and glutes more into the frame for better power delivery and longer endurance. At the same time this would take some level of strain from my calves – being smaller muscles they tend to fatigue more quickly. The few small changes I left with are a bonus that should result in a more comfortable ride and provide a little more power. 

You might not think that’s great value for $285. I choose to view it from a long-term perspective; I was able to confirm that my riding was not going to create long-term physical problems due to poor position on the bike. I think that’s a good outcome.

Standard fit is $285 for one bike, two bikes is $395

Approximately two hours. Three hours for a two-bike fitting 

At the outset a thorough questionnaire builds a profile of the rider, taking into account height and weight, riding style, riding history, past injuries and desired outcomes.

The Precision Fit jig doesn’t look much like a bike, but its bars and seat are fully adjustable in a two dimensional plane enabling measurement and recording of virtually any possible cycling position.

Saddles and handlebars are easily swapped according to measurements taken during the fit.

Purely Custom’s jig is a belt drive system with crank length adjustment built in. The rear pulley is connected to a resistance unit that provides a load so the rider’s position can be assessed in a real-world riding scenario.

Beside the actual positioning jig, the software of Precision Fit is one of the most important features of Trek’s system. It enables capture and analysis of video, power, and position inputs before providing suggested modifications to position.

The rider’s current bike setup can be measured and transferred to the jig as a starting point for the assessment.

The seatpost and the handlebar mounting post track fore and aft along rails and provide height adjustability, while the crankset and the resistance units are fixed in position at the centre and rear of the jig.

Laser levels are used to provide accurate vertical alignment reference and comparison.

A high frame rate camera captures slow motion video of the cyclist in motion and tracks the movement of black and white dots stuck to the rider’s feet, knees, hips and torso.  Video is fed back to the system computer, where range of motion data is analysed and corrections to position are suggested if required.

The laser here is tracking up the foot arch through the knee and hip and shoulder.

Shoulder width measurement is taken for correct bar width selection.

Flexibility through the lower back allows a more efficient riding position.

The rider’s leg and hip range of motion is checked prior to getting on the jig.

Without firm, comfortably fitting shoes a rider’s stability is compromised and effective power transmission is diminished.

Inseam measurement is recorded to gauge optimum saddle height.

Bontrager have developed a saddle selection seat to accurately measure the width of your sit bones and from there make choices about saddles that will fit your body best. The white section of the seat is a clear envelope filled with white gel. When you sit on it, your sit bones squeeze the gel away to show a colour beneath – which correlates to colour coded saddles in their range.

Once on the jig, high-contrast dots are positioned on the rider’s ankles, knees, hips, and torso for tracking via the video camera. The way these dots move and the limits of their movement provide critical data for the system to analyse.

Lateral excursion of the knees during pedalling is assessed with the laser level.

This laptop is showing the effective power output of each leg at various points through the pedalling cycle. Maximum power output is not one of the focus areas of a Precision Fit, but it’s interesting to see the variations from side to side and throughout each revolution.

Leave a Reply

What do you think?

196 Points
Upvote Downvote
Darren 'Dazza' Strudwick winning the 1984 Collie Donnybrook.

The Third Saturday in August: When Collie Flowers

Mavic’s Ksyrium Elite wheelset tips the scales at 660g front and 860g rear without skewers.

Cannondale Synapse Hi-Mod 2 Red Review