Lecture 18 Flashcards
What is whole body center of mass located on the body
Approx just in front of lumbosacral junction in standing posture
May move outside the body
What is center of gravity
The point through which the force of gravity acts on an object or system
COM and COG have the same…
Position
Tissue mechanics focuses on
Bones
Ligaments
Cartilage
Tendons
What is a load
An externally applied force
What are the different types of loading
Axial
Bending
Shear
What is axial loading
Loading acts along longitudinal axis of a body
What is involved in axial loading
Compression
Tension
What is compression
A load that squeezes the parts of a body together
What is tension
A load that pulls the parts of a body apart
What is bending loading
A load applied perpendicular to the longitudinal axis of a body causing a body to curve
What is involved in bending
Three point bending
Four point bending
What is three point bending
Three forces applied
What is four point bending
Four forces applied
What is the effect of bending determined by
Cross section area
Length of body
Distribution of the material around the neutral axis
What is area moment of inertia
Combined effect of cross section area and how it is distributed from the neutral axis
A measure of the bodys resistance to bending
During bending what loading occurs on one side and what loading on the other side
Tensile loading on one side
Compressive loading on the other
What is shear loading
Two forces are directed towards each other
But the forces are not along the same line and instead they are directed parallel to the surface of a structure
What does shearing cause to happen to an object
Two surfaces to move in opposite parallel directions
Causes one part of the body to move parallel past another part
What is Shear loading broken up into
Direct
Torsion
What is torsional loading
Loads that exists when there is a twist around the neutral axis
What is stress
What is the equation
What is the unit
The way a force is distributed within a body
Force / area
Unit N/m^2
What is strain
The change in dimension normalized to the original dimension
What is the equation of strain
Change in dimension / original dimension
What is the equation for elastic modulus
Stress / strain
What is strain energy
The amount of energy that the body can absorb as it deformed
What is strain energy density
The amount of energy that can be absorbed by a normalised piece of tissue
What is bones function
Provides a rigid framework that gives body shape
Functions as a set of rigid links and mechanical levers
Provides attachment sites for muscle tendon complexes
Protects the CNS and various internal organs
What is bone mineral content
Total amount of mineral in bone
What is bone mineral density
The mineral content in an area or volume of bone
Overall strength of the bone is affected by
Bone mineral density
Where the bone is placed
Bone is considered…
Why
Asymmetric
Bone is stronger in compression vs tension
Bone is stronger in tension vs shear
Males have greater… (bone)
Peak bone mass
Rate of gain for bone mineral content
Females have… (bone)
Transient decrease in bone mass around the menopause age of 45 - 60
Bone is a what tissue
Dynamic
Disuse and aging have what effect on bones
Inverse relationship with bone health
Exercise has what effect on bones
Beneficial effect on mechanical properties of bone
Weight bearing exercise has what effect on bones
Direct relationship with bone health
Exercise should be: (in order to help bone health)
Dynamic loading
Moderate to high loading rate
Short duration
Long rest periods - allows tissue adaptation to new load
