biomechanics Flashcards

1
Q

biomechanics

A

The mechanical concepts applied to the human body and function
Includes the forces and the motion produced

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2
Q

force

A

Force = magnitude of push or pull action (F = Mass x Acceleration)

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3
Q

scalar

A

Scalar = describes only magnitude (how much) (i.e., ounces, grams, kilos)

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4
Q

vector

A

Vector = Measure of Magnitude (how much) and direction (of the push/pull)
Force is a Vector

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5
Q

mass

A

The amount of matter a body contains

How big something is

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6
Q

kinetics

A

Kinetics describes what causes motion

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7
Q

torque

A

Torque = force that produces rotation around an axis

ex) a hammer pulling a nail out
ex) doing a bicep curl

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8
Q

friction

A

Friction = force between two surfaces. Attempts to prevent motion of one surface over another
ex) a runners shoes create friction

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9
Q

velocity

A

Velocity = force + speed

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10
Q

law of inertia

A

Law of Inertia = an object in motion wants to stay in motion, an object at rest wants to stay at rest.
Need to generate enough force to get the object out of state of inertia
The greater the mass, the more force is needed to change the inertia

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11
Q

law of inertia

A

Objects as rest will stay at rest until force is applied.
Objects in motion will stay in motion until force is applied.
Ball Example
Seat belt example

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12
Q

law of acceleration

A

Law of Acceleration = the amount of acceleration (increasing speed/velocity) depends on the strength of the force applied to the object.
The amount of acceleration is proportionate to the amount of force applied.
The greater the mass, the more force needed to achieve the same acceleration as something with a smaller mass

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13
Q

Acceleration

A

Any change in velocity of an object
Kick a ball and see how far it travels.
Kick it twice as hard and it should go twice as far.
When the ball starts moving, it is accelerating.
If you were to kick it even harder, it would travel proportionately farther.
More force= more acceleration proportionate to that force

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14
Q

The amount of acceleration depends on…

A

The amount of acceleration depends on the strength of the force applied.

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15
Q

acceleration and direction

A

Acceleration can also deal with change in direction.
Force is needed to change direction.
Change in direction depends on the force applied (ie amount of force and direction of force)

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16
Q

If you were to apply the same force to two objects of differing mass, the object with the greater mass will…

A

If you were to apply the same force to two objects of differing mass, the object with the greater mass will accelerate less.
Acceleration is proportionate to the mass of an object

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17
Q

Law of Action-Reaction

A

Law of Action-Reaction = for every action, there is an equal and opposite reaction

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18
Q

Sources of Forces

A
Internal:
--Muscle contraction
--Ligament restraint
--Bony support
External:
--Gravity
--Resistance 
--Friction
19
Q

Important to remember these three characteristics about force

A

Important to remember these three characteristics about forces
–Magnitude (vector)
–Direction (vector)
–Point of application
A force is a push or a pull and movement is caused when one force becomes greater than another.

20
Q

linear forces

A

Different than linear MOTION (rectilinear and curvilinear)

Linear forces are still in a straight line

21
Q

types of linear forces

A

parallel forces
concurrent forces
resultant forces

22
Q

parallel forces

A

Parallel forces: occur in the same plane in the same or opposite direction (three point splint)

23
Q

concurrent forces

A

Concurrent forces

Two or more forces acting on a common point but in different directions

24
Q

resultant force

A

Resultant force

Effect of concurrent forces

25
Q

force couple

A

Force couple: forces occurring in equal and opposite directions

26
Q

Rotary Force = Torque

A

Force that produces movement around an axis

Equals the product of the force magnitude and the length of the moment arm

27
Q

axis

A

The pivot point

In people, in most cases this is the joint

28
Q

resistance

A

Is what the lever system is attempting to move or lift
It is counterbalanced by force
Example
With exercise we would consider this the weights.

29
Q

force

A

The primary force behind the lever system.
This is what makes the lever go into action and counter balances the resistance.
In people, this would be the muscles contracting. – the force is applied at the INSERSTION!

30
Q

ARF

A

A Axis: Joint
R Resistance: Weight
F Force: Muscle

31
Q

types of Levers

A

Levers
First class
See Saw

Second class
Good for power
Wheelbarrow

Third class
Good for speed & distance
Screen Door

32
Q

how to tell the difference between the different levers

A

If A is in the Middle = First Class
If R is in the Middle = Second Class
If F is in the Middle = Third Class

33
Q

first class lever

A
First Class levers
Few in the body
Head on neck
Axis in the middle
Resistance on one end
Force on the other end
See saw
34
Q

an ex of a first class lever in the body

A

• Relax your neck so that your head drops slowly forward.
• The head is a heavy object—about 4.5 kilograms and acts as the resistance.
• Your head drops forward when you relax your neck because your head and neck work like a first-class lever.
• The axis is at the top of the neck
The muscles in the neck provide an input force that allows you to raise your head.
• When you relax these muscles, gravity causes your head to go forward.

35
Q

second class levers

A
Second Class Levers
Best for power
Few in the body
Axis on one end
Resistance in the middle
Force on the other end
Brachioradialis
36
Q

second class lever in the body

A

Plantar flexors lifting the body where the metatarsals are the axis, the resistance is the weight of the body pushing down, and the force is the muscle contraction pulling up.
Brachioradialis – axis =elbow,
resistance = weight of forearm
force = insertion of the muscle

37
Q

third class levers

A

Third Class Levers
Most common in the body
Best for distance and speed (aka ROM)
Biceps

38
Q

what class of levers is the bicep?

A

Biceps ( 3rd Class)
With concentric contraction, where elbow is axis, resistance is weight of the hand, and force is contraction of bicep, pulling the hand back up
Biceps (2nd Class)
With eccentric contraction, where elbow is the axis, weight of the hand is the force, and the resistance is the bicep pulling upward.

39
Q

2nd vs 3rd class levers

A
Biceps is a third class lever
Due to location of insertion on 
    the proximal radius.
As the biceps contracts, it applies
the force to the forearm.
Resistance is distal forearm and 
Hand (and whatever you put in 
your hand)

Brachioradialis is a second class lever.
Due to the insertion on the distal radius
In this case, the forearm is the resistance,
and the distal forearm is where the force is
applied.

40
Q

What Factors Cause Classes to Change

A

Application of resistance
–Brachioradialis can be third class if you put a weight in
the hand.
Direction of movement in relation to gravity.
–Concentric movement against gravity is typically third
class lever
–Eccentric movement with gravity is second class lever
–Biceps example

41
Q

Mechanical Advantage = ?

A

Mechanical Advantage = Leverage

MA = FA / RA

42
Q
what are second class levers designed for?
what are third class levers designed for?
A
Second class levers designed for power
Third class levers designed for speed and distance
Important to know for MMT, transfers, equipment modifications
43
Q

mechanical advantage

A

Defined as the ratio between the force arm and the resistance arm.
A shorter force arm requires more force
A longer force arm requires less force
Can apply to therapeutic exercise
Airsplint example
Applies to MMT – we want to give the muscle the best possible advantage.
Shoulder example