The Project
T36 100m Dash, 2008 Paralympic Games, Beijing
As a research and design engineer intern at Loughborough University's Sports Technology Institute, I worked on the Elite to High Street Project (E2HS), a research program investigating the development and validation of customized footwear for elite athletes and then applying this process to consumer footwear. In our case study, "Engineering Gold Medals", we designed and manufactured a customized sprint spike for a high profile British Paralympic sprinter suffering from cerebral palsy.
1. Form and Function: Natural Mechanics
Gray's Anatomy, Medial View of the Foot
The athlete's condition resulted in lack of motor control of the tibialis posterior, which runs down the calf around the ankle joint and to the metarsal heads. This critical muscle group allows the foot to act as a lever, and allows plantar flexion of the foot during the toe-off propelling the body forwards and upwards, and maintains a proper form. When non-functional, the arch of the foot collapses, causing ankle significant inward rolling of the ankle, known as pronation. This has led to several injuries to the athlete; however, other orthotic inserts have caused foot injuries as well due to their inability to dynamically change shape.
2. High Speed Video Analysis of Running Gait
Multi-angle High Speed Video at 2000 Frames/Sec
Here, we used three linked high-speed video cameras to simultaneously record the athlete's gait from different angles. Upon analysis of the individual's foot strike we noted the midfoot landing, with heel contact, which is atypical of sprinters whose short contact time is spent entirely on the toes. Similarly, 2cm of slippage can be seen in the final toe off, due to lack of traction at the toes.


3. Photogrammetric Deformation and Strain Analysis
GOM - Aramis High-Speed Dynamic Strain Mapping System
In designing the shoe's upper, we took an novel approach and used the GOM-Aramis 3D Strain and Deformation Analysis System conventionally used in automotive engineering, to understand the foot deformation during foot strike. The Aramis system, utilizes stereo high-speed video cameras in concert with photogrammetric strain-mapping software to analyze the dynamics of materials under stress, and visualize the strain. Using Aramis, we were able to isolate regions of the foot that needed the most support, allowing a targeted approach to footwear design.
   
4. Initial Sketch of Strapping System
Design of Proposed Strapping System
With an understanding of the mechanics of the foot's musculoskeletal system, and regions requiring support, we designed an initial strapping system. It had two major components: an elastic strap which would replicate the function of the tibialis posterior, and an elastic, forefoot strap to support the arch of the foot and prevent pronation.

Click image to download design documentation.
5. Mock Up of Strapping System
Prototype 1
To the right is the initial mockup of the strapping system, which I used to pattern the straps.

Click image to download design documentation.
6. Working Prototype
Prototype 2
I designed and prototyped this proof-of-principle model for initial testing. Upon initial testing, we recognized the need for more comfortable ankle strap anchors that would allow free movement of the Achilles tendon. This was achieved by custom-molding the ankle anchor using thermo-set plastic and padding with memory foam.

Upon further testing, we determined that the impulse delivered during the contact phase of the gait would need to be mitigated with a more supportive system. We stripped down a prescription ankle brace for Posterior Tibial Tendon Dysfunction, designed for walking, and integrated it with our strapping system. The firm support on the medial side of the ankle helped prevent pronation.

Click image to download design documentation.
7. User Testing and Feedback
High Speed Video Analysis at 2000 frame/sec
After several design iterations, we brought our working prototype to the athlete's training facility for user testing and feedback. Once again, using high-speed video, we captured the foot strike during. The athlete noted a remarkable change in his running gait, whereas previously his heel would collapse to the ground during the contact phase, he was now able to maintain a forward stance on his toes, which is more efficient for sprinting.
       
8. Designing a Bespoke Outsole
CAD Design of Outsole
Conventional treatment of gait abnormalities revolves around injury prevention during training, but rarely are customized orthotics used correct gait during competition. This is due to the lack of orthotics designed for integration with racing footwear. Using reverse-engineering systems, we were able to scan the athlete's foot, and with supervision of a podiatrist, develop a customized orthotic integrated directly into the outsole.
 
9. Rapidly Manufactured Integrated Orthotic Outsole System
High-Speed Laser Scintered Outsole
Whereas conventional manufacturing techniques, such as injection molding, would limit the form of the outsole, using high-speed laser sintering, a rapid manufacturing technique pioneered at Loughborough University, were able to create new forms and control material properties. Building on Dr. Dan Toon's previous work regarding bending stiffness of outsoles and optimal power transfer, we were able to optimize the nylon density and rigidity. Additionally the positioning and angle of the spike wells were tailored for the athlete's gait and foot strike pressure profile. The outsole was designed to interface with the strapping system for a unified approach to correcting gait.
10. Final Design and Manufacture
Final Prototyping
During our user testing, the athlete noted there was still some discomfort in the arch, due to the stiffness of the support. To solve this, we employed an inflatable pneumatic bladder for the arch support, whose pressure the athlete could adjust to his desired level of support or comfort on a given day. The slight compressibility of the bladder allows for shock attenuation and allows the support structure to dynamically change shape at various points of the gait.

In addition to the pneumatic bladder, with the functional issues addressed, I sought to streamline the design of the strapping system, so that it was less cumbersome and lighter in weight. This alpha prototype of the integrated orthotic and strapping system was sent to a garment technologist for manufacture, and final assembly was completed at New Balance of Boston.
ENGINEERING GOLD MEDALS
The Process of Designing Personalized Footwear for Elite Athletes
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Design and Photography by Gihan Amarasiriwardena © 2009. All media and intellectual property, property of Gihan Amarasiriwardena, Dr. Daniel Toon, Loughborough University Sports Technology Institute. All rights reserved © 2009.