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Biomechanics PT > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

When does equilibrium happen?

A

this exist when object are at rest where all the F acting upon a body are balanced

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2
Q

What is a lever

A
  • simple machine
  • elongated, ridig object
  • rotates around fixed point ( axis)
  • has ability to change sped, distance, direction of applied force, force strength
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3
Q

What is an effort of a lever

A

this is a force applied to one point

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4
Q

what is a resistance

A

this is the load located at some other point

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5
Q

what is the effort arm

A

part of the lever from axis to point of effort or F

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6
Q

what is the resistance arm

A

part of lever from axis to point of resistance or load

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7
Q

when will movement happen?

A

this will occur when effort exceeds resistance

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8
Q

What is a 1st class lever

A

effort —–axis—— load

  • axis is always in the middle
  • can create a balance
  • see saw
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9
Q

what is a 2nd class lever

A

axis——load——-effort

  • the lad will also be closer to the axis
  • will over come a large resistance
  • wheel barrow
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10
Q

what is a 3rd class lever

A

axis—-effort—– load

  • effor arm will always be shorter than load arm
  • ↑ ROM and ↑ speed
  • your arm
  • the most in the human body
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11
Q

what is dynamic equilibrium

A

bodies in motion with all acting forces resulting in equal and oppositely directed inertial f

  • sum F(x) -ma(x)=0
  • sum F(y) -ma(y)=0
  • sum T(G) - ix=0
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12
Q

what is stability

A

resistance to both linear and angular acceleration. so basically resistance to disruption of equilibrium

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13
Q

what is balance

A

ability to control equilibrium

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14
Q

what is center of gravity

A

the point aroudn which a body weight is equally balanced in all direction

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15
Q

what is the line of gravity

A

vector from the COG vertically downward toward the center of the earth

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16
Q

what is the base of support

A

area bound by the outermost regions of contact between a body and the support surface
(if your line of gravity in the base of support you will be stable)

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17
Q

what can increase a bodys stability

A

↑ body mass
↑ Fr btwn the body and the surface of contact
↑ the size of the bos in the direction of an external force
-horizontally position the COG near the edge of the BOS on the side of the external force
-vertically positioning the COG as low as possible

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18
Q

what is stress

A

external force on body are resisted by internal forces

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19
Q

what is strain

A

external forces that caused deformation of tissue

-deformation will all depend on the tissue

20
Q

what is Tension

A

occur at analysis plane and result of force that tends to pull apart molecules that bond object together

  • act L to analysis plane
  • Stress= F/A
21
Q

What is compression

A

axial stress that tends to push molecules together

22
Q

what is shear

A

this act parallel to analysis plane

- tends to slide molecule past each other

23
Q

what is bending

A

this will produce different stresses at analysis plan

  • will have deformation by curving
    • tension on the elongating side
    • compression on the shorten side
24
Q

what is torsion

A

occurs when torques act about the long axis of an object and has shear force btwn molecule of left/ right side of analysis plane

25
Q

what is stiffness

A

ration of stress/strain in a loaded material

– this is the extent to whcih it resists deformation in response to an applied force

26
Q

what is the yield point

A

is the point the stress strain curve where additional stress will cause permanent change

27
Q

what is toughness

A

ability of tissue to absorb energy

28
Q

what is collagen

A
  • fibrous protein
  • most in connective tissue
  • the arrangement provide low failute strain and high tensile strenght
  • BUT unable to resist compression
29
Q

what is Bone

A
  • absorbs majority of compression
  • -30-35% collagen
  • -1-2% ground substance
  • -45% mineral
  • -20% water
  • – how health and how well it works depends on age and health
  • BUT weakest in shear
30
Q

what are the 3 types of cartilage

A

1 hyaline cartilage- best at compression
2 fibrocartilage- compression and tension
3 elastic cartilage- more elastic

31
Q

What are tendon and ligaments

A

–70% water
–25% collagen
–5% groudn substance
fibers are // or nearly // to the functional axis
** ligs are more elastic then tendons
*** ligs have high tensile strength but no compression or shear and are weaker than tendons

32
Q

what are the 2 component of a muscle

A

Active- contraction determines stiffness

Passive- muscle stretched

33
Q

what is Parallel elastic component

A

passive elasticity derived from muscle membranes

34
Q

what is series elastic component

A

acts as a spring to store elastic energy in tendons

35
Q

what is concentric

A

involving shortening

36
Q

what is eccentric

A

involving lengthening

37
Q

what is isometric

A

involving no change

38
Q

what are parallel fibers of a muscle

A

they are // with the longitudinal axis of the muscle. doesnt have to extend the whole muscle

  • PCAS= small (force producing ability)
  • Force=small
  • ROM=large
39
Q

what are pennate fiber of a muscle

A

lie at an angle to the longitudinal axis of the muscle and attaching to the tendon and will extend the entire length of the muscle
** the angle of the pennation ↑ as tension ↑ in the muscle

  • PCSA= huge (force producing ability)
  • Force= huge
  • ROM= small
40
Q

force - velocity relationship

A

look at graph in slides page 5 (3b)

41
Q

what is stretch- shortening cycle

A

actively tensed muscle that is stretched just prior to contraction result in a more forceful contraction than the absence of the prestetch
**think of the reason you bend down before you jump

42
Q

what are some factors that affect muscular strength

A

tension generating

moment arms

43
Q

what is tension generating

A

capability of the mscle tissue whcih is in turn affected by

  • -muscle cross section area
    • training state of muscle
44
Q

what is moment arms

A

they are the muscle crossing the joint in turn affected by:

  • -distance btwn muscle attache to bone and joint center
    • angle of the muscle attachment to bone
45
Q

muscular strength

A

read the last slide on 3b page 6

46
Q

equation for linear strain

A

e= change in length/ original length

47
Q

equation for elastic

A

E= change in stress / change in strain

Biomechanics PT (7 decks)

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