Biomechanics of Walking

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Locomotion
Gait Parameters During Level Walking
Kinematics of Level Walking
Kinetics of Level Walking

  1. Simoneau G.G., 2002. Kinesiology of Walkign. In: Neumann, D.A. (ed). Kinesiology of the Musculoskeletal System: Foundations for Physical Rehabilitation. St. Louis, Missouri: Mosby. pp. 523-569.
  2. Hamilton, N., & Luttgens, K., 2002. Kinesiology, Scientific Basis of Human Motion, 10thed. Madison, WI, Brown & Benchmark. Chapter 19, pp. 467-494.

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Objectives: After studying this topic, the students will be able to

  • identify different types of locomotion
  • describe a typical gait cycle
  • describe methods to measure the gait and the related parameters
  • to understand ground reaction forces and how it works on the body during level walking
  • explain the changes in kinematics and kinetics during level walking

  • Locomotion

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    Definition of Locomotion

  • the act or power of moving from place to place by means of oneˇ¦s own mechanisms or power
  • the result of the action of the body levers propelling the body
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    Types of Locomotion

  • on foot: walking, running, ascending or descending ramp or stairs, or jumping
  • on wheels: bicycling, roller skating, ice skating, or wheelchair propelling
  • on hands and/or knees or hands and feet: walking on hands, creeping or crawling, crutch walking, stunts
  • rotary locomotion: cartwheels, handsprings, or rolls
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    A Typical Gait Cycle

  • the duration that occurs from the time when the heel of one leg strikes the ground to the time at which the same leg contacts the ground again
  • 2 phases
  • stance phase (62%)
  • swing phase (38%)
  • A typical gait cycle lasts 1-2 sec, depending on speed.

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    Stance Phase (Support Phase)

  • the duration when the foot in contact with the ground
  • the duration from heel strike to toe off
  • 3 subphases
  • initial contact periodˇG from heel strike to foot flat
  • midstance periodˇG from foot flat to heel off
  • propulsive periodˇG from heel off to toe off
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    Swing Phase (Recovery Phase)

  • the duration when the foot in the air
  • the duration from toe off to heel strike
  • 3 subphases
  • acceleration
  • midswing
  • deceleration
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    Gait Parameters During Level Walking

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    Recording the Gait Cycle

  • pneumatic switch (Marey, 1873)ˇG 1st person to record the duration of sole contact
  • electric switch (Scherb, 1927)ˇG using 3 separate switches
  • interrupted-light photography (Murray et al., 1964)
  • pressure transducer (Andriachi et al., 1977)
  • motion analysis system
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    Time Variables

  • stance time
  • single support time
  • double support time
  • durationˇG about 22% of the gait cycle totally
  • decrease when the speed of walking increases
  • increase in the elderly or patients with balanced disorders
  • swing time
  • stride or step time
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    Distance Variables

  • stride length
  • decrease in the elderly and increase as the speed of walking increases
  • step length
  • wide of base
  • degree of toe-out
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    Velocity Variables

  • cadenceˇG steps per minute
  • comfortable speedˇG 80-110 steps/min
  • slow speedˇG <70 steps/min
  • fast speedˇG >120 steps/min
  • walking speedˇG distance/unit of time
  • increase with increased cadence and stride length simultaneously
  • decrease with decreased angle of toe out and increased limb length or weight
  • increased speed results in decrease in duration of all the component phases
  • walking velocity
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    Other Kinematic Variables

  • displacement of center of mass
  • angle change of each joint
  • linear acceleration
  • angular acceleration
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    Kinematics of Level Walking

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    Displacement of Body COM

  • Walking is a translatory motion of the body that is accomplished by the alternating rotary motions of both lower extremities
  • COM moves forward Þ COM beyond anterior edge of BOS Þ the other foot moves forward to ­ BOS
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    Vertical Displacement of Body COM

  • pathˇG a sinosoid curve
  • amplitudeˇG ~2"
  • highest point: immediately after COM passes over the WB leg
  • lowest point: at the termination of the swing phase of the other leg
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    Lateral Displacement of Body COM

  • pathˇG a sinosoid curve
  • amplitudeˇG ~2"
  • to keep the COM over the weight-bearing foot
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    Kinetics of Level Walking

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    Forces That Control Walking

  • gravity (body weight)
  • air resistance
  • internal muscle forces
  • ground reaction forces
  • normal componentˇG vertical forces
  • shear component ˇG anterior-posterior and medial-lateral friction forces
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    Ground Reaction Forces

  • definitionˇG the forces applied to the body by the ground, as opposed to those applied to the ground, when an individual takes a step


  • in Cartesian ayatemˇG Fx, Fy, Fz, Mx, My, Mz
  • vertical component
    • double peaks
      • 1st peak at heel strikeˇG the action of body momentum
      • 2nd peak at push-offˇG contraction of calf muscle
    • peak value = 120% BW
    • lower than BW during midstance as a result of balancing the upward momentum of the COM

  • anterior-posterior component
    • the magnitude and direction of the anterior-posterior shear force depends on the position of the COM relative to the location of the foot
      • in the posterior direction at heel strike for slowing the forward progression of the body
      • in the anterior direction at toe off for propelling the body forward
      • the larger the step length, the greater the shear forces because of the greater angle of between the lower extremity and the floor
    • peak value = 20% BW
    • sufficient friction force between foot and ground is necessary for preventing slipping down
    • the propulsive force of one limb is applied simultaneously to the braking force of the other limb when the weight is transferred from one limb to the other

  • medial-lateral
    • the magnitude of the medial-lateral shear force depends on the position of the COM relative to the foot
      • in the lateral direction at heel strike
      • in the medial direction at the rest of stance phase
      • the larger the step width, the greater the shear forces because of the greater angle of between the lower extremity and the floor
    • peak value = ~5% BW
    • wide variety depending on different foot types
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    Trajectory of Center of Pressure

  • At heel strike, the COP is located lateral to the midpoint of the heel
  • At midestance, the COP moves more laterally
  • From heel off to toe off, the COP moves medially from the metatarsal heads to the bog toe

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    Joint Moment

  • At heel strike, the line of action of the ground reaction forces passes posterior to the ankle joint, posterior to the knee joint, and anterior to the hip joint, leading to promote ankle plantarflexion, knee flexion, and hip flexion.
  • To prevent collapse of the lower extremity, these external moments are counterbalanced by internal joint reaction moments that are created by ankle dorsiflexors, the knee extensors, and the hip extensors.
  • net momentˇG the summation of the external and internal moments
  • do NOT indicate the direction of motion
  • e.g. cocontraction of agonisits and antagonists
  • e.g. quadriceps avoidance
  • Joint Power

  • definition
  • the rate of work performed by controlling muscles
  • the product of the net joint moment and the joint angular velocity
  • significanceˇG indicating the net rate of generating or absorbing energy by all muscles and other connective tissues crossing the joint
  • positive value indicates power generation, reflecting a concentric contraction
  • negative value indicates power absorption, reflecting an eccentric contraction
  • Ankle Kinetics

  • definition
  • the rate of work performed by controlling muscles
  • the product of the net joint moment and the joint angular velocity
  • significanceˇG indicating the net rate of generating or absorbing energy by all muscles and other connective tissues crossing the joint
  • positive value indicates power generation, reflecting a concentric contraction
  • negative value indicates power absorption, reflecting an eccentric contraction
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    Established on 05/05/2003 and Last Updated 05/20/2003 by Huei-Ming Chai, PT, Phd
    © 2003 ®ă´f±Ó at School of Physical Therapy, National Taiwan University, Taipei
    All Right Reserved