Heel-shoe interactions and the durability of EVA foam running-shoe midsoles.

A finite element analysis (FEA) was made of the stress distribution in the heelpad and a running shoe midsole, using heelpad properties deduced from published force-deflection data, and measured foam properties. The heelpad has a lower initial shear modulus than the foam (100 vs. 1050 kPa), but a higher bulk modulus. The heelpad is more non-linear, with a higher Ogden strain energy function exponent than the foam (30 vs. 4). Measurements of plantar pressure distribution in running shoes confirmed the FEA. The peak plantar pressure increased on average by 100% after 500 km run. Scanning electron microscopy shows that structural damage (wrinkling of faces and some holes) occurred in the foam after 750 km run. Fatigue of the foam reduces heelstrike cushioning, and is a possible cause of running injuries.

[1]  R. F. Ker,et al.  The effects of isolation on the mechanics of the human heel pad. , 1996, Journal of anatomy.

[2]  T Y Shiang,et al.  The nonlinear finite element analysis and plantar pressure measurement for various shoe soles in heel region. , 1997, Proceedings of the National Science Council, Republic of China. Part B, Life sciences.

[3]  B. Nigg,et al.  Relationship between plantar pressure distribution under the foot and insole comfort. , 1994, Clinical biomechanics.

[4]  T Y Shiang,et al.  The effect of insoles in therapeutic footwear--a finite element approach. , 1997, Journal of biomechanics.

[5]  P. Aerts,et al.  Deformation characteristics of the heel region of the shod foot during a simulated heel strike: the effect of varying midsole hardness. , 1993, Journal of sports sciences.

[6]  The mechanical properties of the human heel pad , 2000 .

[7]  J. Taunton,et al.  A prospective study of running injuries: the Vancouver Sun Run “In Training” clinics , 2003, British journal of sports medicine.

[8]  B. Nigg,et al.  A kinematic comparison of overground and treadmill running. , 1995, Medicine and science in sports and exercise.

[9]  M J Mueller,et al.  Generalizability of in-shoe peak pressure measures using the F-scan system. , 1996, Clinical biomechanics.

[10]  Martyn R. Shorten,et al.  RUNNING SHOE DESIGN : PROTECTION AND PERFORMANCE , 2001 .

[11]  N.J. Mills,et al.  Modelling the Gas-loss Creep Mechanism in EVA Foam from Running Shoes , 2001 .

[12]  T S Gross,et al.  Discrete normal plantar stress variations with running speed. , 1989, Journal of biomechanics.

[13]  N. J. Mills,et al.  Simulating the effects of long distance running on shoe midsole foam , 2004 .

[14]  Ewald M. Hennig,et al.  In-Shoe Pressure Distribution for Running in Various Types of Footwear , 1995 .

[15]  E. Hennig,et al.  Pressure distribution measurements for evaluation of running shoe properties. , 2000, Sportverletzung Sportschaden : Organ der Gesellschaft fur Orthopadisch-Traumatologische Sportmedizin.

[16]  R. F. Ker,et al.  The mechanical properties of the human heel pad: a paradox resolved. , 1995, Journal of Biomechanics.

[17]  G. Baroud,et al.  Material properties of the human calcaneal fat pad in compression: experiment and theory. , 2002, Journal of biomechanics.

[18]  Y. Itzchak,et al.  In vivo biomechanical behavior of the human heel pad during the stance phase of gait. , 2001, Journal of biomechanics.

[19]  J Woodburn,et al.  Observations on the F-Scan in-shoe pressure measuring system. , 1997, Clinical biomechanics.

[20]  M. Kester,et al.  Shock absorption characteristics of running shoes , 1985, The American journal of sports medicine.

[21]  J. Woodburn,et al.  Observations on the F-Scan in-shoe pressure measuring system. , 1996, Clinical biomechanics.

[22]  Roger Bartlett,et al.  Sports Biomechanics: Reducing Injury and Improving Performance , 1999 .

[23]  Peter R. Cavanagh,et al.  Biomechanics of Distance Running. , 1990 .

[24]  E. Boyko,et al.  Reliability of F-Scan In-Shoe Measurements of Plantar Pressure , 1998, Foot & ankle international.