Anatomical biomechanical situations

Question 1

What is the lumbosacral junction force?

Answer 1

• Generated by the weight of the upper body through the vertebral column.
• It pushes vertically down on the sacrum.

Question 2

What would a steeper L5 joint with regard to the lumbosacral joint lead to?

Answer 2

• Smaller normal force at that joint.
• Articular cartilage would be compressed less.
• Descrease the chance of damage.
• Greater stress on ligaments holding the bone in place.

Question 3

What would occur if Vastus medialis obliquus were to atrophy following ACL surgery for example?

Answer 3

• This causes vastus lateralis to pull the patella more laterally.
• This causes the patella to not track properly and be pulled sideways off the groove.
• The VMO pulls the patella upwards + medially to counteract laterally pull.

Question 4

Why is there greater torque at the knee during flexion compared to extension?

Answer 4

• The knee is more stressed while flexed than extended.
• Muscles, ligaments, cartilage and bone are all stressed in a flexed position.

Question 5

Why do muscles attach to bones close to joints, when their torque would be increased if they attached further away?

Answer 5

• Inserting a muscle further from a joint increases the moment arm.
• Which increases torque.
• Bit this means muscles can shorten at most 30% of their resting length.
• There is a reduced range of motion.
• Reduced speed of motion.

Question 6

What is muscle synergy?

Answer 6

Where muscles combine to cancel out unwanted secondary actions and together produce a desired movement.

Question 7

Describe the moment arm for brachioradialis.

Answer 7

• Has the largest moment arm for elbow flexion.
• Muscle acts at a great distance from the elbow joint axis.

Question 8

Describe the moment arm of the brachialis.

Answer 8

• Has a small moment arm.
• Muscle origin and insertion are close to the below joint.

Question 9

What are the characteristics of the biceps brachii to generate torque?

Answer 9

• Has a dural origin causing larger muscle mass + force-generating capacity.
• Pennation of fibres increases the CSA + produces greater force.

Question 10

What are the characteristics of the brachialis to generate torque?

Answer 10

• Has a more direct line of pull on the ulna in elbow flexion.
• Has a short moment arm.

Question 11

What are the characteristics of the brachioradialis to generate torque?

Answer 11

• Larger moment arm during elbow flexion.
• Greater muscle length which contributes to larger moment arm + torque production.

Question 12

When in knee extension what is the function of the ITB band?

Answer 12

• ITB passes in front of the knee’s axis of rotation.
• ITB has an extension moment arm.
• Contributes to extension of the knee in a fully extended position.

Question 13

When in knee flexion what is the function of the ITB band?

Answer 13

• ITB passes behind the knee’s axis of rotation.
• ITB has a flexion moment arm.
• Contributes to flexion of the knee in a fully flexed position.