Neural & CSA - Factors affecting Strength Flashcards
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?
SLOW –> MEDIUM –> FAST TWITCH
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
