lecture 4: biomechaics Flashcards
what are the passive strtuctures of th musculoskeltal system
bones
carinlage
joiints
ligaments
what are the active elements of the musuloskeltal sysmte
muscles/tendons
what is the MSK system
systems capable of resisiting or generation motion at joints
what is biomechanism
the strudy of the structure and functon of living systems through principles of mechanics
what is biomechannics in terms of the MSk
largerely the study of movement (locomotion)
=forces (kinetics)
movement (kinematics
whats the name for forces
kiinetics
whats the name for movment
kinematics
what is tthe function of knowing biomechanism
treating muscles bones, joints as lever systems helps to understand their function, if if you cant remember it
why use biomechanisms for dysfunction
many patietnes will have symptoms that reflect inablity and/or weakness in performing certain movements
what is the definition of a lever
a simple machine consisting of a rigid body that can rotate at a fixed point (fulcrum) in response to forces applied somewhere along its length
what is torque
the tendency of a force to cause an object to rotate around a certain points
what is the formula for torque
torque= force x perpendicualr distance to the fulcrum (lever)
Ffor the same force, would a half lever length or full lever length generate most torque
full levre length
what happens is the force and lever are parralel
no torqur created
in the MSK, what is considered the lever
the bones
in the MSK, what is considered the fulcrums
joints
in the MSK, what is considered the forces applied
external (gravity) or muscular
=creates torques at the joints
true or false: muscles can produce force by pushing
false, muscles can only pull (ie: muscles work thru tension)
true or false and why: MSK lever systems are composite
true because there are greater than 2 muscles that generate torques on opposite sides of the joint (ie: triceps vs biceps brachii)
whta is the agonist and give ane xample
perform the action (ex: bicep flexion of elbow)
what is an antagonist and give example
performs opposite action of agonist
(ex: tricps extends the elbow)
what is the synergiest and give example
assists the agonists (brachialiss assists in. biceps in elbow. flexion)
what are. stabilizers and give. examples
stabilize the joints, fine tunes the movements
(ex: anconeus stabilizes elbow jointns in extension)
what are the muscle common external forces
gravoty
ground raection forces
friction
what are ground reactiton fcores
for every force there is an equal and opposite force (ex: gravity vs the ground pushing back p)
what is the difference between load arm and lever arm
load arm is the distance between the joints to the load
and the lever arm is the distance btween the joints (fulcrum) to the muscles line of action
external force is AKA
load
distance to. load is AKA
load arm
internal muscle force is AKA
effort
distance to effort is AKA
lever arm
when is equilibrium reached
torques are equal and cancel out (effort=load)
how do we get from torque to actual angular motion
torques are not equal
angular motion (rotation) direciton and speed depends on which torque is greatest
what is angular motion
force that generations rotational force
what does angular motion’s speed and direction depend on
which troque is greatest
Picture a man holding the points stead (equilibirum), explain the muscle involvement and the torques
isometric contraction of the biceps (effort) that generates equal and opposite torque to resist the torquecreated by weight of the pint
picture a man taking a sip of his beer and explain the muscles and torqur involved
biceps torque is greater tthan the pint torque
=causes elbow flexion through concentric cocntraction of the biceps (fibers shortneing)
picture a man putting his beer down after drinking and explain the muscles and torqur involved
pint torque is greather than biceps torque which causes elbow extension but controlled through the eccentric conraction of the biceps
how can you get more torque
increase the force (ie: larger muscle)
longer lever arm
increase D (upside down T)
how can some mnuscle lever systems be boostted
by bony protructions that length the lever arm (exL processes, tubercles
=improves muscle ability to generate torque)
when you squat, what external force is applied to the femur and what torque is produced at the knee
trunk weight
what kind of angular motion would squatting created
flexion of the knee
what would resistt the trunk weight
extensors of the knee (quads)
how does quadricep effort chagne with increases knee flexion
incrase flexion=increase effort (more gravity load arm increases)
how does muscle contrtaction change with increasing/decreasing flexion
static=iso
down squation-eccenttric
up squat= concentric
angular motion AKA
rotation
fulcrum defintion
center of rotation= axis
external force aka
load
out-force
resistnace
internal force AKA
muscle force
effort
load arm is condiered what lever
out lever
lever arm is consideered what lever
in. lever
what is the def of torque
moment of force
