Effects of Age on the Effects of Age on the Landing Techniques of Landing Techniques of

Boys and GirlsBoys and Girls Ashley SwanderAshley Swander1

Michael PavolMichael Pavol2

1Dept. of Mechanical Dept. of Mechanical EngineeringEngineering

2Dept. of Nutrition & Exercise Dept. of Nutrition & Exercise SciencesSciences

Oregon State University Oregon State University

HHMI Summer 2006HHMI Summer 2006

http://biggirlinthemiddle.com/UAvOR05/index.html

BackgroundBackgroundMotivation:Motivation:

Increasing number of Increasing number of non-contact ACL non-contact ACL injuries in female injuries in female athletesathletes

Women 2-8 times Women 2-8 times more likely to suffer a more likely to suffer a serious knee injury serious knee injury than men than men

Estimated 38,000 ACL Estimated 38,000 ACL injuries occur in injuries occur in female athletes in the female athletes in the U. S. annuallyU. S. annually

http://www.orthone.com/sport/acl.asphttp://www.orthone.com/sport/acl.asp

BackgroundBackground

Women have Women have different landing different landing techniques than mentechniques than men

Do girls and boys Do girls and boys have similar landing have similar landing techniques?techniques?

When do techniques When do techniques diverge?diverge?

Ongoing 4-year Ongoing 4-year studystudy

Dynamic Knee Abduction(From Hewett et al. 2006)

PurposePurpose

In Year One Data:In Year One Data:Determine if there are differences in Determine if there are differences in landing techniques between pre-landing techniques between pre-pubescent boys and girlspubescent boys and girls

Hypothesis: Hypothesis: Pre-pubescent boys and girls have Pre-pubescent boys and girls have similar landing techniquessimilar landing techniques

MethodsMethods

Subjects:Subjects:

Jumping Group Jumping Group

7 boys and 6 girls7 boys and 6 girls

7 mo. x 250/week drop landings off 24” box7 mo. x 250/week drop landings off 24” box

Control GroupControl Group

17 boys and 8 girls17 boys and 8 girls

7-10 years old7-10 years old

MethodsMethods

Static TrialStatic Trial

Drop jump off 24” Drop jump off 24” boxbox

Arms folded across Arms folded across chestchest

Step offStep off

Land with one foot Land with one foot on each force plateon each force plate

20 jumps 20 jumps

Data CollectedData Collected

Motion capture Motion capture systemsystem

Force platesForce plates

Data AnalysisData Analysis

Variables:Variables:

3-D knee joint angles3-D knee joint angles

Resultant knee joint moments (i.e. Resultant knee joint moments (i.e.

torques)torques)

At touchdownAt touchdown

Maximum value (touchdown end Maximum value (touchdown end

of landing)of landing)

StatisticsStatistics

2-Factor analyses of variance2-Factor analyses of variance

Factors: Factors:

SexSex

Jumping vs. ControlJumping vs. Control

Covariate:Covariate:

AgeAge

Performed for each angle and torquePerformed for each angle and torque

Right Right Knee Knee

Angles Angles and and

MomentMomentss

+ / –

ResultsResultsKnee angles at touchdownKnee angles at touchdown

-5

0

5

10

15

20

25

Flexion Abduction Internal Rotation

An

gle

(d

eg

ree

s)

Boys Girls

*

Maximum Knee AnglesMaximum Knee Angles

0

10

20

30

40

50

60

70

80

90

100

Flexion

An

gle

(d

egre

es)

0

2

4

6

8

10

12

14

16

Abduction Adduction

An

gle

(d

egre

es)

Boys Girls

*

*

Maximum Knee MomentsMaximum Knee Moments

*

ConclusionsConclusionsLanding technique differs between boys Landing technique differs between boys and girlsand girls

Sex-differences differ from those found in Sex-differences differ from those found in adultsadults

GirlsGirls knee abduction angle at touchdownknee abduction angle at touchdown

maximum knee abduction anglemaximum knee abduction angle

BoysBoys maximum knee adduction anglemaximum knee adduction angle

maximum knee extension momentmaximum knee extension moment

Both sexes have risk factors for ACL injuryBoth sexes have risk factors for ACL injury

AcknowledgementsAcknowledgements

Howard Hughes Medical InstituteHoward Hughes Medical Institute

Dr. Michael PavolDr. Michael Pavol

Dr. Kevin AhernDr. Kevin Ahern

Funding:Funding:HHMIHHMI

URISCURISC

Dr. PavolDr. Pavol

College of EngineeringCollege of Engineeringhttp://deseretnews.com/dn/print/1,1442,635165805,00.html