practice/quiz questions EXAM 1 Flashcards
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?
3
- the perpendicular distance between the line of force and the axis of rotation is the greatest
flexion of the skater’s right knee is about which axis of rotation?
mediolateral
- tibia is flexed relative to the knee
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:
acceleration of A=B
- the acceleration of both is 0 - they have the same velocity the whole time
the two position/time graphs indicate motion of an object over time. distance traveled by each object are related as follows:
distance A > B
- the area under the curve = the distance traveled
- curve A has more area, so it has more distance
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.
greater than
- vector composition: Mx > My
estimate the location fo the person’s whole-body center of mass in each of the pictures below
red is original COM, green is new COM with movement
the position of the pitcher’s right hip
flexed, internally rotated, abducted
- left hip higher than the right, so the right hip is abducted
at the knee during a downward squat, what arthrokinematic motions do you expect?
femur roll into flexion, anterior glide
tibial roll into flexion, posterior glide
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:
lose energy
- hysteresis
the greatest total force of a maximally active muscle will be at
the longest physiologic length of the muscle
- the greatest active force would be at the intermediate length near the resting length
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?
160
- 280 (full hamstring length) - 120 (if hip was flexed) = 160
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?
gluteus maximus
according to the chart, which of the following muscles are concentrically active during the pre-swing (PSw) phase of gait?
soleus
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?
anterior deltoid
- line of pull - eccentrically
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?
biceps brachii
in the picture, what are the internal and external moments acting on the right leg and foot segment?
weight of the body
JRF
GRF
probably some others
muscle activation vs. muscle action
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
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?
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
consider the mechnical energy of the gymnast. if the gymnast hols this position for 5 seconds, the following occurs
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
a smaller femoral angle of inclination (coxa varus) has the mechanical advantage of ____, relative to the normal angle
increased amoment arm for hip abductor muscles
what explains the linear force of 250-300% body weight during static single-limb standing?
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
what muscle attaches to the iliotibial band?
gluteus maximus
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.
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
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.
the same
from the A/P graph below, it can be determined that the person is
speeding up
- area of forward > area of backward
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?
increase landing time
what is the relative magnitude of the muscle force in this example, if the segment is static?
force M > S
- Mv = S + F
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?”
there is compression at the joint due to a rection force between the upper arm and lower arm
based on the ground reaction force represented in the picture, which of the following external demand moments has the greatest magnitude?
knee flexion
which of the following is a kinetic measure
ground reaction force
- kinematics - with no forces
- velocity, acceleration, joint angle
in anatomical position, the humeroulnar joint relative to the radiocarpal joint is
proximal
a muscle synergist
acts coopertively with another muscle
in arthrokinematic motions, multiple points along one rotating articular surface contacting multiple points on another articular surface is termed
roll
select the most specific term for motion that occurs between two articular surfaces from the list below
arthrokinematics
a uniaxial joint has how many rotational degrees of freedom
1
the perimysium is a connective tissue structure that surrounds
the entire fascicle
consider the glenohumeral joint in anatomical position. in which situation would the posterior deltoid muscle need to be eccentrically active
when glenohumeral flexion occurs
the endomysium is a connective tissue structure that surrounds
the entire muscle fiber
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
knee
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
less positive ankle plantar flexor work and more hip flexor work
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
40
the following results of an intact and properly functioning patella, compared to someone wiht a removed patella
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
a common method to stretch the piriformis muscle is to tlengthen it by having the hip flexed and
externally rotated
what is a mechanical characteristic of a patellectomized knee
reduced quadriceps femoris moment arm about the mediolateral knee axis
what is considered the most common orthopedic sports injury
inversion (lateral) ankle sprain
persons with chronic ankle instability tend to have greater _____ at the start of the stance phase of walking
position of ankle/foot inversion
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)
true
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.
equal to
in the picture (section B), J represents the joint reaction force at the elbow. the force:
creates no moment (torque) about the mediolateral elbow axis
considering the free-body diagram of a body segment in B, what forces result in production of a moment about the axis of rotation
My
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
can create a compressive or tensile load at the elbow depending on joint angle
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
is in the same direction as the moment (torque) produced by the manual resistance from the tester
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
quadriceps femoris
comparing the drop vertical jump task performance of participants before and after the “landing instruction” intervention, Mizner and colleagues found
the ground reaction force was less than after the instruction
mizner and colleages suggest from their study results of “drop vertical jump task” performance before and after the “landing instruction” intervention, that
“softer” landings reuced damns on the knee with reduced knee abduction moment demand
in the mizner article, joint moments at the hip, knee, and ankle were presented as
external moments
