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25 Cards in this Set
- Front
- Back
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what is a lever system
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levers which rotate around a axis by means or external force a basic way to transmit energy and do work energy is derived from muscle contraction
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what is the point of application
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point at which contracting muscle is attached to the moving bones (insertion0
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what is effort
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force acting at its point of application
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what is effort arm
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movement arm for effort distance from the axis of rotation to the point of muscle attachment (origin)
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what is the point of acceleration of resistance
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center of gravity of mass of the lever (point of balance)can change with weight of object
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what is resistance
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force acting at its application point having a vector in the opposite direction of the effort
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what is the resistance arm
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moment arm for resistance distance from th axis of rotation to the resitance vector
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what is a second class lever
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EA>RA
magnifies force |
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What is a third class lever
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RA>EA
magnifies speed |
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what does tension in the ligaments do
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resists motion at weight bearing joints
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what factors limit the ability to stand in the static position
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forces compressing bones against each other
tension of ligaments resist motion motion occurs stretching ligments |
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why does the static position require momentary muscle contraction
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to reestablish osseous position and relieve tension on the ligaments
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what is hypermobility
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any motion in a direction outside its normal plane of motion causes instability
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what does hypermobility cause
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momentary subluxation of a joint
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what is subluxation
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a state of partial dislocation joint margins compress on one side and seperate on the opposite side
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what are the results of subluxation
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functional adaptations or degenerative joint disease
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what are the two forces acting on weight bearing bones
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compression force
rotational force |
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what does compression force do to stability
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enhances osseous stability
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what does rotational force do to stability
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ehances osseous instability
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what happens when angulation of forces at a joint are small
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compression is achieved and stability is increased
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what happens when angulation of forces at a joint are large
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more rotational force is seen creating instability
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what effects does muscle activity have on angulation at a joint
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keeps angulation of forces low increasing stability
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what happens to angulation in a pronated foot
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increases angulation and decreases stability
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what happens to angulation in a supinated foot
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decreased angulation and increased stability
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what is a result of muscles having to work harder to maintain stability
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muscle imbalance
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