||Stiffness Effects and Biomechanical Implications in Rocker-Soled Shoes
||Department of BioMedical Engineering
vertical ground reaction force
Rocker-soled shoes provide a way to reduce the possible concentration of stress, as well as change movement patterns, during gait. This study attempts to examine how plantar force and spatio-temporal variables of gait are affected by two rocker designs, one with softer and one with denser sole materials, by comparing them with the barefoot condition and with flat-soled shoes.
Outer surfaces of the rocker shoes were curved upward at front and rear; middle section is flat. The front apex is designed to follow the line from the 1st to the 5th metatarsal heads, which is about 60% of the shoe length from the heel. The rear apex is designed to fall under the junction of the plantar fascia and calcaneus, which is about 25% of the shoe length from the heel. Shoe soles have three layers including upper midsole, bottom midsole, and outsole and using three different typically non-linear materials. All material properties were conformed to ASTM standards.
Kinematic data, vertical ground reaction force, and plantar force were acquired using Vicon Motion System, AMTI force plate, and Pedar insole system, respectively. Eleven subjects’ gait parameters during walking and jogging were recorded. Each subject was asked to perform eight different tasks; the order of the four foot-ground interface conditions (barefoot, flat-soled shoes, rocker-soled shoes with softer material, and rocker-soled shoes with denser material) and the two activities (walking and jogging) was randomly assigned. The experiment collected in total 264 gait cycles, and for each relevant event analyzed the parameters of plantar force, duration of event, and angle.
Our results showed that compared with barefoot walking, plantar forces were higher for flat shoes while lower for both types of rocker shoes, the softer-material rocker being the lowest. The plantar force of flat shoes is greater than the vertical ground reaction force, while that of both rocker shoes is much less, 13.87-30.55% body weight.
However, as locomotion speed increased to jogging, for all shoe types, except at the second peak plantar force of the denser sole material rocker shoes, plantar forces were greater than for bare feet. More interestingly, because the transmission of force was faster while jogging, greater plantar force was seen in the rocker-soled shoes with softer material than with denser material; results for higher-speed shock absorption in rocker-soled shoes with softer material were thus not as good. In general, the rolling phenomena along the bottom surface of the rocker shoes as well as an increase in the duration of simultaneous curve rolling and ankle rotation could contribute to the reduction of plantar force for both rocker designs. The possible mechanism is the conversion of vertical kinetic energy into rotational kinetic energy.
To conclude, plantar force is related to foot-ground interface and deceleration methods. Apart from the design of shoe-soles and the thickness of shoe heels, different shoe-sole materials and stepping speed are also significant factors in inducing compensatory postures in the feet. Rocker-design shoes with a material suited to step speed could achieve desired plantar force reduction through certain rolling phenomena, shoe-sole stiffness levels, and locomotion speeds.
Figure Captions IX
Table Captions XII
Chapter 1 Introduction 1
1.1 Background 1
1.2 Literature review 4
1.2.1 Rocker shoes 4
1.2.2 The strengths of rocker-sole design 5
1.3 Objectives 6
Chapter 2 Materials and Methods 7
2.1 Participants 7
2.2 Foot-ground interface conditions 7
2.2.1 Flat 8
2.2.2 Rocker-1 8
2.2.3 Rocker-2 11
2.3 Equipment and instruments 11
2.3.1 Motion capture system 11
2.3.2 Vertical ground reaction force measurement system 12
2.3.3 Plantar force measurement system 12
2.4 Biomechanical parameters measurement 12
2.4.1 Procedure 12
2.4.2 Calculating values for constructing the Pedotti diagram 16
2.4.3 Analyzing parameters of event forces, duration, angles, and centre of pressure shift 17
2.4.3 Statistical analysis 20
Chapter 3 Results 22
3.1 Material testing 22
3.2 Plantar force and duration 23
3.3 Comparisons of Rocker-1 and Rocker-2 27
3.4 Foot angle and gait pattern 29
3.5 Centre of pressure shift and ground reaction force vector angle 31
Chapter 4 Discussion 40
4.1 Compensatory phenomena induced from shoes 40
4.2 Comparisons of shoe sole materials between Rocker-1 and Rocker-2 42
4.3 Comparisons of four types of foot-ground interface 43
4.4 Comparisons with other rocker-soled shoes 46
4.5 Limitations 47
Chapter 5 Conclusions 49
 D. J. Janisse, and E. Janisse, “Shoe modification and the use of orthoses in the treatment of foot and ankle pathology,” Journal of the American Academy of Orthopaedic Surgeons, vol. 16, no. 3, pp. 152-158, Mar, 2008.
 K. A. Boyer, and T. P. Andriacchi, “Changes in running kinematics and kinetics in response to a rockered shoe intervention,” Clinical Biomechanics (Bristol, Avon), vol. 24, no. 10, pp. 872-876, Dec, 2009.
 T. Stöggl, A. Haudum, J. Birklbauer, M. Murrer, and E. Müller, “Short and long term adaptation of variability during walking using unstable (Mbt) shoes,” Clinical Biomechanics (Bristol, Avon) vol. 25, no. 8, pp. 816-822, Oct, 2010.
 J. D. Chapman, S. Preece, B. Braunstein, A. Hohne, C. J. Nester, P. Brueggemann, and S. Hutchins, “Effect of rocker shoe design features on forefoot plantar pressures in people with and without diabetes,” Clinical Biomechanics (Bristol, Avon), vol. 28, no. 6, pp. 679-685, Jul, 2013.
 L.-T. Chang, F.-C. Su, K.-A. Lai, and K.-H. Tsai, “Gait Analysis after Shoe Lifts in Adults with Unilateral Developmental Dysplasia of the Hip,” Journal of Medical and Biological Engineering, vol. 25, no. 3, pp. 137-141, 2005.
 J. T. Long, J. P. Klein, N. M. Sirota, J. J. Wertsch, D. Janisse, and G. F. Harris, “Biomechanics of the double rocker sole shoe: gait kinematics and kinetics,” Journal of Biomechanics, vol. 40, no. 13, pp. 2882-2890, 2007.
 K. A. Myers, J. T. Long, J. P. Klein, J. J. Wertsch, D. Janisse, and G. F. Harris, “Biomechanical implications of the negative heel rocker sole shoe: gait kinematics and kinetics,” Gait & posture, vol. 24, no. 3, pp. 323-330, Nov, 2006.
 S. Sobhani, J. Zwerver, E. van den Heuvel, K. Postema, R. Dekker, and J. M. Hijmans, “Rocker shoes reduce Achilles tendon load in running and walking in patients with chronic Achilles tendinopathy,” Journal of science and medicine in sport, vol. 18, no. 2, pp. 133-138, Mar, 2015.
 L. Stewart, J. N. A. Gibson, and C. E. Thomson, “In-shoe pressure distribution in "unstable" (MBT) shoes and flat-bottomed training shoes: a comparative study,” Gait & Posture, vol. 25, no. 4, pp. 648-651, Apr, 2007.
 K. Postema, P. E. T. Burm, M. E. v. d. Zande, and J. v. Limbeek, “Primary metatarsalgia the influence of a custom moulded insole and a rockerbar on plantar pressure,” Prosthetics and Orthotics International, vol. 22, pp. 35-44, 1998.
 A. S. Sousa, R. Macedo, R. Santos, F. Sousa, A. Silva, and J. M. Tavares, “Influence of prolonged wearing of unstable shoes on upright standing postural control,” Human movement science, vol. 45, pp. 142-153, Feb, 2016.
 G. Waddington, and R. Adams, “Football boot insoles and sensitivity to extent of ankle inversion movement,” British Journal of Sports Medicine, vol. 37, no. 2, pp. 170-175, Apr, 2003.
 A. A. Priplata, B. L. Patritti, J. B. Niemi, R. Hughes, D. C. Gravelle, L. A. Lipsitz, A. Veves, J. Stein, P. Bonato, and J. J. Collins, “Noise-enhanced balance control in patients with diabetes and patients with stroke,” Annals of neurology, vol. 59, no. 1, pp. 4-12, Jan, 2006.
 J. Hijmans, J. Geertzen, P. Dijkstra, and K. Postema, “A systematic review of the effects of shoes and other ankle or foot appliances on balance in older people and people with peripheral nervous system disorders,” Gait & Posture, vol. 25, no. 2, pp. 316-323, Feb, 2007.
 P. S. Schaff, and P. R. Cavanagh, “Shoes for the insensitive foot: the effect of a "rocker bottom" shoe modification on plantar pressure distribution,” Foot and ankle, vol. 11, no. 3, pp. 129-140, Dec, 1990.
 B. M. Nigg, and B. Segesser, “Biomechanical and orthopaedic concepts in sport shoe design,” Medicine and science in sports and exercise, vol. 24, no. 5, pp. 595-602, 1992.
 M. Peduzzi de Castro, S. Abreu, V. Pinto, R. Santos, L. Machado, M. Vaz, and J. P. Vilas-Boas, “Influence of pressure-relief insoles developed for loaded gait (backpackers and obese people) on plantar pressure distribution and ground reaction forces,” Applied Ergonomics, vol. 45, no. 4, pp. 1028-1034, Jul, 2014.
 S. Sobhani, J. Hijmans, E. van den Heuvel, J. Zwerver, R. Dekker, and K. Postema, “Biomechanics of slow running and walking with a rocker shoe,” Gait & posture, vol. 38, no. 4, pp. 998-1004, Sep, 2013.
 Ministry of Health and Welfare. "BMI testing.," http://health99.hpa.gov.tw/OnlinkHealth/Onlink_BMI.aspx.
 C. van Schie, J. S. Ulbrecht, M. B. Becker, and P. R. Cavanagh, “Design criteria for rigid rocker shoes,” Foot and Ankle International, vol. 21, no. 10, pp. 833-844, Oct, 2000.
 A. Leardini, M. G. Benedetti, L. Berti, D. Bettinelli, R. Nativo, and S. Giannini, “Rear-foot, mid-foot and fore-foot motion during the stance phase of gait,” Gait & Posture, vol. 25, no. 3, pp. 453-462, Mar, 2007.
 B. D. Wit, D. D. Clercq, and P. Aerts, “Biomechanical analysis of the stance phase during barefoot and shod running,” Journal of Biomechanics, vol. 33, no. 3, pp. 269-278, Mar, 2000.
 W. L. Wu, D. Rosenbaum, and F. C. Su, “The effects of rocker sole and SACH heel on kinematics in gait,” Medical engineering & physics, vol. 26, no. 8, pp. 639-646, Oct, 2004.
 ASTM, "D3575-08: standard test methods for flexible cellular materials made from olefin polymers," American Society for Testing and Materials, 2008.
 ASTM, "D638-10: Standard test method for tensile properties of plastics," American Society for Testing and Materials, 2010.
 R. Verdejo, and N. J. Mills, “Heel-shoe interactions and the durability of EVA foam running-shoe midsoles,” Journal of Biomechanics, vol. 37, no. 9, pp. 1379-1386, Dec, 2004.
 L. Wang, Y. Hong, and J. X. Li, “Durability of running shoes with ethylene vinyl acetate or polyurethane midsoles,” Journal of sports sciences vol. 30, no. 16, pp. 1787-1792, Dec, 2012.
 P. Larson, E. Higgins, J. Kaminski, T. Decker, J. Preble, D. Lyons, K. McIntyre, and A. Normile, “Foot strike patterns of recreational and sub-elite runners in a long-distance road race,” Journal of sports sciences, vol. 29, no. 15, pp. 1665-1673, Dec, 2011.
 D. E. Lieberman, M. Venkadesan, W. A. Werbel, A. I. Daoud, S. D'Andrea, I. S. Davis, R. O. Mang'Eni, and Y. Pitsiladis, “Foot strike patterns and collision forces in habitually barefoot versus shod runners,” Nature, vol. 463, no. 7280, pp. 531-535, Jan 28, 2010.
 J. M. A. Melvin, S. Preece, C. J. Nester, and D. Howard, “An investigation into plantar pressure measurement protocols for footwear research,” Gait & Posture, vol. 40, no. 4, pp. 682-687, Sep, 2014.
 R. Squadrone, and C. Gallozzi, “Biomechanical and physiological comparison of barefoot and two shod conditions in experienced barefoot runners,” The Journal of Sports Medicine and Physical Fitness, vol. 49, no. 1, pp. 6-13, Mar, 2009.
 D. C. Low, and S. J. Dixon, “Footscan pressure insoles: accuracy and reliability of force and pressure measurements in running,” Gait & Posture, vol. 32, no. 4, pp. 664-666, Oct, 2010.
 C. S. Nicolopoulos, E. G. Anderson, S. E. Solomonidis, and P. V. Giannoudis, “Evaluation of the gait analysis FSCAN pressure system: clinical tool or toy?,” The Foot, vol. 10, no. 3, pp. 124-130, 2000.
 M. Castro, S. Abreu, H. Sousa, L. Machado, R. Santos, and J. P. Vilas-Boas, “Ground reaction forces and plantar pressure distribution during occasional loaded gait,” Applied ergonomics, vol. 44, no. 3, pp. 503-509, May, 2013.
 S. B. Kambhampati, “Constructing a Pedotti diagram using excel charts,” Journal of biomechanics, vol. 40, no. 16, pp. 3748-3750, Jun, 2007.
 V. Berki, M. A. Boswell, D. Ciltea, L. M. Guseila, L. Goss, S. Barnes, N. Berme, G. R. McMillan, and B. L. Davis, “Expanded butterfly plots: A new method to analyze simultaneous pressure and shear on the plantar skin surface during gait,” Journal of biomechanics, vol. 48, no. 10, pp. 2214-6, Jul, 2015.
 I. V. Caekenberghe, V. Segers, P. Aerts, P. Willems, and D. De Clercq, “Joint kinematics and kinetics of overground accelerated running versus running on an accelerated treadmill,” J R Soc Interface, vol. 10, no. 84, pp. 20130222, Jul 06, 2013.
 T. Marasovic, M. Cecic, and V. Zanchi, “Analysis and interpretation of ground reaction forces in normal gait,” Wseas Transactions on Systems, vol. 8, no. 9, pp. 1105-1114, 2009.
 G. Liu, and K. Y. Liang, “Sample size calculations for studies with correlated observations,” Biometrics, vol. 53, no. 3, pp. 937-947, Sep, 1997.
 T. S. Keller, A. M. Weisberger, J. L. Ray, S. S. Hasan, R. G. Shiavi, and D. M. Spengler, “Relationship between vertical ground reaction force and speed during walking, slow jogging, and running,” Clinical Biomechanics (Bristol, Avon) vol. 11, no. 5, pp. 253-259, Jul, 1996.
 I. J. Ho, Y. Y. Hou, C. H. Yang, W. L. Wu, S. K. Chen, and L. Y. Guo, “Comparison of plantar pressure distribution between different speed and incline during treadmill jogging,” Journal of Sports Science and Medicine, vol. 9, no. 1, pp. 154-160, Mar, 2010.
 M. R. Shorten, "The myth of running shoe cushioning."
 M. R. Shorten, and M. Mientjes, “Heel impact force during running is neither heel nor impact and does not quantify shoe cushioning effects.,” Footwear Science, vol. 3, pp. 41-58, 2011.
 D. C. Kerrigan, J. R. Franz, G. S. Keenan, J. Dicharry, U. Della Croce, and R. P. Wilder, “The effect of running shoes on lower extremity joint torques,” American Academy of Physical Medicine and Rehabilitation, vol. 1, no. 12, pp. 1058-1063, Dec, 2009.
 J. Bonacci, P. U. Saunders, A. Hicks, T. Rantalainen, B. T. Vicenzino, and W. Spratford, “Running in a minimalist and lightweight shoe is not the same as running barefoot: a biomechanical study,” British Journal of Sports Medicine, vol. 47, no. 6, pp. 387-392, Apr, 2013.
 M. F. Bobbert, M. R. Yeadon, and B. M. Nigg, “Mechanical analysis of the landing phase in heel-toe running,” Journal of Biomechanics, vol. 25, no. 3, pp. 223-234, Mar, 1992.
 S. Forghany, C. J. Nester, B. Richards, A. L. Hatton, and A. Liu, “Rollover footwear affects lower limb biomechanics during walking,” Gait & posture, vol. 39, no. 1, pp. 205-212, Jan, 2014.
 S. Sobhani, E. R. v. d. Heuvel, R. Dekker, K. Postema, B. Kluitenberg, S. W. Bredeweg, and J. M. Hijmans, “Biomechanics of running with rocker shoes,” Journal of Science and Medicine in Sport, May, 2016.