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ANKLE VS. HIP POWER FOR HUMAN WALKING

ANKLE VS. HIP POWER FOR HUMAN WALKING. Cara L. Lewis, PT, PhD Dan Ferris, PhD Human Neuromechanics Laboratory University of Michigan Ann Arbor, MI USA. Simple Bipedal Walking Model. “Powered” by gravity. Impulse push. Hip torque. Powered Bipedal Walking Model (Kuo 2002).

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ANKLE VS. HIP POWER FOR HUMAN WALKING

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  1. ANKLE VS. HIP POWER FOR HUMAN WALKING Cara L. Lewis, PT, PhD Dan Ferris, PhD Human Neuromechanics Laboratory University of Michigan Ann Arbor, MI USA

  2. Simple Bipedal Walking Model • “Powered” by gravity

  3. Impulse push Hip torque Powered Bipedal Walking Model(Kuo 2002) 4 times less costly

  4. Impulse push Hip torque Powered Bipedal Walking Modelapplied to human gait Is there an inherent tradeoff in human gait?

  5. Effect of Push-off during Gait • Hypothesis: changes in ankle push-off would be inversely related to the hip moment

  6. Effect of Push-off during Gait • Methods: • 10 subjects (7 females, 3 males) • Walk on a custom split-belt force-measuring treadmill at 1.25 m/s • Recorded kinematics and kinetics of ankle, knee and hip joints

  7. ? ?  push-off natural  push-off Effect of Push-off during Gait • 3 Conditions:

  8. 20 dorsiflexion 0 -20 Push-off -40 Natural AnkleMoment (Nm) -60 Push-off -80 plantar flexion -100 -120 -140 10 20 30 40 50 60 70 80 90 100 % Gait Cycle Effect of Push-off during Gait: Peak Ankle Moment

  9. 40 30 20 10 0 * Push-off Natural Push-off Effect of Push-off during Gait:Ankle Angular Impulse (Nms) 20 dorsiflexion 0 -20 -40 AnkleMoment (Nm) -60 -80 plantar flexion -100 -120 -140 10 20 30 40 50 60 70 80 90 100 % Gait Cycle

  10. 280 240 200 160 120 80 40 0 Push-off Natural Push-off Effect of Push-off during Gait:Peak Ankle Power (W) 200 150 100 Power (W) 50 0 -50 -100 0 10 20 30 40 50 60 70 80 90 100 Gait Cycle (%)

  11. ? ?  push-off natural  push-off Effect of Push-off during Gait • 3 Conditions:

  12. Flexion 60 50 Extension 60 40 40 50 30 20 40 20 * 30 10 0 20 0 Hip Moment (Nm) 10 -20 0 Push-off -40 Natural * * Push-off -60 -80 10 20 30 40 50 60 70 80 90 100 % Gait Cycle Effect of Push-off during Gait:Peak Hip Moment flexion extension

  13. 10 60 40 5 * 20 0 0 Hip Moment (Nm) -20 Push-off -40 Natural Push-off -60 -80 10 20 30 40 50 60 70 80 90 100 % Gait Cycle Effect of Push-off during Gait: Hip Flexion Angular Impulse (Nms) flexion extension

  14. 60 10 40 20 5 * * 0 Hip Moment (Nm) -20 0 Push-off -40 Natural Push-off -60 -80 10 20 30 40 50 60 70 80 90 100 % Gait Cycle Effect of Push-off during Gait:Hip Extension Angular Impulse (Nms) flexion extension

  15. 90 60 40 * 30 30 20 * 0 10 0 Push-off Natural Push-off Effect of Push-off during Gait:Hip Power (W) 100 50 Power (W) 0 -50 0 10 20 30 40 50 60 70 80 90 100 GaitCycle(%)

  16. 0.8 * 0.6 0.4 0.2 0.0 Effect of Push-off during Gait:Speed and Step length • Speed: treadmill • Step length (m)

  17. Effect of Push-off during Gait • Increasing push-off decreases both hip flexion and hip extension peak moment and angular impulse • Decreases hip flexion peak power

  18. Clinical Implications • Anterior hip pain • Acetabular labral tears • Increased anterior joint force due to muscle • Idiopathic hip osteoarthritis: • Progress faster with higher joint forces • Large percentage of joint force due to muscle 18

  19. Acknowledgements • Dan Ferris • Human Neuromechanics Laboratory, University of Michigan • Human Biomechanics and Control Lab, University of Michigan • Funding: • National Institutes of Health (NIH) If anyone needs to be to the Schiphol Airport by 6AM Friday morning, please see me after about sharing a taxi. 19

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