Musculoskeletal Flashcards
Define angle of pull
The angle formed by the muscle force vector relative to the bone on which the muscle is attached
What does the angle of pull depend on
The origin and insertion of the individual muscle
What does the angle of pull vary with?
- The joint angle
- The origin and insertion
What is the rotary component of the resultant force vector?
vertical/perpendicular ocmponent
T/F The vertical/perpendicular component never passes through the axis of rotation
True
What is the stabilizing/ destabilizing component of the resultant force vector?
The horizontal/parallel component
T/F The horizontal/parallel component never passes through the axis of rotation
False, it always passes through the axis of rotation
The angle of pull affect the ______ ______ of the _____ and ____ components of the resultant vector
Relative magnitudes; perpendicular; parallel
What does the angle of pull also affect?
The direction of the parallel component of the resultant vector
T/F A muscle that acts primarily as a stabilizer during one action may act as the primary rotator in a different action
True
Why can’t some muscles achieve every angle of pull?
Because of constraints of origin and insertion
Hamstrings
Rotary and stabilizing/destabilizing
Gastrocnemius
stabilizing
Popliteus
Rotary and stabilizing/ destabilizing
Links = _____
joints
Bones = _____
Semi-rigid bodies
How is force applied in the human body and what does it cause
Force is applied to segments by muscle contractions causing motion at the joints
What is the most abundant type of lever in the human body
Third class lever
Where is the motive force (muscle) in a third class lever system?
Between the fulcrum (joint) and resistive force (segment)
Why does human torque production have a mechanical disadvantage?
Because it uses a third class lever system
How do you compensate for mechanical disadvantage?
reducing segments moment of inertia
How do you reduce a segments moment of inertia
- reduce the mass
- keep the mass close to the axis of rotation
What reduces mass in the body
Bones because they are hollow
Where are the muscles located that move one segment
They are located on the more proximal segment
What is the only thing attached to the segment of interest?
The distal tendon
Each successively proximal segment must have _____ muscle ____ because more ____ is needed
more; mass; torque
Why is more torque needed for limb mass distribution?
- To accelerate each progressively more massive segment
- to drive the inertias of all distal segments
What kind of effect is created in limb mass distribution
A tapering effect
Where is most of the mass located and what does it lower?
Most of the mass is located near the axis of rotation and it lowers the rotational inertia
