Download Electrode Placement for Chest Leads, V1 to V6

chapter
3
Principles
of Motion
and Stability
Define:
• Biomechanics
• Developmental biomechanics
What Changes From A to B?
Click image to view video
A
Click image to view video
B
Changes Are Predictable
• Based on optimizing principles of motion
and stability
• Can be seen across variety of motor skills
• Often produce more force, velocity, or
accuracy
Newton’s First Law
• An object at rest stays at rest and an object
in motion stays in motion until acted upon
by a force.
• Inertia is resistance to motion related to
mass.
• Momentum is the product of mass and
velocity.
Newton’s First Law, Simplified
• We must exert force to
– move objects
– move ourselves
• More inertia means that
– it is harder to move
– more force application is required
Newton’s First Law:
Child Learns to Swing a Bat
– What must the child learn about inertia?
– What must the child learn about momentum?
Moving an Object Farther or Faster
• Increase force.
• Increase distance over which force is
applied.
Adding Distance to Improve a Kick
• Increase step
length (linear
distance).
• Increase range of
motion (rotational
distance).
Click image to view video
Newton’s Second Law
• Object’s force is related to mass and
acceleration (F = m  a).
• Object’s acceleration is related to force
applied and inversely related to mass
(a = F/m).
Newton’s Second Law
• A person can throw only as hard as he or
she can throw.
• Given a constant force level, how could you
increase acceleration when throwing a ball?
Newton’s Third Law
• To every action, there is an equal and
opposite reaction.
• When you push on something, it pushes
back on you!
Using Newton’s Third Law
Oppositional movements and directional force
Force Generation Aided
by Oppositional Movements
Click image to view video
Click image to view video
Force Generation Aided by Planer
Movements
• Use force in the
plane of motion
where you want to
move yourself or
an object.
• Avoid rotational
movements that
reduce force in the
desired plane.
\insert video clip 3.6, ID#
323946 (from 4E CDROM, Auxiliary, Standing
Long Jump, example 6)\
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Increasing Velocity:
Rotating Limbs and Projected Objects
• Increase rotational velocity (swing it faster).
• Increase relative length (fully extend it at
release or contact).
Why Not Keep Limb
Extended Throughout?
The leg would have too much rotational
inertia.
Click image to view video
Click image to view video
Force and Time
• To make an object move, increase force
application for a given time.
• Example: karate chop to bricks.
• To make an object stop, increase time over
which a given force is applied
• Example: soft landing in gymnastics.
Question:
What developmental skills involve learning to
absorb force?
Stability and Balance
• Stability: ability to resist movement
• Balance: ability to maintain equilibrium
• Stability–mobility trade-off
Increasing Stability
• Increase base of support.
• Lower the center of gravity.
Increasing Balance
• Increase stability.
• Improve strength, coordination, and
proprioception.
Take-Home Messages
• The principles of motion and stability apply to all
actions and objects.
• Be aware of changing individual constraints.
• Manipulate task and environment to aid in optimal
skill performance.
• Not everyone will become proficient.