Lecture 7

Question 1

In external moments , what does the GRF do?

Answer 1

Flexes the knee

Question 2

What does the internal moment do?

Answer 2

Counteracts external moment

opposite sign to external moment

Question 3

If the GRF passes in front of the AJC, what which direction is the ankle flexing?

Answer 3

Ankle must be dorsiflexing

Question 4

If the GRF passes behind the HJC, what is it doing to the hip?

Answer 4

It is extending the hip (the hip muscles are active)

Question 5

If the GRF passes through the HJC, what is it doing to the hip?

Answer 5

There is no extension or flexion (the hip flexion moment is zero)

Question 6

If the GRF passes in front of the HJC, what is it doing to the hip?

Answer 6

It is flexing the hip (the hip muscles are passive/not active)

Question 7

In which direction does the GRF act most of the time when considering the hip moment?

Answer 7

The GRF is adducting the hip most of the time

Question 8

How does the GRF affect knee flexion?

Answer 8

If it passes behind the KJC, it flexes.
If it passes in front the KJC, it extends.

Question 9

What are the conditions for power generation?

Answer 9

Internal moment and angular velocity are acting in the same direction

Concentric muscle action (muscle shortening)

Question 10

What are the conditions for power absorption?

Answer 10

Internal moment and angular velocity are acting in opposite directions

Excentric muscle action (muscle lengthening)