The ‘Wet Footprint Test’ is a Furphy

I was almost not going to bother writing this as I thought that the so-called ‘wet footprint test’ was coming up less often, so more and more people are taking notice of it not being a good test on which to make a prescription of a running shoe. I did a Google search and used the search tools to restrict it to pages Google had found in the last month. OMG … I could not believe how many recent references there are to still using this test.

The wet footprint test is where you get your feet wet and then stand on something like a paper towel and then it reveals your arch shape. Perhaps you can see a low arch, neutral arch or a high arch foot from this. This is claimed as the basis of how your foot functions dynamically and should be the basis for the decision making when wanting to choose a running shoe (ie overprontion etc).

The ‘Wet Footprint Test’ is a furphy¹.

The evidence for prescribing a running shoe based on plantar foot shape has clearly been debunked by the work of Knapik et al in three studies². According to the three studies, if you prescribed a running shoe based on plantar foot shape, it does not affect the injury rate. Mind you, that is all they actually showed and some have taken this research to imply that the whole ‘pronation’ and running shoes paradigm is wrong. It may or may be wrong, but you can not draw that conclusion from this research. Foot pronation and supination has many components to it (eg calcaneal eversion, forefoot abduction, medial midfoot bulging, lower arch profile) and the wet footprint test only measures one of them. You can still have a ‘normal’  arch profile on the wet footprint test, but still have, for example, an everted calcaneus and an abducted forefoot (this is why the Foot Posture Index was developed to take all those components into account).

The reason that they probably found no impact on the injury rate is possibly the well documented large body of literature on the lack of a correlation between static measures of foot posture and dynamic function. However, it should be pointed out that many of the ‘static’ parameters used in most of those studies are hardly ever used in clinical practice. The emphasis today is more toward clinical tests, that are still static, but are more concerned with determining loads and forces driving motion rather than the amount of actual motion or posture of the foot.

Those fancy pressure measuring devices that you see in so many retail outlets are also the same thing and are only determining plantar arch shape. Just because they do it dynamically by walking over the platform with fancy graphics on a computer as opposed to the messy wet test on paper, does not make it necessarily any better for prescribing a running shoe. Its just a high tech way to determine the arch shape, which Knapik et al showed does not result in a reduction of injury if you base your running shoe prescription on that.

For more, Ian Griffiths reviewed more of the evidence behind running shoes prescription and Peter Larsen reviewed some of the static measures vs dynamic function.

As always, I go where the evidence takes me until convinced otherwise, and the evidence tells me that the wet footprint test and its high tech derivations are not supported by the evidence (ie its a furphy).

1. A ‘furphy’ is Australian slang for something that is erroneous.

2. 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.

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.

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.

 

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7 Responses to The ‘Wet Footprint Test’ is a Furphy

  1. Kevin A. Kirby, DPM April 20, 2013 at 9:35 pm #

    Craig:

    The word “furphy” must be a New Zealand/Australian dialect…can you translate that into American English? 😉

    Cheers,

    Kevin

  2. Craig April 20, 2013 at 9:38 pm #

    “A ‘furphy’ is Australian slang for something that is erroneous.”

  3. Asle August 2, 2013 at 4:08 pm #

    I get what you mean with a “furphy”. I like your search for evidence. I just want to add my story. I have had a wet footprint that shows flat feet and I know that has been my problem all my life. So a couple of years ago I would get a wet footprint that showed flat feet. After 2 years of using shoes with no support and some barefoot running, my wet footprint is completely different. It now shows what some would say a “healthy foot” where the plantar fascia does not touch the ground. Do you mean this is something I can not relate to at all and does it not mean my arches are better than before? I am a little confused here.

  4. Craig norton March 23, 2014 at 12:44 am #

    The wet test may not be the most scientific way to prescribe the proper footwear but it is useful to sales staff in a retail setting if they are taught about the implications for foot patterns.while standing a flat foot may appear to have the same foot pattern as a severe pronation.Both types would benefit from a high stability shoe that would provide increase structure to the foot making it a more efficient lever arm.For the severe pronator it would be an added benefit by reducing navicular drop,reducing the torsional forces in the lower extremely.

  5. Ian Griffiths March 23, 2014 at 11:17 am #

    Craig,

    The wet foot test tells us very little and is in no way predictive of an individuals dynamic mechanics, nor injury risk. Furthermore there is a growing body of evidence which directly contradicts your statement about which foot “patterns” require high stability shoes. Perhaps this is uncomfortable to hear given you appear to have built a company upon the erroneous and out dated paradigm of shoe selection?

    As Craig says – we need to go where the evidence takes us.

    • Craig Norton August 12, 2014 at 4:13 am #

      Hi Ian,
      Totally disagree with you and i am not uncomfortable to say so.A excessive pronated foot and a flat foot are both poor lever arms because of their mobile characteristics at full weight bearing.To make them a more structured and efficient lever arm they need to be placed in a shoe that provides more stability.We have found this to be a more effective approach over the last 10 years fitting 60,000 customer/patients .Our method for shoe selection is the result of structural parameter testing of athletic shoe,clinical observations and our extensive background in sport medicine.Please view our test site at http://www.opistest.com .
      Craig

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