Lecture 16 - Revision questions

Question 1

What structure is responsible for the behaviour of ligaments?

Answer 1

• Elastin

Question 2

Ultimate stress occurs at what point of the stress stain relationship curve?

Answer 2

• Failure point

Question 3

Weight acceptance occurs during what component of the gait cycle?

Answer 3

• Loading response

Question 4

The ability of a material to absorb energy during plastic deformation before failure is called what?

Answer 4

• Toughness

Question 5

By how much ( of resting length ) can a muscle stretch before rupture ?

Answer 5

• 160%

Question 6

The technique of surface EMG is not generally used to provide information on what ?

Answer 6

• Single motor action potentials

Question 7

What is a causative extrinsic factor that effects EMG signal ?

Answer 7

• Orientation of electrodes with respect to direction of fibres.

Question 8

The hip and ankle positions during an isokinetic knee extension protocol are an important consideration because they alter the length of which biarticular muscles?

Answer 8

• Rectus Femoris and Gastrocnemius

Question 9

During an isokinetic testing protocol. What happens to the duration of the isokinetic phase as the angular velocity increases

Answer 9

• Decreases

Question 10

Which of the following sports performers would most likely to display bilateral facilitation and why?

• Sprinters
• Tennis players
• Cyclists
• Weightlifters
• Untrained subjects

Answer 10

• Weightlifters
• This is because bilateral facilitation is when greater force is generated with both legs together, in comparison to the sum of each legs maximal force.
• Weightlifter predominantly use both legs to lift wright in movements such as squats, power cleans etc., compared to cyclists or sprinters which are single leg sports.

Question 11

How should the measurement of anatomical cross sectional area (ACSA) of a muscle be made?

Answer 11

• Perpendicular to the long axis o the muscle

Question 12

What is the advantage of an in-parallel muscle fibre arrangement?

Answer 12

• Greater maximum force

Question 13

What is the effect of the low pennation of the gastrocnemius in comparison to the high pennation of the soleus?

Answer 13

• The gastrocnemius has increased ROM

Question 14

Contralateral hamstring- quadriceps imbalances greater than what percentage are associated with increased injury risk?

Answer 14

• 10%

Question 15

The contraction velocity of type 2 motor units compared to that of type 1 motor units is what?

Answer 15

• Three times greater.

Question 16

How do muscles with small physiological cross sectional area (PCSA) produce high joint torques?

Answer 16

• By having a large momentum arm.

Question 17

Which of the following testing conditions should not be violated when performing strength and power measurements?

• Movement pattern
• Joint velocity
• Load characteristics
• Posture
• All of the above

Answer 17

• All of the above

Question 18

The anterior posterior (x-direction) ground reaction fore at foot contact with the ground during landing from a drop jump was 180N. if the foots mass was 1.2kg and its X acceleration was 50m/s, what was the anteroposteiror joint force reaction at the ankle, and how do you calculate this ?

Answer 18

• Calculation is Fx + Frx = Max
• Fx is the ground reaction force e.g. 180N
• FRx is speed multiplied by the foots mass e.g. 1.2 x 50 = 60
• To calculate the joint reaction force you take away Fx from Frx e.g. 60 - 180 = -120
• Answer is -120N

Question 19

What electrical variable is measure when analysis muscle activity using electromyography (EMG) ?

Answer 19

• Voltage

Question 20

The term pronation (at the subtalar joint) is often used interchangeably with what other term?

Answer 20

• Eversion