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Physiology of Exercise > Physiology of Strength and Power > Flashcards

Physiology of Strength and Power Flashcards

1
Q

How is a muscle action produced?

A

A result of the activation signal produced by the nervous system and the force produced by the muscle-tendon unit. This leads to joint action

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2
Q

Innovation Ratio

A

The ratio between the number of fibres that are innovated by a single neuron.

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3
Q

What is a motor unit comprised of?

A

Alpha motoneurone
Spinal cord
Axons
Fibres

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4
Q

Why is the size of the motor neuron and motor unit important?

A

The activation signal from the motor unit needs to be transformed into contractile activity. Done in an orderly fashion (size principle)

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5
Q

How do neurotransmitters depolarise cells?

A

Through the post-synaptic membrane

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6
Q

Muscle spindles

A

receptors in the muscle that are sensitive to changes in the muscle length

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7
Q

Muscle contraction

A

Muscles contract to shorten the muscle and reduce the stimulus. This happens quickly and allows us to regulate where we are in space

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8
Q

Golgi-tendon organs

A

Receptor that controls tension in the muscle
They send an inhibitory signal into the alpha motoneurone - protective mechanism against excessive tension of the muscle.

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9
Q

The size principle

A

Smaller motor units are recruited first. As a greater force is produced, bigger motor units are recruited.
As motor units are recruited, a twitch occurs (basic contractile response to an action potential).
Lot of twitches are produced at the same time

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10
Q

Producing very high forces

A

We have to discharge motor units at very high frequency and this leads to a summation of the twitches (tetinus).

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11
Q

Max contraction

A

Max contraction for a few seconds (jumping before a sprint) the twitch amplitude of a motor unit will increase and force production will increase acutely.

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12
Q

What does a warm up do?

A

Primes the nervous system to drive the muscles at a higher capacity than it would do with no warm up.

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13
Q

How to increase the force producing

A

You need to recruit more motor units to increase twitch size or discharge motor units at a higher frequency (rate coding)

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14
Q

What happens when you recruit new motor units?

A

the twitches summate and the force production is bigger

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15
Q

Fine motor control muscle (muscles of the finger)

A

Muscles will recruit units at 50% of max force so any further increase will come from discharging at a higher frequency. This is to maintain the resolution of the action, son it remains accurate with low errors.

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16
Q

High force muscles

A

Recruit more motor units to increase the output

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17
Q

Rate coding

A

The first recruited units (smallest units) will reach higher discharge rates that those units recruited later - has more time to develop the discharge rate.

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18
Q

What dictates how fast you can produce force?

A

How high the rate coding is at the beginning and how quickly you are able to recruit all motor units.

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19
Q

Fatigue and max force production

A

When we fatigue our max production capacity decreases. New units are recruited and the rate coding is adjusted. The discharge frequency is increased in the motor units.

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20
Q

The change point of fatigue and force production

A

The later the direction of change point the longer the task (using this you can predict how long a person can perform that action). The later that point the longer the task.

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21
Q

Contractile element of the muscle fibre

A

Active portion of the muscle
Characterised by force length

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22
Q

Sarioelastic element of the muscle fibre

A

can be divided into active (elasticity of the myofibril and the sliding filament/cross bridges) and passive components (tendons and connective tissues)

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23
Q

Paraelastic element of the muscle fibre

A

modulator that transmits the force from the fibres onto the skeleton

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24
Q

Tendons

A

Passive component of force production through recall of the tendon.
At longer length muscles the recall has a greater contribution
Can train the force-length relationship

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25
Q

Force - Velocity relationship

A

Muscles can adapt for lots of different loads, by modulating the velocity at which the muscle contracts.
High loads = slower contraction to reach the force needed
Can modulate by increasing the temperature of a muscle, all values will increase

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26
Q

When is max power produced?

A

About 1/3 velocity is when you produced the max power

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27
Q

How are fibres are arranged in the muscle?

A

Series
Parallel

28
Q

Series

A

range of motion of muscle is maximised because length at which muscle can operate increases, maximises velocity in the force production

29
Q

Parallel

A

maximises force, increases strength

30
Q

Maximising muscle mechanical properties

A

To maximise force, operate at about 1/2 length of the muscle. Sacrifice speed
To max power, sacrifice force production

31
Q

Stretch-shortening cycle

A

Series of actions makes the movement more economical.
Allows tendon to store elastic energy, can invoke some reflex into that muscle - produce higher forces.

32
Q

How to increase muscle performance?

A

Improve neural activation and muscle-tendon force.
There is a skill element as well - training in a specific way helps you to be strong in the way you need for sport

33
Q

Training adaptations in first few weeks of resistance training

A

An untrained person starting resistance training will increase strength rapidly.
First few week = no increase in muscle mass, increase is due to skill adaptations and neural adaptations

34
Q

Training adaptations after training for a few year

A

Increases in strength are largely a result of an increase in muscle size and increase in contractile proteins that are in muscle tissue.
Other adaptations are relevant but they are smaller contributors to strength increase.

35
Q

Neural adaptations

A

Adaptations in the cortical centre (motor cortex) due to strength training result in an decreasing inhibitory input in the motor cortex.
Alpha motoneurone is the main transducer of activation signals to muscle contractions

36
Q

Where do inputs from the nervous system converge?

A

Alpha motoneurone

37
Q

Performing resistance training on an untrained person will cause:

A

Recruitment of more motor units
Discharging motor units at a higher frequency

38
Q
A
39
Q

The effect of strength training on the threshold of recruitment

A

The threshold at which recruitment will occur will decrease with strength training - more effective at producing force.

40
Q

Derecruitment

A

time at which the muscle relaxes (motor unit is not active). Unaffected by training.
Happens in certain situations (stroke)

41
Q

What happens when we are performing an action?

A

We don’t just use the agonist, there are also lots of synergists involved as well as the antagonist. These protect the joints and the bones, but are counterproductive to force production

42
Q

H reflex

A

The electrophysiological equivalent to a tendon-tap reflex

43
Q

Muscle spindles

A

Muscle receptor that detects length and rate of change of length in the muscle
Project via the interneuron (transmits information from one side of the body to the other)
Have an inhibitory effect - when they are excited they inhibit the antagonist muscle, so we can move freely not stiffly.

44
Q

Electromyography (EMG)

A

Not the best way to measure muscle activation - has limitations
It is a very simplistic view of the role of the antagonist

45
Q

Antagonist coactivation

A

After 8 weeks of training, strong evidence that by using complex simulation procedures on nerves you can reduce the activation of the antagonist.
Increase the activation of the agonist and decrease the activation of the antagonist - a combo of these increase force

46
Q

Why is muscle size important?

A

there is a close linear relationship (high correlation) between cross sectional area of the muscle and the force they can produce

47
Q

What is strength also influenced by

A

Genetic components
Muscle mechanical properties (how tendons attach)
Environmental factors - can’t control these

48
Q

Estimated force =

A

cross sectional area x tension a fibre can produce

49
Q

How to increase muscle size

A

By increasing the amount of contractile proteins you have in the muscle tissue and connective tissue (hypertrophy)

50
Q

Specific Tension

A

how much tension a specific fibre can theoretically produce. Bigger fibres have greater tension

51
Q

Myonuclei

A

Fills up with contractile proteins when you put stimulus on the muscle.
Limits you very quickly on building up muscle.
Can only take on so many proteins

52
Q

Satellite cells

A

Single nuclei cells
Activated by protein synthesis
Signalling pathways to trigger protein synthesis involve gene expression
Progress into myonuclei so can be filled with contractile proteins as well

53
Q

Ratio of protein synthesis and breakdown

A

Each training session you do causes protein breakdown
If ratio between breakdown and synthesis is positive = growing muscle
If ratio is negative no muscle growth = overtraining

54
Q

What happens when there is a muscle stimulus?

A

You will trigger the signalling pathway which activates mTOR (enzyme)

55
Q

Signalling protein goal

A

activate mTOR which leads to protein synthesis and hypertrophy.
Proteins are stacked in parallel (maximises force production) - increases force producing capacity of the muscle
Proteins in series would maximise length of the muscle and the velocity with which it would contract

56
Q

Why is mechanical tension needed?

A

to maintain the muscle mass you have for normal daily function

57
Q

Exercising individuals at different intensities

A

protein synthesis will be maximised by using higher loads - high loads not necessary for hypertrophy
As long as you reach a given threshold of a muscle you will increase the muscle mass. Need to go into failure and need to do a lot of sets

58
Q

H-zone

A

where the thick and thin filaments overlap during contractions

59
Q

Why aren’t sarcomeres aligned perfectly?

A

They are at a slight angle.
When there’s enough tension and the thin filaments are being pulled it causes a rupture in the Z-disk and that causes the repair of the muscle (protein synthesis)
Mechanical tension has to be high or the Z-disk won’t rupture

60
Q

Muscle damage

A

Occurs when you perform certain actions (something new)
Causes a disruption in the extracellular matrix of the muscle which leads to a cascade of processes that are linked to information that excites receptors in the muscle and you feel soreness
Soreness typically delayed - after 2 days, slowly disappears

61
Q

Why is muscle damage more prevalent in eccentric contractions

A

forces are high and doing contractions at longer muscle lengths
You are putting your muscle in a position where it will produce higher forces and it will cause a greater disruption in the sarcomere

62
Q

Muscle damage and mechanical tension

A

Difficult to separate
Difficult to introduce muscle damage without mechanical tension and it’s difficult to induce hypertrophy without mechanical tension

63
Q

Blood flow restriction training

A

Reducing blood flow causes the accumulation of metabolites during exercise in the muscle. Blood can’t get in to remove the metabolites
Done at fairly light loads
At a given percentage of max it induces hypertrophy

64
Q

Hypertrophy

A

accumulation of proteins within a given muscle fibre

65
Q

Specificity of strength

A

The way we express and how we express the neural activation and power is important.
More typical resistance training causes increase of strength in concentric contractions, not as much eccentric

66
Q

Hyperplasia

A

the splitting of a muscle into two cells. The daughter eventually becomes an adult muscle cell.
Increases cell count in the body and size in a more effective way

Physiology of Exercise (11 decks)

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