Playground Surface TestingBackground Research

Martyn R. Shorten, Ph.D.

Portland Oregon, USA

Playgrounds

High AvailabilityPublicSchoolsHome

High Risk

Playground Surfacing – Background Research

Injury RatesInjury Statistics

205,850 Emergency Room admissions during 1999

Frequency1 per 1.3 minutes

Occurrence1 per 1333 children

Accident TypeInjury Statistics

Collisions17%

Falls70%

Injury TypeInjury Statistics

LimbFractures

33%

HeadInjuries

10%

Cuts,Bruises,SprainsStrains

46%

FatalitiesInjury Statistics

Source: US CPSC: Tinsworth and MacDonald, 2001

147 deaths between January 1990 and August 2000

Head Injury75%Entrapment

Falls21%

Risk FactorsInjury Statistics

Equipment height

Equipment design

Parental supervision

Maintenance

Mixed use

Surfacing as a Risk FactorInjury Statistics

Falls to the surface:• 20% of deaths• 70-80% of injuries

Shock Attenuating Surfaces:• Potential for lower injury risk

Playground Safety InitiativesPlayground Surfacing and Playground Injuries

CPSC Handbook(1975)

Safety Advocates

Legislation

Equipment Design

Surfacing Standards

Playground Surfacing MaterialsPlayground Surfacing

Loose-Fill Surfaces• Organic

– Bark Dust– Wood– Engineered Wood Fiber

• Inorganic– Sand– Gravel– Shredded foam / rubber

Playground Surfacing MaterialsPlayground Surfacing

Unitary Surfaces• Rubber / Urethane• Poured-in-Place• Tiles

Performance CriteriaPlayground Surfacing

Standards• ASTM F1292• EN 1177, etc.

Performance CriteriaPlayground Surfacing

Standards• ASTM F1292• EN 1177, etc.

Fall Height

Performance CriteriaPlayground Surfacing

Standards• ASTM F1292• EN 1177, etc.

Fall Height

Test Method• Instrumented headform• Triaxial Accelerometer

Performance CriteriaPlayground Surfacing

Standards• ASTM F1292• EN 1177, etc.

Fall Height

Test Method• Instrumented

headform• Triaxial Accelerometer

Critical Fall Height

Performance CriteriaPlayground Surfacing

Historical efforts tobase performancecriteria on (head)injury risk data

g-maxHead Injury Criterion

Brain Injury Mechanisms

Diffuse Axonal InjuryBrain Injury Mechanisms

Normal Axons

Traumatized Axons

Metabolic Cascade:

• Ca and K ion release

• Disruption of neural function

• Compensation

• Increase energy expenditure

• Metabolic distress

• Increased vulnerability

Mild Traumatic Brain InjuryBrain Injury Mechanisms

Normal Axons

Traumatized Axons

Long Term Consequences:

• Second Concussion Syndrome

• Cumulative Effects

Abbreviated Injury ScaleBrain Injury Mechanisms

AIS 1 2 3 4 5 6Degree Minor Moderate Serious Severe Critical Survival

Injury Uncertain

Headache, DizzinessLoss of Consciousness

Skull FractureNeurological Damage

HemorrhageBrainstem DamageTissue Disruption

Abbreviated Injury ScaleBrain Injury Mechanisms

AIS 1 2 3 4 5 6Degree Minor Moderate Serious Severe Critical Survival

Injury Uncertain

Headache, DizzinessLoss of Consciousness

Skull FractureNeurological Damage

HemorrhageBrainstem DamageTissue Disruption

Abbreviated Injury ScaleBrain Injury Mechanisms

AIS 1 2 3 4 5 6Degree Minor Moderate Serious Severe Critical Survival

Injury Uncertain

Headache, DizzinessLoss of Consciousness

Skull FractureNeurological Damage

HemorrhageBrainstem DamageTissue Disruption

Impact Tolerance of the Brain

• Cadaver studies• Animal studies• Human volunteers

– Automotive Industry– Aerospace Industry– Military

AccelerationImpact Tolerance of the Brain

0

20

40

60

80

100

0 5 10 15 20Time, ms

Acce

lera

tion,

g

gmax

Wayne State CurveImpact Tolerance of the Brain

Gadd Severity IndexImpact Tolerance of the Brain

0

20

40

60

80

100

0 5 10 15 20Time, ms

(Acc

eler

atio

n)2.

5 /100

0

Gadd Severity IndexImpact Tolerance of the Brain

0

20

40

60

80

100

0 5 10 15 20Time, ms

(Acc

eler

atio

n)2.

5 /100

0

Head Injury CriterionImpact Tolerance of the Brain

Prasad-Mertz CurvesImpact Tolerance of the Brain

AIS

1

Prasad-Mertz CurvesImpact Tolerance of the Brain

AIS

1

Prasad-Mertz CurvesImpact Tolerance of the Brain

AIS

1

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

HIC Score

Prob

abilit

y of

Inju

ryPrasad-Mertz CurvesImpact Tolerance of the Brain

No InjuryAIS

1

Prasad-Mertz CurvesImpact Tolerance of the Brain

No InjuryAIS

1

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

HIC Score

Prob

abilit

y of

Inju

ryPrasad-Mertz CurvesImpact Tolerance of the Brain

No InjuryAIS

1

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

HIC Score

Prob

abilit

y of

Inju

ryPrasad-Mertz CurvesImpact Tolerance of the Brain

No InjuryAIS

12

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

HIC Score

Prob

abilit

y of

Inju

ryPrasad-Mertz CurvesImpact Tolerance of the Brain

No InjuryAIS

12

3

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

HIC Score

Prob

abilit

y of

Inju

ryPrasad-Mertz CurvesImpact Tolerance of the Brain

AIS

12

34

No Injury

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

HIC Score

Prob

abilit

y of

Inju

ryPrasad-Mertz CurvesImpact Tolerance of the Brain

AIS

12

34

5

No Injury

Prasad-Mertz CurvesImpact Tolerance of the Brain

AIS

12

34

5 6

No Injury

Prasad-Mertz CurvesImpact Tolerance of the Brain

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

HIC Score

Prob

abilit

y of

Inju

ry

AIS

12

34

5 6

No Injury

Prasad-Mertz CurvesImpact Tolerance of the Brain

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

HIC Score

Prob

abilit

y of

Inju

ry

AIS

12

34

5 6

No Injury

Prasad-Mertz CurvesImpact Tolerance of the Brain

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

HIC Score

Prob

abilit

y of

Inju

ry

AIS

12

34

5 6

No Injury

Prasad-Mertz CurvesImpact Tolerance of the Brain

HIC = 1000

Prasad-Mertz CurvesImpact Tolerance of the Brain

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000

HIC Score

Prob

abilit

y of

Inju

ry

AIS

12

34

5 6

No Injury

Are Impact Tests Good Surrogates?Surface Shock Attenuation Tests

• Mass

• Energetics

• Geometry

• Flexibility

0

500

1000

1500

3 6 9 12Fall Height, feet

HIC

0

100

200

300

g-max

Critical Fall HeightPlayground Surfacing

0

500

1000

1500

3 6 9 12Fall Height, feet

HIC

0

100

200

300

g-max

Critical Fall HeightPlayground Surfacing

0

500

1000

1500

3 6 9 12Fall Height, feet

HIC

0

100

200

300

g-max

Critical Fall HeightPlayground Surfacing

Critical Fall Height:7 feet

0

1

2

3

4

Gravel Sand WoodChips

WoodFibre

ShreddedRubber

Cri

tica

l Fa

ll H

eig

ht, m

ete

rsShock Attenuation PerformancePlayground Surfacing Materials

25 cm uncompressed depth 15 cmthickness

Loose-Fill Unitary

Benefits of Shock AttenuationPlayground Surfacing

Non-conforming surfaces• 2.3 times greater injury risk

NonConforming

Conforming

Relative Injury Risk

Chalmers et al, 1996

2.3

1

Benefits of Shock AttenuationPlayground Surfacing

Non-conforming surfaces• 2.3 times greater injury risk

Surfacing MaterialsConcrete

Rubber

BarkDust

Relative Injury Risk

12

5

Mott et al, 1997

Relative Injury Risk

Benefits of Shock AttenuationPlayground Surfacing

Non-conforming surfaces• 2.3 times greater injury risk

Surfacing Materials

Severe head injuries

Sand

1

6

Sosin et al, 1993; Laforest et al, 2000

1.7

Grass

Asphalt

Impact Test IssuesPlayground Testing

Positives:

•Good faith attempt to evaluate injury risk

•Documented effectiveness

•Bias of risk estimates

“True” HIC EstimationAre Impact Tests A Good Surrogate

0%

20%

40%

60%

80%

100%

0 500 1000 1500

HIC Score

Prob

abilit

y of

Inju

ryAdjusted HIC scores

12

3

4

5

In-filled Conventional

Impact Test IssuesPlayground Testing

Limitations:

•Data QuantityApplicabilityValidity

•Method BiofidelityReproducibility and repeatability

Head injury focus

•Concussion

“Concussus”

“to shake violently”