Sci Basis 2

Front 1

Biomechanics

Back 1

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

Front 2

Task Dynamics

Back 2

Put together special purpose devices from dynamical components that produce coordinated movement patterns

i.e. Degrees of Freedom and Force Supplying components

Front 3

What DOF and components/pieces are used in building a pogo stick?

Back 3

Single linear DOF (translational)

Components:
pedal, stick, spring

Front 4

What DOF and components/ pieces are used in building a pendulum

Back 4

1 DOF (rotational)

Components: string in ceiling, weight, gravity

Front 5

If added muscle moment to pendulum, what would this start to look like?

Back 5

If add kick to it-- like walking

Kick = push off

Front 6

Glut Max gait pattern

Back 6

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

Front 7

Triceps Surae weakness

Back 7

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

Front 8

Adult Walking: Exploiting Dynamics

Back 8

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

Front 9

Child: Learning the Ropes

Back 9

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!

Front 10

Child: Bernstein Theory

Back 10

With learning:
1) Complement, not oppose gravity force
2) Be efficient with muscle activation and timing

Front 11

Biomechanics

Back 11

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

Front 12

Task Dynamics

Back 12

Put together special purpose devices from dynamical components that produce coordinated movement patterns

i.e. Degrees of Freedom and Force Supplying components

Front 13

What DOF and components/pieces are used in building a pogo stick?

Back 13

Single linear DOF (translational)

Components:
pedal, stick, spring

Front 14

What DOF and components/ pieces are used in building a pendulum

Back 14

1 DOF (rotational)

Components: string in ceiling, weight, gravity

Front 15

If added muscle moment to pendulum, what would this start to look like?

Back 15

If add kick to it-- like walking

Kick = push off

Front 16

Glut Max gait pattern

Back 16

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

Front 17

Triceps Surae weakness

Back 17

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

Front 18

Adult Walking: Exploiting Dynamics

Back 18

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

Front 19

Child: Learning the Ropes

Back 19

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!

Front 20

Child: Bernstein Theory

Back 20

With learning:
1) Complement, not oppose gravity force
2) Be efficient with muscle activation and timing

Front 21

What is required for the performance of skilled actions?

Back 21

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

Front 22

Dynamic Resources (DRs)

Back 22

Springs, friction, muscular forcing, mass, length = dynamical components in the neuro-muscularskeletal system

"Machine parts"-- bag of parts

Front 23

The Dynamics of SPD

Back 23

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

Front 24

SPD: Design Issues

Back 24

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.

Front 25

Single DOF System

Back 25

Simplest machine: frictionless mass-spring system

Phase plane, Time series, Phase angle, Equation of motion

Front 26

Discrete targeting devices

Back 26

For reaching, grasping

Brings you somewhere and holds you there

Front 27

Sustained rhythmic devices

Back 27

For polishing, locomotion
Stable, rhythm

Front 28

Equation of Motion

Back 28

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

Front 29

Mass spring vs. Pendulum: Different yet Similar

Back 29

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

Front 30

Undamped

Back 30

Neither loses nor gains energy
= simple mass-spring

Front 31

Damping

Back 31

Real-life systems are not frictionless and display both energy losses and gains.

Friction force (resists motion) + Spring Force = Inertial Force

Front 32

Point Attractors

Back 32

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)

Front 33

Stability

Back 33

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.