How to choose the correct frame size

Cycling has become increasingly popular in the UK over the last 10 years due in part to the success of the British Cycling team in major competitions as well as British cyclists such as Bradley Wiggins and Chris Froome winning the Tour de France. This year Yorkshire is holding the Tour de France Grand Depart and this will inevitably create interest and a surge in people taking up cycling.
If you are new to cycling then choosing a bike is no longer a simple process as there are many different types depending on the terrain you want to cycle on such as road, trails, cross country or sometimes a combination of these. Whether you want to compete in triathlons, road races or the increasingly popular sportive then bikes will have different specifications for each. Even road can have variations between the type of riding you want to do for example some will have lower head tubes for more aggressive aerodynamic riding or higher for longer days in the saddle.

If you are new to cycling and want to see if it is something that you will enjoy then the best option is to buy an entry level bike that is both reasonably priced but at the same time is still a decent bike. You will often be able to research what bike is right for you and check out reviews online. The more you spend the better the components and lighter the frames can become, but this is not necessary when first starting out.

Choosing the correct size is very important for comfort, efficiency and ultimately injury prevention. Bicycle companies have different sizing methods but mostly they either use small to large etc sizes or centimetre/inches measurements. There are also frames more specifically for females taking in to account anatomical variations such as pelvic and shoulder widths. Most brands have basic charts that you can view on line that correlate your height and in inseam measurements to a frame size. This is useful to get an idea of what size frame may be appropriate for you.

The problem with a standard bike size and the components added are that they don’t take in to account the complexities of the individual human in motion and that we are all different shapes and sizes. For example two people can be the same height yet may have different leg lengths and more specifically different lengths of shin or thigh bones as well as varying trunk and arm lengths to name a few.
A correct bike fit is crucial and this isn’t always offered at the bike stores but is necessary in preventing future problems occurring as well as optimising efficiency and comfort. Cycling is a low impact activity but due to the repetitive nature of the pedalling action any small problems will be amplified and an injury or discomfort may occur.

The majority of these complaints are due to overuse, poor technique and fundamentally incorrect bike fitting. A recent study from Norway interviewed 101 professional cyclists and identified that out of 94 injuries 45% had lower back pain, 27% knee pain and 13% lower leg pain over the previous 12 months.
Lower back pain is the most common complaint when reviewing the research literature on cycling and may be due to many factors;

Over reaching due to incorrect frame size or stem length
Incorrect saddle positions such as over tilting, too far forward or backwards or to high
Underlying poor sitting postures on and off the bike
Handle bars too low due to short head tube
Incorrect pedal crank length

Knee problems will also be related to many of the causes for lower back pain but too high or low saddles are one of the prime reasons for knee pain as well as the cleat and pedal interface if you decide to try a specific shoe and a cleat to connect you to the bike. When looking at the knee position relative to the hips and ankles/feet the base of the knee cap (more specifically the bony lump below the knee called the tibial tuberosity) needs to be over the pedal spindle. This measurement is affected by saddle position as well as a few other variables (for a more detailed look at the fundamentals of a bike fit on the Hallamshire Physiotherapy website).
As you can see choosing a bike isn’t easy but it is worth the effort to get it right to optimise your enjoyment and hopefully a lifetime of cycling. If you require a bike fit or some basic information then please contact us at the Hallamshire Physiotherapy clinic.

Matt W


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