ES370- torque and moments

definition and formula of torque

-turning effect produced by a force

-angular or rotary force

-T = F x r

torque is motion of a _______ system. ___________ is fixed in space

-restrained

-axis of rotation

the line of action of the force must be ________ from a system, not _________ it

-away

-through

what is the perpendicular rule when calculating torque?

either force or radius must be perpendicular to one another *not both

moment arm definition and formula

-the shortest perpendicular distance between the axis of rotation (r) and the line of action of force (F)

-radius must be ⟂ to force

-T= F x r⟂

lever arm definition and formula

-perpendicular distance between the point of force application (F) and the axis of rotation (r)

-force must be ⟂ to radius

-T= F⟂ x r

factors that influence torque

magnitude, point of application, direction (linear), and line of action

a counterclockwise direction generates a ______ torque and a clockwise direction generates a ________ torque

-positive

-negative

torque production is ________ throughout ROM. this contributes to why there is a _________ _________ in lifts

-variable

-"sticking point"

the ________ also changes throughout ROM

moment arm (Dperp)

at what ROM is elbow torque the greatest?

mid range

what is the fastest and easiest way to change a torque?

change the radius

according to static equilibrium, the sum of all torques should equal

0

how would a patellectomy affect torque production?

-torque production and quadriceps moment arm would be reduced.

-patella increases moment arm

all muscles generate _________ _________ which produce ___________ __________ about the joints they cross

-internal forces

-internal torques

as the moment arm of an external torque increases, what also increases?

the contribution of muscle force to movement

ex: in a lateral shoulder raise, holding the weights further from the body requires greater torque (greater radius)

how does a low squat bar placement influence moment arm and muscle force contribution?

-even split for the hip and knee

-greater moment arm for hip flexors

how does a high squat bar placement influence moment arm and muscle force contribution?

-greater moment arm in knee

-quad dominant

how does a front squat bar placement influence moment arm and muscle force contribution?

more hip flexor and quad dominant

human motion is considered to be what kind of motion?

-combination of translation and rotation (general motion)

-generated by a series of torques

how do muscles contribute to internal moments?

-generating muscle forced (muscle tension)

-acting as a muscle lever arm (origin/insertion distance to joint axis)

concentric contractions occur when muscle internal moment and motion is in the ________ direction

same

characteristics of the rotary muscle force component (Fr)

-perpendicular to the bone segment

-creates internal moment

-creates motion

characteristics of the non-rotary muscle force component (Fnr)

-perpendicular to rotary component, parallel to bone segment

-does not contribute to internal moment

-causes joint compression (stabilizing) or distraction (destabilizing)

-maintains joint integrity, benefits ligament injury

joint position influences the _________ and ___________ of muscle force components

-magnitude

-direction

the angle formed by the line of action and bony segment dictates the:

ratio of rotary to non rotary components

the internal moment created by a muscle is dependant on 3 things:

-muscle force (F)

-radius or moment arm (r)

-angle of pull

joint torque consists of _________ and _____________ contributions

-muscle (internal)

-non-muscle (external)

what may occur when muscles produce multiple torques? what direction will motion occur in?

-muscles create opposite joint torques (agonist/antagonist)

-motion occurs in the direction of the net torque

what is the purpose of the antagonist muscle during co-contraction (3 things)?

-control velocity of motion

-maintain joint integrity (stabilizing/ compressive)

-can benefit ligament injury

in static equilibrium, muscles produce _________ ____________ (no changes in angles, in line with static equilibrium)

isometric contractions

a force couple is an __________ and __________ pair of forces. positioned on the __________ sides of the axis of rotation. produces torque in the ________ direction

-equal and opposite

-opposite

-same

in the human body, what is an example of an external moment (non-muscle contribution)?

-segment mass (bone) will cause a joint moment

-any external object attached or held by segment will produce a joint moment

equilibrium is a state characterized by _________ forces and torques

-balanced

-zero net forces and torques

-motionless or static

3 conditions for static equilibrium

-sum of all horizontal forces equals 0

-sum of all vertical forces equals 0

-sum of all torques equals 0