Biomechanical Aspects Of Sport Shoe And Surface Design Flashcards
In which plane is rear foot motion monitored?
2D frontal plane
From behind
How is rear foot motion monitored?
Place markers to create segment at top & bottom of calf and top & base of heel to track relative angle between foot and shank
Clarify which leg you’re monitoring
In 2D approach of rear foot monitoring, we look at the relationship between …………. & ………….
Inversion & eversion
In 3D approach of rear foot monitoring, we look at the relationship between …………. & ………….
Pronation and supination
What is excessive eversion classified as?
12 degrees
Considerations when classifying max eversion?
12 degrees Won’t be true for all athletes
Could have an athlete that everts more then 12 but doesn’t get injured
Could have an athlete that everts less than 12 but still gets injured
Describe rear foot movement graph
Y axis = rear foot angle
X axis = time
anything above 0 is inversion
Below 0 shows movement towards eversion
Maximum eversion is the max rear foot angle.
Static assessment definition
The use of visual assessments only - running shops use this.
Shoe stability (motion control) definition? How is it quantified?
Ability of shoe to resist excessive (12 deg) or unwanted motion of the foot and ankle,
Quantified by measuring rear foot movement
Eversion definition
A movement in which the plantar surface of the foot rotates away from mid line of the body (little toe up)
Inversion definition
A movement in which the plantar surface of the foot rotates towards the midline of the body (big toe up)
Shoe design characteristics:
Describe heel flare
When a lateral or medial border is built on the heel of the shoe to increase shoe stability and therefore reduce rear foot movement
Results of increased medial heel flare
Author
Reduced magnitude of eversion during stance
= reduced rear foot movement
Clarke et al., 1983 or Nigg & Morlock, 1987
Result of lateral heel flare
Authors
Reduced leverage length
= reduced rear foot movement
(Shortened length of movement arm between axis of rotation and point where force is being applied)
Nigg & Morlock, 1987
Issue with heel flares
Could change the shape and width of parts of the shoe which could minimise some of the cushioning properties that the shoe provides
Describe medial post of shoe
Part of the midsole that’s firmer than rest of midsole
E.g. Plastic moulding - a butterfly effect on base of shoe that prevents rocking action
What determines how much stability the medial post gives a shoe
Shape and size of post
In what type of shoe is a medial post never found in?
Cushioned
Disadvantage of shoes with medial post?
Adds weight to shoe
Which parts of foot does a medial post stabilise and what does this prevent?
Midsole, rear foot
Arch pronation
Authors that found that shoes with a high density medial post reduced rear foot movement?
Cheung & Ng, 2007
Describe orthotic devices
In other words - an insole
What did Clarke et al., 1983 investigate in relation to orthotic devices?
The influence of orthotic devices on rear foot movement
Findings of Clarke et al., 1983 (2)
Eversion occurs without orthotic device support
With orthotic device, more alignment between shank and heel to reduce angle of eversion and rear foot movement
In which circumstances should biomechanics and podiatry be used to assess the effects of orthotics on rear foot movement?
Podiatry - static assessments in an unloaded (not standing) position to decide whether insole is needed
Biomechanics - investigate the effects of orthotic device on running, walking or when static
Disadvantage of orthotics?
To much cushioning adds instability
Orthotic devices:
Findings of Mundermann et al., 2003?
Orthotic devices reduce peak eversion and eversion velocity which lowers injury risk
Orthotic devices:
Findings of Nigg et al., 1998
Orthotic devices have no influence on movement - no change in eversion characteristics
Orthotic devices:
Findings of Gross et al., 1991
Orthotic devices helped 75% of distance runners
25% showed worse symptoms, no change or picked up an injury from the device
Summary or shoe properties: Medial posting Medial properties Heel flare Orthotic devices
Medial posting - some Evidence of increase stability; Cheung & Ng, 2007
Medial properties - high density materials can increase stability; Cheung & Ng, 2007
Heel flare - medial and lateral flare can be influential in reducing rear foot eversion and therefore rear foot movement; Nigg & Morlock, 1987
Orthotic devices - some evidence of increased stability; Gross et al., 1991
Describe Surface cushioning
The ability of a surface to reduce peak impact forces by providing cushioning athlete during ground contact
Typical ground reaction force -time history?
Y axis = vertical ground reaction force (1-2BW)
X axis = time (ms)
Initial peak is impact peak, second peak is active peak
What is the duration of impact phase for a typical heel toe runner?
Approx 50milliseconds
What does the steepness of the curve in a ground reaction force - time history show?
Rate of loading
When curve is really steep, loading rate is high
When curve is flatter, loading rate is low
What information regarding shoe and surface design does a ground reaction force-time history provide?
Cushioning
What type of force is linked with injury risk?
impact force
With an increase in shoe cushioning, what is known to be reduced?
Loading rates (steepness of curve)
What effect does barefoot running have on ground reaction force-time histories.
Steeper curve
How does barefoot running influence foot strike?
And what does this depend on?
See more of a forefoot or mid foot strike
Depending on speed
Why is a forefoot or mid strike observed in barefoot running?
Author who found this?
Foot is presented flatter to ground to compensate for higher impact at the heel
Dixon et al., 2005
How can friction be varied in hard tennis courts?
Very amount of sand put into acrylic paint that coats the court. More sand = more friction
Influence of temperature on surface design
Very high temperatures can make court sticky = more friction
How to test surface properties?
Use a portable skid resistance tester. (Industry standard)
Depending on resistance of surface, foot will continue to swing upwards after ground contact.
Distance above ground is then measured
Regarding player - shoe - surface relationship, when can an inversion injury occur? (2)
(1) lack of kinaesthetic awareness and foot placement
(2) when there’s a sudden change in shoe - surface interaction
What is the coefficient of friction influenced by?
Shoe - surface variation
What did Gheluwe & Deporte, 1992 find?
That the surface is more influential on stability than the shoe
In shoes, what’s the relationship between increased performance and injury risk?
Example
Contradictory relationship.
E.g. Football boots.
Early 1900’s - hard leather, lace up above ankle, heavy boots (1kg) with HIGH STABILITY
1954 - ‘Adi’ (Adolf) Dassler made LIGHT (360g), below ankle laced boots
Since then, the game has got faster, more skilful and dynamic.
An attitude swing to boost performance with less emphasis on injury
What did Bentley et al., 2010 find in regard to football shoes?
Blades lead to higher plantar pressure and injury risk
What did Henning, 2006 find in relation to the injury-performance relationship?
Injury prevention ranked low on priority list
Typical characteristics of shoes highlighted in advertising (5)
Shock absorbing/ cushioning Motion control Traction Weight Comfort
