Biomechanics of Exercise Training

Question 1

What is Moment Arm?

Answer 1

Determines the force to produce or prevent the rotation of an object around an axis

It is the perpendicular distance from the line of action of force to the joint of interest

Question 2

Knee Varus Vs Knee Valgus

Answer 2

Knee Varus
- bow-legs –> this line passes medial to the center of the knee, increasing force across the medial tibiofemoral compartment

Knee Vaglus
- knock-knee –> the axis passes lateral to knee centre, increasing force across the lateral compartment

Question 3

Knee Osteoarthritis
(What is it and what does it cause)

Answer 3

A degenerative joint disease that affects the knee

Causes progressive loss of articular cartilage
- Cartilage degradation enzymes higher in OA

Question 4

What cause medial compartment loading?

Answer 4

Bow-legs increase the line of action of the GRF
–> increasing the moment arm to the line of force
–> Larger moment arm cause increased degeneration and pain

Question 5

What causes an ACL injury?

Answer 5

Caused by lateral forces acting on the knee or shank
- Knee Valgus force (abduction moment)

Question 6

What increases the risk of an ACL injury?

Answer 6

• Excessive Knee Valgus (particularly when landing)
• Landing on 1 leg causes increased forces on the knee joint
  (landing on both legs is more ideal)
• Land and twist motion causes increased Valgus moment
• Excessive GRF Valgus Moment

Question 7

Point of ‘no return’
think ACL injury

Answer 7

Internal rotation of the femur (thigh)
External rotation of the shank

Question 8

Anatomical risk factors for ACL injury

Answer 8

Knee Valgus
Knee Hyperextension (locking)
Intercondylar notch size
Integrity of the menisci

Question 9

Difference between Internal and External moment arms

Answer 9

Internal
- Due to what is inside you (AKA a muscle)
- Distance between joint and muscle tendon

External
- Due to a load
- Distance between joint and point of force