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Andy Pruitt: Q&A

Pete Muir
29 Mar 2016

The father of modern bike fitting and creator of Specialized’s Body Geometry concept tells Cyclist about the art of matching bike to rider

Cyclist: How did you first get into treating and fitting cyclists?

Andy Pruitt: I got my start in sports medicine when my high-school American football coach sent me to a summer school for athletic training back in 1964. I took my first class and I’ve been doing sports medicine professionally since 1972. In the 70s I became director of sports medicine at the University of Colorado. I was providing medical care for the Nike Running Club out of Boulder and was part of the test programme for the original Nike Waffle shoes, so I had this interest in biomechanics, and when cyclists started showing up with knee injuries I knew it had to be something to do with the way they rode their bikes. I did my first medical bike fit around 1978. Taylor Phinney’s mother [Connie Carpenter-Phinney, 1984 Olympic Road Race gold medal winner] was my first bike fit.

Cyc: What was the old-school thinking on bike fitting?

AP: Bike fitting in the 1970s was based purely on the Italian and Belgian traditions, and it was all in the X-Y plane – the side view. It focused on saddle height, saddle fore and aft and handlebar position. Knee injury was epidemic in those days and what I started doing had very little to do with the X-Y plane, it was all Z plane – front view. I looked at hip, knee and foot alignment, arch control, arch collapse, custom orthotics, customising shoes and pedals.

Cyc: Is bike fitting a science or an art?

AP: There is no more experienced medical bike fitter in the world than me. That is not bragging – I started it, I’ve lived this thing. I would say that what I do is 90% science based, but there is this little piece that is just ‘how it looks’. No machine can capture that last little piece. That’s just in my eyes from 40 years. The guy in your local bike shop is probably 60% science and 40% ‘swag’ (scientific wild-assed guess), but the more experienced they get, the greater that percentage of science goes up.

Cyc: Can anyone be a bike fitter with the right technology at their fingertips? 

AP: No, no, no, no. Technology can enhance what a good fitter does; technology cannot do the fit. That motion capture camera cannot evaluate your foot structure or determine how much arch support you need. Don’t let a poor bike fitter hide behind technology. Don’t let them baffle you with sizzle and smoke. If I do a bike fit on you with a plumb bob and goniometer [a device for measuring knee angle] and my naked eye, it is going to be the exact same fit that you’d get with a $75,000 motion capture biomechanics monitor. The difference is that with the technology I can show it back to you. I can say, ‘Here’s what you were doing; here’s what you’re doing now.’ 

Cyc: How much can riders determine their own best fit by feel?

AP: My advice to riders is: don’t confuse familiarity with something that could be better. A lot of people say to me, ‘I’m a toe pointer.’ Oh yeah? That’s because your saddle’s too high! 

Cyc: Are pro riders tough to convince when it comes to changing their position?

AP: The pros are easy to work with. They’re not set in their ways like some older riders are. The first time we did a pro squad with the responsibility of fitting the team – it was Saxobank in about 2003 [back then called Team CSC] – most of the guys didn’t even know what size bike they were riding. A while back Tom Boonen came to us for a performance fit and after I did all my measurements I said, ‘Tom, why are you on a 46cm handlebar?’ He said, ‘I’m not sure, I think my junior coach told me I would grow into it.’ I put him on a 44cm handlebar and he said, ‘Whoa, this feels so much more comfortable.’ And his sprint turnover time, thanks to the shorter levers, got quicker. Aerodynamically it saved him 25 watts at 50kmh, which is huge. 

Cyc: Is there anyone in the pro peloton you think looks wrong on the bike?

AP: Froome! Oh God, is he ugly on a bike! But the bike and the person have to be married together. I know who fit Chris Froome – I trained him – it’s Todd Carver [creator of the Retül
bike fitting system], so I can guarantee you that that’s as pretty as Chris can get. 

Cyc: What are the most common mistakes people make when setting up their bikes?

AP: Saddle choice. The saddle is the centre of the fit universe. If I’m on a saddle that’s too narrow, I’m going to tend to clench my pelvic floor muscles and rock myself back on my bum, and then I need a shorter stem. But if I get on a saddle that lets me sit on my sit bones, it changes my weight distribution on the bike and it changes the stem length. Never buy a saddle just because it matches your paint job, and don’t accept the one that comes with the bike. Finding the right saddle shape is step one, and if you don’t get that right then the rest of the fit won’t work.


Cyc: When you start a fit do you prioritise comfort, medical issues, power or aerodynamics?

AP: Bike fitting is a dynamic thing. Your fit can evolve and it’s rarely a one-and-done. Take Sylvain Chavanel. The first time we saw him he was six days post spine surgery, so we put him in a post-operative position and over several months we evolved his position as he recovered. Our first goal was just to get him back on the bike and train him aerobically, and then our last goal was to get him into a time-trial position. I think bike fitting should be done at least annually. Even if you don’t change anything, you should take the opportunity to look at your position. 

Cyc: How does your fitting expertise influence bike design at Specialized?

AP: The Roubaix [SL4 review here] was my idea. I was in a development meeting and Mike Sinyard, the owner of the company, said, ‘Let’s go round the room and each of you tell me your dream bike.’ Of course, all these 20-something engineers were saying, ‘It needs to be stiffer, it needs to be lighter…’ When it got to me, I said, ‘Well, it needs vertical compliance and an adequate head tube…’ It was like I’d pooped my pants; they couldn’t get away from me fast enough, but then Mike said, ‘Great idea; build me one.’ The Roubaix was born. There’s not a product leaves the building where fit has not been considered.

Cyc: Is there any new area of fitting that you are focusing on at the moment?

AP: I can’t tell you. There is a huge missing piece and I think technologically we are on a real threshold for both fit and performance. I’m not even sure if it can be achieved. Just because I want to see something doesn’t mean that the engineers can figure out how to let me see it. I would like to prove or disprove some of the things we’ve been teaching for decades, and if they’re not true, I want to be the one to know it.

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