Effects of Age on the Landing
Techniques of Boys and Girls
Ashley Swander1
Michael Pavol2
1Dept. of Mechanical Engineering
2Dept. of Nutrition & Exercise
Sciences
Oregon State University
HHMI Summer 2006
http://biggirlinthemiddle.com/UAvOR05/index.html
Background
Motivation:
Increasing number of noncontact ACL injuries in
female athletes
Women 2-8 times more
likely to suffer a serious knee
injury than men
Estimated 38,000 ACL
injuries occur in female
athletes in the U. S. annually
http://www.orthone.com/sport/acl.asp
Background
Women have different
landing techniques than
men
Do girls and boys have
similar landing
techniques?
When do techniques
diverge?
Ongoing 4-year study
Dynamic Knee Abduction
(From Hewett et al. 2006)
Purpose
In Year One Data:
Determine if there are differences in landing
techniques between pre-pubescent boys and girls
Hypothesis:
Pre-pubescent boys and girls have similar landing
techniques
Methods
Subjects:
Jumping Group
7 boys and 6 girls
7 mo. x 250/week drop landings off 24” box
Control Group
17 boys and 8 girls
7-10 years old
Methods
Static Trial
Drop jump off 24” box
Arms folded across chest
Step off
Land with one foot on
each force plate
20 jumps
Data Collected
Motion capture system
Force plates
Data Analysis
Variables:
3-D knee joint angles
Resultant knee joint moments (i.e. torques)
At touchdown
Maximum value (touchdown
end of landing)
Statistics
2-Factor analyses of variance
Factors:
Sex
Jumping vs. Control
Covariate:
Age
Performed for each angle and torque
Right Knee
Angles and
Moments
110
Angle (Degrees)
90
70
50
30
10
-0.03-10
0.02
0.07
0.12
0.17
0.22
0.27
-30
-50
Time (seconds)
50
Moment (Nm)
0
-0.03
0.07
0.17
0.27
-50
+/–
-100
Flex/Ext
-150
Abd/Add
Ext/Int Rotation
-200
Time (seconds)
Results
Knee angles at touchdown
25
Boys
Girls
Angle (degrees)
20
15
10
*
5
0
-5
Flexion
Abduction
Internal Rotation
Maximum Knee Angles
100
16
90
14
Girls
*
12
70
Angle (degrees)
Angle (degrees)
80
Boys
60
50
40
30
10
*
8
6
4
20
2
10
0
Flexion
0
Abduction
Adduction
Maximum Knee Moments
35
*
Boys
% BW x BH
30
Girls
25
20
15
10
5
0
Extension
Adduction
Abduction
Internal
Rotation
Conclusions
Landing technique differs between boys and girls
Sex-differences differ from those found in adults
Girls
knee abduction angle at touchdown
maximum knee abduction angle
Boys
maximum knee adduction angle
maximum knee extension moment
Both sexes have risk factors for ACL injury
Acknowledgements
Howard Hughes Medical Institute
Dr. Michael Pavol
Dr. Kevin Ahern
Funding:
HHMI
URISC
Dr. Pavol
College of Engineering
http://deseretnews.com/dn/print/1,1442,635165805,00.html