Transcript Ankle support purpose

The preferred balance leg absorbs
more energy than the preferred
striking leg in single leg landings
Steve McCaw, Mitch Waller, Kevin Laudner & Pete Smith
Landing
• Landing = moving body to rest
• Integral to many sport activities and Activities of Daily
Living
• Implicated in a variety of lower extremity injury
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Ankle sprain
Osteoarthritis
ACL damage
good model to investigate
Mechanism(s) of injury
Mechanism of energy absorption
• Interesting phenomenon on its’ own.
Landing Research
Perform two leg landing, only one leg analyzed
• “Dominant Leg”
• Madigan & Pitcoe, J EMG & Kinesiology, 2003
• Effects of fatigue on landing biomechanics
• Pollard et al, Clin J Sport Med, 2006
• Pre and post season evaluation of injury training
• “Preferred Limb” (lead leg when drop jumping)
• Kulas et al, J App Biomech, 2006
• A, K & H energy absorption and LE impedance
Bilateral comparisons of Lower Extremities
• “Right” vs “Left”
• Schot et al, MSSE, 1994
• Quantify bilateral asymmetry
• “Dominant” vs “non-dominant”
• Hewett et al, J Bone Joint Surg, 2004
• Investigate MS changes with maturation
Hewett, Meyer & Ford
Hewett, Meyer & Ford
Increased
maximum valgus
angle reflects
decreased
neuromuscular
control
General Concept of Lateral Preference
• Guiard, Y. (1987). Asymmetric Division of Labor in Human Skilled
Bimanual Action: The Kinematic Chain as a Model. J Motor Behavior,
19:4:486-517.
• Unimanual tasks*
• Dart throwing, brushing teeth
• Bimanually symmetric
• In phase: Rope skipping, weightlifting
• Out of phase: rope climbing
• Bimanually asymmetric
• Dealing cards, cursive writing
• Individuals exhibit a preference for one of the two possible ways
of assigning two roles to two hands
Dynamic Dominance Hypothesis
Sainburg, RL. (2005). Handedness:
differential specialization for
control of trajectory and position.
Exerc Sport Sci Rev,33:4:206213.
• Hemispheres /limb systems
specialized for complementary
functions
• Dominant side: controlling
limb trajectory dynamics
• Non-dominant side:
controlling limb position
A. Non-dominant arm slightly more accurate
B. Dominant arm used less elbow muscle torque
Applicable to Lower Extremity?
Nunome et al, 2006. Segmental dynamics of soccer instep
kicking with the preferred and non-preferred leg. J Sports
Science, 24:5:529-541
• Highly skilled players achieved a well-coordinated inter-segmental
motion for both the preferred and non-preferred leg
• Faster leg swing observed for the preferred leg
• result of larger muscle moment
Purpose
Compare
LE kinetics and energetics
between single-leg drop landings
onto preferred striking & balance legs
Hypothesis
Preferred balance limb will absorb more
energy than the preferred striking limb
Methods
• 21 college-age female volunteers
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• 21.5±2.2 y
• 1.64 ± 0.08 m
• 65.2 ± 8.2 kg
• Regular lander
• Free of LE traumas
10 trials R & L leg
• Random order
• “Land comfortably”
• 32cm bench
Force Platform (1000 Hz )
3 cameras (200 Hz)
• Sagittal plane kinematics
Inverse dynamics for JMF
• JMP = JMF •ω
Paired t-tests (α = .05)
Modified
Waterloo
Handedness
Questionnaire
•Identify
preferred
“action” leg in
bilaterally
asymmetric
tasks
•Strong
agreement with
ball “striking”
leg
Joint Position
Joint Angle (degrees)
Preferred Striking Leg
Preferred Balance Leg
Time to Max Knee Flexion (%)
Joint Torque (N·m•kg-1 )
Joint Torque
Preferred Striking Leg
Preferred Balance Leg
Time to Upright Stance(%)
Joint Mechanical Power (W/kg)
Joint
Power
Preferred Striking Leg
Preferred Balance Leg
Time to Upright Stance(%)
Percent Energy Absorption
%Contribut ion 
Hip ± SD%
Hip±SD%
Knee±SD%
Knee ± SD%
Ankle ± SD%
Preferred Striking
Ankle±SD%
Preferred Balance
Work Joint
Total Work
Relative joint
contributions
will be
significantly
different.
Conclusions
• Bilateral Preference Concept [Guiard, 1987] &
Dynamic Dominance Hypothesis [Sainburg, 2005]
may apply to lower extremity
• PBL better energy absorber than PSL
• LE comparisons should identify analyzed limb
according to preference rather than dominance
• Appropriate limb terminology should be utilized