Bikefit Science:
Position of the Cleat
Cleat position is very important for efficient pedalling, comfort and prevention of cycling injuries. Variations in cleat position can influence saddle position therefore when bike-fitting positioning of cleats should always be preceded with saddle, bar and stem adjustments. There are 5 variables to contemplate with respect to cleat position
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Fore & Aft (front to back)
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Cant (varus / valgus tilt)
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Rotational angle (toe-in and toe-out)
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Lateral position (side-to-side)
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Whether to shim (leg-length difference)
1. Fore and Aft cleat position
A foot within a modern carbon-fibre soled cycling shoe functions as a lever. The efficiency of that lever depends on its length from the fulcrum (Figure 1). The lever length is determined by the distance between the fulcrum (ankle joint) and the centre of the cleat when engaged in the pedal system. Of the little research available, the fore-and-aft cleat position appears to have little impact on the ability to deliver power (4).
Figure 1
Figure 2
However, while there are variations, the time honoured, and by the far most common cleat position used - by the majority of professionals, is with the centre of the 1st Metatarsophalangeal joint (1) (ball of big toe joint) positioned over the centre of the pedal spindle (Figure 2) (5,6).
A study (14) has shown that peak pressures pass through the 1st Metatarsophalangeal head or in close vicinity (Figure 3). These findings provide a logical rationale in support of positioning the 1st Metatarsophalangeal joint over the centre of the pedal spindle (11). In some cases, riders with large feet, then the cleat can be moved slightly backwards towards the heel to reduce the length of the lever arm.
The further forward the cleat is positioned towards the toes, the harder the calf muscles have to work to control and stabilise the foot owing to the lengthening lever arm. Moreover, this forward cleat position places more stress on the Achilles tendon with increased risk of overuse injury. Conversely, if the cleat is too far back towards the heel bone the length of the lever arm reduces and this limits the rider’s ability to sprint or climb while out of the saddle.
Figure 3
Generally, the longer the effort required particularly ultra-distance endurance events, the further back the cleat ought to be positioned - towards the heel bone. A small number of riders including professionals and elite triathletes use a mid-foot cleat position represented as positions 1 & 2 in (Figure 1). This unusual cleat position offers both advantages and disadvantages. Although only anecdotal, mid-foot cleat positions may offer advantages for some cyclists involved in ultra-distance endurance events.
2. Cant
Cant is the angle (tilt) that the forefoot makes when presented to the pedal which is called tilt. Varus tilt is when the big toe is elevated from the pedal and the little toe sits on the pedal. Conversely, Valgus tilt is when the big-toe sits on the pedal and the little toe is elevated from the pedal. As pedal forces increase so does the amount of misalignment (tilt) - this occurs in the direction that allows the forefoot to become parallel with the pedal.
Research suggests that approximately 85% of cyclists have forefoot varus (tilt). Cant wedges are becoming increasingly common in cycling. Competitive riders realise the potential power output and stability benefits wedges can offer. The concept behind cant wedges is to accommodate for misalignment of the lower-limb and foot, which results in forefoot tilt (varus or valgus). Essentially, there are two different types of wedge; the In-The-Shoe Wedge (ITS) shown in Figure 4. Wedge types are made from stiff plastic and can be used to address either varus or valgus tilts simply by reversing the wedge.
Figure 4
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Cant or forefoot tilt results in the motion known as pronation or supination. Forefoot tilt is more apparent when the foot is subjected to high loads experienced during the downstroke of intense pedalling. Pronation is a tri-plane motion consisting of simultaneous movements; abduction, dorsiflexion and eversion and can occur at the subtalar joint or mid foot.
Figure 5
Apart from the obvious inward tilting of the forefoot which causes the knee to ‘wobble’ and deviate inwards towards the top-tube with resultant power loss – the foot also tends to abduct (move outwards) (9). This motion causes the foot to toe-out as depicted by the red arrow in Figure 5. Consequently, pedal systems with limited rotational float may not offer sufficient float to accommodate increasing toe-out positions during the downstroke - for cyclists with excessive forefoot tilt. This means the foot remains locked in a position with inadequate rotation to dissipate harmful stresses; these harmful stresses get transferred upwards through the kinetic-chain.
Cleats can be moved inwards (side-to-side) and/or a spacer washer placed between the crank-arm and pedal to prevent the heel from brushing the crank-arm or chainstay.
When cant has been correctly addressed, the foot, knee and hip should remain in the same sagittal plane (tracking up and down in a near vertical motion) - Figure 6. As a result, power output improves, the foot no longer abducts (moves outwards) on the downstroke – the need for extra float and/or side-to-side cleat adjustment is often negated. Limited float pedal systems may be better for some riders with low levels of forefoot tilt and lower-limb misalignment. However, in these cases, attention to proper cleat alignment is paramount(5,7,8).
Figure 6
3. Rotation angle (toe-in or toe-out)
The introduction of the current float pedal systems is to provide competitive cyclists some degree of rotational float. The concept of the pedal / cleat systems with rotational float is to disperse harmful stresses and to accommodate lower limb and foot misalignment. It also helps prevents overuse injuries that may happen when harmful stresses surpass the abilities of the human tissue e.g. tears. Consequently if the cyclist leg and foot does not have a natural linear motion (by traveling up and down in a straight line) then restricting the foot (lack of pedal float) will create an extra restriction at the foot / pedal interface (12, 16).
All cyclists have injury thresholds and frequently high training loads may often be the likely cause for lower limb injuries especially knee related injuries.
From the development of the ‘Clipless Pedals’, studies have shown that the conventional float pedal systems may have the potentials to help limit unnecessary distorted loads of the knee - associated to overuse injuries by promoting greater linear knee motion. The other advantage for the cyclist is that it doesn’t compromise the power output (17,18).
Interestingly in 1984 the manufacturer (Look) with the help of professional cyclist Bernard Hinault, initially tested the rigid float clipless pedal system. Eventually it came available on the market in 1986 which placed undesirable stress on the knees and incidence rates of knee injuries increased.
In1987 although heavily first criticised by competing pedal manufacturers Jean Beyl invented the Time pedal system (known as the Bioperformance). The Bioperformance provided free rotational float with marginal lateral motion of the foot. Research studies demonstrated that the alleged criticisms of power loss were incorrect by competing manufacturers and soon professional cyclists adopted the new Bioperformance pedal system. Following the success of the free rotational float pedal system knee injuries significantly reduced within 18 months and other manufacturers quickly followed by modifing their pedal systems with varying degrees of rotational float.
Today, the present ‘clipless pedal systems’ such as Shimano, Look and Time use spring loaded mechanisms to engage a self-centering device to permit the various degrees of rotational motion (normally between 4° to 8°) (10). This allows the shoe to return to the preset position of neutral alignment against greater intensities of resistance. Consequently the Speedplay pedal system can provide 0° to 15° of free float rotational motion. The potential benefits of the Speedplay pedal system design enables greater float and free float in which the foot does not have to work against a spring loaded resistance device.
4. Lateral position (side-to-side)
Preferably the knee should virtually track in an vertical line (straight up and down) and remain directly over the second toe during the pedal revolution. For anatomical reasons this may not be always be possible for some cyclists that have wider hips. Cyclists with wider hips need their feet to be set further apart than those cyclists with narrow hips. Cyclists that adopt a pedal stance position that is too narrow may often have their knees flicking out over top dead centre of the pedal stoke. A wider pedal stance can be created by simply adjusting the cleat position or instead a shim washer may be used between the crank and pedal in which both methods can be helpful.
5. Packing Shims for leg-length differences (LLD)
For anatomical leg length differences (LLD) (Figure 7) which are predominant ‘Packing Shims’ may be used to help compensate or correct the problem. Although controversial, if the ‘Shims are fitted and installed incorrectly potentially they can be harmful.
Throughout the assessment and diagnoses of LLD, it is crucial that great care is given. Assessment and diagnoses of LLD should only be performed by a skilled, qualified Sports Medicine Clinician (19) - or by an appropriate trained Health Professional within the Bikefit team that has a good level of input.
Figure 7
Only when a true anatomical LLD has been reliably diagnosed Packing Shims should be fitted. A true anatomical LLD is identified where there is a difference in bone length (tibia or femur) exists. However where there is a clear indication of shortening of one leg without bone length difference this is referred to as a functional LLD. This may be due to a number of factors for example:
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Pelvic dysfunction
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Muscle weakness
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Muscle imbalances
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Unilateral foot pronation
Often muscle imbalances and pelvic dysfunction can generally be corrected by means of manual physical therapy and rehabilitation interventions.
The only way to establish a precise true anatomical LLD is by radiographic intervention such as an X-ray or by means of a scanning device. However a well skilled, qualified clinician may often gain a sound clinical judgement by using a range of simple differential diagnostic tests (19-24).
From research studies, it is estimated that the prevalence of anatomical LLD affects 90% of the population. However the mean is small and often considered unlikely to be significant in the clinical environment despite being prevalent (25,26). Nevertheless despite the mean being small, during competitive cycling, anatomical LLDs may likely disrupt the cyclist performance potentials significantly.
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Science of Bikefit:
Introduction | Three Traditional Riding Positions | Foot/Shoe/Pedal Interface | Custom Made Cycling Insoles | Position of the Cleat
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