Factors affecting strength Flashcards
Stength
define strength as the maximal force that a muscle or
muscle group can generate at a specified velocity
Causes of injury
Absorption mechanics
Asymmetry
Cross sectional area accounts for 50% strength differences between individuals, why?
Neural
Fibre type
Types of fibres
Type 1 - Slow twitch
Type 11a - fast twitch fatigue resistant
Type 11x - fast twitch hybridisation
Factors affecting muscle strength and power
Fibre type
Joint position
Joint velocity
Muscle architecture - CSA
How are muscle fibres recruited
Muscle fibres are
recruited by single
neurons – motor unit
What is innervation number
Is the number between fibres and axons
High innervation number - high force production
Neural feedback
Interneuron - spine - nerve contains
Efferent (alpha) neurones - activates muscle fibres
Afferent neurons - provides feedback
Intrafusal muscle fibres
monitor the homeostasis
of the contractual muscle
fibres
send electrical feedback
through the Gamma
Motor Neurons
Renshaw cells
Control the activation and feedback thresholds
Co-contractions Agonists and Antagonists
Development of skills
– Reduced co contraction
• Strength training adaptations
– Reduced co contraction
• Absorption of impacts
– Injury risk impaired cocontraction
- Fatigue
– Performance enhancement reduced co-contractions
PNF
Stretch - efferent tyoe 2
Contraction - alpha motor neuron
Feedback - gamma
Renshaw cell - confused which override the sensory feedback
Bilateral deficit (BLD)
The maximum voluntary force produced by a subject with two limbs activated simultaneously is less than the sum of the forces when the same time limbs are active independently.
e.g. cyclists
Bilateral facilitation (BLF)
The maximum voluntary
force produced by a subject with two limbs activated simultaneously is more than the sum of the forces when the same time limbs are active independently.
e.g. weightlifters
Maximal conduction velocity of a large alpha motor neuron is
up to 101 m/s
