What is 'the physio bike fit'?

The physio bike fit is is a process of biomechanical assessment and fitting the bike to the rider while considering the rider's current anatomy and needs.

We start by finding out where the rider is now and where they wish to be.

Establishing where the rider would like to be is the easy part, we just ask.

The current position is a little more of a challenge.

The process starts with a discussion to ascertain any current injuries or discomfort on or off the bike.

This leads into a basic history of the rider's physical condition.

Following this the physical examination starts, with the purpose of highlighting asymmetries of strength, flexibility and stability.

The off bike posture is very important as I am yet to meet anyone who spends more of their waking hours on the bike than they do off it and this will influence what we see on the bike.

Taking time to thoroughly look at both static and dynamic off bike posture is vital in assisting the rider in understanding how they can improve by considering simple changes to, for example, their work station or phone using habits.

Other, non-cycling, physical activities will almost always play a big part in body posture, particularly activities that require a repeated activity asking one side of the body to do something different to the other as the primary activity, for example racket sports or golf.

Posture is assessed using both static, for example standing or sitting, and dynamic, for example squatting or lifting the heels, tests.

Flexibility is also assessed on both a global and specific level. For example looking at where the joint ranges of motion are more or less stiff. Particular attention is paid to the lower limb, though it is amazing how many cyclists are unable to place their arms in the 'TT' position off the bike.

During the off-bike assessment, feedback is constant to how movement patterns will alter the on bike position and movements.

Looking at how the movement is achieved is key not just that it is achieved. This includes both active and passive movements.

Active movements are performed by the rider, they are in control of and causing the movement to take place and will demonstrate patterns of movement.

Passive movements, are performed by the fitter moving the body part (generally a limb) for the rider. The purpose here is to assess tension in the body and how the movement is limited and the effects the movement has on other parts of the body.

Patterns found here will provide clues as to what will be seen on the bike.

A common example of a simple movement pattern that can alter on bike movement is how the longitudinal 'arch' of the foot behaves on loading. When walking normally the toes can be 'pulled back' towards the shin bone and tension the structures on the sole of the foot. This is know as the 'Windlass Mechanism'.

In a rigid soled cycling shoe this is not possible and the 'arch' can flatten under load. This in turn can lead to a rotation inwards of the knee on the standing leg. This is considered in conjunction with other biomechanical findings during the assessment and feedback is constantly provided for the rider. 

This underlines the importance of the assessment to help the rider understand what is happening as they cycle. The combination of both passive and active movements to assess muscle and joint actions allows in the uncovering and understanding of habitual and mechanical movement and posture patterns.

An example of an habitual posture pattern would be standing talking with one foot turned out, whilst an example of a mechanical posture could be cause of the foot being turned out this would only be uncovered by looking at other movements and passive assessment of the joints involved.

Once all the weight bearing assessment has been completed it is time to relax and go through the passive movement assessment.

Particular attention is paid to what is happening in the muscles and joints around the pelvis. Asymmetry, weakness, restricted range of motion or tension here will almost without exception transfer on to the bike in some way. 

This part of the assessment is helpful in discovering the causes of some of the off bike movement patterns already witnessed and will point to movement patterns that are likely to be seen on the bike.  

Once on the bike, after a warm up period, markers are placed on various parts of the rider's anatomy and HD video is recorded from both the front and the side of the rider.

The purpose of this is to assess the initial position of the rider and to more deeply examine how any issues in strength, stability or flexibility noted off the bike manifest themselves on the bike.

The HD video footage is examined in real time, slow motion and frame by frame to help the rider understand what is happening and why.

At this point, if there are fitting issues that require immediate attention, these are addressed and the video is retaken and this part of the process is revisited.

The next step in the process is to attach the two Retul harnesses, one for each side of the body, to specific points on the rider's limbs and torso.

This allows the Retul system to take accurate measurements of what is happening while the rider is pedalling under load.

With the aid of the rotating platform the capture of information is made from both sides of the rider in one continuous action. The main benefit of this is the removal of left versus right error due to stopping and starting.

The information captured allows for a further review of the rider's dynamic position.

Any required adjustments are discussed as the information is assessed and then made.

As a point of process only one alteration is made to the bike at a time.

This serves the purpose of allowing the rider to assess the feeling of the alteration and for the fitter to assess the alteration. A further capture is taken from both sides of the rider.

The rider comfort together with the new data is then assessed.

We continue with this process until either the optimum position is reached or the best available position is gained.

The difference between these two eventualities can be that the bike is not the ideal size or geometry for the rider or the rider is lacking in his or her physical state preventing further progress at the time of the fit.

Both will be obvious to the rider and examples could be a bike that does not allow enough adjustment in the saddle height to accommodate the riders leg length or rider who cannot pedal efficiently due to injury.

Throughout the process the comfort of the rider and the data findings are discussed to help with this.

The adjustment process itself always starts with the feet. As the major source of energy input into the bike the foot position in relation the pedal is key.

The pedal cleat interface adjustment is limited to how and where the cleat is attached to the sole of the shoe, with some manufacturers offering more adjustment than others. There are some additional adjustments that can be made by the addition of footbeds, wedges or shims, but the reason of each of these needs to be clear.

If there is excessive knee movement due to poor position or hip muscular tension then a 'cleat wedge' is unlikely to be a long term fix... This underlines the importance of the off bike assessment.

Next, the saddle height is adjusted. The aim here is to provide a saddle height allowing balance/stability and effective propulsion through the pedal. On road race type bikes with a very low 'stack' height  this can be limited by the relative height of the handlebars. In cases where the rider is considerably lacking in flexibility the ideal saddle height is restricted by the drop from the saddle to the handlebars by discomfort for the rider. This is often experienced as discomfort in the lower back or in the saddle contact area due to the lack of flexibility.       

As the seat tube angle on bikes is inclined rearwards (away from the bottom bracket towards the rear wheel) any increase in saddle height will move the saddle rearwards and conversely any reduction in vertical distance from the bottom bracket will result in the saddle moving forwards on the bike.

To take this into account the next adjustment is moving the saddle in the fore and aft plane. As most saddles are designed for at least a specific point to be horizontal this is also checked. The fore aft position of the saddle will have an impact on the fore aft position of the rider. One of the most commonly used measurements for an 'ideal' position for this is the 'knee over foot/pedal' position.

This can be measured in a static manner when the crank arm is at horizontal as in the image below.

However, as most riders sit differently on the bike when moving the Retul system measures this in a dynamic manner when under load and pedalling.

There are a couple of basic points to consider here;

• If the saddle is moved in the aft direction the distance from the bottom bracket is increased and so then is the effective saddle height. The converse is also true if the saddle is moved forward.
• The position of the foot on the pedal is controlled to a large extent by the cleat position on the sole of the shoe, not to mention the fit of the shoe to the foot inside it.
• People with short femurs, or long femurs and shorter torsos may have issues on some bikes with reaching the bars and achieving an ideal position.
• Riders on the edge of the 'fit window' will be more find the accuracy of the fit is more sensitive to crank length, this is particularly true for shorter (often female) riders.

There are many other salient points (lay back seat posts for example), but these few are worth initial consideration.

While the saddle position is considered, for riders with specific comfort issues we also look at the saddle shape and utilize the saddle pressure monitoring device this produces a 'pressure map' of the saddle live as the rider cycles.

The aim of this is to check for pressure build up on the rider that may not be immediately apparent and could be contributing to any discomfort.

we have 35 different shape saddles here to help find a suitable shape for the rider.

Once the most suitable position is ascertained for the rider, the front of the bike is addressed. This includes the bars, stem and brake levers.

The reach to the brake lever hoods needs to be comfortable in both height and distance from the rider. Within the adjust ability offered from the existing bike components an ideal fit is aimed to be found, if this is not possible an adjustable stem can be employed.

This allows for greater adjust ability to work with the ideal fit.

The angle of the brake lever hoods is also address to help create a neutral position for the wrists.

While also being more comfortable this also helps to reduce the direct impact of road vibration on the wrists and neck.

Once the process has been completed and any fine tuning applied a second set of video is taken. This is then assessed and compared to the pre-fit video and the rider's experience of comfort is discussed.

While there are other measurements that we are able to utilise during the process, however, this forms the basis for each fit performed.

At the end of every session the bike is measured and these measurements are provided, together with images and fit reports to the rider, in most cases these measurements can then be transferred to other bikes without the need to pay for another fit.

Thank you for reading.

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Happy Miles!