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FORM and function: Ronan Descy

Our Perspective on Human Performance

FORM and function: Ronan Descy

FORM and function: Ronan Descy

Understanding fit methodology


CPS In-Motion has spent some time talking to Ronan Descy of FORM in south-west London. Ronan has developed an extensive reputation and experience in bike fitting over the last decade. Here are some of the points he made during our recent chat……


Thoughts on the commercial bike-fit market….

“The different types of branded fitting systems such as Retül, BGFit, Shimano etc used by bike fitters can be a confusing subject for outsiders to negotiate. There are so many choices available, it’s hard for potential “fittees” to decide which option to go for. Fit processes such as the ones mentioned above are all like recipes – essentially guidelines for fitters to follow – a set of criteria on which they can base their work. These processes are typically a combination of both sound and questionable premises, and often rely on specific fitting equipment, the tools which fitters use to gather information and make decisions by; goniometers, lazers, plumblines; 2D & 3D motion capture; performance software.”


Ronan believes the processes and tools should be considered independent of the fitters themselves.


What differentiates between bike-fitters today?

“Fitters are like cooks, some good, some bad, some who work to the letter of the recipe and others who use it simply as a starting point. It’s hard to know as a customer whether one is engaging a unique and able fitter, a generic process, neither or both”. Ronan believes that although ‘the recipe’ is a good idea in principle “It is just a recipe, and in order for this recipe to be elevated to the highest possible level, rules need to be broken.”

One of Ronan’s key aims is to engineer the most realistic and life-like environment possible during a fit. The reason for this is simple; it gives the closest window into how riders perform in the real world and in this way guides him in positioning you better.


“FORM’s fit methodology is based on a functional and fully dynamic process.”


A fully dynamic fit means that Ronan will not stop you mid pedal-stroke to take measurements or to hang a plumb line from your kneecap, but rather make adjustments based on visual feedback from watching the fluid riding process and transition between positions.


Ronans perspective on dynamic bike-fitting…

“To be honest I can’t at this point imagine any other way. A fully dynamic fit process does not rely on generic measurements or on simply setting you up within ‘optimum parameters’, whether these parameters are established using hand tools, video capture or 3D motion capture. Each rider has a unique set of circumstances and equipment and generic, semi-stationary or measurement-based is simply not good enough”

Each riders’ unique circumstances create a specific challenge which force Ronan to make sense of all these aspects using an individual, personalised approach.


How do you replicate the life-like environment you mention?

“FORM’s studio is fitted with a revolving and elevating fit platform which allows me to see the rider from all angles and test their climbing technique on a slope. Changing slope and positions during a fit is key as this shows how the rider relates to both the terrain and the changing angles of the bike. I also use 2D video capture as a way of demonstrating to each rider all the important aspects of their ‘biomechanical picture’, particularly those elements which need changing.”

Ronan goes on to describe how the basis of a good bike fit is to increase physical performance.

“Performance increases when dysfunction decreases. Dysfunction is caused by poor physical condition and bad positioning. Bad positioning in turn creates an environment which challenges the body, forcing it to counteract and adjust, leading to dysfunction.”


Overall, Ronan’s philosophy and the principles based at FORM is to liberate the body and allow it to perform in it’s natural state, free of dysfunction.


You can contact Ronan here to find out more for own unique requests.

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