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 Landing = moving body to rest Integral to many sport activities and Activities of Daily Living Integral to many sport activities and Activities of Daily Living Implicated in a variety of lower extremity injury Implicated in a variety of lower extremity injury Ankle sprain Ankle sprain Osteoarthritis Osteoarthritis ACL damage ACL damage A good model to investigate A good model to investigate Mechanism(s) of injury Mechanism(s) of injury Mechanism of energy absorption Mechanism of energy absorption Interesting phenomenon on its’ own. Interesting phenomenon on its’ own.

Landing Research Perform two leg landing, only one leg analyzed Perform two leg landing, only one leg analyzed “Dominant Leg” “Dominant Leg” Madigan & Pitcoe, J EMG & Kinesiology, 2003 Madigan & Pitcoe, J EMG & Kinesiology, 2003 Effects of fatigue on landing biomechanics Effects of fatigue on landing biomechanics Pollard et al, Clin J Sport Med, 2006 Pollard et al, Clin J Sport Med, 2006 Pre and post season evaluation of injury training Pre and post season evaluation of injury training “Preferred Limb” (lead leg when drop jumping) “Preferred Limb” (lead leg when drop jumping) Kulas et al, J App Biomech, 2006 Kulas et al, J App Biomech, 2006 A, K & H energy absorption and LE impedance A, K & H energy absorption and LE impedance Bilateral comparisons of Lower Extremities Bilateral comparisons of Lower Extremities “Right” vs “Left” “Right” vs “Left” Schot et al, MSSE, 1994 Schot et al, MSSE, 1994 Quantify bilateral asymmetry Quantify bilateral asymmetry “Dominant” vs “non-dominant” “Dominant” vs “non-dominant” Hewett et al, J Bone Joint Surg, 2004 Hewett et al, J Bone Joint Surg, 2004 Investigate MS changes with maturation Investigate MS changes with maturation

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: Guiard, Y. (1987). Asymmetric Division of Labor in Human Skilled Bimanual Action: The Kinematic Chain as a Model. J Motor Behavior, 19:4: Unimanual tasks * Unimanual tasks * Dart throwing, brushing teeth Dart throwing, brushing teeth Bimanually symmetric Bimanually symmetric In phase: Rope skipping, weightlifting In phase: Rope skipping, weightlifting Out of phase: rope climbing Out of phase: rope climbing Bimanually asymmetric Bimanually asymmetric Dealing cards, cursive writing Dealing cards, cursive writing Individuals exhibit a preference for one of the two possible ways of assigning two roles to two hands 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: Hemispheres /limb systems specialized for complementary functions Hemispheres /limb systems specialized for complementary functions Dominant side: controlling limb trajectory dynamics Dominant side: controlling limb trajectory dynamics Non-dominant side: controlling limb position 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, Segmental dynamics of soccer instep kicking with the preferred and non-preferred leg. J Sports Science, 24:5: Highly skilled players achieved a well-coordinated inter-segmental motion for both the preferred and non-preferred leg 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 Faster leg swing observed for the preferred leg result of larger muscle moment result of larger muscle moment

Purpose Compare LE kinetics and energetics 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 21 college-age female volunteers 21.5±2.2 y 21.5±2.2 y 1.64 ± 0.08 m 1.64 ± 0.08 m 65.2 ± 8.2 kg 65.2 ± 8.2 kg Regular lander Regular lander Free of LE traumas Free of LE traumas 10 trials R & L leg 10 trials R & L leg Random order Random order “ Land comfortably ” “ Land comfortably ” 32cm bench 32cm bench Force Platform (1000 Hz ) Force Platform (1000 Hz ) 3 cameras (200 Hz) 3 cameras (200 Hz) Sagittal plane kinematics Sagittal plane kinematics Inverse dynamics for JMF Inverse dynamics for JMF JMP = JMF ω JMP = JMF ω Paired t-tests (α =.05) Paired t-tests (α =.05)

Modified Waterloo Handedness Questionnaire Identify preferred “action” leg in bilaterally asymmetric tasks Identify preferred “action” leg in bilaterally asymmetric tasks Strong agreement with ball “striking” leg Strong agreement with ball “striking” leg

Joint Position Joint Angle (degrees) Time to Max Knee Flexion (%) Preferred Striking Leg Preferred Balance Leg

Joint Torque Time to Upright Stance(%) Joint Torque (N·mkg -1 ) Preferred Striking Leg Preferred Balance Leg

Joint Power Time to Upright Stance(%) Joint Mechanical Power (W/kg) Preferred Striking Leg Preferred Balance Leg

Percent Energy Absorption Relative joint contributions will be significantly different. Ankle±SD% Hip±SD% Ankle ± SD% Hip ± SD% Knee ± SD% Preferred StrikingPreferred Balance

Conclusions Bilateral Preference Concept [Guiard, 1987] & Dynamic Dominance Hypothesis [Sainburg, 2005] may apply to lower extremity Bilateral Preference Concept [Guiard, 1987] & Dynamic Dominance Hypothesis [Sainburg, 2005] may apply to lower extremity PBL better energy absorber than PSL PBL better energy absorber than PSL LE comparisons should identify analyzed limb according to preference rather than dominance LE comparisons should identify analyzed limb according to preference rather than dominance Appropriate limb terminology should be utilized Appropriate limb terminology should be utilized