Week 3 pt. 2: Test 1

Question 1

what are the challenges of using movement analysis vs just a diagnosis

Answer 1

human movement is complex

influenced by environmental, psychologic, physiologic, and mechanical factors

Question 2

solution to using movement analysis in practice

Answer 2

start with kinematic eval (motions) and kinetics (forces)

study these effects on body

study the musculature

Question 3

what is newtons first law

Answer 3

law of inertia

body at rest will stay at rest unless acted on by an external torque

Question 4

what is newtons second law

Answer 4

law of acceleration

acceleration of a body is directly proportional to the force causing it

acceleration takes place in the direction of the force

acceleration is inversely proportion to mass

F=ma

Question 5

what is newtons 3rd law

Answer 5

for every force there is an equal and opposite reaction

Question 6

what is mass

Answer 6

property of a physical object that quantifies the amount of matter it contains

stays the same regardless of location (i.e. not gravity dependent)

resistance that a body of matter offers to change in its position or speed upon application of force

Question 7

what is inertia

Answer 7

directly proportional to mass

the tendancy of an object to remain unchanged

i.e. more inertia in a 7lb ball than a 5lb one; takes more force to move it

Question 8

what is the center of mass

Answer 8

point from which its weight force acts

closely coincides with COG

in human body, COM in anatomical position lies just anterior to S2

Question 9

what happens if COM is not supported

Answer 9

becomes unbalanced and there tends to be rotation

Question 10

describe COM in a segment of the body vs the whole extremity

Answer 10

segment = relatively stable

whole extremity = can change when the segment relationships change

Question 11

what is the difference between a force and a torque

Answer 11

force is required to start/stop/change linear motion

torque is required to start/stop/change rotational motion

Question 12

what is static equilibrium

Answer 12

linear and rotational velocities are at zero

Question 13

what is dynamic equilibrium

Answer 13

when linear and/or rotational velocities is not zero but is constant

Question 14

what is mass moment of inertia (I of a body)

Answer 14

resistance to change a body’s angular velocity

linear counterpart to inertia

depends on the mass of the body but ALSO on the distribution of mass about the axis of rotation

Question 15

describe how COM of separate limb segments can affect the mass moment of inertia

Answer 15

COM of separate segments do not move (i.e. thigh vs calf)

BUT depending on the movement of the limb, the distances of the COM segments can change relative to the axis of rotation (i.e. the hip)

this change can thus alter the mass moment of inertia

(for example extending the leg back would increase the mass moment of inertia compared to a neutral position because the calf/thigh are further from the hip)

Question 16

would a longer or shorter limb have a greater mass moment of inertia

Answer 16

a longer limb

Question 17

during the swing phase of running, why is there knee flexion and dorsiflexion

Answer 17

reduced torque needed to accelerate/decelerate

Question 18

what is the equation for torque

Answer 18

torque = F x moment arm

unit = Newton meters (Nm)

Question 19

how is torque related to mass moment of inertia

Answer 19

inversely proportional

Sum of T = I x a

Question 20

what is momentum

Answer 20

quantity of motion possessed by a body

Question 21

what is impulse? relevance?

Answer 21

force applied over a period of time

the body develops mechanisms to lessen peak external forces by prolonging the time (i.e. landing with prolonged joint motion and eccentric motion)

i.e. foot contact of gait; foot pad increases duration of loading

Question 22

what is work

Answer 22

W = force x linear displacement

or W = torque x angular displacement

Question 23

what is power

Answer 23

power = work / time or rate of work

positive power = work done by concentrically active muscles

negative power = work done by external load against eccentrically activated muscles

isometric = NO WORK

Question 24

how does newtons 3rd law apply to the human body

Answer 24

foot produces a force on the ground during walking and the ground produces a ground reaction force (GRF) in the opposite direction, but in equal magnitude

Question 25

describe posteriorly directed forces vs anterior directed forces in relation to GRF

Answer 25

posterior = i.e. initial floor contact

anterior = i.e. propulsion impulses

if they are equal, net change is 0 and momentum stays the same

Question 26

what is anthropometry

Answer 26

measurement of features of the human body

Question 27

what is the significance of joint reaction forces (JRF)

Answer 27

often major focus of treatment programs designed to lessen pain and prevent further joint degeneration in persons with arthritis

If you reduce the magnitude of these joint forces it allows changes in activation patterns that ultimately decrease the total weight transmitted through the joint

Question 28

when does Mx (x component of biceps muscle force) create a compression vs distractive force on the elbow joint

Answer 28

compressive when directed towards the elbow

distractive when directed away from the elbow

Question 29

what elbow position maximizes the potential for both internal and external torque

Answer 29

90 degrees