Cycling Biomechanics

NJD Sports Injury Clinic
Poor cycling biomechanics can lead to discomfort, overuse injury and power-loss
Like Retul, we offer computerised bike fitting in Lancashire•West Yorks•Cumbria

Cycling Biomechanics

our bike fitting uses a 3-step integrated process to optimise pedaling biomechanics

Introduction

Cycling biomechanics can be described as the complexed interaction between man-and-machine, which is influenced by many variables. Efficient injury free cycling constitutes a marriage of perfect harmony between man-and machine - profoundly dependent on efficient pedaling symmetry. During one hour, a rider averages about 5,000 pedal revolutions. The smallest amount of malalignment, whether anatomic, biomechanical or mechanical, can lead to discomfort, poor performance and overuse injury.

       

                    **Assessment of both man-and-machine is prerequisite to effective Bikefitting**
Professional Bike fitters should examine both rider and bike

Marriage between man-and-machine

Efficient biomechanics in cycling (pedaling symmetry) relies on an integrated approach of man-and-machine. As such, cycling has been described as “a marriage between the adaptable human body and adjustable machine” (1). Harmony is achieved through proper set-up parameters (Bikefit) at the three-contact points i.e. saddle, pedals, and handlebars (2). Just as cycles are designed to be discipline-specific to meet given demands (e.g. mountain-bike, road bike, and triathlon bike) it follows that cyclists should adopt discipline-specific body positions (3,4).  Harmony can be disrupted by mechanical, biomechanical or anatomical factors. Harmony is coherently interlinked by using a sports science and sports medicine approach (5,6). Our published article in the Costa Blanc News (Spain) examines man-and-machine through "Knowing Your Riding Position"........click for more details

 

 

  

     
pedaling biomechanics in cycling, lancashire, manchester

References

  1. Pruitt, A. (2003) Body positioning for cycling, in E. Burke (ed.) High-Tech Cycling, USA: Human Kinetics
  2. Burke, E., & Pruitt, A. (2003) Body positioning for cycling,  High-Tech Cycling, USA: Human Kinetics, pp. 69-92
  3. Ashe, M., Scroop, G., Frisken, P., Amery, C., Wilkins, M., and Khan, K. (2003) Body position affects performance in untrained cyclists, British Journal of Sports Medicine, 37:441-444
  4. Bini, R., Hume, P., and Croft, J. (2012) Cyclists and triathletes have different body positions on the bicycle, European Journal of Sports Science, DOI: 10.1080/17461391.2011.654269
  5. Callaghan, M.J. (2005) Lower body problems and injury in cycling, Journal of Bodywork and Movement Therapies, 9:226-236
  6. Phillips, E., Davids, K., Renshaw, I., and Portus, M. (2010) Expert performance in sport and the dynamics of talent development, Journal of Sports Medicine, 40(4):271-283

 

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optimise pedaling biomechanics

The optimal pedaling cadence paradox

Despite great attention little consensus exists

Pedaling cadence has received a great deal of attention from cyclists, coaches and researchers in an effort to identify the cadence that optimises power output, while minimising metabolic cost and muscle fatigue. Despite great attention, the research literature appears to present conflicting results with little consensus as to the optimal pedaling cadence.

 

Complexed topic with multiple factors

A principal reason for this is the multiple factors involved, these can be categorised into 3 main groups i.e. Physiological, Biomechanical and Environmental. The rider’s physiology and genetic make-up play a major role in determining a rider’s cycling biomechanics and performance levels. Muscle fibre type within our legs influences cadence along with many other factors. Research suggests that muscle fibre type, distribution, contraction velocity and recruitment influence energy expenditure (metabolic cost) and the energetically optimal cadence during pedaling – especially when riding at different intensities.

 

Muscle fibre type

Our leg muscle fibre profiles can be categorised into two types: Slow Twitch fibre (ST), or Fast Twitch fibre (FT) dominant. While FT and ST muscle fibers vary in their mechanical and energetic properties the proportional distribution varies between individual riders. Smaller, skinnier riders tend to be ST dominant. These fibres prefer lower forces and hence favour higher cadences. Larger, bulkier riders have more FT fibres, which favour the higher forces associated with lower cadences and bigger gears. If you are a larger rider, through aerobic training, you can develop your ST profile and you may eventually find yourself spinning that little bit faster as a result.

 

Environmental considerations

Environmental factors such as terrain and racing conditions often influence or dictate pedaling cadence and style. Generally, road racers when riding on flat terrain will spin incredibly quickly. The fast spinning allows them to respond and accelerate quickly if someone makes a break while conserving leg muscles from fatigue. Conversely, when climbing the road racer will use a slower cadence for reasons mentioned below. Similarly, the experienced mountain biker will often use larger gears and slower cadence when riding over rough, dry terrain, because the pedals can be used as platforms to lift the body off the saddle to better negotiate obstacles. A good technical rider will rest very little body weight on the saddle when riding this kind of terrain.

 

Preferred versus optimal cadence

Many studies have reported that the ‘preferred cadences’ selected by riders of 80-100rpm are higher than metabolically optimal ones of 50-70rpm. However, the term ‘preferred cadence’ can be misleading, as it implies that a rider freely adopts their chosen cadence, rather than their cadence being dictated by Physiological, Biomechanical and Environmental factors. For example, elite and professional riders adopt a cadence of ~60-70rpm on hills compared with their normal 90-100rpm. Anecdotal evidence suggests that this drop in cadence is due to the high muscular stress from gravitational resistance when climbing. In contrast, on flat terrain the predominant resistance is the wind, which is proportional to speed, enabling riders to ease / reduce muscular stress – especially when drafting. Drafting allows a rider to reduce their aero-drag, which leads to reduced loading on the leg muscle, which in turn allows the rider to increase pedaling cadence.

Therefore, it has been suggested that ‘preferred cadence’ for each individual rider may represent an instinctive compromise between a cadence that minimises cardiovascular stress (metabolic cost) and that which minimises leg muscle stress. Where, the optimal cadence for minimising metabolic cost has been reported at 60-70rpm; the optimal cadence to minimise muscle stress is in the region of 100-110rpm. Thus, the preferred optimal cadence represents 80-90rpm for most occasions.
 

Conclusion

Although unsubstantiated, researchers often cite “self selected cadence is often the best”. Our body is amazingly adaptive and over time it learns to adapt and function efficiently under the circumstances it finds itself in. For physiological and biomechanical reasons we have different optimum cadences. Therefore within reason, optimum pedaling cadence becomes “self selected” to meet the varying physiological and biomechanical factors and the prevailing environmental conditions.

 

Key References used in this article

Ansley L. & Cangley, P. (2009) Determinants of ‘optimal cadence’ during cycling. European Journal of Sports Science, 9(2): 61-85
Barratt, P., Korff, T., Elmer, S., and Martin, J. (2011) Effect of crank length on joint-specific power during maximal cycling, Medicine and Science in Sports and Exercise,
Bertucci, W, Arfaoui A, & Polidori G. (2012) Analysis of the pedaling biomechanics of master’s cyclists. Journal of Science Cycling, 1(2): 42-46.
Ettema, G. & Loras, H. (2009) Efficiency in cycling: a review. European Journal of Applied Physiology, 106: 1-14.
Hansen, E. & Smith, G. (2009) Factors Affecting Cadence Choice During Submaximal Cycling and Cadence Influence on Performance. International Journal of Sports Physiology & Performance, 4(1); 3-17
Umberger B., Gerritsen K. & Martin P. (2006) Muscle fiber type effects on energetically optimal cadences in cycling. Journal of Biomechanics, 39(8): 1472-1479
Vercruyssen F. & Brisswalter J (2010) Which factors determine the freely chosen cadence during submaximal cycling? Journal of Science & Medicine in Sport, 13(12): 225-231.

 
 

Evolution of Clipless Pedal Systems

Research studies have demonstrated that modern float pedal systems have the potential to reduce undesirable knee stresses associated with overuse knee injuries. Despite the use of modern-day clipless pedal systems, overuse knee remain arguably the most common cycling injury, affecting an estimated 40% to 60% of all regular cyclists. However, the introduction of rotational float found in modern clipless systems facilitates a more linear knee motion resulting in lower incidence levels.

In 1984, the French-based ski binding manufacturer (Look) first tested a rigid float-less clipless pedal with the help of professional cyclist Bernard Hinault.  This clipless system was introduced to the market in 1986. However, this rigid float-less system placed undesirable stress on the knees and as a result the incidence of knee injuries escalated.  In 1987, Jean Beyl invented the Time pedal system, known as Bioperformance. This design provided free rotational float with some lateral motion.  At first the Bioperformance system received much criticism from competing pedal manufactures. However the alleged claims of power loss due to the introduction of float were proved incorrect following conclusive research studies. Thereafter, professional cyclists quickly adopted the system, and subsequently other manufactures modified their pedal systems to include varying degrees of rotational float. Within 18 months, the incidence of knee injuries reduced significantly – and fell below previous levels associated with traditional quill-pedal and strap systems.

 

Comparison of modern clipless pedals

Most modern-day clipless pedal systems (e.g. Shimano, Time, and Look) use spring loaded devices which employ a self-centering mechanism which allows varying degrees of rotational motion (typically 4° to 8°). This type of design automatically, through spring tension, brings the shoe back to the preset neutral alignment.  The Speedplay zero pedal systems offer 0° to 15° of free float rotational motion.  Potentially, Speedplay offers three benefits; increased rotational float, free float (meaning the foot does not have to work against spring loaded resistance) and a very low stack height. Speedplay pedals are strongly recommended for those cyclists that have poor lower-limb biomechanics – typically leg and foot malalignment.

Key References:

Farrell, K.C., Reisinger, K.D., & Tillman, M.D. (2003) Force and repetition in cycling: possible implications for Iliotibial band friction syndrome. The Knee, 10, 103-109.
Gregory, R.J., & Wheeler, J.B. (1994) Biomechanical factors associated with shoe/pedal interfaces. Sports Medicine, 17(2), 117-131.
Hannaford, D.P.M., Moran, G.T., & Hlavac, A.M. (1986) Video analysis and treatment of overuse knee injury in cycling: a limited clinical study. Clinics in Podiatric Medicine and Surgery, 3, 671-678.
O’Brien, T. (1991) Lower extremity cycling biomechanics: a review and theoretical discussion, Journal of American Podiatric Medical Association, 81(11):585-592
Ruby, P., Hull, M.L., Kirby, K.A., & Jenkins, D.W. (1992) The effect of lower-limb anatomy on knee loads during seated cycling. Journal of Biomechanics, 17(2), 1195-1207.
Wheeler, J.B., Gregory, R.J., & Broker, J.P. (1995) The effect of clipless float design on shoe/pedal interface kinetics and overuse knee injuries during cycling. Journal of Applied Biomechanics, 11, 119-141.

 

Last updated July 2014

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