4) Running Shoes

Question 1

What is the purpose of running shoes?

Answer 1

• Protection (from environment)
• Injury prevention:
  ○ Motion control
  ○ Attenuation of impact forces
• Provide traction
• Comfort
• Performance

Question 2

Describe the running shoe anatomy.

Answer 2

• Upper (protection, heel stability)
• Midsole (Cushioning, impact attenuation, energy return, load distribution, torsion control)
• Outsole (protection, traction, cushioning)
• Stack height - height of outsole

Question 3

Explain the relationship between running shoes and human interaction:

Answer 3

All linked (Mechanical - biomechanics - performance & perception)

Question 4

What does shoe mass affect?

Answer 4

• Impacts metabolic cost & running economy
• Shoe mass degrades running economy
• Increases mechanical work (muscles working harder)

Question 5

Give an example of where altering shoe mass helped improve performance.

Answer 5

Reducing shoe mass by 100g per shoe reduces marathon record by 57.5 seconds (by 0.78%)

Question 6

What is Longitudinal bending stiffness?

Answer 6

Resistance against bending with external load applied perpendicularly to longitudinal axis.

Question 7

What technology is used to alter the LBS?

Answer 7

○ Carbon fibre plate (stiff, strong, low mass)

○ Curved carbon infused rods (mirror the metatarsals in foot)

• Laser sintered nylon (changed bending stiffness of sprint spikes)

Question 8

What methods are used to test LBS?

Answer 8

Testing methods:

• 3 point bend test (load pin and 2 supporting pins, measure force and displacement which gives stiffness)
• Cantilever bend test (fix front of shoe and lift heel up) -> Stiffness = change in torque/ change in angle

Question 9

Do heavier runners benefit from more or less stiff shoes?

Answer 9

More stiff.

Question 10

Which running shoe reduced the cost of running by 4%?

Answer 10

The Nike Vaporfly 4%

Question 11

What are the affects of altering the longitudinal bending stiffness?

Answer 11

○ Minimise energy loss at metatarsal phalangeal joint(mpt)

○ Modify joint lever arms

○ Support normal mtp function

○ Teeter totter affect (point of force moves towards front of plate, Grf produces upwards force at heel

Question 12

What is the purpose of the midsole?

Answer 12

Protective medium between ground and muscoskeletal system.

Redistribution of force or shock attenuation.

Question 13

What are examples of midsole materials?

Answer 13

• EVA (injection moulded)
• TPU (pellets)
• PEBA (TP elastomer)
• TPEE (TP elastomer)

Question 14

What testing method is used for midsole materials?

Answer 14

Compression testing - load & unload

Question 15

What variables are assessed in midsole material testing?

Answer 15

• Stiffness
• Energy absorbed
• Energy returned
• Hysteresis (energy lost)

Question 16

What is muscle tuning paradigm?

Answer 16

Using impact forces as input signals to measure where in the central nervous system the forces are being sensed.

Tuning muscles using EMG activity to reduce soft tissue vibration. Improves performance and comfort.