Lecture 5 - Injury in Sport & Exercise: Controllable Factors (2)

Question 1

What are the essential characteristics of a running shoe?

Answer 1

• Attenuation of single / multiple impact forces
• Preservation of foot stability (rearfoot control)
• Adequate friction / traction
• Provision of different footstrike type
• Heat dissipation
• Comfort

Question 2

What is the effect of barefoot runiining on the calf muscles?

Answer 2

• Increases the level of loading on them and is very effective for sprinting as it increases the use of the SSC, however this can cause injury in unprepared muscles.

Question 3

What is surface impact attenuation?

Answer 3

• Measurement of reduction of impact forces.

- The % of reduction of the max impact force on a surface compared with that generated on concrete.

Question 4

What are two features in running shoes that assist with rear foot control.

Answer 4

• Material used - materials of the two sides of the midsole should be different (lateral = softer, medial = denser).
• Heel sole shapes: a) flared, b) neutral, c) rounded. A
  reduction of the flare can decrease joint pronation.

Question 5

What is surface hardness ?

Answer 5

• Resistance to penetration out of 100
• Hard surfaces = stiff
• Soft = compliant
• E.g. frozen grass has higher resistance than normal grass

Question 6

By what percentage is the injury rate higher in artificial tennis surfaces and why?

Answer 6

• 200%
• Artificial surfaces do not allow the same degree of
  sliding as natural ones and they also resist rotation.

Question 7

What is compliance ?

Answer 7

• The opposite of stiffness
• Low compliance = high risk of injury
• High compliance = low performance

Question 8

By what percentage do the following parts of the shoe absorb energy?

• Midsole wedge
• Outsole
• Insole
• Insole board
• Sock

Answer 8

• Midsole wedge - 60%
• Outsole - 20%
• Insole - 10%
• Insole board - 3%
• Sock - 2%

Question 9

What is surface resilience and some examples?

Answer 9

• Resilience - The amount of energy returned as a percentage of the amount of energy absorbed at impact.
• Measured from 0-100.
• e.g soccer 20-45%, cricket 20-34%, tennis grass, 42%, synthetic 60%

Question 10

What are the general criteria for selecting ruining shoes?

Answer 10

• Performance
• Protection
• Comfort
• Durability
• Weight
• Price
• Taste / Fashion

Question 11

Why can running on soft ground be detrimental to some runners?

Answer 11

• The surface absorbs energy and returns little, which can be particularly detrimental to those who rely to a greater extent on lower limb muscle elasticity.

Question 12

Give some examples of artificial surfaces, and their properties.

Answer 12

• Concrete/Asphalt
   - High resilience (fast surfaces), good traction
   stiff (hard) – low compliance (injury risk)
• Outdoor Elastomer Surfaces (e.g. Tartan)
   - Good traction and high resilience
   expensive, degradation
• Bound-Crumb Polymeric Surfaces
   - All-weather surfaces
• Synthetic turf
   - High resilience, low injury risk, good for correct playing characteristics
   - No agreement regarding a default structure and composition

Question 13

What impact force variables are considered for injury ?

Answer 13

• Peak vertical force,
• Time to peak vertical force
• Peak loading rate
• Time to peak loading rate

Question 14

What is friction and traction?

Answer 14

• Friction = Grip

- Traction = Pull

Question 15

What are the 7 parts to a running shoe?

Answer 15

• Uppers
• Midsoles and Wedges: the shock absorption
  parts of the shoe
• Outsoles: durable and abrasion-resistant polyurethane rubbers
• Insole board: A fibre-board that provides the rigid base for the rest of the shoe.
• Insole: This part contributes to the reduction of impact forces, perspiration absorption and comfort.
• Heel counter: provides rear-foot stability and claimed to prevent excessive pronation
• Inserts: These help to reduce impact and increase rear-foot stability.

Question 16

What are some examples of natural surfaces and what properties do they have?

Answer 16

• Turf, clay, cinders, ice, snow.
• Great impact attenuation, good resilience, long life
• Problems: frequent use, weather

Question 17

Why does running on sand have a higher energy cost that grass?

Answer 17

• A reduction in elastic energy potentiation, caused partly by an increase in contact time (and thus a longer delay between the eccentric and concentric actions of the lower limb muscles).
• Could also be because sand’s compliant nature requires increased leg stiffness that requires increased muscle activity to stabilise the lower limb joints.