16_18- Footwear Flashcards
What changed in the 70s which made running shoes start to become much better?
People started running to become fit/to improve performance in other sports
What are the different functions of the outsole, midsole, and heel counter in a running shoe?
Outsole: interface bw ground and shoe
Midsole: provides cushioning and supprt
Heel counter: provides stability and motion control
Why does the posterolateral portion of a running shoe tend to wear out the quickest while most of the shoe remains untouched?
Avg forward velocity at heel contact is 1m/s, and most people are heel-strikers.
After heel strike, shoe is not moving until just before foot is lifted off the ground
Your patient has a strike index of 8%. This would indicatethat the patient is a:
A. Forefoot striker
B. Midfoot striker
C. Rearfoot striker
Rearfoot striker - SI is measure of point of initial contact as a percent of the length of the shoe
Individuals with pes planus tend to have the most pressure in the (heel/forefoot) while individuals with pes cavus tend to have the most pressure in the (heel/forefoot) during gait.
Forefoot; heel
What are the risks of having too much cushioning in a running shoe? Too little?
Too much: shoe will bottom out
Too little: excessive shock to leg
Where should a shoe bend relative to the structures of the foot?
Behind the metatarsals
What is the major effect of a shoe’s weight on function?
Every 100g increases energy expenditure by 1%
Which factors help reduce over-pronation? A. Stiff heel counter B. Increased heel height C. Increased medial midsole stiffness D. Straight last
All of the above
How is the subtalar joint affected differently on heel contact depending on if you’re wearing running shoes vs. barefoot? What is the result?
Barefoot: ground reaction forces go right through subtalar joint axis, so no rotation forces generated
Running shoes: larger shoe width creates moment arm for GRF on subtalar joint
Result: more likely to over-pronate with running shoes
Why are anterior shin splints more likely when wearing running shoes vs running barefoot?
The heel of running shoes creates a larger moment arm for plantarflexion, which means tib ant needs to resist more force
Early running shoes caused problems such as overpronation and increased plantarflexion moments. How is this resolved in newer running shoes?
Double-density sole + rounded lateral heel
Lateral part is softer to absorb extra pronation GRF generated at heel strike
Medial part is harder to resist pronation
True or false: the vast majority of runners who over pronate develop overuse injuries
False - 40-50% of runners with excessive pronation do NOT have overuse injuries
BUT individuals with injuries have an avg of 2-4degrees of increased pronation compared to non-injured runners
The transfer of pronation into tibial pronation has been found to be the best predictor of overuse injuries. Which is more likely to cause injury:
a) 20 degree angle of the axis of rotation between talus and tibia
b) 60 degree angle of the axis of rotation between talus and tibia
B - will lead to 13 degrees if tibial rotation (vs only 3 degrees if angle is 20deg)
What is the “last” of the running shoe?
What kind of last is ideal for oversupinators?
Overpronators?
Line from the middle of the heel to the middle of the big toe
Overpronators: straight
Oversupinators: curved
The most common last configuration in modern running shoes is: A. Board last B. Combination last C. Strobel board last D. Slip last
C - board made of cloth or thin sheet of EVA glued to midsole
Which 4 tests should you do on a patient’s shoe to check for motion control?
- Torsional rigidity (dish-rag)
- Heel counter rigidity (pinch test)
- Flexion stability (fold test)
- Upper stability (shelf test)
At what point in the shoe should a fold in the flexion stability test?
Behind met heads
What is the role of heel counter rigidity in running
Proprioception (NOT buttressing)
What is the difference between a positive and negative heel drop? What are their advantages?
Positive heel drop = heel height > toe height. Found in most running shoes to reduce over-pronation b/c is dorsiflexes the hallux, encouraging subtalar joint supination through the Windlass effect
Negative heel drop = heel height < toe height. Helps encourage midfoot strike rather than heel-strike