Exam 2 (angular Kinematics + Torques & moments

Which of the following would be a segment angle?

The angle of the thigh relative to the right horizontal during a squat

true statement regarding knee flexion angles

• knee flexion is associated with force absorption

• Individuals with cerebral palsy demonstrate less knee flexion than individuals without cerebral palsy

• Individuals with ACL tears demonstrate less knee flexion

Which of the following is an example of a segment angle?

Foot-strike angle during running

If your hip joint angle is 30degrees, what anatomical position is it in?

Flexion

The Q-angle is greater in women & is associated with knee pain

False

How can we increase tangential velocity of a baseball bat sweet spot?

Rotate shoulder at the same angular velocity & use a longer bat

What is a moment arm?

The shortest, perpendicular distance between the axis & point of force application

Which scenario would result in torque definitively decreasing?

decrease moment arm, keep force the same

which scenario involves increasing torque by increasing the moment arm?

grabbing a longer wrench to loosen a bolt

True statements regarding segment angles

• Thigh angle when performing a squat is an example of a segment angle

• Foot strike angle (angle of foot relative to the ground) is a segment angle

• Segment angles are the angle between a body segment & a reference line

Individuals with cerebral palsy (CP)

have decreased knee flexion angles

A positive joint angle would mean

the knee is in flexion

What do we call the link between linear & angular kinematics 

Radius

During the knee extension exercise, which variable represents curvilinear distance?

The length of the path a point on your leg traveled

As the radius length increases

curvilinear distance increases

If all other variables are constant, which of the following scenarios would result in tangential velocity increasing?

swinging faster (increase angular velocity)

True statement regarding centripetal acceleration

• leaning in & pushing hard laterally would increase horizontal GRF

• Banked curves make producing horizontal GRFs easier

• Increased velocity requires more centripetal acceleration to turn

What does the patella do?

It increase the length of the quadriceps moment/lever arm

Which of the following is an example of co-contraction being beneficial ?

Higher hamstrings co-contraction after ACL injury

Component of internal moment

• Muscle force/tension

• Muscle moment /lever arm

• muscle angle of pull

If the non-rotary component of muscle force is going away from the joint, it is a 

de-stabilizing force

How does changing angle of pull influence internal moment magnitude?

The internal moment is highest when the angle of pull is 90o

If there is an external ankle dorsiflexion moment, what is our response?

Internal ankle plantarflexion moment

How does doing a pushup on an incline (box, wall, etc.) make it easier?

It shortens the moment arm

True statements regarding the knee adduction moment (KAM)

• It pushes the knee laterally & compresses the medial knee

• It is associated with thinner medial knee cartilage

• It is a predictor of severity & pain in people with knee OA

• It is increased in individuals with ACL injury

In the FBD below, how many torques would go into the equation of ΣT=0?

3

If you wanted to increase your stability while playing basketball, what would you do?

• Wear shoes with a high coefficient of friction

• Increase knee flexion

• Stand with your feet further apart

• Keep your bodyweight vector within your base of support

If you are at a mechanical advantage, which of the
following statements is true?

You can produce less muscle force than the resistive force to move

Why do longer golf clubs lead to the ball being hit further?

 

They have faster tangential velocity due to the longer radius

Which of the following scenarios would result in an increase in centripetal acceleration?

 

Leaning in towards the center & pushing hard horizontally

External moment

Any external object held

Ground reaction force

segment mass/weight

If there is an external knee flexion moment, what must our muscles produce to maintain joint position/static equilibrium?

 

Internal knee extensor moment