Kinetics Flashcards
What is a force?
a push or a pull that can produce, arrest or modify movement
what is the equation for force?
F=ma
what is forced measured in?
Newtons
what is force directionally proportional to?
acceleration of mass
What structure of the human body produce the greatest force?
muscles
What is a vector?
a vector has a magnitude and direction; represented by arrows
what is an example of point force application?
center of pressure
what is a musculoskeletal loads?
force that acts on the body
What are ground reaction forces?
arise as our body makes contact with the ground
What is dynamic valgus?
movement pattern known to be and at risk movement pattern for ACL injury
What are externally derived loads?
Gravity
impact
friction
wind
What cause internally derived body loads?
muscle activation
tissue deformation
joint reaction force
What is a joint reaction force?
force that arises in response to another force
How do healthy tissue respond to load?
deform but resist change in structure and shape
what is load response dependent on?
tissue
What is tissue stress?
force or load generated within the tissue that resists deformation, divided by its cross-sectional area
Stress-Strain Diagram
x-axis: % of stress measured
Y: tissue stress measured in Newton millimeters squared
stress is the amount of force arising within the tissues to resist components or particles from being pulled apart
strain represents how much that tissue changes as its loaded; percent deformation
What tissue strain?
amount a tissue deforms under force or load; usually expressed as a percent change in length (%) or distance (mm)
What does the toe region represent?
Tissue is being loaded need to take up slack
what does the slope of linear represent?
the stiffness of the tissue also known as Young’s modulus
what is Hooke’s laws?
in the elastic limits of the tissue, the relationship between stress and strain is linear
what is Young’s modulus?
linear relationship which represents the stiffness in tissue
Is the slope higher or lower when the stiffness is high?
High
Is the slope higher or lower when the stiffness is low?
Low
What does the elastic region represent?
deformation energy when tissues returns to its original shape or length after loading; all stored energy is released
What is the yield point?
transition between elastic and plastic; load results in a marginal increase in stress
What causes plastic deformation?
micro-failure of tissue under continued load
What happens during plastic deformation?
tissue is permanently deformed; energy cannot be recovered once load is released
what is ultimate failure point?
tissue fails and is unable to hold additional load
What tissues are viscoelastic?
Bone
Muscle
fibrocartilage
capsule and ligament
tendon
articular cartilage
What is viscosity?
fluid like component to behavior of tissue
What is elasticity?
ability of material to return to its original shape after loading
What is creep?
continued deformation of material over time as it is subjected to a constant load
What factors impact Musculoskeletal loads?
Loading magnitude
loading rate
loading type
what is loading magnitude?
how much a tissue is loaded
what is loading rate?
the speed at which a tissue is loaded
What is loading type?
the way in which tissue is loaded
What are the types of musculoskeletal loads?
Unloaded
Tension
compression
bending
shear
torsion
combined loading
what is tension loading?
two forces pull on an object in different directions
ex: ankle sprain
what is compression loading?
forces that push or pull the surface of objects together or brings the end of an object closer; arises via muscle contraction
ex: humerus pulled against glenoid by deltoid muscle
What is bending load?
deformation of tissue that occurs at right angles to its longitudinal axis
ex: coxa vara results in an increased bending load on the neck of the femur
During Bending load which side undergoes compression load?
Concave side
During bending load which side undergoes tension load?
convex side
What is shear load?
unaligned parallel force that move on part of a body in one direction and another part in the opposite direction
ex: Cam type morphology in femoroacetabular impingement syndrome creates abnormal shear load between the femur and acetabulum