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View Full Version : Summary of responses re question about "Flat feet and theload-bearing capacity of soldiers"



dmcfarlane
12-06-2007, 09:10 AM
Dear all,

Here is a summary of the best responses to my earlier question on flat feet.

Deydre Teyhen, (Assistant Professor, U.S. Army-Baylor University) said that in the USA there is no restriction based on arch type for joining the military though there was a time in which flat feet did result in exclusion in the military but that was a long time ago). Indeed epidemiologists have determined that people with high arched feet actually have more injuries (Jones and Knapik, 1999).

Becky Avrin Zifchock drew my attention to a cross-sectional study on the effect of age on arch structure that found that there was no significant relationship between arch height and increasing age (Zifchock et al, 2006). However, this study was not longitudinal and did not follow individual people as they aged.

Pamela Haibach (Assistant Professor, State University of New York) commented that flat feet can often cause chronic pain and joint problems resulting from exercise (and other physical activities such as labouring).

Chris Kirtley also said that the problem of flat feet is indeed a myth and varus (high-arched) feet are much more of a risk factor and provided a reference (Rudzki, 1997). She noted that I probably meant to say Valgus rather than Varus.

Louis DiBerardino (Graduate Student, University of Illinois, Urbana) said that though she has varus she can easily walk for 18 holes of golf (about 4 miles) carrying a 40 lb golf bag and she has often encountered circumstances where people with normal arches have complained more about foot ache more than she does.

Jon Donnelly (PhD student, UWA Biomechanics) commented that in theory during gait the ligaments of normal arches of human feet (particularly those that run down the longitudinal axis) absorb energy during contact (in normal arches) and passively return it during push off thus taking away the energy demand needed by the posterior muscles of the leg and making gait more efficient. Consequently Without a flat-footed person without proper arched would in theory need to produce more force from their muscles and this might cause secondary injuries to the lower limb. However, he was not aware if the predictions of this theory and has actually been measured in a human foot during gait.

Aaron Derouin (Ergonomic Engineer) said that someone with true flat feet or pes planus is unable to form an arch in their foot dynamically. To test for pes planus you should manipulate the foot by dorsiflexing it using the Windlass test (Bolgla and Malone, 2004); if no arch appears they are truly flat footed. He said that you can also take x-rays to measure the size and shape of the navicular as this bone is often does not have a normal shape (i.e. the shape it has in a person with a normal arch). Moreover if the person is truly flat footed then the person loses all the functions that an arch provides because the foot acts as a mobile adaptor during weight acceptance up to mid-stance and as rigid lever at toe off. He speculated that without the ability to absorb shock in the feet as well and adapt to uneven terrain in the long term a soldier with flat feet would become fatigued more easily and might be unable to bear as much weight.

He provided two references to papers that discuss theories of that type; one related to the prevention of lower extremity stress fractures (Jones et al, 2002) and the other related to feet and fighting (Linker, 2007). This theory is also discussed in "The Spinal Engine" (Gracovetsky, 1989).

Kevin McQuade (Associate Professor, University of Washington) mentioned that a few years ago when he was trekking in Nepal he noticed that "all the porters had flat feet, wore only flip-flop sandals or flimsy tennis shoes and carried loads very high compared to a standard western backpack load" but they actually don't wear a backpack as we do; given a large load they prefer to put a strap around it "to carry from their forehead". Please try to do a biomechanical analysis of that scenario someone! However, he stressed that porters are not quite the same as sherpas (sherpas tend to be guides with high altitude training and they enjoy a higher social standing.

Regards,

David McFarlane MAppSc (Ergonomics)
Ergonomist, WorkCover NSW

References

1. B Jones and J Knapik, (1999), "Physical Training and Exercise-Related Injuries. Sorveillance, Research and Injury Prevention in Military Populations", Sports Medicine, 1999 Feb, 27 (2), pages 111-125 (see Figure 1).

2. R Zifchock, I Davis, H Hillstrom, and J Song, (2006), "The effect of gender, age, and lateral dominance on arch height and arch stiffness", Foot Ankle Int, 2006 May;27(5):367-72.

3. Christopher Kirtley, (2006), "Clinical Gait Analysis: Theory and Practice", [Churchill Livingstone Elsevier].

4. S Rudzki, (1997), "Injuries in Australian Army recruits. Part III: The accuracy of a pretraining orthopedic screen in predicting ultimate injury outcome", Military Medicine, 162(7): 481-483.

5. L Bolgla and T Malone, (2004), "Plantar Fasciitis and the Windlass Mechanism: A Biomechanical Link to Clinical Practice", J Athl Train. 2004 Jan-Mar; 39(1): 77-82.
6. B Jones, S Thacker, J Gilchrist, C Kimsey and D Sosin, (2002), "Prevention of Lower Extremity Stress Fractures in Athletes and Soldiers: A Systematic Review", Epidemiologic Reviews 2002, 24: 228-247.
7. B Linker, (2007), "Feet for Fighting: Locating Disability and Social Medicine in First World War America", Social History of Medicine 2007 20(1):91-109.

8. S Gracovetsky, (1989), "The Spinal Engine", [Springer-Verlag, New York].

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