EQUILIBRIUM + REVERSE DYNAMICS

Question 1

dynamometry

Answer 1

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

Question 2

what is dynamometry NOT good for

Answer 2

full body kinetic analysis of complex movement

Question 3

inverse dynamics

Answer 3

-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

Question 4

what is inverse dynamics good for + not good for

Answer 4

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

Question 5

what are measured with a force plate

Answer 5

-GRF
-free moment
-COP

Question 6

what are the unknowns of solving equilibrium/inverse dynamics

Answer 6

-joint reaction force
-joint moments

Question 7

what are the inputs for inverse dynamics problems

Answer 7

-motion capture
-manual measurements
-force plates

Question 8

for inverse dynamics, where do we always start

Answer 8

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

Question 9

moment of force

Answer 9

the turning effect of applied forces

Question 10

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

Answer 10

-only linear acceleration
-no moment of force

Question 11

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

Answer 11

-linear acceleration
-rotation, moment of force

Question 12

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

Answer 12

smaller

Question 13

a force causes what acceleration + what moment of force

Answer 13

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

Question 14

do pure moments cause translation

Answer 14

no- they are pure torque

Question 15

force couple

Answer 15

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

Question 16

what do we use joint reaction force for

Answer 16

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

Question 17

increased co-contraction causes what

Answer 17

higher contact force

Question 18

what does loading of a joint tell us

Answer 18

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

Question 19

do joint replacements have a life span

Answer 19

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

Question 20

instrumented joint replacements

Answer 20

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

Question 21

internal joint moment

Answer 21

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

Question 22

external joint moment

Answer 22

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

Question 23

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

Answer 23

false

Question 24

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

Answer 24

-joint moment
-joint reaction force

Question 25

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

Answer 25

using movement kinematics + GRF to calculate over joint kinetics

Question 26

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

Answer 26

false

Question 27

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

Answer 27

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

Question 28

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

Answer 28

false

Question 29

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

Answer 29

depending on the instrumentation it MAY BE tissue specific

Question 30

what contributes to a joint torque/moment calculated via inverse dynamics? -muscles -bony contact -all of these -ligaments

Answer 30

all of these

Question 31

an isometric contraction should be related to ____ -no mechanical work performed -positive mechanical work performed -negative mechanical work performed

Answer 31

no mechanical work performed

Question 32

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

Answer 32

zero

Question 33

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

Answer 33

negative

Question 34

what does the area underneath the instantaneous power curve represent? -work -impulse -force -velocity

Answer 34

work

Question 35

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

Answer 35

false

Question 36

mechanical efficiency is used for what type of movements

Answer 36

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

Question 37

primary muscles involved in jumps (same for all)

Answer 37

-gluteus maximus -quadriceps femoris -gastrocnemius