Neural & CSA - Factors affecting Strength Flashcards Preview

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Flashcards in Neural & CSA - Factors affecting Strength Deck (19):

What is strength?

Maximum force a muscle can generate at a specific velocity


In terms of strength and injury, what is absorption and asymmetry?

Absorption --> hamstrings:quad ratio prevent ACL

Asymmetry --> one side of the body stronger than another


How much does muscle size have an impact in strength differences in individuals?

CSA accounts for 50% of strength differences due to neural and fibre types


What are the different fibre types?

Type I, Type IIa, Type IIx


What happens during neural recruitment of muscle fibres?

1) Recruit fibres in cerebral cortex which activates neurons in the spine

2) Axons recruit muscles and innovate at the top

3) Feedback innovates at the bottom of the muscle

4) Nerves accelerate the transition from spine to muscle (trainable)

5) Sliding Filament Theory --> myosin slides over actin for muscle contractions to occur


How do electrical impulses alter?

When muscle twitches, wave stimulation causes small movements of the muscle

Wave summation --> fused (high forces stimulate)


How does size of the nerve affect conduction velocity?

What affects this?

Big nerves = FTF = increases velocity and electrical conductivity
Small nerves = STF = reduced electrical activity and slow conduction

Nerve thickness and resistance


What is the relationship between muscle units and innervation number?

Muscle fibres recruited by a single neuron = MU's
Innervation no. = ratio between the fibres and axons
High IN = high force, Low IN = finite motor skills


How does the biceps brachii and abductor pollus differ in terms of fibres?

Biceps - increased motor axons and innervation no.

Abductor - reduced axons and innervation no.


What is the order of recruitment of muscle fibres?



What is the difference between efferent and afferent neurons?

Efferent - activate the muscle fibres

Afferent - provides feedback


What is the role of Intrafusal muscle fibres?

Monitor the homeostasis of contractual muscle fibres
Send electrical feedback through gamma motor neurons


What are some of the feedback mechanisms we use?

Muscle Spindle - concentric
Tendon Organ - stretch and relax
Joint Receptors - outside the capsule
Renshaw Cell - activation and feedback


What is the role of the Renshaw Cell in terms of reducing co-contractions?

How does skill development affect co-contractions?

Renshaw Cell inhibits the contraction and focuses on either the primary mover or inhibiting the secondary mover

Improving performance reduces this co-contraction


What is PNF stretching?

Proprioreceptive Neuromuscular Facilitation

Activates the neuromuscular function to stretch past the normal point


How can we confuse the sensory feedback?

Stretch phase - efferent Type II
Feedback - gamma
Contraction = alpha motor neuron
Renshaw Cell - confused so overrides sensory feedback


What is PAP?

Implement resistance prior to explosive movement has improved subsequent performance above personal bests


How does PAP work?

1) Confuses the Renshaw Cell
2) 1st contraction activates larger MU's
3) Reduced inhabitation by Renshaw Cell occurs
4) 2nd contraction recruits other large MU's for a different muscle action


How can injury affect neural adaptations?

After injury, neural pathway is trained on one side and not the other - so have to retrain that side