The Basics Flashcards
1
Q
Objectives
- Define Torque and differentiate types of torque
- Discuss the joint forces created by various types of lever systems and torques created during human movement
A
fyi
2
Q
For a PTA, the purpose of studying clinical kinesiology (how the body moves) is to understand the forces acting on the human body causing movement (biomechanics) and to manipulate these forces in treatment procedures so that human performance may be improved and further injury may be prevented
A
Clinical Kinesiology
3
Q
built on the study of mechanics from the field of physics.
it is the study of how forces lead to movement in the human body.
A
Biomechanics
4
Q
what is concerned with the effects of forces acting on objects.
A
Mechanics
5
Q
Humans can see movement but forces affecting motion are never seen and seldom felt. What are 4 main forces on the body:
A
- Gravity
- Muscle tension
- External resistance
- Friction
Where these forces act in relation to positions and movement of the body in space is fundamental to the ability to produce human movement and to modify it
6
Q
weight of body parts and attachments such as splints, casts, eating utensils, books or weights
A
Gravity
7
Q
produce forces on the bone segments by active contraction or by being passively stretched
A
Muscles
8
Q
exercise pulleys, manual resistance, doors or windows
A
Externally applied resistances
9
Q
can provide stability if optimum, retard motion if excessive and lead to instability if inadequate
A
Friction
10
Q
deals with NON-movement systems
A
Statics
11
Q
deals with moving systems and can be divided into two parts:
A
Dynamics
12
Q
forces causing movement in a system
A
Kinetics
13
Q
the science of motion of bodies in space, osteokinematics and arthrokinematics
A
Kinematics
14
Q
how the bones move in space without regard to the movement of joint surfaces
A
Osteokinematics
15
Q
how adjoining joint surfaces move in relation to each other
A
Arthrokinematics
16
Q
a quantity having both magnitude (size) and direction
A
Vector
17
Q
Force is a
A
vector
18
Q
a push or a pull action that can be represented as a vector
A
Force
19
Q
describes only magnitude
Length, area, speed, volume and mass
A
Scalar
20
Q
refers to the amount of matter that a body contains
A
Mass
21
Q
the property of matter that causes it to resist an change of its motion in either speed or direction
A
Inertia
22
Q
a description of motion with regard to what causes motion
A
Kinetics
23
Q
the tendency of force to produce rotation about an axis
A
Torque
24
Q
a force developed by two surfaces
Prevents motion of one surface across another
A
Friction
25
a vector that describes speed and is measured in units
Feet per second
Miles per hour
Velocity
26
NO motion can occur without a force
what are some internal forces?
muscular contraction, ligamentous restraint, tendon restraint, bony support
27
NO motion can occur without a force
## Footnote
what are some external forces?
gravity, weight, friction, etc.
28
Push vs Pull
* Push creates compression
* Pull creates tension
* Movement occurs when one side of force is greater than the other (tug of war)
29
Forces are vector quantities. A vector quantity describes both ?
magnitude and direction
30
results when two or more forces are acting along the same line
Linear force
31
occurs in the same plane and in the same or opposite direction
Parallel force
32
two or more forces must act from a common point but pull in different directions
Concurrent force
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The net effect of these two concurrent forces is called the __________ force and lies somewhere in between
resultant
34
known as the moment of force
The ability of force to produce rotation about an axis
Rotary force
Torque
35
The amount of torque on a lever depends on-
1. the amount of force that is applied
2. and the distance it is from the axis
36
Torque (in the body) is the amount of force needed by a _________________ to cause\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.
1. muscle contraction
2. rotary joint action
37
“the torque arm” - is the perpendicular distance between the muscles line of pull and center of the joint (axis of rotation)
Moment arm
38
Torque is greatest when the angle of pull is at\_\_\_ degrees and decreases as the angle of pull either decreases or increases from the perpendicular position
90
39
When nearly all of the force generated by the muscle is directed back into the joint, pulling the bones together.
Stabilizing force
40
This occurs in joints when they are close to 0 degrees. They have a small moment arm, therefore the force is directed at stabilizing the joint and not at producing angular movement or torque.
Stabilizing force
41
Most of the force generated by the muscle is directed at moving the joint and not _______ the joint
stabilizing
42
As a muscle contracts, the amount of angular force or stabilizing force changes how?
Angular force increases, stabilization force decreases
43
Past 90 degrees, the stabilizing force becomes a \_\_\_\_\_\_\_\_\_\_\_force because the force is directed away from the joint
dislocating
44
Angular Force (Torque)
When the angle of pull is at 90 degrees, the perpendicular distance between the joint axis and line of pull is much larger
45
When an object is balanced and all torques acting on the object are even, the object is in a
State of Equilibrium
46
How stable is the State of Equilibrium?
Depends primarily on the relationship between the object’s center of gravity and base of support
47
the mutual attraction between the earth and an object
Gravity
48
always directed vertically downward toward the center of the earth
Gravitational force
49
the balance point of an object at which torque on all sides is equal
Center of gravity – COG
50
the part of the body that is in contact with the supporting surface
Base of Support (BOS)
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an imaginary vertical line passing through the COG toward the center of the earth (pg. 100)
Line of Gravity (LOG)
52
The degree of stability (resistance to being overthrown) of a body depends on four factors:
1. The height of the center of gravity above the base of support
2. The size of the base of support
3. The location of the gravity line within the base of support
4. The weight of the body
53
Stability is enhanced by
* Low center of gravity
* Wide BOS
* Gravity line at center of support
* Heavy weight
54
Instability is enhanced by
* High COG
* Narrow BOS
* Light weight
55
occurs when an object is in a position that to disturb it would require its COG to be raised
Stable equilibrium
56
occurs when only a slight force is needed to disturb the object
Unstable equilibrium
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occurs when an object’s COG is neither raised nor lowered when it is disturbed
Neutral equilibrium
58
Rules for COG
* The lower the COG, the more stable the object
Shorter people vs Tall people
* The COG and LOG must remain within the BOS for an object to remain stable
* The wider the BOS, the more stable the object
* When the COG is no longer over the BOS, the object will fall
* Stability increases as the BOS is widened in the direction of the force
Person vs Wind
* The greater the mass of the object, the greater the stability
* The greater the friction between the
* supporting surface and BOS, the more stable the body will be
Ice vs carpeting
* People have better balance while moving if they focus on a stationary object, not a moving object
Using adaptive equipment
59
* Playground seesaw, force is pushing up, the weight of the other child is the resistance
* If the distance is not equal between the force and resistance, more effort is needed to make the lever work.
First class levers – FAR – F=force (effort), A=axis (fulcrum), R=resistance (load)
60
Frequently used for maintaining postures or balance
Examples:
* Atlanto-occipital joint – the head is balanced by neck extensor muscle force
* Intervertebral joints in sitting or standing where the weight of the trunk is balanced by the erector spinae muscle forces acting on the vertebral axis
First Class Levers
61
Wheelbarrow – the wheel at the front is the axis, the contents is the resistance and the person pushing the wheelbarrow is the force
Second class lever – ARF – A=axis (fulcrum), R=resistance (load), F=force (effort).
62
Provide a force advantage such that large weights can be supported or moved by a smaller force
Examples:
* Limited examples in the body
* The only muscle example is the pull of the plantar flexors and the brachioradialis and the wrist extensors to maintain the position of elbow flexion
* This brachioradialis changes to a 3rd class lever when a weight is placed in the hand
Second Class Levers
63
1. The most common lever in the body
2. The resistance arm is always longer than the force arm (requires more force but moves a larger distance) and the mechanical advantage may be 0.1 or lower
3. All three levers demonstrate that what is gained in distance is lost in force and conversely what is gained in force is lost in distance
4. Third class levers typically favor distance while second class levers favor force (8-29)
Third Class Levers
64
* The brachioradialis is typically a 2nd class lever but if you put a weight in your hand, the resistance from the weight acting with gravity changes it to a 3rd class lever
* The weight of the object (5 pounds vs 100 pounds) will typically not change the class of the lever
Weight changes (8-30) Factors that can change class
65
Concentric vs eccentric movement - regarding the biceps and extension. If you place a weight in the hand and extend the elbow, your biceps is now a 2nd class lever
Factors that can change class Direction of movement (8-31)
66
The ratio between the force arm and the resistance arm
Mechanical Advantage
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The mechanical advantage (MA) of a lever is determined by?
dividing the length of the force arm by the length of a resistance arm
MA = FA / RA
If the force arm is 2 feet and the resistance arm is 1 foot, the MA would be 2
If the force arm is 1 foot and the resistance arm is 2 feet, the MA would be ½ and therefore it would have half of the torque or rotary force
68
MA = FA / RA
If the force arm is 2 feet and the resistance arm is 1 foot, the MA would be?
2
69
MA = FA / RA
If the force arm is 1 foot and the resistance arm is 2 feet, the MA would be?
½
and therefore it would have half of the torque or rotary force
70
Simple machines/levers – what is gained in force is lost in __________ and vice versa
distance
71
To move an object using less force (MA\>1) will also require that force arm to move a greater distance.
In other words, if we want to use less force we have to?
go farther to produce torque.
72
To move an object using more force (MA\<1) will require that force arm to move a lesser distance.
If we use more force, we don’t have to what?
go as far to produce torque.
73
If the MA = 1, the system would be balanced as in a?
class 1 lever
74
fyi
Less force is needed when the mechanical advantage is greater
fyi
75
In 2nd and 3rd class levers, you want to move the \_\_\_\_\_\_\_\_of weight closest to the _______ so the resistance arm is shorter
load ,axis
76
FYI-Distractive Components of Weights
Weights applied to the extremities frequently exert traction on joint structures which may or may not be therapeutically desirable
fyi
77
Consists of a grooved wheel that turns on an axle with a rope or cable riding in the groove
* Goal – change direction of a force or to increase or decrease the magnitude of a force
Pulleys
78
a simple pulley attached to a beam/weight
* Does not provide any mechanical advantage to the force, but only changes the direction
Fixed pulley
79
one end of the rope attached to a beam and the rope runs through the pulley to the other end where the force is applied
* The load is suspended from a moveable pulley and is supported equally by both segments on either side
* Half of the force is needed to lift, but the rope has to be pulled twice the distance
* Mechanical advantage of the force is 2
Moveable pulley
80
Several structures in the human body are called pulleys because they have properties of a\_\_\_\_\_\_\_pulley
single
81
A pulley may provide a mechanical advantage to the muscle by lifting the tendon away from the????
* Quadriceps and the patellar tendons
* Not only change the direction of pull as the knee flexes but improves the force arm distance because of the position of the patella
joint axis
82
Less common, but a simple machine found in the body (8-36)
* Typically used to increase the force exerted
* Large radius (wheel) requires less force and a small radius requires more force to move
Mechanical advantage, MA = radius of the wheel/radius of the axle
The larger the mechanical advantage, the easier it is to turn the handle bu_t again_ the farther the handle needs to be turned
Wheels and Axles
83
* A flat surface that slants or a ramp (8-39)
* The longer the distance of the ramp, the less effort it takes to execute the task
* The shorter the distance of the ramp, the more effort it takes to execute the task
Inclined Plane
84
