Biomechanics of Cycling
To optimise your cycling (pedalling) biomechanics we use the 3-step integrated bike fitting process.
The biomechanics of cycling is complex as it involves man and machine influenced by many variables. To prevent the risk of a cycling injury it involves harmony between man and machine which is profoundly dependent on efficient pedalling symmetry.
On average a cyclist performs about 5,000 pedal revolutions an hour. During this process poor performance, overuse injuries and discomfort may occur by the smallest degree of mal-alignment whether it is anatomical, biomechanical or mechanical factors.
We will assess both you and your bike.
Using the correct set-up parameters of bike-fit e.g. the 3 contact points, saddle, pedals, and handlebars (2) designed to meet the demands of your chosen sport. Harmony between you and your machine can be achieved by adopting specific body positions and by adjusting your bike set up ready to meet specific demands.(3,4,1).
Harmony is clearly interlinked by using a sports science and sports medicine approach (5,6)
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Optimising pedalling biomechanics
In recent years pedalling cadence has received enormous attention by researchers, cyclists and coaches, to distinguish the cadence that optimises the power output, while minimising metabolic cost and muscle fatigue. However to date the research has surprisingly conflicting results with minimal consensus regarding the optimal pedalling cadence (7,10,12).
Although a complex subject, there are many reasons why this maybe, due to 3 main opinions i.e. Physiological, Biomechanical and Environmental factors (8).
Physiological / Biomechanical – This depends on the cyclist physiology and genetic structure, to determine levels of performance and biomechanics. Research suggests that the type of muscle fibre effects cadence due to distribution, contraction, velocity and recruitment which may influence the energy expenditure (metabolic cost) and energetic optimal performance when pedalling at different intensities (9).
Types of muscle fibre
The profiles of leg muscle fibres can be categorised into two groups: Slow Twitch fibre (ST), or Fast Twitch fibre (FT) dominant. Both muscle group fibres differ in their mechanical and energetic properties and the relative distribution differs between each individual rider - for example smaller and thinner riders have a tendency to be ST dominant (11). This may explain why these fibres favour lesser forces and therefore favour greater cadences. Whereas the bulkier and larger rider has a tendency to have more FT fibres, which favour higher forces that are linked with lesser cadences and bigger gears.
If you are a larger rider we can help you change your profile through aerobic exercise training to help grow your ST profile which may enable you to spin that little bit quicker!
The racing terrain and conditions may often effect or dictate your pedalling cadence and style. Cyclists that ride on flat terrains will generally spin faster, this permits them to react and accelerate faster if somebody makes a break while preserving leg muscles from fatigue. On the other hand when a road cyclist climbs the road they will use a lesser cadence for reasons explained below. Likewise, the more proficient the rider is such as a mountain biker for example will have a tendency to use larger gears and fewer cadences when cycling over rough or dry terrains. This is because they will often use little body weight on the saddle by using the pedals as a platform to negotiate obstacles better.
Preferred vs Optimal Cadence
Numerous studies have suggested that the ‘preferred cadences’ chosen by riders of 80-100rpm are greater than metabolically optimal ones of 50-70rpm. Although the word ‘preferred cadence’ can be confusing, as it suggests that a cyclist spontaneously adopts their selected cadence instead of their cadence being imposed by Physiological, Biomechanical and Environmental causes. For instance an elite cyclist may adopt a cadence of ’60-70rpm’ on hills compared with their usual 90-100rpm.
According to subjective anecdotal opinions, research suggests that the decline of cadence maybe due to the increased muscular stress from the gravitational resistance forces when climbing. Whereas when a cyclist is riding on flat terrains the main resistance is the wind relative to speed, allowing the rider to ease / decrease the muscular stress particularly when drafting. Drafting permits the rider to decrease the aero-drag which helps to limit loading on the leg muscles which in turn enables them to increase their pedalling cadence.
According to the research this would imply that the ‘preferred cadence’ for each cyclist may determine a natural compromise between a cadence that limits cardiovascular stress (metabolic cost) and that which reduces the muscle stress in the rider’s leg. Reports have suggested where the optimal cadence for reducing metabolic cost at 80-70rpm the optimal cadence to reduce muscular stress is in the area of 100-110rpm. Therefore this would suggest that the ‘preferred optimal cadence’ is 80-90rpm for most occasions.
Despite the unconfirmed evidence, researchers generally mention “self- selected cadence” is usually better. The human body is surprisingly adaptable and over a period of time it learns to adjust and function efficiently under the conditions it finds itself in. For physiological and biomechanical purposes we have different optimum cadences. Therefore this would imply within reason that the optimum pedalling cadence becomes “self-selected” to meet the variable demands of physiological and biomechanical factors and the prevailing environmental conditions.
Evolution of Clipless Pedal Systems
Researchers have found that the modern clipless float pedal systems limit adverse knee stresses (13). Despite their use, research estimates that 40% to 60% of overuse knee injuries still affects regular riders. With the insertion of the more modern and up to date variable rotational float clipless systems, it has shown to help riders develop a more linear knee motion thus reducing lower incidence rates of knee injuries.
Comparison of Modern Clipless Pedals
Today the modern and up to date clipless pedal systems such as Shimano, Time and Look use spring loaded devices to engage a self-centering mechanism to allow variable degrees of rotational motion which is usually between 4° to 8°(14,15-18). This modern style of design is automated through spring tension to return the rider’s shoe to the pre-set neutral alignment.
Other systems such as the Speedplay zero pedal systems offer 0° to 15° of free float rotational motion. This has three potential benefits firstly the foot does not have to work against a spring loaded resistance, secondly it offers increased rotational float with a low stack height and thirdly Speedplay pedals are highly recommended for riders that have poor lower-limb biomechanics especially with leg and foot mal-alignment (18).
Read more about how we can help you understand and avoid your bike related pain.
For those of you who'd like to know more - here's the science...
Science of Bikefit:
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