Lecture 7 - Factors effecting strength: Neural & CSA

Question 1

What do high and low innervation number in a muscle correlate to?

Answer 1

• High - large force production

- Low - Small force production, more for fine motor skills.

Question 2

Definition of strength ?

Answer 2

• The maximal force that a muscle or muscle group can generate at a specified velocity.

Question 3

In what order are muscle fibres innervated ?

Answer 3

• Slow (type 1)
• Medium (type 2a)
• Fast (Type 2x)

Question 4

Which muscle fibres monitor homeostasis and send electrical feedback through the gamma motor neuron.

Answer 4

• The intrafusal fibres.

Question 5

What effect can the development of strength and skill training have on the Renshaw cell?

Answer 5

• Can reduce the capacity for co contraction meaning that a muscle is able to fully exert all of it force even though this could lead to injury.

Question 6

What Is post activation potentiation (PAP) ?

Answer 6

• Implementing a resistance exercise prior to an explosive movement has improved subsequent performance.

Question 7

The maximal conduction velocity of a large alpha motor neuron is what ?

Answer 7

• Up to 101 m/s

Question 8

What are the muscle structure factors that effect strength and power?

Answer 8

• Fibre type
• Innervation ratio
• Cross sectional area
• Pennation angle

Question 9

What is innervation number?

Answer 9

• The ratio between fibres and axons.

Question 10

What inhibits muscle length and how can this be confused?

Answer 10

• A neural mechanism inhibits muscle length but this can be altered by performing PNF stretching.
• This works by confusing the Renshaw cell which overrides the sensory feedback allowing the muscle to be taken to a greater range.

Question 11

What is the Renshaw Cell?

Answer 11

• Cell which controls the activation and feedback threshold, subsequently allowing different signals through.

Question 12

What are type 1, type 11a and type 11x muscle fibres?

Answer 12

• Type 1 - Slow twitch
• Type 11a - Fast twitch fatigue resistant
• Type 11x - Fast twitch (Fastest)

Question 13

How does PAP work to increases power output?

Answer 13

• The first contraction at a heavy weight activates the large motor units.
• This reduces the inhibition of the Renshaw cell.
• This results in the second contraction recruiting more larger motor units.

Question 14

What is a Bilateral deficit (BLD) ?

Answer 14

• The sum of the maximal contraction of two libs simultaneously is less than the sum of the two limbs being activated independently.
• E.g both together = 1000
• Left individual = 550
• Right individual = 550
• Independent added - 1100

Question 15

What are the 4 types of electrical impulses?

Answer 15

• Twitch
• Wave summation
• Unfused (incomplete) tetanus
• Fused (complete) tetanus

Question 16

By what percentage does cross-sectional area account for strength differences?

Answer 16

• 50%

- Other 50% is accounted for by neural drive and fibre type.

Question 17

What are the three types of neurons

Answer 17

• Efferant (Alpha) neuron which activate muscle fibres
• Afferant neurons which provide feedback.
• Both are contained n the spine in the interneuron,.

Question 18

What muscle inefficiency’s can lead to ACL injury’s?

Answer 18

• Glute complex weakness

- Quadriceps hamstrings strength imbalance

Question 19

What is Bilateral facilitation (BFL) ?

Answer 19

• The maximum sum of forces with two limbs simultaneously is greater that the sum of the two limbs being activated independently.
• E.g both together = 1000
• Left individual = 400
• Right individual = 400
• Independent added - 800