Locomotion- Walking and Running LECTURE 6

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24 Terms

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Features of walking

  1. No aerial phase

  2. 1 or 2 feet on the ground

  3. slow

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Features of Running

  1. Aerial phase

  2. 0 to 1 foot on the ground

  3. Fast

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IN both→ the energy

  • Move up and down

  • accelerates and decesrates

    → Kinetic and potential energy oscillate in a regular way

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Potential vs Kinetic energy in walking

Out of phase

  • Kinetic highest when Potential is the lowest

→ Model: inverted pendulum

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Potential vs Kinetic energy in running

In phase

  • Kinetic highest when potential the highest

    • .eg the highest when in the air

→ Not like the pendulum

  • decelerates at the lowest postion→ all energy into the ground

    → how get this back?→ Elastic energy stores it:

    • Model: bouncing ball

    • elastic energy is re-coverted to kinetic energy

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Walking speed limit

Only feasible whilse body weight> centripetal force

mg> m v²/l

Around 3m/s

<p>Only feasible whilse body weight&gt; centripetal force</p><p>mg&gt; m v²/l</p><p>Around 3m/s</p>
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How to racewalkers achieve higher walking speeds?

  • sticking the pelvis out

  • increasing he radius of the arc l

    → higher speeds are possible

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Types of gaits in quadrupeds

  1. Walking

  2. Running

  3. Gallop→ 2 forlimbs move in phase, followed by two hind limbs

<ol><li><p>Walking</p></li><li><p>Running</p></li><li><p>Gallop→ 2 forlimbs move in phase, followed by two hind limbs</p></li></ol><p></p>
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Advantage of using a gallop?

  • Larger stride lengths

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How do cheetahs increase their stride length even more?

  • Elastic flexion and extension of the spinal column

  • Also have two areial phases

<ul><li><p>Elastic flexion and extension of the spinal column</p></li><li><p>Also have two areial phases</p></li></ul><p></p><p></p>
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Why can’t horses do this?

  • Must have a stiff back

  • needed for backbone support

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At what speeds do animals change gaits?

  • Upper limit of walking speed can be generalised to predict running speeds at which animals change gait

Re-written as v²/gl< 1→ Froude Number (Fr)

  • Twice the ratio of kinetic to potential energy!

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How do gaits differ?

  • in the type of exchange between kinetic and potential energy

    9 e.g walking is pendulum but running is a spring)

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What does it mean for two movements to have the same Froude number

  • Dynamically similar

e.g a small and large pendulum winging through the same angle

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Different sized animals can change gaits at the same Froude numbers

  • e.g walk-trot transition at Fr=0.5

  • trop-gallop transtion at Fr= 2.5

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