Week 1- Kinetics of Human Movement Flashcards
Kinetics
A branch of the study of mechanics that describes the effect of forces on the body
Force
Push or pull that can produce, arrest, or modify movement
Load
Force acting on the body
How do healthy tissues respond to changes in structure and shape
Typically able to partially resist changes in structure and shape
Stress
Force generated as a tissue
resists deformation
Strain
Ratio of a tissue’s deformed
length to its original length
Regions of the Stress-Strain Curve
- Nonlinear region
- Linear region
- Elastic region
- Yield point
- Plastic region’
- Ultimate failure point
Nonlinear region of the Stress-Strain Curve
- Unloading, or “uncrimping” of tissue
- Up to ~2% of strain
Linear/elastic region of the Stress-Strain Curve
- Physiologic upper limit of tissue strain
- Experience stretch
- If strain < 4%, tissue will return to original length
Yield point of the Stress-Strain Curve
The change in length is reversible
Plastic region of the Stress-Strain Curve
Change in length is NOT reversible
Ultimate failure point of the Stress-Strain Curve
Microfailure accumulates until irreversible deformation takes place
Tension
Equal and opposite loads applied away from the surface of a structure
Compression
Equal and opposite loads applied toward the surface of a structure
Shear
Opposing loads applied parallel to the surface of a structure
Torsion
Opposing loads are applied to
the surface of a structure resulting in twisting about an internal axis
Bending
Combination of three or more loads applied to a structure, causing it to bend about an axis external to itself
Combined forces
Combination of two or more loading modes applied to a structure at the same time
Viscosity
Ability of a material to resist flow and dampen shear forces
Elasticity
Property of a material demonstrated by its ability to return to its original length after the removal of a deforming force
Viscoelasticity
- Property of a material expressed by a changing stress-strain relationship over time
- Exhibited by all body tissues in which the properties of viscosity & elasticity are combined
Time-Dependent Properties
- Creep
- Hysteresis
- Stress-relaxation
Creep
Progressive strain of a material when exposed to a constant load over time
Hysteresis
- Lag of an effect when forces acting upon a material are changed - Energy is often lost as heat
Stress-relaxation
Decrease in the stress within a structure in the presence of a constant strain
Internal force
Produced from structures within the body (active or passive)
External force
Produced by forces outside of the body (eg. gravity, physical contact, etc.)
Internal torque
Product of the internal force (muscle) and internal moment/lever arm
Internal Moment Arm
Perpendicular distance between axis of rotation and the internal force
External Torque
Product of external force (eg. gravity) and the external moment arm
External Moment Arm
Perpendicular distance between axis of rotation and the external force
