TA Session #1

Question 1

What happens to active and passive muscle tension, respectively, as you stretch a muscle beyond its optimal length?

-They both increase
-They both decrease
-Active tension increases while passive tension decreases
-Active tension decreases while passive tension increases

Answer 1

Active tension decreases while passive tension increases

-Explanation: Active tension is generated when the overlapping filaments are drawn together. Via the length-tension relationship, a muscle is able to produce maximal force when there is maximal overlap between myosin + actin filaments, this is called the optimal length. As you stretch the muscle, there is less overlap, decreasing active tension. Passive tension is generated by the noncontractile components as you stretch the muscle, thus increasing as length increases.

Question 2

In a position of maximal elbow flexion, which muscle would be actively insufficient?

-Teres minor
-Triceps brachii
-Biceps brachii
-Anconeus

Answer 2

Biceps brachii

-Explanation: Active insufficiency occurs when a muscle shortens so much that is cannot produce maximal tension or force to contract further, limiting the degree of motion possible at the joints it crosses. When you flex your elbow to end range, the biceps muscle is so short that the sarcomeres don’t have any room to shorten more, limiting their ability to generate force.

Question 3

In a position of maximal knee extension and hip flexion, which muscle would be passively insufficient?

-Quadriceps
-Biceps femoris
-Soleus
-Gluteus maximus

Answer 3

Biceps femoris

-Explanation: In maximal knee extension, the quadriceps muscle is shortened, making it actively insufficient. Both knee extension + hip flexion stretch the hamstring muscles. So in this position, the hamstrings are being stretched to their maximal length, making them passively insufficient. The soleus muscle + gluteus maximus do not cross the knee joint.

Question 4

Which color vector represents the force of the biceps that is going to generate torque about the elbow?

-Blue arrow going up
-Red arrow going slanted up and to the right
-Green arrow going to the right

Answer 4

Blue arrow going up

-Explanation: The red vector represents the force of the biceps. The green vector is the parallel component of the force of the biceps which represents the compression of the forearm against the humerus. The blue vector is the perpendicular component which represents the force that will cause rotation of the forearm around the elbow axis (torque).
-Watch biceps as a vector video for this concept

Question 5

You are at Southwest Rec after a long day of class. You decide to go over to the free weights section and do some bicep curls. Which of the following correctly pairs the working agonist muscle with the type of muscle activation when you move from elbow extension into flexion?

-Biceps brachii; eccentric
-Brachioradialis; concentric
-Brachialis; isometric
-Biceps brachii; concentric

Answer 5

Biceps brachii; concentric

-Explanation: During the elbow flexion phase of a bicep curl, the primary agonist muscle is the biceps brachii. During flexion, the biceps is shortening, making this a concentric movement.

Question 6

Which of the following best describes the close-packed position of a joint?

-Articular surfaces are relatively free to move in relation to one another
-Joint surfaces are maximally congruent and the ligaments and capsule are maximally taut
-The joint is unstable and prone to dislocation
-The joint is in its resting position with minimal stress on surrounding structures

Answer 6

Joint surfaces are maximally congruent and the ligaments and capsule are maximally taut

-Explanation: This is the definition of the close-packed position. In this state, the joint surfaces fit together tightly, and the surrounding soft tissues (ligaments and capsule) are stretched and stabilized. This is the most mechanically stable position of the joint.

Question 7

After acing your midterm, Dr. Bishop flexes his elbow while raising his hand to give you a high-five. In what plane does this action occur?

-Frontal plane
-Transverse plane
-Sagittal plane
-Paper plane

Answer 7

Sagittal plane

-Explanation: Generally, flexion + extension occur in the sagittal plane. Abduction + adduction occur in the frontal plane. Internal + external rotation occur in the transverse plane.

Question 8

When the arm is abducted away from the body, the humeral head is rolling ________ and gliding _________.

-Down, up
-Down, down
-Up, down
-Up, up

Answer 8

Up, down

-Explanation: When the arm is being abducted, the humeral head slides down to counteract the upward rolling motion + keep the humerus in the glenoid socket.

Question 9

T/F: Torque increases as you move further away from the lever arm.

Answer 9

False

-Explanation: Distance increases proportionally + force decreases proportionally as you move further away from the lever arm. Torque remains the same.
-Torque = distance x force

Question 10

What is the definition of a force couple?

-Muscles that pull in opposite directions + cause movement in opposite directions
-Muscles that pull in opposite directions to cause movement in the same direction
-Muscles that pull in the same direction to cause movement in the same direction
-Muscles that pull in the same direction to cause movement in opposite directions

Answer 10

Muscles that pull in opposite directions to cause movement in the same direction

-Explanation: The deltoid + rotator cuff is a perfect example of this. The rotator cuff counteracts the upward pull of the deltoid to raise the arm above the head.

Question 11

Which of the following exercises contains a second-class lever?

-Triceps pushdown
-Standing heel raise
-Barbell biceps curl
-Prone hamstring curl

Answer 11

Standing heel raise

-Explanation: In a second class lever, the load is in between the fulcrum + the effort. A calf raise is the best example of a second class lever found in the body. In this example, the fulcrum is the ball of the foot, the load is the body’s weight, + the effort is the muscle force being applied by the gastrocnemius + the soleus.

Question 12

Which of the following upper arm muscle groups and types of muscle actions are associated with a standing triceps pushdown?

-Elbow flexors eccentric + elbow flexors concentric
-Elbow flexors concentric + elbow extensors eccentric
-Elbow extensor eccentric + elbow extensors concentric
-Elbow flexors eccentric + elbow extensors concentric

Answer 12

Elbow extensors eccentric + elbow extensors concentric

-Explanation: During a triceps pushdown, your elbow extensors (triceps brachii + anconeus) work concentrically (shortening) on the downward phase of the movement + eccentrically (lengthening) on the upward phase of the movement.

Question 13

Which of the following knee movements and planes are associated with a prone HS curl?

-Knee extension, sagittal plane
-Knee extension, frontal plane
-Knee flexion, frontal plane
-Knee flexion, sagittal plane

Answer 13

Knee flexion; sagittal plane
-(bonus- occurs in the frontal-horizontal axis)

-Explanation: The sagittal plane divides the body into L/R halves. Knee flexion occurs in this plane + about the medial to lateral axis of motion (aka frontal to horizontal).

Question 14

During the upward movement of a bench press, which of the following identifies the motion occurring at the shoulder joint, and is this exercise open chain or closed chain?

-Horizontal adduction in the transverse plane; open chain
-Horizontal adduction in the transverse plane; closed chain
-Flexion in the transverse plane; open chian
-Flexion in the frontal plane; closed chain

Answer 14

Horizontal adduction in the transverse plane; open chain

-Explanation: During the upward movement of a bench press, the primary motion at the glenohumeral joint is horizontal adduction, as the glenohumeral joint is moving the humerus towards the midline. It occurs in the transverse plane as the humerus moves across the body. about a superior to inferior axis. This is an open chain movement as the distal segments of the movemnt, in this case your hands, are not fixed + are free to move.
-Open chain: distal segments not fixed

Question 15

Which of the following best describes the roll and glide of the GH joint in external rotation?

-Roll posterior, glide anterior
-Roll inferior, glide superior
-Roll anterior, glide posterior
-Roll superior, glide inferior

Answer 15

Rolls posterior, glides anterior

-Explanation: During ER of the glenohumeral joint, the convex humeral head rolls posterior on the concave glenoid fossa. To maintain proper joint alignment (so the humeral head doesn’t just roll off the back of the glenoid fossa), the humeral head must slide forward on the glenoid fossa. This follows the convex-concave rule that states when a convex surface (humeral head) moves on a concave surface (glenoid fossa), the roll + glide are in opposite directions.

Question 16

Based on the convex-concave rule, the femur rolls ________ on the tibia and glides ______ on the tibia during knee flexion (closed-chain)

-Rolls anterior, glides posterior
-Rolls posterior, glides posterior
-Rolls posterior, glides anterior
-Rolls anterior, glides anterior

Answer 16

Rolls posterior, glides anterior

-Explanation: Based on the convex on concave ruling, when a convex surface such as the femoral condyles move on a concave surface, in this case the tibia, the convex surface will roll + glide in opposite directions to keep the joint stable so that the convex surface does not just roll off the concave surface.

Question 17

T/F: Open-chain kinematics occurs when the distal end of a limb is not fixed and therefore does not allow for multiple degrees of freedom

Answer 17

False (DOES have multiple degrees of freedom)

-Explanation: Open chain kinematics is described as when the distal end of a segment is not fixed + it DOES have multiple DOF. On the other hand, closed chain kinematics is described as when the distal end of a segment is fixed + it doesn’t have multiple DOF.

Question 18

You go to the gym and are pumped because it’s chest day, but then you remember that you have to do an ACL rehab that day. Which of the following is a knee closed-chain exercise?

-Bicep curls
-Banded knee extension
-Hamstring curls
-Squats

Answer 18

Squats

-Explanation: Remember that closed chain exercises are when the distal end of a segment is in a fixed position + has limited DOF. All the options are incorrect because they have the distal end of the segment in a non-fixed position.

Question 19

In the action of ankle dorsiflexion, the full ROM is limited by the tightness of the soleus and gastrocnemius muscles because of…

-Muscle deficiency
-Passive insufficiency
-Active insufficiency
-Energy insufficiency

Answer 19

Passive insufficiency

-Explanation: Dorsiflexion ROM is being limited by tight calf muscles, which are the antagonists of the dorsiflexor muscles on the front of the leg. The antagonist muscle is limiting the action of the agonist muscles by being too short.

Question 20

Fine motor control muscles typically have…

-Fewer muscle fibers but larger number of muscle units
-Fewer muscle fibers + fewer number of muscle units
-More muscle fibers + larger number of muscle units
-More muscle fibers but fewer number of muscle units

Answer 20

Fewer muscle fibers but larger number of muscle units (=precise movements)

-Explanation: Muscles used for fine motor control are made up of many small motor units. Each motor unit controls only a few fibers, allowing very precise movement. Having lots of these small units gives the muscle both control + enough strength.

Question 21

Where is the human COM, and is it fixed?

-S2, no
-L4, yes
-L4, no
-S1, yes

Answer 21

S2: No (dependent on position + possible external factors)

Question 22

T/F: The scapulothoracic joint is a gliding joint

Answer 22

False

-Explanation: The scapulothoracic joint is NOT a true joint. There is no ligament or cartilage attachment between the scapula + the thorax that is typically seen in other joints.

Question 23

What is the smallest functional unit of a muscle fiber?

-Myosin
-Sarcomere
-Fibril
-Actin

Answer 23

Sarcomere
-Mostly made up of the proteins actin + myosin which form the cross bridges + allow for the contraction of muscle fibers

Question 24

Passive insufficiency is when…

-The agonist muscle is too tight (overstretched)
-The antagonist muscle is too tight (overstretched)
-The agonist muscle is short and can’t contract well
-The antagonist muscle is short and can’t contract well

Answer 24

The antagonist muscle is too tight (overstretched)

-Explanation: The antagonist is stretched so far across multiple joints that is limits further motion
-Ex: if you flex your wrist + try to form a fist, your antagonists are too tight + are preventing you from doing a full fist motion

Question 25

What type of joint is the shoulder? How many planes of motion does it occur in? -Pivot joint; 3 planes -Ball and socket; 3 planes -Saddle joint; 2 planes -Hinge joint; 2 planes

Answer 25

Ball-and-socket; 3 planes

Question 26

At which sarcomere length is skeletal muscle capable of generating maximal active force? -Very short lengths, because actin filaments overlap excessively -Intermediate lengths, because optimal crossbridge overlap occurs -Very long lengths, because passive tension dominates -Force is constant regardless of sarcomere length

Answer 26

Intermediate lengths, because optimal crossbridge overlap occurs. -Explanation: The length-tension relationship in skeletal muscle describes how sarcomere length influences the force a muscle fiber can generate. At very short lengths, actin filaments overlap excessively, interfering with crossbridge formation + reducing force production. At very long lengths, actin + myosin barely overlap, so only a small number of crossbridges can form, again reducing force.

Question 27

When the forearm moves closer to the humerus during a bicep curl, the movement occurs in which plane and about which axis? -Sagittal plane, frontal axis -Frontal plane, sagittal axis -Transverse plane, vertical axis -Sagittal plane, longitudinal axis

Answer 27

Sagittal plane, frontal axis -Explanation: elbow flexion/extension occurs in the sagittal plane, with rotation about a frontal (mediolateral axis)

Question 28

Name two of the main muscles that are a force couple during scapular rotation -Serratus anterior + traps -Traps + rhomboids -Serratus anterior + rhomboids -Levator scapula + traps

Answer 28

Serratus anterior + traps -Explanation: These 2 muscles work together, with their opposing linear forces creating rotational torque that produces upward rotation of the scapula as the arm is elevated. The force couple of the traps + serratus help to upwardly rotate the scapula during shoulder abduction past 90 degrees. If the serratus is weak or impaired, the scapula will not stay up against the rib cage.

Question 29

In osteokinematics, the proximal and distal segments are defined how in an open chain activity? -Proximal segment moves, distal remains fixed -Distal segment moves relative to a fixed proximal segment -Both segments always move equally -Proximal and distal segments only refer to limbs

Answer 29

Distal segment moves relative to a fixed proximal segment -Explanation: In osteokinematics, the distal segment typically moves relative to a fixed proximal segment (e.g., the forearm moves around the humerus during a bicep curl). The proximal segment is usually considered stable, but in closed-chain movements (like a pushup or squat), the distal segment can be fixed, + the proximal segment moves instead.

Question 30

Which lever system is most common in the human body? -First class -Second class -Third class -An equal amount is found

Answer 30

Third class -Explanation: The most common lever system in the human body is the third class lever, where the effort is applied between the fulcrum + the load. This setup allows for greater speed + ROM, even though it requires more force to move the load. Examples include the biceps doing a curl, where the elbow is the fulcrum, the hand holds the load, + the muscle applies effort in between.