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33 Cards in this Set
- Front
- Back
Biomechanics
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Mechanical (Newtonian) laws applied to biological systems-- concerned with kinematic (motion) results of kinetics (forces)
Ex. static and dynamic equilibrium Focus on organismic and environmental constraints The relationship between the forces that can be produced by the body. Captures not only the forces produced by the organism, but the interaction of those forces with the environment. **Provides a lawful way to understand how variations of a particular movement form/pattern can result from impairments (CCV) Ex. glut max gait pattern, triceps surae weakness |
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Task Dynamics
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Put together special purpose devices from dynamical components that produce coordinated movement patterns
i.e. Degrees of Freedom and Force Supplying components |
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What DOF and components/pieces are used in building a pogo stick?
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Single linear DOF (translational)
Components: pedal, stick, spring |
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What DOF and components/ pieces are used in building a pendulum
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1 DOF (rotational)
Components: string in ceiling, weight, gravity |
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If added muscle moment to pendulum, what would this start to look like?
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If add kick to it-- like walking
Kick = push off |
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Glut Max gait pattern
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If glut max is weak and no compensatory postural adjustments are made, the torso will be thrown into flexion at heel strike and balance will be lost.
But with compensatory hip extension posture at heel strike, the induced flexion moment is reduced and balance is maintained |
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Triceps Surae weakness
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Increased knee flexion during stance phase
Weak triceps surae cannot prevent dorsiflexion during stance phase (would cause falling-forward loss of balance) Compensatory knee flexion moves center of mass back over the support base. This creates tendency to collapse vertically. Why? Requires compensatory increase in quads activity to prevent collapse |
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Adult Walking: Exploiting Dynamics
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Adults have learned to sparingly and efficiently add active muscle forces only when and where it is necessary.
To initiate swing, give small push off torque (start pendulum) At stance: give it a a torque in opposite direction **Active forces supplement passive forces |
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Child: Learning the Ropes
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Initial Swing: ok...similar to adult but...
Mid Swing/Terminal swing: hip flexor stays active, opposing gravity. Even worse, muscle flexion continues even when motion changes to extension. Very insufficient! |
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Child: Bernstein Theory
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With learning:
1) Complement, not oppose gravity force 2) Be efficient with muscle activation and timing |
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Biomechanics
|
Mechanical (Newtonian) laws applied to biological systems-- concerned with kinematic (motion) results of kinetics (forces)
Ex. static and dynamic equilibrium Focus on organismic and environmental constraints The relationship between the forces that can be produced by the body. Captures not only the forces produced by the organism, but the interaction of those forces with the environment. **Provides a lawful way to understand how variations of a particular movement form/pattern can result from impairments (CCV) Ex. glut max gait pattern, triceps surae weakness |
|
Task Dynamics
|
Put together special purpose devices from dynamical components that produce coordinated movement patterns
i.e. Degrees of Freedom and Force Supplying components |
|
What DOF and components/pieces are used in building a pogo stick?
|
Single linear DOF (translational)
Components: pedal, stick, spring |
|
What DOF and components/ pieces are used in building a pendulum
|
1 DOF (rotational)
Components: string in ceiling, weight, gravity |
|
If added muscle moment to pendulum, what would this start to look like?
|
If add kick to it-- like walking
Kick = push off |
|
Glut Max gait pattern
|
If glut max is weak and no compensatory postural adjustments are made, the torso will be thrown into flexion at heel strike and balance will be lost.
But with compensatory hip extension posture at heel strike, the induced flexion moment is reduced and balance is maintained |
|
Triceps Surae weakness
|
Increased knee flexion during stance phase
Weak triceps surae cannot prevent dorsiflexion during stance phase (would cause falling-forward loss of balance) Compensatory knee flexion moves center of mass back over the support base. This creates tendency to collapse vertically. Why? Requires compensatory increase in quads activity to prevent collapse |
|
Adult Walking: Exploiting Dynamics
|
Adults have learned to sparingly and efficiently add active muscle forces only when and where it is necessary.
To initiate swing, give small push off torque (start pendulum) At stance: give it a a torque in opposite direction **Active forces supplement passive forces |
|
Child: Learning the Ropes
|
Initial Swing: ok...similar to adult but...
Mid Swing/Terminal swing: hip flexor stays active, opposing gravity. Even worse, muscle flexion continues even when motion changes to extension. Very insufficient! |
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Child: Bernstein Theory
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With learning:
1) Complement, not oppose gravity force 2) Be efficient with muscle activation and timing |
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What is required for the performance of skilled actions?
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Define task specific coordinative structures, across appropriate sets of muscles and joints
--> to ensure that it is tailored to the task at hand and the time-span required Construct an appropriate Special Purpose Device |
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Dynamic Resources (DRs)
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Springs, friction, muscular forcing, mass, length = dynamical components in the neuro-muscularskeletal system
"Machine parts"-- bag of parts |
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The Dynamics of SPD
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Dynamic Resources --> Dynamical System (Special Purpose Device, Coordinative Structure) --> Coordinated Movement Pattern
Measure/Examine Pattern If want to Change/Rehab Pattern: Ex. Wagenaar- Improve Parkinsons' patients gait by increasing stride frequency with metronome |
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SPD: Design Issues
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The process of constructing SPD from DRs is similar to the process of constructing tools/prosthetic devices or from a hardware toolkit
Both types of devices need to provide a successful match b/n the device's design and the set of current task, environmental, and organismic constraints. Ex. Pliers and Scissors use single DOF. But Pliers contact surfaces designed for gripping/compression. Scissors contact surfaces for cutting/shearing. |
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Single DOF System
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Simplest machine: frictionless mass-spring system
Phase plane, Time series, Phase angle, Equation of motion |
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Discrete targeting devices
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For reaching, grasping
Brings you somewhere and holds you there |
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Sustained rhythmic devices
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For polishing, locomotion
Stable, rhythm |
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Equation of Motion
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Compact and precise way to describe the dynamics that underlie an observed movement
F = m x a Sum of forces applied to an object = (object mass) x (object acceleration) F = -kx (spring force) Inertial force = - (stiffness) x (displacement) Therefore, -kx = ma |
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Mass spring vs. Pendulum: Different yet Similar
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Physically different:
DOF -Mass-spring = translational DOF -Pendulum = rotational DOF Potential Energy -Mass-spring = deformation of spring length -Pendulum = relative height of mass Dynamical Behavior is very similar: An elastic spring and a "gravity spring" -Nearly identical phase plane trajectories for small oscillations |
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Undamped
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Neither loses nor gains energy
= simple mass-spring |
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Damping
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Real-life systems are not frictionless and display both energy losses and gains.
Friction force (resists motion) + Spring Force = Inertial Force |
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Point Attractors
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The behavior of a damped mass-spring system is attracted to a single point in the phase plane called an equilibrium point (place it is reaching for)
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Stability
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Having reached its equilibrium point, a point attractor system will remain there if there are no disturbing forces. If perturbed away from its equilibrium point, the system will RETURN to it.
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