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Biomechanics Exam 3 > EQUILIBRIUM + REVERSE DYNAMICS > Flashcards

EQUILIBRIUM + REVERSE DYNAMICS Flashcards

1
Q

dynamometry

A

direct measurement of force + torques using instrumentation
-often specific to tissues

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2
Q

what is dynamometry NOT good for

A

full body kinetic analysis of complex movement

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3
Q

inverse dynamics

A

-process of indirectly quantifying net joint forces + net joint moment from kinematic motion capture data + typically ground reaction force data from force plates
-it is a method involving sequential equilibrium analysis of segments of the kinetic chain of the body starting with a distal segment + moving proximally

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4
Q

what is inverse dynamics good for + not good for

A

-great for full body joint-wise kinetic analysis
-limited to providing tissue specific info

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5
Q

what are measured with a force plate

A

-GRF
-free moment
-COP

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6
Q

what are the unknowns of solving equilibrium/inverse dynamics

A

-joint reaction force
-joint moments

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7
Q

what are the inputs for inverse dynamics problems

A

-motion capture
-manual measurements
-force plates

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8
Q

for inverse dynamics, where do we always start

A

distal segment
-this is where forces are known since we use GRF

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9
Q

moment of force

A

the turning effect of applied forces

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10
Q

force applied that acts through the COM causes what acceleration + what moment of force

A

-only linear acceleration
-no moment of force

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11
Q

force applied that doesn’t act through COM (force is on only one side of something) causes what acceleration + what moment of force

A

-linear acceleration
-rotation, moment of force

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12
Q

closer you hit to COM, smaller/larger the moment (turning effect)

A

smaller

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13
Q

a force causes what acceleration + what moment of force

A

-net acceleration = 0
-net force = 0
-there is still a turning effect

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14
Q

do pure moments cause translation

A

no- they are pure torque

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15
Q

force couple

A

2 opposopposing forces (equal + opposite direction) applied to different ends of a body (different but parallel lines of action) whose effect is a pure torque or moment

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16
Q

what do we use joint reaction force for

A

-helps us move up the kinetic chain to solve for other joint torques + joint reaction forces
-estimate of the joint contact force

17
Q

increased co-contraction causes what

A

higher contact force

18
Q

what does loading of a joint tell us

A

says something about the degradation of the cartilage at that joint; joint space becomes very narrow

19
Q

do joint replacements have a life span

A

yes
-if someone gets a joint replacement relatively young, will probably need a replacement before they die

20
Q

instrumented joint replacements

A

joint replacements with strain gauges (transducer converting force to an electrical change in voltage) + transmitter (so there are no wires sticking out of the joint to directly read joint contact forces

21
Q

internal joint moment

A

what you generate with the muscles + tissues of the body
-ex: flexor torque of knee
-roles are to resist load + generate acceleration of that joint

22
Q

external joint moment

A

moment being applied; essentially what would happen to that joint of your body if you were to relax

ex: force of gravity, GRF, etc.; force that will move joint in absence of muscle activation

23
Q

true/false: you may begin inverse dynamics analysis at any segment of the body

A

false

24
Q

typically in solving equilibrium + inverse dynamics problems for a segment of the body, what are our unknowns in that are solve for (rather than measured/estimated) in the equilibrium equations? (mark all that apply)

-joint moment
-GRF acting on the segment
-joint reaction force
-force due to gravity acting on the segment

A

-joint moment
-joint reaction force

25
Q

which of the following is an accurate description of the process of inverse dynamics?

-using movement kinematics + GRF to calculate over joint kinetics
-using kinematics + GRF to calculate muscle forces
-using joint moments to find body segment accelerations

A

using movement kinematics + GRF to calculate over joint kinetics

26
Q

true/false: for inverse dynamics it is good enough to draw a free body as a single point through which all forces touching that body act

A

false

27
Q

moving up the kinetic chain (from 1 segment analysis to the next) in inverse dynamics is possible because of…

-Newton’s 3rd law
-Newton’s 1st law
-Hooke’s law
-Newton’s 2nd law

A

Newton’s 3rd law
-Newton’s 3rd law allows us to move up the chain by applying an equal + opposite joint moment + joint reaction force to the next segment in the chain

28
Q

true/false: inverse dynamics can tell you how much torque a specific muscle is generating during a complex movement

A

false

29
Q

dynamometry has which of the following features?

-it indirectly calculates forces
-it provides a “zoomed out view” of the kinetic strategies of a complex movement
-depending on the instrumentation it MAY BE tissue specific
-it doesn’t require any instrumentation to measure forces

A

depending on the instrumentation it MAY BE tissue specific

30
Q

what contributes to a joint torque/moment calculated via inverse dynamics?

-muscles
-bony contact
-all of these
-ligaments

A

all of these

31
Q

an isometric contraction should be related to ____

-no mechanical work performed
-positive mechanical work performed
-negative mechanical work performed

A

no mechanical work performed

32
Q

what would be the instantaneous power of the force due to gravity at the apex of vertical projectile motion?
consider v1 to be the initial projectile motion velocity, d to be the height of the projection, t to be the flight time up to the apex, and v2 to be the velocity at the apex

-Fg*(v2+v1)/2

-zero

-Fg*d/t

A

zero

33
Q

consider the point mass method for calculating work done by the body. what would be the work done if the person ran downhill at a constant velocity over a given nonzero time interval?

-zero
-negative
-positive

A

negative

34
Q

what does the area underneath the instantaneous power curve represent?

-work
-impulse
-force
-velocity

A

work

35
Q

true/false: gas exchange would be a good way to measure the physiologic cost of the high jump in effort to quantify the mechanical efficiency of the movement

A

false

36
Q

mechanical efficiency is used for what type of movements

A

steady state- running, cycling, etc.
-not something like powerlifting

37
Q

primary muscles involved in jumps (same for all)

A

-gluteus maximus
-quadriceps femoris
-gastrocnemius

Biomechanics Exam 3 (5 decks)

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