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Following a media frenzy in 2010, the concept of running barefoot came under rather close scrutiny.  With respect to its potential long term risks/benefits the research is not yet available, so for many professionals the jury is still out and they remain healthily sceptical.  However these same professionals generally recommend road running shoes based on a model which has been used for decades.  At this point in time it seems only fair that this is re-visited and also put under the same scrutiny, with some of the available research relevant to running shoes looked at in closer detail.  This blog aims to do just this; to discuss how road running shoes are currently ‘prescribed’, and to see if there is any rationale for this current practice.

History

Road running shoes can be generally split into 3 groups – motion control shoes, stability shoes, and neutral/cushioned shoes.  Historically we have all been told that there are 3 main foot types (what a fantastic coincidence I hear you cry…) – the ‘flat’ or ‘pronated’ foot, the ‘normal’ or ‘neutral’ foot, and the ‘high arched’ or ‘supinated’ foot.

1. Flat/Pronated foot = Motion Control shoe 2. Normal/Neutral foot = Stability shoe 3. High/Supinated foot = Neutral/Cushioned shoe

It is not entirely clear where this model of shoe selection came from.  It’s conception may have been based upon the work of Colonel Harris and Major Beath, who performed an Army foot survey back in 1947, and whilst doing so invented an ingenious new method of assessing footprints.1 It was in 1980 that ‘The Running Shoe book’ showed the first picture (as far as I’m aware) of the three arch types and how these may relate to running shoe selection.2 Despite the lack of certainty regarding its origins, pretty much every edition of Runners World magazine printed since has regurgitated this information, as have most running shoe shop assistants, not to mention numerous websites (including those of many major shoe companies and sports injury professionals).  For several decades runners have therefore been advised to check their footprints (often easily assessed by observing the mark a wet foot leaves behind) and pick the corresponding shoe.  They are told this ensures ideal alignment and minimises injury risk.  Simples.  Or is it?

Before we continue take a look at the following foot (a freeze frame during running):

Have a think about what running shoe you would recommend for this individual based on the visual information you have.

To identify whether the well known model of shoe selection is appropriate we need to break it down and analyse the preconceptions it is based upon.  These are:

(A)   Pronation is consistently predictive of injury.

(B)   All individuals should be aligned identically (i.e. ‘normal’ or ‘neutral’).

(C)   The wet foot test (i.e. foot shape) is predictive of dynamic function.

(D)   Running shoe technology will actually achieve what it claims to.

If these points are not true, or not backed up by research, then the entire model falls apart.  So, let’s take a look at these preconceptions one at a time.

(A) Pronation is consistently predictive of injury.

Running stores and magazines seem to be fixated on pronation.  Most shoes are marketed with respect to how much ‘pronation control’ they offer.  Why is this?  Well, it has generally been thought that a more pronated foot type is a significant risk factor for injury.  However the fact is that there are very few prospective studies which have actually shown this, with numerous studies actually concluding that there is no association between foot type and injury.3-9Two studies have even shown that a pronated foot is actually a protective factor against injury.10,11

The point I’m trying to make is that the relationship between foot mechanics and lower limb injury is still not as well understood as we think (or as we would like).  But what we do know is that functioning in a pronated position does not mean that you will necessarily get injured.  In fact the experimental evidence suggests you are much more likely to get injured from training errors12 or from dysfunctional hip musculature.13

Verdict = Pronation is not consistently predictive of injury

(B) All individuals should be aligned identically (i.e. ‘normal’ or ‘neutral’).

When referring to ‘ideal’ alignment what is actually meant?  What exactly is ‘normal’ when it comes to the alignment of the lower extremity?  Answer: We don’t know.  The word ‘normal’ is probably an inappropriate word to apply to the human body.  As far as normal foot alignment or mechanics is concerned, the normal (average) foot type reported in sampled populations is actually mildly to moderately pronated.14-17 So why then is the main aim of the current running shoe selection model to align runners to ‘neutral’ (i.e. the foot sitting perpendicular to the horizontal ground)?

When we consider that the subtalar joint (the joint where pronation and supination occurs) has variable anatomy 18,19it seems obvious that function will not be the same for everyone, and therefore that the ‘optimum’ position to be in would differ from person to person.  Unsurprisingly, differences in foot alignment between individuals is reported to be high.20

It still amazes me that in a world where human variation is so vast in almost every aspect of our being, that when it comes to running there is a suggestion that we should all be in one particular alignment or position.  The reality is that each of us most likely has own preferred alignment – a subject specific ‘normal’.

Verdict = Individuals should not all be aligned similarly. ‘Normal’ alignment is subject specific.

(C) The wet foot test (i.e. foot shape) is predictive of dynamic function.

The association between static foot measures and dynamic function has been well researched in the literature.  Several different methods of assessing foot shape, arch height and foot posture in static standing have been investigated, with the conclusions generally being that there is no association between these measures and dynamic function (what the foot does when we actually run).21-25

The work which really puts the wet foot test out of business was completed by a team of researchers from the US army over the last year or so.  Their prospective studies assigned running shoes based on plantar foot shape prior to basic military training, and investigated if this influenced injury risk at all.  They showed that assigning running shoes based on the footprint shape had little influence on injury risk in Air Force Basic Training,26 Marine Corps Basic Training,27and Army Basic Combat Training.28

Verdict = Foot shape is NOT predictive of dynamic function.  The wet foot test is nonsense.

(D) Running shoe technology will actually achieve what it claims to.

The technology that shoes provide can be generalised into 2 main areas.  They offer cushioning, and market this as essential for the dampening of the high impacts associated with running, and they offer increased durometer (stiffer/harder) midsoles which are aimed at controlling or reducing pronation.  These technologies have been called into question before, with some researchers suggesting that the protected environment a modern running shoe provides will diminish sensory feedback, resulting in inadequate impact moderating behaviour and actually serve to increase injury risk.29,30

A 2010 study concluded that the prescription of shoes with elevated cushioned heels and pronation control systems tailored to an individuals foot type was not evidence based31 and another very recent piece of research suggested this approach was overly simplistic and potentially injurious.32 How did the latter study come to this conclusion? Well to very briefly summarise: every single runner in their study who had been classified as having a ‘highly pronated’ foot type and was subsequently put into a motion control shoe reported an injury during a 13 week half marathon training programme.  Let me repeat that – highly pronated feet that were put into motion control shoes resulted in injury.  Yet that is exactly what the current shoe selection model suggests.  So, let’s go back to the video gait analysis snapshot:

Given what you have read so far, what shoe would you recommend this person now? Has it changed from earlier?

Back to the running shoe research:  Numerous studies agree that shoes with softer midsoles (cushioned/neutral shoes) result in greater pronation values, and shorter times to reach maximum pronation i.e. they make individuals pronate more, and pronate quicker.33-36 Does this sound bad to you? [If so go back and read the research which refutes preconception (A)].  Most of these studies also concluded that harder/stiffer midsoles (such as those found in stability and motion control shoes) significantly decrease the speed and magnitude of pronation.  Some of these shoes now also have a slight varus tilt (they are higher on the inside of the heel than they are on the outside).  Research has also shown that this decreases foot level pronation.37,38 (Remember these studies are just investigating kinematics/alignment and not injury).

So ‘anti-pronatory’ shoes with stiffer midsoles are actually doing what they promise to.  The problem is we don’t know whether we need them to do it for us or not.  And as an aside, varus posting/tilting was shown in one study to increase tibial shock and vertical loading rates.39 (Is this perhaps why all those injuries occurred in the motion control shoes in the aforementioned study?)

Finally, let’s not forget cushioning.  That must reduce the amount of force we are subjected to when running – right?  Wrong.  As shoe cushioning decreases runners modify their patterns to maintain constant external loads.40 However, it is thought to contribute to comfort, and this seems to be the most important variable on which to select sports shoes, which we will talk about shortly.

Verdict = There is very little research investigating the relationship between running shoes and injury prevention.  Stiffer midsoles do reduce pronation speed and magnitude, but in doing so may increase vertical loading rates.  Running shoe ‘cushioning’ may be a myth.

Summary

It seems that the current model upon which running shoes are recommended/chosen is erroneous.  Its foundations are based upon preconceptions which have been shown to be false.  Due to significant within-species variation it is ridiculous to try and align people identically, (and to aim to do so in a pre-selected ‘normal’ position which is highly unlikely to be ‘normal’ for most individuals is potentially injurious).  Shoes do seem to generally achieve what they claim to.  However, our understanding of whether they actually need to achieve these variables (and who would benefit from each variable) is poor at present.

And so, the current method of being recommended a shoe still continues (and I imagine it will for some time).  Why?

  1. Very few people realise it is erroneous.
  2. At the moment we do not have anything to replace it with.
  3. It is fantastically simple.
  4. People don’t generally like change.

The future

Moving forward, a much better model would be to focus on identifying an optimum midsole stiffness (which may be variable) for an individual, combined with their optimum alignment/movement patterns for a given activity (i.e. the position in which their injury risk is minimised and their performance is maximised, irrespective of its visual alignment). However, much more research is required before we fully understand how to clinically achieve this.

The concept of intelligent shoes which modify their midsole characteristics depending on the step by step requirements and effectively ‘tune’ themselves to the wearer and the surface they are on may sound like something from Back to the Future, but it is probably only a matter of time before we start seeing this sort of advancement in our running shoe technology.  However, it doesn’t change the fact that we need a greater understanding of injury risk factors, and that these are still likely to be subject (and activity) specific.

Conclusions

So where does this leave the runner choosing a pair of shoes in 2011? There are many choices. Neutral? Stability? Motion Control? Vibram Five Fingers? Barefoot? Hopefully by now you realise that there is no simple answer.

All decisions could and should be based on one main factor in my opinion: comfort. Believe it or not comfort has been linked to injury frequency reduction41 and is thought to be the most important variable for sports shoes, and a focal point for any future sports shoe development.42 We all know that comfort is subjective and subject specific43 so with that in mind only the wearer can confidently choose the most appropriate shoe for themselves.  [Be wary of the shop assistant/Podiatrist who tells you the exact make and model shoe which is best for you]. What one person finds comfortable will differ greatly from another; perhaps this is why some people find that stiff supportive shoes work best for them, and others discovered that barefoot running was the answer to their long history of injury woes.

As most runners know, it can often be a little bit of trial and error with regard to finding the ‘right’ shoe.  Once you’ve found what works for you (or if you have found it already) then don’t change it.

Irrespective of the advice given in the shoe shop/magazines about your ‘pronation’; on current evidence you may be just as well off picking a shoe based on comfort alone, and subscribing to a course of Pilates and adopting sensible training habits.

P.S. How are you getting on with your decision on what shoes to recommend for this chap?

References

  1. Harris RI, & Beath T: (1947). Referenced from a secondary source: The Journal of Bone & Joint Surgery (1950), Vol 32B, No 1, p143-144.
  2. Cavanagh PR: The Running Shoe Book, Anderson World, Inc., Mountain View, California, 1980.
  3. Barrett JR, Tanji JL, Drake C, et al: High versus low-top shoes for the prevention of ankle sprains in basketball players. A prospective randomized study. The American Journal of Sports Medicine 21: 582, 1993.
  4. Twellaar M, Verstappen FT, Huson A, et al: Physical characteristics as risk factors for sports injuries: a four year prospective study. International Journal of Sports Medicine 18: 66, 1997.
  5. Wen DY, Puffer JC, Schmalzried TP, et al: Injuries in runners: a prospective study of alignment. Clinical Journal of Sport Medicine 8: 187, 1998.
  6. Beynnon BD, Renstrom PA, Alosa DM, et al: Ankle ligament injury risk factors: a prospective study of college athletes. Journal of Orthopaedic Research 19: 213, 2001.
  7. Hetsroni I, Finestone A, Milgrom C, et al: A prospective biomechanical study of the association between foot pronation and the incidence of anterior knee pain among military recruits. Journal of Bone and Joint Surgery Br88: 905, 2006.
  8. Reinking MF, Austin TM, Hayes AM: Risk factors for self-reported exercise-related leg pain in high school cross-country athletes. Journal of Athletic Training 45: 51, 2010.
  9. Franettovich M, Chapman AR, Blanch P, et al: Altered neuromuscular control in individuals with exercise-related leg pain. Medicine and Science in Sport and Exercise 42: 546, 2010.
  10. Giladi M, Milgrom C, Stein M, et al: The low arch, a protective factor in stress fractures. Orthopaedic Review 14: 81, 1985.
  11. Cowan D, Jones B, Robinson J: Foot morphologic characteristics and risk of exercise related injury. Archives of Family Medicine 2: 773, 1993
  12. James SL, Bates BT, Osternig LR: Injuries to runners. American Journal of Sports Medicine 6: 40, 1978.
  13. Ferber R, Hreljac A, Kendall KD: Suspected mechanisms in the cause of overuse running injuries: a clinical review. Sports Health: A Multidisciplinary Approach 1: 242, 2009.
  14. Sobel E, Levitz SJ, Caselli MA, et al: Re-evaluation of the relaxed calcaneal stance position. Journal of the American Podiatric Medical Association 89: 258, 1999.
  15. Scharfbillig R, Evans A, Copper A, et al: Criterion validation of four criteria of the foot posture index. Journal of the American Podiatric Medical Association 94: 31, 2004.
  16. Redmond A, Crosbie J, Ouvrier R: Development and validation of a novel rating system for scoring standing foot posture: the foot posture index. Clinical Biomechanics 21: 89, 2006.
  17. Redmond AC, Crane YZ, Menz HB: Normative values for the foot posture index. Journal of Foot and Ankle Research 1: 6, 2008.
  18. Bruckner J: Variations in the human subtalar joint. Journal of Orthopaedic and Sports Physical Therapy 8: 481, 1987.
  19. Forriol Campos F, Gomez Pellico L: Talar articular facets. Acta Anatomica 134: 124, 1989.
  20. Nester CJ: Lessons from dynamic cadaver and invasive bone pin studies: do we know how the foot really moves during gait? Journal of Foot and Ankle Research 2: 18, 2009.
  21. Razeghi M, Batt ME: Foot type classification: a critical review of current methods. Gait and Posture 15: 282, 2002.
  22. Hamill J, Bates BT, Knutzen KM, et al: Relationship between selected static and dynamic lower extremity measures. Clinical Biomechanics 4: 217, 1989.
  23. McPoil TG, Cornwall MW: The relationship between static lower extremity measures and rearfoot motion in gait. The Journal of Orthopaedic and Sports Physical Therapy 24: 309, 1996.
  24. Cashmere T, Smith R, Hunt A: Medial longitudinal arch of the foot: Stationary versus walking measures. Foot and Ankle International 20: 112, 1999.
  25. Trimble MH, Bishop MD, Buckley BD, et al: The relationship between clinical measurements of lower extremity posture and tibial translation. Clinical Biomechanics 17: 286, 2002.
  26. Knapik JJ, Brosch LC, Venuto M, et al: Effect on injuries of assigning shoes based on foot shape in air force basic training. American Journal of Preventative Medicine 38: S197, 2010.
  27. Knapik JJ, Trone DW, Swedler DI, et al: Injury reduction effectiveness of assigning running shoes based on plantar shape in marine corps basic training. American Journal of Sports Medicine 38: 1759, 2010.
  28. Knapik JJ, Swedler DI, Grier TL, et al: Injury reduction effectiveness of selecting running shoes based on plantar shape. Journal of Strength and Conditioning Research 23: 685, 2009.
  29. Robbins SE, Hanna AM: Running-related injury prevention through barefoot adaptations. Medicine and Science in Sports and Exercise 19: 148, 1987.
  30. Robbins SE, Gouw GJ: Athletic footwear: Unsafe due to perceptual illusions. Medicine and Science in Sports and Exercise 23: 217, 1991.
  31. Richards CE, Magin PJ, Callister R: Is your prescription of distance running shoes evidence-based? British Journal of Sports Medicine 43: 159, 2010.
  32. Ryan MB, Valiant GA, McDonald K, et al: The effect of three different levels of footwear stability on pain outcomes in women runners: a randomised control trial. British Journal of Sports Medicine (2010). doi: 10.1136/bjsm.2009.069849.
  33. Clarke TE, Frederick EC, Hamill CL: The effects of shoe design parameters on rearfoot control in running. Medicine and Science in Sports and Exercise 15: 376, 1983.
  34. Hamill J, Bates BT, Cole KG: Timing of lower extremity joint actions during treadmill running. Medicine and Science in Sports and Exercise 24: 807, 1992.
  35. Wit BD, Lenoir M: The effect of varying midsole hardness on impact forces and foot motion during foot contact in running. Journal of Applied Biomechanics 11: 395, 1995.
  36. Kersting UG, Bruggermann GP: Midsole material-related force control during heel-toe running. Research in Sports Medicine 14: 1, 2006.
  37. Van Woensel W, Cavanagh PR: A perturbation study of lower extremity motion during running. International Journal of Sports Medicine 34: 1844, 1992.
  38. O’Connor K, Hamill J: The role of selected extrinsic foot muscles during running. Clinical Biomechanics 19: 71, 2004.
  39. Perry SD, Lafortune MA: Influences of inversion/eversion of the foot upon impact loading during locomotion. Clinical Biomechanics 10: 253, 1995.
  40. Kong PW, Candelaria NG, Smith DR: Running in new and worn shoes: a comparison of three types of cushioning footwear. British Journal of Sports Medicine 43: 745, 2009.
  41. Mundermann A, Stefanyshyn DJ, Nigg BM: Relationship between footwear comfort of shoe inserts and anthropometric and sensory factors. Medicine and Science in Sports and Exercise 33: 1939, 2001.
  42. Nigg BM: Biomechanics of Sports Shoes, Topline Printing Inc, Calagary, Alberta, Canada, 2010.
  43. Miller JE, Nigg BM, Liu W, et al: Influence of foot, leg and shoe characteristics n subjective comfort. Foot and Ankle international 21: 759, 2000.
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Heel pain is an incredibly common condition and there are very few Podiatrists who won’t see it on a daily basis in their clinics.  There are numerous different causes of heel pain, (not all mechanical), but the area that this blog entry is going to focus on in particular is the plantar calcaneal/heel spur.  It is yet another source of controversy, with no definitive agreement on the relationship of the spur and the surrounding tissues, or the actual source of the symptoms (if any) seen clinically.

Historically, it has been commonly accepted that heel spur formation is an abnormal finding and very closely correlated with the symptoms of heel pain.  It was reported that excessive traction (pulling) of the plantar fascia on its attachment at the heel resulted in chronic inflammation, which in turn resulted in a reactive ossification and subsequent extra bone forming in the shape of a ‘spur’. 1-3 This is perhaps why heel spurs and ‘plantar fasciitis’ are still to this day thought by many to be one entity.  Causation has been a point of confusion; does the traction and inflammation cause a heel spur, or does a heel spur cause tissue inflammation?  A chicken and egg scenario.  It is not uncommon to see statements that ‘plantar fasciitis’ is caused by heel spurs (admittedly this is on websites rather than academic journals), but is this factually correct?

The plantar calcaneal spur has been classically described as a bone outgrowth localised just anterior to the medial tuberosity of the calcaneus.4 This can not often be palpated clinically, but only seen radiologically as shown in the x-ray on the right above.

Another long term belief has been that individuals with heel pain are more likely to have pronated (flat) feet.5,6 As research has shown that lowering of the medial longitudinal arch of the foot increases plantar fascial tension7 it is easy to see how the connection between foot pronation, heel pain and heel spurs has been made.  However the concern is that any individual who presents to a specialist with heel pain and ‘flat feet’ could be hastily assigned a diagnosis of “plantar fasciitis caused by a heel spur”.  This is clearly unacceptable, and a specialist should have a much more thorough understanding of the research behind the pathological process.  So, how common are heel spurs?  Are they always problematic? Are they actually caused by traction? And what is their relationship with the plantar fascia?

How common are heel spurs?

Studies have shown that heel spurs are more common in pain free individuals than first thought, and it has been reported that anywhere between 11 and 27% of the population have radiographic evidence of a spur.5,8-13 Clearly this suggests they are not always associated with symptoms, and are not necessarily considered as ‘abnormal’ as once thought.  Interestingly, even a study performed over 45 years ago on 323 patients concluded that the plantar calcaneal spur was never the cause of pain and probably a normal manifestation of the aging process.14

However, the research does suggest that calcaneal spurs do seem to be over-represented in certain groups, such as females,10,11,13 individuals with osteoarthritis15,16 and older people.11,13,15,16 Calcaneal spurs have also found to be more common in those who are overweight.17

Where are heel spurs?

MRI of heel spur (arrow). PF=plantar fascia. M=1st layer of foot muscles

As I have already mentioned, it has long been thought that heel spurs and plantar fascia problems were undeniably linked.  Google ‘heel spurs’ and the term ‘plantar fasciitis’ is never far behind.  However, it is interesting to hear how the anatomic studies report the actual location of the bony protrusion.  Far from agreeing it resides solely within the plantar fascia as once thought, many studies found it can also be found above the plantar fascia.4,12,18 Some found it was much more commonly located in the other intrinsic musculature, (namely Flexor Digitorum Brevis and Abductor Digiti Minimi)4,18,19 and one study was as bold to firmly conclude that spurs do not develop within the plantar fascia.20

What is clear is that there is huge variability in the location of heel spur formation, and if we cannot unequivocally state that the spur is within the fascia (which we cannot) then the validity of its link with ‘plantar fasciitis’ is questionable.

What causes heel spurs?

As previously mentioned, the traditional theory for formation of plantar calcaneal spurs is what Menz and colleagues16 refer to as the longitudinal traction hypothesis, i.e. the plantar fascia pulling on the heel bone and causing the formation of a spur.  Despite the anatomical studies showed that the spur is far from consistently found in the fascia, it has been suggested that there could be an element of tensile force exerted on the calcaneus from a variety of the other structures which attach to it.4,19

An alternative theory, termed the vertical compression hypothesis16 and was proposed by Kumai and Benjamin in 2002.20 This theory suggests that calcaneal spurs are outgrowths which form in response to repetitive vertical stress in an attempt to protect against microfractures.  This idea is supported by histological studies which show that the bony trabeculae are NOT aligned in the direction of soft tissue traction.16,18 Li and Muehleman18 found that the direction of the trabeculae suggested that the force causing the pathological response was consistent with the external ground reaction force vector.

Conclusions

So what does all this mean in plain English?  It means that we used to think a spur was caused by the plantar fascia pulling on the bone.  This is highly unlikely as the spur is seldom found in the plantar fascia.  If traction is the cause it is more likely to be caused by other musculature such as Flexor Digitorum Brevis or Abductor Digiti Minimi.  However these bony protrusions could instead be caused by the repetitive vertical loading (the heel continuously hitting the floor, and the floor of course hitting it back) with the spur forming as a protective mechanism.  Of course we cannot overlook the fact that there may be a combination of both traction and compression present in the aetiology of spur development.  We also know that anywhere up to a quarter of the population may have a heel spur, but this will not always be problematic.

So, in summary:

The pathophysiology of plantar calcaneal heel spurs is poorly understood.

The presence of a plantar calcaneal spur does not always lead to the development of heel pain.

Plantar calcaneal spurs do appear to be associated with obesity, osteoarthritis and the aging process.

It is unclear whether spur formation is due to longitudinal traction of the plantar tissues or an adaptive response to vertical loading/compression (or both).

It is erroneous to assume there is a causal relationship between plantar calcaneal spurs and ‘plantar fasciitis’.

References

  1. DuVries, H.L. (1957). Heel spur (calcaneal spur). Archives of Surgery, 74: 536-542.
  2. Furey, J.G. (1975). Plantar fasciitis: the painful heel syndrome. Journal of Bone and Joint Surgery Am, 57: 672-673.
  3. Bergmann, J.N. (1990). History and mechanical control of heel spur pain. Clinics in Podiatric Medicine and Surgery, 7: 243-259.
  4. Abreu, M.R., Chung, C.B., Mendes, L. et al. (2003). Plantar calcaneal enthesophytes: new observations regarding sites of origin based on radiographic, MR imaging, anatomic, and paleopathologic analysis. Skeletal Radiology, 32: 13-21.
  5. Prichasuk, S., Subhadrabandhu, T. (1994). The relationship of pes planus and calcaneal spur to plantar heel pain. Clinical Orthopaedics and Related Research, 306: 192-196.
  6. Irving, D.B., Cook, J.L., Young, M.A. et el. (2007). Obesity and pronated foot type may increase the risk of chronic plantar heel pain: a matched case-control study. BMC Musculoskeletal Disorders, 8: 41.
  7. Kogler, G.F., Solomonidis, S.E., Paul, J.P. (1996). Biomechanics of longitudinal arch support mechanisms in foot orthoses and their effect on plantar aponeurosis strain. Clinical Biomechanics, 11: 243-252.
  8. Rubin, G., Witten, M. (1963). Plantar calcaneal spurs. American Journal of Orthopaedics, 5: 38-41.
  9. McCarthy, D.J., Gorecki, G.E. (1979). Anatomical basis of inferior calcaneal lesions: a cryomicrotomy study. Journal of the American Podiatric Medical Association, 69: 527-536.
  10. Shama, S.S., Kominsky, S.J., Lemont, H. (1983). Prevalence of non-painful heel spur and its relation to postural foot position. Journal of the American Podiatric Medical Association, 73: 122-123.
  11. Banadda, B.M., Gona, O., Vas, R., et al. (1992). Calcaneal spurs in a black African population. Foot & Ankle, 13: 352-354.
  12. Barrett, S.L., Day, S.V., Pignetti, T.T. et al. (1995). Endoscopic heel anatomy: analysis of 200 fresh frozen specimens. Journal of Foot & Ankle Surgery, 34: 51-56.
  13. Riepert, T., Drechsler, T., Schild, H. et al. (1996). Estimation of sex on the basis of radiographs of the calcaneus. Forensic Science International, 77: 133-140.
  14. Lapidus, P.W., Guidotti, F.P. (1965). Painful heel: report of 323 patients with 364 painful heels. Clinical Orthopaedics and related Research, 39: 178-186.
  15. Gerster, J.C., Vischer, T.L., Bennani, A. et al. (1977). The painful heel. Comparative study in rheumatoid arthritis, ankylosing spondylitis, Reiter’s syndrome, and generalised osteoarthritis. Annals of the Rheumatic Diseases, 36: 343-348.
  16. Menz, H.B., Zammit, G.V., Landorf, K.B. et al. (2008). Plantar calcaneal spurs in older people: longitudinal traction or vertical compression? Journal of Foot & Ankle Research, 1:7.
  17. Sadat-Ali, M. (1998). Plantar fasciitis/calcaneal spur among security forces personnel. Military Medicine, 163: 56-57.
  18. Li, J., Muehleman, C. (2007). Anatomic Relationship of Heel Spur to Surrounding Soft Tissues: Greater variability than previously reported. Clinical Anatomy, 20: 950-955.
  19. Smith, S., Tinley, P., Gilheany, M. et al. (2007). The inferior calcaneal spur – Anatomical and histological considerations. The Foot, 17: 25-31.
  20. Kumai, T., Benjamin, M. (2002). Heel spur formation and the subcalcaneal enthesis of the plantar fascia. The Journal of Rheumatology, 29: 1957-1964.

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The supination resistance test holds particular interest for me as I am currently doing some research into it myself for my Masters degree at Manchester University.  To my knowledge it first appeared in the literature some 18 years ago (Kirby & Green, 1992).  It is a very quick and simple test to perform, but like most clinical tests will need to be performed many times on many different feet before the clinician will feel comfortable with it.  The main reason I feel it is so important is that it gives insight into the forces acting on the foot during weightbearing; something which we cannot physically see, and the importance of which are discussed in this blog.

Historically when examining the weightbearing foot all of our attention has been on its visual appearance (or posture).   Indeed these visual observations and measurements still form the main portion of an objective clinical assessment, and for many will also dictate the prescription variables for foot orthoses.  The potential problem with solely relying on visual alignment (or kinematics as they are referred to in biomechanics terminology) is that there is surprisingly little literature which shows that foot posture is actually predictive of injury.  What this means is that the pronated foot type is not necessarily as evil as we had previously thought.  Dr Christopher Nester of Salford University sums things up perfectly in his recent paper from the Journal of Foot & Ankle Research:

Rather than continue to apply a poorly founded model of foot type where the focus is to make all feet mechanically ‘normal’ we must embrace variation between feet and develop patient specific models of foot function.

In addition to this when we look at the research of how orthoses exert their effects (or ‘work’) it is clear that kinematic responses to orthoses are also variable and subject specific (Nigg et al, 2003; Huerta et al, 2009).  This means that not all feet will respond the same if given the same orthotic prescription.  And even if they did respond in a predictable way would this mean they would all get better?  Sadly not, as Zammit and Payne discovered in 2007, when they investigated the relationship between kinematic response to an orthotic device (how much it ‘realigned’ the rearfoot) and the reduction in the individuals symptoms; and found that there was no correlation between the two.

Confused? So was I.  I was taught that a pronated foot was a huge risk factor for injury.  I was then taught to measure how much it was pronated, write a prescription based on this number and the orthotic device I issued would duly realign the foot into ‘neutral’ and the patients symptoms would of course disappear.  It was a simpler time as you can imagine.

Not until I read an excellent research paper by Williams et al (2003) in the Medicine and Science in Sports and Exercise Journal did it start to make sense to me.  This research took a group of individuals and made them run in 3 conditions: no orthoses, ‘standard’ orthoses and inverted orthoses (between 15-25 degrees inverted).  It measured the kinematics (alignment) and the kinetics (the forces we can’t see).  The results were astounding – there was no statistically significant difference in rearfoot alignment between the 3 conditions.  However, when looking at the forces involved (particularly how hard Tibialis Posterior had to work) the more inverted an orthotic device was significantly reduced the demand on the soft tissues.  The inverted orthoses reduced this demand almost 4-fold when compared to the no orthoses condition.  Immediately we realised that our orthoses made people pain free by reducing damaging force, and not by ‘re-aligning’ them.

So what does all of this have to do with the supination resistance test? Well it is one of very few tests which give us insight into these forces (which may well be more predictive of injury risk and may better determine orthoses prescriptions than our visual assessment techniques do).  If a foot requires a large force to supinate it then it is assumed that a greater contractile force from extrinsic supinators, such as Tibialis Posterior, may be required functionally (does this increase injury risk?)  It may also dictate the sort of orthotic device which would be most appropriate.  The harder it is to supinate a foot then the greater force an orthotic device would need to cause a supination moment, and conversely the easier it is to supinate a foot then the lower the force required from an orthotic device.

So how is the test performed?

  1. The patient is asked to stand in a relaxed position on two feet
  2. They are instructed to relax their feet during the test, and not help in any way
  3. The clinician places the tips of the index and middle fingers just beneath the navicular
  4. The clinician pulls directly upward (parallel to the tibia)
  5. The clinician notes the magnitude of force that is required to supinate the foot from its resting position
  6. The test is performed on the other foot

When done in this clinical setting the test is a little subjective, but with repetition gives the clinician a good idea of the forces involved (and despite its subjectivity may still offer more important information that visual assessment).

The research team at La Trobe University in Melbourne took this one step further and built a machine which quantitatively measured this supination force in Newtons.  They found some fascinating results:

  1. The manual version of the test (as described above) is reliable for experienced users
  2. The amount of force required to supinate a foot is only weakly related to how pronated it is
  3. The amount of force required to supinate a foot is highly correlated to the subtalar joint axis position (I won’t go into this now – it is worthy of its own blog entry and will get one in due course)
  4. Body weight explains about a third of the force required to supinate the foot

These findings are what we see clinically when performing the test – the force to supinate feet is variable, and does not seem to be hugely influenced by body weight (I have experienced a 13 year old girl who weighed 7 stone have a higher supination resistance than a 19 stone rugby prop forward).

The team at La Trobe have also done much research which has not been published yet (personal communication with Craig Payne) and one which interests me particularly.  They took 28 individuals all who had problems with only one limb and all of which had been previously considered to be due to ‘excessive pronation’.  They recorded the Foot Posture Index (a protocol which classifies feet into categories based on visual observations) on the injured side versus the uninjured side, and then measured the supination resistance on the injured side versus the uninjured side.  They found that when looking at foot posture the injured side was more pronated in 15 out of the 28 subjects.  However when looking at supination resistance it was higher on the injured side in 25 out of the 28 subjects.  Does this tell us that supination resistance is more predictive of injury that foot posture? Well not quite as it was a cross-sectional design, but it certainly suggests this is worth investigating further in a prospective study.

The supination resistance test is probably now one of the key things from my assessment of patients which dictates my orthoses choices.  I pay more attention to it than I do the foot posture.  However further work is required to fully understand supination resistance and whether it is prospectively predictive of injury risk (or can validly be used to determine dynamic kinematic responses to different levels of force from foot orthoses).

References

Picture from: Kirby, K. A. (2002). Supination Resistance Test. Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002 (pp. 155). Payson, Arizona: Precision Intricast, Inc.

Huerta, J. P., Moreno, J. M. R., & Kirby, K. A. (2009). Static response of maximally pronated and nonmaximally pronated feet to frontal plane wedging of foot orthoses. Journal of the American Podiatric Medical Association, 99(1), 13-19.

Kirby, K. A., & Green, D. R. (1992). Evaluation and nonoperative management of pes valgus. In S. DeValentine (Ed.), Foot and Ankle Disorders in Children (pp. 295).  New York: Churchill Livingstone.

Nester, C. J. (2009). Lessons from dynamic cadaver and invasive bone pin studies: do we know how the foot really moves during gait? Journal of Foot & Ankle Research, 2 (18)

Nigg, B. M., Stergiou, P., Cole, G., Stephanyshyn, D., Mundermann, A., & Humble, N. (2003). Effect of shoe inserts on kinematics, centre of pressure, and leg joint moments during running. Medicine & Science in Sports & Exercise,35, 314-319.

Noakes, H., & Payne, C. B. (2003). The reliability of the manual supination resistance test. Journal of the American Podiatric Medical Association, 93 (3), 185-189.

Payne, C. B., Munteanu, S., & Miller, K. (2003). Position of the subtalar joint axis and resistance of the rearfoot to supination. Journal of the American Podiatric Medical Association, 93 (2), 131-135.

Payne, C. B., Oates, M., & Noakes, H. (2003). Static stance response to different types of foot orthoses. Journal of the American Podiatric Medical Association, 93 (6), 492-498.

Williams, D. S., McClay Davis, I., & Baitch, S. P. (2003). Effect of inverted orthoses on lower-extremity mechanics in runners. Medicine & Science in Sports & Exercise, 35, 2060-2068.

Zammit, G. V., & Payne, C. B. (2007). Relationship between positive clinical outcomes of foot orthotic treatment and changes in rearfoot kinematics. Journal of the American Podiatric Medical Association, 97, 207-212.



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It seems that barefoot running is a particularly hot topic at present, and no matter where you turn you are reading things about it.  In the last several weeks it has turned up on thousands of blogs, in magazines and even made it onto the BBC News.  There have been all sorts of sensational headlines and quotes regarding barefoot running, but what is the truth?

Firstly it should be mentioned that when we talk about barefoot running we are usually also referring to running in ‘minimalist’ shoes such as Vibram Five Fingers or Newton runners (to name but two).  This is not a new debate, and has been raging on for quite some time – the reason for the media hype recently is due to two studies which were published within a month of each other back in Dec 2009/Jan 2010.  Unfortunately what followed was some terrifically inappropriate and inaccurate reporting by the media, and some energetic and passionate use of these misrepresented facts by the barefoot running community.

I am often asked whether (as a Podiatrist) I feel threatened by barefoot running.  The answer is a clear no.  I have no bias and I go where the research tells me.  However rather than just read someones one line summation of a research paper I instead read the entire paper thoroughly myself, and critique the methodology and conclusions made.  Things in my head are kept strictly objective and factual.  This blog entry intends to take a look at the two articles responsible for the recent media circus:

Kerrigan, D. C., Franz, J. R., Keenan, G. S., et al. (Dec 2009). The Effect of Running Shoes on Lower Extremity Joint Torques. PM&R, 1 (12), 1058-1063.

What did they do?

They took 68 runners who usually ran in shoes.  They put them all in what they called a ‘neutral’ running shoe and made them run on a treadmill.  They then made them all run on the treadmill again (at the same speed) but barefoot.  They measured the torques at the hip knee and ankle in both conditions.

What did the media/barefoot running community report?

Headlines usually were along the lines of: ‘Running Shoes Cause damage to hips, knees and ankles’

What are some of the problems with this research?

(1) The shoes every runner was given were a pair of Brooks Adrenaline.  This is clearly a ‘Stability’ shoe and not a neutral shoe.  When researchers are getting such simple facts as this wrong it is a concern.  Not to mention the fact that this may not have been an appropriate shoe for all 68 runners (nor a shoe some of them may have been used to) and little things like this seriously question the validity of the results obtained.

(2) None of the 68 runners were used to barefoot running.  This could account for why the torques were so much lower (someone running barefoot for the first time is bound to be more tentative about striking the ground).  Would it not have been a better idea to use habitual barefoot runners?

(3) This was performed on a treadmill.  Can the results therefore be extrapolated to overground running?

(4) The main author, Dr Kerrigan is a 100% equity holder in JKM Technologies and is the developer of a new and upcoming running shoe technology (the CDC suspension system).  This potential financial conflict of interest was not stated.  Some may think it suspicious that research produces conclusions which are geared towards the eventual release of a ‘barefoot technology’ shoe product.  Watch this space…

Lieberman, D. E., Venkadesan, M., Werbel, W. A. et al. (Jan 2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature. 463, 531-535.

What did they do?

They had 5 groups of different runners (some barefoot runners, some shod runners, some from USA, some from Kenya).  They had them all run at preferred speed on the track and data on the foot position and forces were recorded.

What did the media/barefoot running community report?

Headlines were usually along the lines of: ‘Barefoot runners are less likely to experience serious injuries’ or ‘Running barefoot is better for you’

What are some of the problems with this research?

(1) This study had absolutely nothing to do with injury.  It was a comparison of barefoot and shod running.  I honestly have no idea how injury can even be mentioned when discussing this research.

(2) The statistical analysis is flawed.  Unforgivably they only compared 2 out of the 5 groups, and interestingly these were both groups of runners from the USA (despite most of the pictures from the study and alot of the discussions focusing on the Kenyan runners).

(3) They also did not have any age group controls between the 2 groups they compared.  The barefoot group (8 runners) had an average age of 38 years old.  The shod group (8 runners) had an average age of 19 years old.  How can you compare data between 2 groups when one is almost twice as old as the other?

(4) Findings based on a sample size of just 8 runners (even if the statistics were correct) are really not poweful enough to extrapolate to an entire population.

(5) The study was partially funded by Vibram Five Fingers.  Was there a financial conflict of interest?

Very interestingly even the authors of this study (to their credit) are acknowledging that the media has misrepresented their findings:

There are many discrepancies between the way some of the press has reported our paper and what the paper actually reports…we present no data on opinions on how people should run, whether shoes cause injuries, or whether barefoot running causes other kinds of injuries.  We believe there is a strong need for controlled prospective studies on these problems.

The website can be viewed in full here: http://barefootrunning.fas.harvard.edu/index.html

Some final things to consider about barefoot running in general:

  1. Why do no elite runners run barefoot if it is so beneficial?
  2. Every person is individual and what works for one does not work for all.  Not all runners need to strike on their forefoot to be the most efficient runners. For the majority of long distance runners at their normal training speeds, rearfoot striking is actually the preferred manner of running.
  3. Trying to make someone who is naturally a rearfoot striker into a forefoot striker may injure them.
  4. A runner who is a rearfoot striker at 10:00 min/mile pace may be a forefoot striker at 5:00 min/mile pace.  Running speed changes foot strike pattern.

In summary, what are the actual facts currently known about barefoot and shod running?

  1. Running barefoot/minimalist strengthens the intrinsic or postural muscles in the feet and lower leg…. probably, but not absolutely established.. seems sensible though.
  2. Running barefoot/minimalist increases proprioceptive awareness and balance.
  3. Running barefoot/minimalist forces a change in mechanics to adapt to the forces of on the feet.
  4. There are no clinical trials that show an effect of barefoot/minimalist running for a prolonged period of time.
  5. There are no research studies that prove that wearing traditional running shoes increases injuries or that barefoot/minimalist running reduces injuries.

So there you have it… the answer is that with respect to running barefoot and running shod, we don’t actually know which is better for you, or which puts you at greatest risk of certain injuries.  What we do know is that certain groups within the barefoot community (usually with their own agenda or sometimes financial interest) continue to promote their beliefs with poor information.  Whether they don’t bother reading the research themselves, or whether they do read it but through their own ‘lens’ who knows.

I would like to thank Mr Simon Bartold, Prof Craig Payne and Dr Kevin Kirby, without whom my own thinking on this subject would not be the same, and this blog entry would not have been possible.

For more in depth reading of both sides of the ‘discussion’ see the following pages:

Podiatry Arena discussions on barefoot running

Barefoot Running is Bad Blog

Newton Running Blog

Run Natural Blog

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