Biomechanics of Sport Shoes (Lecture 4) Flashcards

Lecture 4 of 5

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1
Q

Describe the anatomy of a sport shoe

A
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2
Q

How are running and basketball shoes adapted for their sport?

A

Running shoes - more cushioned midsole and heel to shock absorb heel strikes
Basketball shoes - High top design and harder heel counter provide more lateral stability

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3
Q

What is the difference between running and walking?

A

The airborne period of time between toe off and foot strike of opposite feet is the difference

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4
Q

What does FS, MS and TO stand for in this schematic?

A
  • Foot strike
  • Mid strike
  • Toe Off
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5
Q

How do animals and humans absorb shock when running differently

A
  • Animal shave a knee-ankle damper system that absorbs the ground reaction force time
  • Humans land on their heels with straight legs while running so the shoes absorb the shock
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6
Q

How do barefoot runners biomechanics differ from a regular runner?

A
  • Barefoot runners don’t have heel shock absorbers so change the landing mechanics
  • Barefoot runners run with a flexed knee and ankle joint to absorb the shock of impact
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7
Q

What is a downside to barefoot running?

A
  • Most of us are not used to running like this, so earlier fatigue and potential risk of injuries due to the additional contact if suddenly changed to this style of running
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8
Q

What did Benno Nigg determine about the plantar region? and what is the purpose of the main receptor?

A
  • The plantar region senses for external stimuli and there are 3 types of receptors
  • The dominant receptor SA 2 Mechana, is sensitive to pain, forcing the runner to change their posture/biomechanics to adjust
  • He theorises that this receptor is not stimulated in running shoes because of the thick midsole cushioning and so runners do not adjust to damage leading to repetitive impact injuries
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9
Q

What is this graph showing?

A
  • When rearfoot striking (conventional running) there is a primary vertical component called the impact peak which tells us the loading rate and initial ground contact force
  • Then following this is another peak which is the active peak where we absorb additional force to the peak, then begin pushing back off the ground
  • In forefoot striking (barefoot running) the energy is absorbed by the knee and ankle and so there is no initial impact peak
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10
Q

What factors may worsen or reduce the initial impact peak?

A
  • The distance/height or force that is being absorbed by the heel strike
  • The thickness of the shoe midsole (thicker cushioning will absorb more)
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11
Q

How can worn shoes lead to injury?

A
  • The cushionability drops
  • leading to greater repetitive stress on heel and plantar region
  • Chronic injury and pain
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12
Q

What are some common injuries caused by repetitive stress?

A
  • Plantar fasciitis, heel spur pain, shin splints
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13
Q

What is the foot bed concept?

A
  • A bed is comfortable if it conforms to the human body contour
  • ie. the areas of high pressure deform more to spread the pressure
  • the sole is the ‘foot bed’ and if it can distribute body weight over a larger surface area to avoid peaks, it will be more comfortable
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14
Q

Why is it that hard insoles are beneficial for the sprinting performance?

A
  • All the lower limb joints flex to lose energy and then extend generating energy upon push off
  • The metatarsal-phalangeal joint soes not do this, it only bends losing energy
  • Hard soles and carbon plates have been put in shoes to avoid this bending and by extension reduce the energy loss
  • This has been recorded to a 2% saving of energy
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15
Q

What is special about these shoes?

A
  • They are said to have the same level of compliance and energy return after 1 million compressions as the first
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16
Q

What is special about these shoes

A
  • These shoes have an inbuilt microprocessor in the arch that compares the present compression with optimum cushioning
  • A sensor in the heel detects the pressure and relays it to the microprocessor
  • If the microprocessor determines that the heel needs to be harder it tells a motor
  • The motor then pulls i tiny cable, increasing the tension and stiffening the heel
17
Q

What are some of the claims made by barefoot minimalistic shoes?

A
  • Strengthen muscles in feet and lower legs
  • Improve ankle ROM
  • Stimulate plantar neural function, helping balance
  • Offers a more natural feel
  • Can improve posture
18
Q

What is was the purpose of these shoes?

A
  • Designed to remove that initial impact peak (offering a continuous roll)
  • Claimed to improve posture and gait, while increasing muscle activity along the posterior chain
  • Reduced stress on knee and hip joints and by extension reduction in pain for osteoarthritic patients
19
Q

What advantage does shear cushioning offer?

A
  • Allows for some anterior and posterior displacement when changing direction
  • absorbing some of the shock caused by a change in direction, making it safer than current shoes, less injury risk
20
Q

What is meant by shoe stability? and how is this quantified?

A
  • The ability of a shoe to maintain an upright and straight ankle joint
  • Quantified by looking at the heel angle or Achilles tendon angle from a posterior frontal plane view
21
Q

What arises when a shoes cannot provide stability/an upright ankle joint in the frontal plain

A
  • Pronation (collapsing inward) or supination (collapsing laterally)
  • Muscles have to work to accommodate and prevent this collapsing
  • Repetitive muscular work can cause discomfort, fatigue and chronic overuse injuries like shin splints
22
Q

Describe the natural pronation and supination that occurs during a foot strike in running

A

1) Just before the heel strike, the ankle is slightly supinated so hits the ground with the lateral edge
2) After landing the foot pronates and the foot rolls inwards moving from a lateral edge to contact to a full plantar surface contact
3) The ankle supinates again to push off the ground

23
Q

If someone experiences pronation during running what does this mean?

A
  • After the supinated initial contact where the lateral edge hits the ground, the ankle pronates too far during that inward roll causing instability
24
Q

What is meant by torsional stiffness in a shoe?

A
  • Imagine the toe of the shoe being flat and the heel twisted as much as possible
  • Therefore it is resistance against twisting in the longitudinal axis
25
Q

What are 2 possible solutions to make shoes more torsionally compliant and hence possibly reduce lateral ankle sprains?

A

1) Hollow inner core shoes
2) Double inner soles

26
Q

How do hollow inner core supposedly shoes reduce likelihood of lateral ankle sprain?

A

1) There is a hollow space in the heel outsole of the shoe
2) The 2 side walls of this hollow space are laterally compliant, deforming so that the rearfoot actually remains straight relative to the forefoot
3) This maintaining of a straight position facilitates the force going through the ankle to go through the centre of the joint

27
Q

What is the mechanism proposed in the double inner sole shoes that reduces likelihood of lateral ankle sprain?

A

1) This shoe has 2 insoles with a smooth interface allowing sliding over each other
2) With this design if the shoe torsionally deforms, the insole remains straight relative to the ankle joint, holding the ankle joint straight and directing the force through the joint safely

28
Q

What feature of shoes has been suggested to increase risk of ankle sprain injury?

A
  • Wide heel
  • A shoe with wider heel causes a torsional force to be applied to the foot at a greater distance from the pivot point (ankle joint)
  • This causes a greater moment and greater degree of ankle inversion
29
Q

What are the key differences between running shoes and basketball shoes?

A
  • Running shoes often provide heel cushioning but lack lateral ankle support
    -, Basketball shoes are high cut offering ankle support but limit the natural range of motion, and lack heel cushioning as this causes a greater level on inversion and less stability
30
Q

What effect have orthotics been found to have on ankle stability and the pressure points?

A
  • Orthotics for the arch and rearfoot have been found to reduce pronation by 5 degrees for hard ones and 2 for soft
  • They also found that the orthotics potentially caused a lateral shift in the centre pressure line of the foot
31
Q

How have biomechanists measure plantar pressure (force through foot and location of the force) in labs?

A
  • Using pressure sensitive insoles
32
Q

What did Nigg discover relating comfort and energy consumption?

A
  • Runners wearing comfortable shoes tended to result in lower energy consumption
33
Q

According to the ACSM guidelines what should you do to select the best running shoes for you?

A

1) Ensure that they are light in weight
2) Have a wide toe box for foot wiggle
3) No slippage in the heel
4) Some degree of pronation is normal
5) A neutral design that does not contain motor control or stabilising components which interfere with foot motion