practice/quiz questions EXAM 1

Question 1

which of the following force vectors acting on a segment has the greatest moment arm for the axis of rotation if all vectors are the same magnitude?

Answer 1

3

• the perpendicular distance between the line of force and the axis of rotation is the greatest

Question 2

flexion of the skater’s right knee is about which axis of rotation?

Answer 2

mediolateral

• tibia is flexed relative to the knee

Question 3

the position of two runners at 0.2 s intervals are represented by the colored squares below. the runners (squares) are moving from left to right. the acceleration of the runners are related as follows:

Answer 3

acceleration of A=B

• the acceleration of both is 0 - they have the same velocity the whole time

Question 4

the two position/time graphs indicate motion of an object over time. distance traveled by each object are related as follows:

Answer 4

distance A > B

• the area under the curve = the distance traveled
  
  • curve A has more area, so it has more distance

Question 5

the muscle force vector (M) will create a compressive force and a moment at the knee joint. the magnitude of the compressive component is ___ the perpendicular component creating the knee moment.

Answer 5

greater than

• vector composition: M_x > M_y

Question 6

estimate the location fo the person’s whole-body center of mass in each of the pictures below

Answer 6

red is original COM, green is new COM with movement

Question 7

the position of the pitcher’s right hip

Answer 7

flexed, internally rotated, abducted

• left hip higher than the right, so the right hip is abducted

Question 8

at the knee during a downward squat, what arthrokinematic motions do you expect?

Answer 8

femur roll into flexion, anterior glide

tibial roll into flexion, posterior glide

Question 9

consider a tissue placed under strain and stretched into the elastic region of the stress-strain curve without injury. when the load is removed the tissue will:

Answer 9

lose energy

• hysteresis

Question 10

the greatest total force of a maximally active muscle will be at

Answer 10

the longest physiologic length of the muscle

• the greatest active force would be at the intermediate length near the resting length

Question 11

if the hip were in anatomical position and the knee was fully extended, what would the relative length of the hamstring muscle gorup be on the x-axis of the diagram?

Answer 11

160

• 280 (full hamstring length) - 120 (if hip was flexed) = 160

Question 12

consuder the gluteus maximus and semitendinosus of the person in the figure for the LE that is being raised. which muscle has a greater moment arm for creating a hip extension moment?

Answer 12

gluteus maximus

Question 13

according to the chart, which of the following muscles are concentrically active during the pre-swing (PSw) phase of gait?

Answer 13

soleus

Question 14

if the person in the picture is slowly lowering the hand weights from position A to B, what is the primary active muscle at the glenohumeral joint?

Answer 14

anterior deltoid

• line of pull - eccentrically

Question 15

if the person in the picture is slowly lowering the hand weights from A to B, what is a helping synergist muscles working with the anterior deltoid?

Answer 15

biceps brachii

Question 16

in the picture, what are the internal and external moments acting on the right leg and foot segment?

Answer 16

weight of the body

JRF

GRF

probably some others

Question 17

muscle activation vs. muscle action

Answer 17

muscle activation: the neuromuscular process of motor unit recruitment to create muscle tension

muscle action: the potential for a muscle to cause movement in a particular direction about a give joint axis of motion

Question 18

consider a person walking up a flight of stair. if you measured body weight, stair height, number of steps, and time, which measure could you calculate?

Answer 18

mechanical work and mechanical power

• weight = force
• height x number of steps = displacement
• force x displacement = mechanical work
• mechanical work/time = mechanical power
• cannot calculate ankle moment - would need moment arms and the forces across the ankle some distance from axis of rotation

Question 19

consider the mechnical energy of the gymnast. if the gymnast hols this position for 5 seconds, the following occurs

Answer 19

none

• generation of mechanical energy would need velocity at COM
• no increase in PE - no change in position/height
• no increase in KE - no movement

Question 20

a smaller femoral angle of inclination (coxa varus) has the mechanical advantage of ____, relative to the normal angle

Answer 20

increased amoment arm for hip abductor muscles

Question 21

what explains the linear force of 250-300% body weight during static single-limb standing?

Answer 21

forces across the joint influenced by muscle moments

• other forces through the hip joint
  
  • stair climb - 300% BW
  • walking - 400-700% BW
  • running - 1000% BW

Question 22

what muscle attaches to the iliotibial band?

Answer 22

gluteus maximus

Question 23

a man is exerting a constant horizontal force on a large moving box. the box is moving across a horizontal floor at a constant velocity. the constant horizontal force applied by the man is _____ the total force that resists the motion of the box.

Answer 23

the same magnitude as

• if the magnitude of the force applied by the man was less than the box, it would slow down
• if the magnitude of the force applied by the man was greater than the box, the box would speed up

Question 24

a 250 lb linebacker collides head-on with a 175 lb running back. during the collision the LB exerts ___ force on the RB than the RB exerts on the LB.

Answer 24

the same

Question 25

from the A/P graph below, it can be determined that the person is

Answer 25

speeding up * area of forward \> area of backward

Question 26

how does a person landing from a drop off of a platform have a greater peak vertical GRF in one trial versus a subsequent trial?

Answer 26

increase landing time

Question 27

what is the relative magnitude of the muscle force in this example, if the segment is static?

Answer 27

force M \> S * M_v = S + F

Question 28

consider a patient with elbow osteoarthritis holding a 15 lb weight. how would you respond to the question from the patient, "why would my elbow be so painful from holding such a light weight?"

Answer 28

there is compression at the joint due to a rection force between the upper arm and lower arm

Question 29

based on the ground reaction force represented in the picture, which of the following external demand moments has the greatest magnitude?

Answer 29

knee flexion

Question 30

which of the following is a kinetic measure

Answer 30

ground reaction force * kinematics - with no forces * velocity, acceleration, joint angle

Question 31

in anatomical position, the humeroulnar joint relative to the radiocarpal joint is

Answer 31

proximal

Question 32

a muscle synergist

Answer 32

acts coopertively with another muscle

Question 33

in arthrokinematic motions, multiple points along one rotating articular surface contacting multiple points on another articular surface is termed

Answer 33

roll

Question 34

select the most specific term for motion that occurs between two articular surfaces from the list below

Answer 34

arthrokinematics

Question 35

a uniaxial joint has how many rotational degrees of freedom

Answer 35

1

Question 36

the perimysium is a connective tissue structure that surrounds

Answer 36

the entire fascicle

Question 37

consider the glenohumeral joint in anatomical position. in which situation would the posterior deltoid muscle need to be eccentrically active

Answer 37

when glenohumeral flexion occurs

Question 38

the endomysium is a connective tissue structure that surrounds

Answer 38

the entire muscle fiber

Question 39

according to the results of the study by Waanders et al., the relative contribution of the _____ joint to total positive leg joint work was relatively negligible (less than 10%) during level walking

Answer 39

knee

Question 40

according to the article by waanders et al., an age-related distal-to-proximal redistribution of joint work occurs for level walking, with older adults having relatively ____ in terms of contribution to total leg joint work, compared to young adults

Answer 40

less positive ankle plantar flexor work and more hip flexor work

Question 41

in typical "scapulohumerial rhythm," it would be most reasonable for a person abducting their shoulder complex at 120 degrees to have ____ degrees of scapulothoracic upward rotation

Answer 41

40

Question 42

the following results of an intact and properly functioning patella, compared to someone wiht a removed patella

Answer 42

increased moment arm for quadriceps femoris muscle group acting baout the mediolateral axis of the knee decreased muscle force requirement for a given internal externsor moment from the quadriceps femoris group

Question 43

a common method to stretch the piriformis muscle is to tlengthen it by having the hip flexed and

Answer 43

externally rotated

Question 44

what is a mechanical characteristic of a patellectomized knee

Answer 44

reduced quadriceps femoris moment arm about the mediolateral knee axis

Question 45

what is considered the most common orthopedic sports injury

Answer 45

inversion (lateral) ankle sprain

Question 46

persons with chronic ankle instability tend to have greater _____ at the start of the stance phase of walking

Answer 46

position of ankle/foot inversion

Question 47

mass moment of inertia about the mediolateral axis of rotation for a diver who is spinning during a dive will increase as the diver moves from a tucked position to an outstretched (T/F)

Answer 47

true

Question 48

person 1 (120 lbs) is walking and reading their phone when they run into person 2 who is standing still (200 lbs). the force exerted on person 1 is ____ the force exerted on person 2.

Answer 48

equal to

Question 49

in the picture (section B), J represents the joint reaction force at the elbow. the force:

Answer 49

creates no moment (torque) about the mediolateral elbow axis

Question 50

considering the free-body diagram of a body segment in B, what forces result in production of a moment about the axis of rotation

Answer 50

M_y

Question 51

the biceps brachii causes a force applied to the insertion site on the forearm when axticated, creating a pull that can be resolved into a component acting in line (X) and a component acting perpendicular (Y) to the longitudinal axis of the forearm. the x component of the force

Answer 51

can create a compressive or tensile load at the elbow depending on joint angle

Question 52

when performed an MMT of the quadriceps femoris muscle group functioning at the knee, the semitendinosus acts as an antagonist. any semitendinosus muscle force would create a moment (torque) about the mediolateral axis of the knee that

Answer 52

is in the same direction as the moment (torque) produced by the manual resistance from the tester

Question 53

during a typical landing phase of a vertical jump (after the foot hits the ground), the primary active muscle group about the mediolateral axis at the knee is the

Answer 53

quadriceps femoris

Question 54

comparing the drop vertical jump task performance of participants before and after the "landing instruction" intervention, Mizner and colleagues found

Answer 54

the ground reaction force was less than after the instruction

Question 55

mizner and colleages suggest from their study results of "drop vertical jump task" performance before and after the "landing instruction" intervention, that

Answer 55

"softer" landings reuced damns on the knee with reduced knee abduction moment demand

Question 56

in the mizner article, joint moments at the hip, knee, and ankle were presented as

Answer 56

external moments