Fundemental Physics Of Tissues Stress Model Flashcards
Force
A push or pull on an object that can cause a change in motion (induce acceleration) or deformation of a mass
Stress
Intensity of internal forces within an object
Causes mechanical failure
Pressure
Force applied perpendicular to unit surface area
Surface stresses = pressures
Strain
Relative amount of deformation of an object when it is subjected to load
Describes change in length relative to the starting length of the object when loading force is applied
Stress and strain
Steeper = higher stiffness
Flatter = lower stiffness
Yield stress = ultimate stress
End = ultimate tensile stress
Issues with root theory
Reliability of measurement; no agreement on measurement of stj neutral as well as passive rom of the stj
Criteria for normal foot alignment - suggests criteria is too stringent and restrictive for the general population
What is the tissue stress mode,
“Injury occurs if the mechanical stresses acting on the tissue are beyond the tolerance of the tissue. Therefore, treatment is directed at reducing the load acting on the tissue and increasing tissue capacity
Stress on tissues - elastic and plastic region and biological responses to stress
Elastic - normal give and take of soft tissues, overuse avoided, tissue irritation and inflammation will be maintained at a tolerable level
Plastic - result in overuse injuries, damage to tissues
Biological - wolf and Davies laws
Mechanism of injury
When the stresses on the tissue are causing more damage than the body can repair
- one off very high stress
- moderate stress applied repetitively or for a long time
Stress and types
Ability of an object to develop internal resistance to loading force
2 types: axial and shear
Axial stress
Tensile stress
Compressive stress
Shear stress
Friction between structures
Non-uniform stress on muscle fibres
Stress between facial layers
Attachment of tendons/d fascia to bone
Bending
Induces compressive and tensile stress (greatest further away from the centre)
Torsion
Induces shear stresses - greatest further away from axis of rotation
Mcppoil and hunt 4 step to assessing and managing mechanical stress-related pathology
- History and identification of stressed tissues
- Application of controlled stresses to involved tissues
- Assessment of pt complaint
- Management program
Can stress be measurement
No directly measured