understanding gmaxpenn state’s center for sports surface research gmax - definition •1 g =...
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![Page 1: Understanding GmaxPenn State’s Center for Sports Surface Research Gmax - Definition •1 G = acceleration due to gravity •Measure magnitude of impact –peak deceleration •Gmax](https://reader030.vdocuments.site/reader030/viewer/2022040812/5e571da97ee5e262c35bbf5b/html5/thumbnails/1.jpg)
Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
Understanding Gmax
![Page 2: Understanding GmaxPenn State’s Center for Sports Surface Research Gmax - Definition •1 G = acceleration due to gravity •Measure magnitude of impact –peak deceleration •Gmax](https://reader030.vdocuments.site/reader030/viewer/2022040812/5e571da97ee5e262c35bbf5b/html5/thumbnails/2.jpg)
Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
Gmax
How much force does the surface absorb?
10% of concussions caused by impact with the surface (Guskeiwicz et al, 2000)
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Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
Gmax - Definition
• 1 G = acceleration due to gravity
• Measure magnitude of impact – peak deceleration
• Gmax = maximum negative acceleration on impact
![Page 4: Understanding GmaxPenn State’s Center for Sports Surface Research Gmax - Definition •1 G = acceleration due to gravity •Measure magnitude of impact –peak deceleration •Gmax](https://reader030.vdocuments.site/reader030/viewer/2022040812/5e571da97ee5e262c35bbf5b/html5/thumbnails/4.jpg)
Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
Gmax
• How many G’s can the surface absorb?
• How much returned to athlete?
– High Gmax = less absorption of force by surface
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Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
How is Gmax tested?
• American Society for Testing and Materials (ASTM)
– Synthetic Turf• F355
• F1936
– Natural Grass• F1702
![Page 6: Understanding GmaxPenn State’s Center for Sports Surface Research Gmax - Definition •1 G = acceleration due to gravity •Measure magnitude of impact –peak deceleration •Gmax](https://reader030.vdocuments.site/reader030/viewer/2022040812/5e571da97ee5e262c35bbf5b/html5/thumbnails/6.jpg)
Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
ASTM F355 – Test Method
• F355 Device
– Drop weighted missile from standard height
– Accelerometer in missile measures impact
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Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
ASTM F355 – Test Method
• Missile – 20 lbs (human head, neck), flat faced
• Drop height – 2 ft. – 1960’s crash tests
(Gadd, 1966, 1971)
– Impact energy during football game (Reid et al., 1971)
![Page 8: Understanding GmaxPenn State’s Center for Sports Surface Research Gmax - Definition •1 G = acceleration due to gravity •Measure magnitude of impact –peak deceleration •Gmax](https://reader030.vdocuments.site/reader030/viewer/2022040812/5e571da97ee5e262c35bbf5b/html5/thumbnails/8.jpg)
Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
ASTM F1936 – Test Procedure
• 3 successive drops on each test point (10 total)
• Gmax – average of 2nd
and 3rd drop
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Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
Maximum Gmax
• 200 G
• >200 G = life threatening head injuries may be expected to occur
• 200 G – accepted by U.S. Consumer Products Safety Commission
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Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
Minimum Gmax?
• No minimum standard
• Too soft = – Decrease in
performance? (Pinnington and Dawson , 2001)
– Increased injury risk?
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Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
Head Injury Tests
• Gmax– Peak of curve
• Severity Index (SI)– Total area under
curve, total time
• Head Injury Criterion (HIC)– Area and time
From Shorten and Himmelsbach, 2003
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Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
HIC
• HIC score = 1000
– “Safe” limit
– Above – risk of fatal head injury is non-zero
• Used for automobile safety, sports equipment
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Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
Other Gmax tests
• Clegg Impact Tester
• ASTM F1702 – Natural Turfgrass
• 5 lb missile, drop height: 18 inches
• Gmax values are lower than F355 (200 = 135)
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Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
Clegg Impact Tester
• Mathematical Relationship (2nd and 3rd
drop) (http://ssrc.psu.edu/infill/infill5.cfm)
F355 = (Clegg + 27.1) / 0.81
R2 value: 0.81
*Penn State surface hardness data (2001-2009) available at http://ssrc.psu.edu/infill/infill5.cfm
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Penn State’s Center for Sports Surface ResearchPenn State’s Center for Sports Surface Research
Gmax
ADVANTAGES
• 200 Gmax level based on safety studies (F355)
• Proactive approach to safety
• Protects field owners from lawsuits
DISADVANTAGES
• Testing small percentage of field
• Routine testing (yearly)
– Cost
• Flat missile – human head?
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Penn State’s Center for Sports Surface Research
Website: http://ssrc.psu.edu
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