Transcript Document

Basic Biomechanics
• Mechanics-study of forces and
motions produced by their action.
• Biomechanics-apply that to the
structure and function of the human
body.
Basic Biomechanics
• Statics deal with factors associated
with nonmoving.
• Dynamics deal with moving systems
– Kinetics are the forces causing the
motion
– Kinematics are time, space and mass of
the moving system.
Basic Biomechanics
• Kinematics– Osteokinematics bones moving in space
in regard to joint surface (flexion)
– Arthrokinematics are the manner in
which joint surfaces move in relation to
each other.(concave)
Basic Biomechanics
• Vector- quantity having both
magnitude and direction
– Force-push or pull action
– You throw a ball with direction and
speed
Basic Biomechanics
• Scalar- has only magnitude.
– Length, area, volume, mass
– Mass is the amount of matter a body
contains.
– Inertia is change in motion in either
speed or direction.
Basic Biomechanics
• Law of Inertia- an object at rest
tends to stay at rest, and an object
in motion tends to stay in motion.
Basic Biomechanics
• Think about what happens with your
head in a car. It is not in motion, so
when acceleration/deceleration
happen your neck is not always
happy.
Basic Biomechanics
• Law of Acceleration-the amount of
acceleration depends on the strength
of the force applied to an object.
Basic Biomechanics
• Acceleration is inversely proportional
to the mass of an object.
– If you roll a soccer ball , then a bowling
ball, with the same force, the heavier
object will not travel as far.
Basic Biomechanics
• Law of action-reaction- every action
there is an equal and opposite
reaction.
– Strength of reaction is equal to strength
of action, just in the opposite direction.
– Harder you
jump harder
you rebound.
Basic Biomechanics
• Go outside and create a
demonstration of one of the laws of
physics for us all to understand.
Basic Biomechanics
• Force (a vector describe magnitude
and direction
– Linear force- 2 forces act on the same
line in the same direction or opposite
direction.
or
Basic Biomechanics
• Parallel Forces– In the same plane and in the same or
opposite directions.
Basic Biomechanics
• Concurrent Forces- two or more
forces act from the same common
point but pull in
different directions
Basic Biomechanics
• Force Couple- two forces act in an
equal but opposite direction resulting
in a turning effect.
Torque
•
–
Angle of Pull: angle between muscle insertion and bone on which it inserts.
–
Angular Force: force of a muscle contributing to bone's movement around a joint axis;
greatest when muscles angle of pull is perpendicular to bone (i.e. 90 degrees).
Stabilizing force: degree of parallel forces generated on the lever (bone and joint) when the
muscles angle of pull is less than 90 degrees.
Dislocating force: degree of parallel forces generated on the lever (bone and joint) when the
muscle's angle of pull is greater than 90 degrees.
Components of Force
–
–
Basic Biomechanics
• State of equilibrium- all torques actin
on it are even.
• Center of gravity- COG-balance point
of an object at which torque on all
sides are equal.
Basic Biomechanics
• Base of support is that part of the
body that is in contact with the
supporting surface. (BOS)
• Line of gravity is the imaginary
vertical line that passes through the
COG to center of earth. (LOG)
• Draw this in your notes pg 78
Basic Biomechanics
• Equilibriums
– Sable- to disturb you would have to
raise COG
– Unstable- only slight force needed to
disturb
– Neutral- COG is not raise or lowered to
disturb.
– Lower COG is more stable.
Basic Biomechanics
• The closer COG is to center of BOS
the more stable you will be
Basic Biomechanics
• Lets try it together.
• Stand up and stand on both legs,
then balance on one standing
straight up.
• Then lean to the side you are
standing on. What changes.
Basic Biomechanics
• List some ways to increase stability
– Wider base of support
– Greater mass (which will decrease
speed)
– Increase friction (carpet vs ice)
– Focus on stationary
Basic Biomechanics
• Simple Machines
– 4 types of Machines
• Lever
• Wheel and Axle
• Inclined plane
• The pulley
Basic Biomechanics
• Lever is a rigid bar that can rotate
about a fixed point when a force is
applied to overcome resistance.
Basic Biomechanics
• A-Axis is the fixed point around
which the lever rotates.
• F-Force causes the lever to move.
(muscle in the body)
• R-Resistance that must be overcome
for motion to occur. ( can be gravity
or the weight to move.)
Basic Biomechanics
Force Arm distance between force and
axis
Resistance arm is distance from axis to
resistance.
A
F
R
Basic Biomechanics
• First-class lever
– Axis is located between the force and
the resistance.
– Balance
Basic Biomechanics
• Second Class Lever
– Has the axis at one end, the resistance
in the middle, and force at the other
end.
– power
Basic Biomechanics
• Third class Leaver
– Has the axis at one end with the force in
the middle and resistance at the
opposite end.
– ROM
Basic Biomechanics
• The body has more 3rd class levers
because the body favors the
advantage of ROM.
• Levers can change class depending
on where the resistance is, if there is
resistance added vs just gravity. Or
if the direction gravity comes from
changes. Pg 83-84
Basic Biomechanics
• Mechanical Advantage- ratio between
the force arm and resistance arm.
MA=FA
RA
Less force is needed when
mechanical advantage is greater.
Page 85 force arm on leg
Basic Biomechanics
• Pulley is a grooved wheel that turns
on axle with rope or cable.
– It allows for change of direction of force
or to change the magnitude of a force.
Basic Biomechanics
• Fixed pulley is one attached to a
beam. It acts like a fist class lever,
it is used to change directions.
• Medical malleolus
Acts as a pulley for the
Tendon of peroneus
longus
Basic Biomechanics
• Movable pulley has one end of the
rope attached to a beam then the
rope runs through the pulley to the
other end where the force is applied.
• What is gained in
force is lost in
distance.
Basic Biomechanics
• Wheel and Axle- a lever in disguise.
– Wheel with a crank attached. It helps
increase the force exerted.
– Large radius requires less force.
Basic Biomechanics
• Incline Plane is a flat surface that
slants.
– It creates more distance with less effort
Simple Machines
• Basic rule of simple machines: what
is gained in force is lost in distance.