BRINGING SCIENCE TO TREATMENT

Frustrating foot pain in cyclists? These 7 treatment strategies can help!

Although rarely discussed, research suggests that foot pain in cycling is surprisingly common. Andrew Hamilton explains how foot/pedal interface can lead to foot pain and gives advice to clinicians with cyclists in their care

Spanish cyclist Joseba Beloki gets a leg massage by his ‘Blind Physio’ Miguel Angel Rubio during the Tour of Spain, 2004. REUTERS/Gustau Nacarino

Although rarely discussed, research suggests that foot pain in cycling is surprisingly common. Andrew Hamiltonexplains how foot/pedal interface can lead to foot pain and gives advice to clinicians with cyclists in their care

The literature is awash with research on the risks to cyclists by impacts resulting from collisions and falls. However, whilethese acute events can lead to severe injury and even fatalities, cyclists are far more likely to suffer from injuries resulting from the action of cycling itself. Indeed, one 2006 study on cycling injuries concluded that the prevalence of non-traumatic injurywas as high as 85%(1).

A survey of the literature on non-traumatic cycling injuries shows that much of the research has been focussed on injuries of the back, neck, arms, hands, buttocks, perineum and knees(2). This is perhaps understandable; cyclists interface with the bike at three different points – the handlebars, the saddle and the pedals (the ‘triangle of contact – see figure 1). Incorrect handlebar shape/settings, saddle design/height or frame geometry can result in excessive loading on joints and muscles and undesirable movement biomechanics, significantly increasing the risk of injury.

Figure 1: The triangle of contact

 

Image from the Tour of the Battenkill Men’s pro UCI race on April 15, 2012.


Overlooked foot

However, of these three contact points, the greatest forces experienced by club/elite cyclists are those at the pedals, where large forces have to be applied to drive the transmission, particularly during sprinting and hill climbs. But unlike overuse injuries relating to the saddle or handlebar interface, the pedal-foot interface has been somewhat overlooked; there’s very little peer-reviewed research available on foot injuries, with those foot injuries that are reported in the literature being mainly descriptions of foot numbness, metatarsalgia, achilles tendonitis and plantar fasciitis(3-5).

Researchers in Seattle assessed the prevalence and incidence of lower leg/foot cycling injuries collated from a meta-review of non-traumatic bicycling injuries(1). The prevalence was reported to be 7%, 13% and 22% respectively, with an incidence rate of 24%. However this data considered both the lower leg and the foot to be one homogeneous unit rather than separate anatomical regions, which therefore negates its usefulness as meaningful foot pain data for the wider cycling population.

In short, there is very little research regarding the frequency, aetiology and/or management of foot pain in cycling available to guide the clinician. The small amount of available literature that is available tends to be descriptive non-systematic literature reviews or opinion. Moreover, where data is reported, participants may not have been sampled robustly. Also, studies have tended to focus only on elite cyclists rather than those engaged in club, recreational and fitness cycling (the vast majority of cyclists).

But in one 2012 study, researchers investigated the cycling habits and injury history of 397 South African cyclists to try and answer the following questions about foot injuries in cyclists(6):

  • What is the distribution of age, gender, foot/pedal interface use and distances cycled amongst cyclists who experience foot pain?
  • What type of pain and in what region of the foot do cyclists typically experience pain?
  • What techniques do cyclists use to try and cope with/overcome foot pain caused by cycling?
  • Are there key groups of cyclists at greater risk of foot pain than others?

A number of key findings became apparent:

  • Over half of the cyclists (53.9%) reported experiencing foot pain whilst cycling.
  •  The forefoot region of the foot that was most likely to be affected by pain (accounting for 61% of foot pain reports).
  •  Participants typically reported pain in the toes and ball of the foot, and described the pain as ‘burning’ and/or ‘numbness’.
  • Cyclists who rode with an attached foot-pedal interface (ieclipless and toe straps/cage) were 2.6 times more likely to suffer foot pain than those who did not.
  • Older cyclists (over 26 years) were more likely to suffer foot pain than younger cyclists.
  • Self-help methods to deal with pain included stopping for a period of time during the ride, shoe removal, walking around and massaging/stretching the foot.

The role of clipless shoe/pedal systems in the aetiology of foot painis unsurprising. Previous studies have demonstrated that clipless systems tend to localise plantar pressures, impacting nerve and blood supply integrity in that region(2,7).

Analysis of the foot-pedal interface

When seated, the foot-pedal interface is the only direct site for energy transfer from the cyclist to the bicycle. In a clipless pedal system, all of the body’s force to make the bicycle move forward is transferred to the pedal through a very small contact area (typically around 60mm2), and there is consistent anecdotal evidence that forefoot pain at this point of energy transfer is common(2,7). The correct cycling shoe construction, insole materials and contoured surfaces can reduce the occurrence of ‘pressure hot spots’ by spreading the load more evenly. Better cycling shoe manufacturers appreciate this fact, and use a combination of specific material types and contoured surfaces to try and minimise forefoot discomfort.

Carbon fiber: good or bad?

Greater shoe stiffness results in less shoe flex and less energy wastage during power transfer, increasing cycling efficiency. This has led to the widespread use of carbon fiber soles, which offer a very stiff and rigid pedalling platform. But does this lead to increased pressure hot spots and foot pain? In one US study, plantar-pressure data were recorded while cycling at 400 watts output (hard!) in two pairs of shoes of the same make and size(7). These were identical except for outsole material and stiffness: one pair employed plastic soles while the other used carbon fiber. The results were as follows:

·     The carbon-soled shoes were 42% and 550% stiffer than plastic shoes when subjected to longitudinal bending and three-point bending, respectively.
·     During pedaling, the carbon fiber shoes produced peak plantar pressures 18% higher than those of plastic design.

The authors concluded that competitive cyclists suffering from metatarsalgia or ischemia should be especially careful when using carbon cycling shoes because the shoes increase peak plantar pressure, which may aggravate these foot conditions.

However, a later study by German scientists suggests that assessing a shoe’s potential to cause foot pain based purely on its construction is flawed(8). Eleven pain-free triathletes were tested on a cycle ergometer at two different cadences (60 and 90rpm) and at two different workloads – 200 and 300 watts. All the subjects performed two trials in a randomised order. These were:

  •  A cycling shoe with its standard insole (control condition).
  • The same shoe but with carbon fiber foot orthoses.

The use of carbon fiber for the construction of the orthoses is relevant because it’s possible to make carbon fiber orthoses that do not yield, even under the highest loads. This in turn means that the foot is held more securely in its desired position/orientation regardless of loading.

As figure 2 shows, peak pressures recorded in the total foot area ranged from 70-75kPa at 200 watts power output, and from 85-110kPa at 300 watts. Despite being stiffer, the carbon fiber foot orthoses reduced peak pressures by around 4.1% compared to the standard insole. Within separate foot regions, rear foot peak pressure was reduced by 16.6%, mid-foot pressure by 20.0% and forefoot pressure by 5.9 %. It was noted however that in the toe region, peak pressure with the carbon orthoses was increased by around 16%.

Figure 2: Peak plantar pressures at 60/90rpm and 200/300 watts(8)


The authors concluded that carbon fiber can serve as a suitable material for foot orthoses because when it comes to pressure reduction, shape/contouring is more important than orthotic stiffness. This might also explain why the carbon-constructed shoes in the US study produced higher peak pressures; the unyielding flat surface of the carbon sole was not contoured to reduce plantar pressure and the standard (non-orthotic) inserts would have offered little help in this respect. By the same token, simply substituting padded insoles in an already uncomfortable cycling shoe is unlikely to result in an automatic remedy for foot pain.

Implications for clinicians

If a cyclist presents with foot pain, the issue of plantar pressure should be considered as a possible cause. This is especially true for competitive cyclists who will potentially ‘push’ up to 40 million pedal cycles during their career! However, excessive plantar pressure does not occur in isolation; contributing causes include:

  • Incorrect bike set up – eg saddle height, saddle fore/aft distance, cleat positioning.
  • Incorrect shoe type – eg wrong type of cleat, sole material, shoe fit (too tight, too narrow, attached too tightly).
  •  The foot type of the cyclist – eg pes planus, pes cavus.
  • The presence of any lower limb biomechanical or structural deformities – eg genu varum, forefoot supinatus, ankle joint equinus).
  • High body weight, especially when the cycling terrain is hilly (which increases the forces experienced in the foot/pedal interface when climbing).
  • Incorrect use of gearing – eg ‘pushing’ a big gear rather than ‘spinning’ a lower gear.

Given the above, clinicians should not only advise on shoe selection (see below), but also be prepared to liaise with the cycling coach (if there is one), or to provide the client with additional learning resources to understand and overcome these issues.

Shoe/foot treatment strategies

  1. Cycling shoes should be selected to afford adequate width and support, especially in the forefoot area (bear in mind that the foot will swell significantly when cycling in warm/hot conditions).
  2. A stiffer soled shoe is not necessarily harmful provided that the footbed/insert is properly structured and contoured to help relieve plantar pressure.
  3. Simply using a flat padded insole in a shoe with a very stiff sole is unlikely to reduce foot pain – indeed, if the shoe is already a snug fit, it could increase it.
  4. When adjusting the upper straps of a cycling shoe, care should be taken to ensure that over-tightening doesn’t occur.
  5. Cyclists who use clipless pedals should experiment with cleat positioning and also ensure that a fair degree of rotational freedom at the heel is allowed during the pedal motion.
  6. Encourage cyclists who suffer with foot pain to take frequent breaks, choose flatter routes and use slightly higher gears (ie‘spin’ more).
  7. In chronic and persistent cases of cycling-induced foot pain, a biomechanical assessment of the foot is recommended. Depending on the results, this might point to a number of further options including stretching/strengthening routines, cycling shoe orthoses and well as treatments to reduce chronic pain and inflammation.

References

1. Sports Med. 2006;36(1):7-18
2. J Bodywork Movement Therapies 2005; 9:226-236
3. Sports Medicine 1994; 17:117-131
4. Sports Medicine 1991; 11:52-70
5. American Podiatric Medical Association 2000; 90:354-376
6. Journal of Science and Cycling 2012; 1(2): 28-34
7. Foot and Ankle International 2003; 24:784-788
8. Sportverletz Sportschaden. 2012 Mar;26(1):12-7

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