Week 2 (part a) Flashcards
Muscle contraction and relaxation involves several steps between depolarisation of the ______ and cross bridge attachment involving ___ and ___
a-motor neuron, myosin and actin
Strength is a function of the number of sarcomeres and muscle fibres in _____, which explains why strength is related to the cross sectional area of a muscle.
parallel (not in series)
Following puberty, ____ muscle mass percentage increases more than ___% from testosterone
boys, 10% (Total 53%)
Girls stays the same at 42%
Despite the dimensional theory stating exponent should be 2.0, a study showed that in schoolboys it was much lower/higher?
higher - Average over 3.0
Factors influencing strength (5)
- Muscle length
- Contraction velocity
- Motor unit type (faster usually stronger)
- Muscle architecture
- Type of contraction (strength higher when lengthening not shortening)
Nerve conduction velocity is….
The speed at which motor and sensory impulses transverse a given section of nerve (m/s)
Nerve conduction velocity is influenced by…. (4)?
- axonal diameter
- local tissue temperature
- age
- height
A newborn has how much nerve conduction velocity of an adult?
Half. It increases rapidly the first year of life.
There is an increase in nerve conduction velocity between ages 0 - 20 that’s associated with…
age and muscle diameter
The level of force of a motor unit can be varied by changing…?
- The number of MUs recruited
- The firing rate of a-motor neurons
Some evidence suggests a lower amount of type ____ fibres in children
Type II
In a review, Dotan et al (2012) hypothesised that children …… type II motor units to the extent typical adults do
do not fully recruit or fully optimise use of type II fibres
The increase in muscle cross sectional area with age (until about age 20-25), is linked not to the _____ but rather _____
the number of fibres but rather the type of fibre (slow twitch decreases and fast twitch increase).
At age 5: Approx ___% fast twitch fibres
35%
At age 30: Approx ___% fast twitch fibres
50%
From a young child to adulthood, the amount of antagonist force increases/decreases
decreases (while agonist force increases)
Blimkie (1989) reported that motor unit activation for knee extensors was significantly higher in younger/older?
older (teens) vs younger (child)
The number of neurons present by early adulthood already exist at birth/early infancy (T/F)
True
Muscle damage releases what into the bloodstream?
creatine kinase
Children appear to have less/more muscle damage compared to adults post exercise
less
Is the development of strength in growing children linked to muscle cross-sectional area?
Somewhat but not all strength
Is the development of strength in growing children linked to nerve conduction velocity?
At some level, yes
Is the development of strength in growing children linked to recruitment of type II motor units?
In theory yes, but lacks evidence
Is the development of strength in growing children linked to the transformation of type I to type II fibres?
Some evidence for it
Is the development of strength in growing children linked to agonist-antagonist co-contraction?
may contribute but most evidence is for dynamic contraction and seems to be less evidence for isometric contraction
Is the development of strength in growing children linked to central inhibition?
Some evidence in young children
Children gain isometric and isokinetic strength as they grow due to …?
Muscular enlargement (fibre hypertrophy)
