Lecture 5 : Why We Stretch

Question 1

5 factors that limit our range of motion

Answer 1

1. active structures
2. passive structures
3. viscosity
4. central nervous system
5. discomfort

Question 2

what are active structures that limit our ROM and they are the only part of the body that can actively ….

Answer 2

muscle fascicles, active tissues in muscle are the only parts of the body that can actively change their tension and length

Question 3

what are passive structures that limit our ROM and how can their length change

Answer 3

tendons, aponeuroses, joint capsules and ligaments contribute to ROM restrictions with passive muscle elongation

can only change length or tension when we passively put load on them

Question 4

how does viscosity effect flexibility (ground substance : what is it and what does it do)

Answer 4

ground substance in connective tissues is a gel like substance which mechanical properties change based on temperature and other things

this can increase or decrease resistance to movement

Question 5

how does the central nervous system affect ROM

Answer 5

a highly activated central nervous system could increase muscle tonus and with a less relaxed muscle inhibit flexibility

Question 6

how does the discomfort affect ROM

Answer 6

pushing a joint to its maximum ROM can be uncomfortable, the ability to tolerate pain may allow some individuals to stretch further than others

Question 7

what are easily stretched muscles called and what are examples

Answer 7

biarticular muscles e.g hamstrings, gastroc, rectus femoris etc

Question 8

what are anatomically impossible muscles to stretch called and what are examples

Answer 8

monoartciular muscles e.g tibialis anterior, masseter, intercostals etc

Question 9

myofibrils can be stretched to what length without damage

Answer 9

twice their resting length without damage

Question 10

what is titin and what is it stretching ability

Answer 10

curly protein bands that sit at the end of your muscle fibrils

massive stretching ability

Question 11

what is fibronectin and what does it do

Answer 11

protein that links to the surface fibre of the muscle, tends to stimulate cells on the surface of the fibre

Question 12

what length of the muscle is the point from which we can usually develop the most active force

Answer 12

at resting length is where the most binding of actin and myosin occurs

Question 13

what occurs beyond resting length of the muscle in terms of actin and myosin and force generated

Answer 13

beyond this length we start elongating, fewer actin and myosin are connected, we are no longer able to produce as much force actively

passive tension increases as active force is reduced

Question 14

what allows us to maintain a certain amount of force production as the muscle elongates and we aren’t able to produce as much force actively

Answer 14

passive tension increases

Question 15

how to train the active component of muscle

Answer 15

resistance training

Question 16

how to train the passive and active component of muscle

Answer 16

eccentric movements

Question 17

what does the evidence say about stretchiing increasing the range of motion

Answer 17

yes acute and chronic stretching has been shown to increase the range of motion in hamstring and gastroc

but there are trivial results regarding impact to muscle stiffness

Question 18

what are the two acute effects of stretching

Answer 18

1. decrease viscosity
2. alter muscle tone

Question 19

what are the thixotropic effects of acute stretching and how this decreases viscosity

Answer 19

thixotrophy is a time dependent property of materials that become less viscous (more fluid like) when moved or stressed but return to more gel like state when left undisturbed

Question 20

in the context of muscles, tendons and connective tissues thixotrophic effects influence …

Answer 20

stiffness, flexibility and resistance to movement

Question 21

without movement, tissues become ….. due to ….

Answer 21

become stiffer, due to the gel like behaviour of intracellular and extracellular components, including actin myosin cross bridges and connective tissue ground substance

Question 22

how does the term move it or lose it link to ground substance

Answer 22

ground substance in tissues becomes stiff with periods of inactivity

Question 23

as viscosity decreases what happens to hysteresis

Answer 23

hysteresis also decreases (tissues become more efficient)

Question 24

in the loading and unloading curve (stress and strain) what does the area under the curve indicate

Answer 24

amount of energy being returned to the body

Question 25

in the loading and unloading curve (stress and strain) what does the area inside the curve indicate

Answer 25

how much energy is lost in the system

Question 26

what does prolonged static stretching do to muscle spindles

Answer 26

leads to a gradual desensitisation of muscle spindles, reducing the stretch reflex and decreasing muscle excitation

Question 27

prolonged stretching leads to the gradual desensitisation of muscle spindles, reduces the stretch reflex and decreasing muscle excitation what does this do (2 and 2 buts)

Answer 27

lowers muscle stiffness and enhances range of motion, but may reduce force output and reaction speed

Question 28

why is force production decreased when there is a gradual desensitisation of muscle spindles

Answer 28

because you are basically ignoring the spinal signal of saying enhance muscle activity, so force production is decreased

Question 29

hold a stretch for longer than how long to be able to desensitize muscle spindles

Answer 29

must hold a stretch for 30 seconds

Question 30

hold a stretch does what to the golgi tendon

Answer 30

activates the GTO mediated inhibitory response, leading to muscle relaxation (autogenic inhibition)

Question 31

what does the GTO mediated inhibitory response lead to (motor unit)

Answer 31

reduces motor unit recruitment, contributing to decreased muscle excitation

Question 32

what does the golgi tendon do

Answer 32

sense the load through the tendon, protects your joints against excessive loading it stimulates the antagonist muscle to turn off

Question 33

what does static stretching do to alpha motor neuron and what does that lead to

Answer 33

reduces alpha motor neuron excitability, leading to decreased voluntary and reflexive muscle activation

Question 34

what type of fibres are highly effected by stretching and desensitisation

Answer 34

type 2 fibres

Question 35

what does static stretching do to CNS mediated changes and what does this contribute to

Answer 35

static stretching may reduce cortical drive from the CNS, reducing the excitability of motor neurons this contributes to a short term decrease in neuromuscular performance following static stretching

Question 36

what does PICs in alpha motor neurons stand for

Answer 36

persistent inward currents

Question 37

what are persistent inward currents and do they do

Answer 37

PICs are slowly inactivating ion currents that can amplify and prolong motor neuron output

Question 38

what are PICs controlled by

Answer 38

descending input from the brainstem, particularly from monoaminergic system (serotonin and norepinephrine)

Question 39

PICs currents allow motor neurons to ....

Answer 39

continue firing even with minimal or no additional input, enhancing force production, muscle tone and reflex activity

Question 40

static stretching typically reduces muscle excitation, and this could involve suppression of ....

Answer 40

suppression of PIC activity through inhibition of spinal excitability

Question 41

how does dynamic acute stretching compare to static stretching in terms of neural excitability

Answer 41

opposite effect

Question 42

what happens to muscle spindle sensitivity in dynamic stretching

Answer 42

enhanced

Question 43

what happens to golgi tendon activation in dynamic stretching

Answer 43

limited

Question 44

what happens to alpha motor neuron excitability in dynamic stretching

Answer 44

increased : increased motor unit recruitment

Question 45

what happens to CNS mediated changes in excitability in dynamic stretching

Answer 45

increased excitability

Question 46

list 4 chronic effects of stretching

Answer 46

- increased stretch tolerance - structural adaptations - promote increased collagen turnover and remodelling in tendon - improved collagen alignment and fibroblast activity in other connective tissue

Question 47

how is stretch tolerance increased from chronic stretching

Answer 47

- inhibition of E reflexes - decrease the feeling of discomfort, reducing the sensitivity of neuroreceptors

Question 48

what are the structural adaptations of chronic stretching

Answer 48

- fascicle length (high volume ) - muscle thickness (high intensity) - increased muscle compliance - the ability to stretch it

Question 49

stretching promotes collagen turnover and remodelling in tendon (how does this differ in static compared to dynamic stretching)

Answer 49

static : reduce tendon stiffness dynamic stretching : increase tendon stiffness

Question 50

what happens to muscle structure from chronic stretching

Answer 50

muscle length increases (sarcomerogenesis)

Question 51

what happens to sarcomeres from chronic stretching and what does this allow for .... and what does that improve

Answer 51

more sarcomeres in series, allows for greater elongation without excessive tension improving functional range of motion

Question 52

what does more saromeres in parallel mean

Answer 52

give us thickness, which gives us more power, strength and force production

Question 53

what does more sarcomeres in series mean

Answer 53

longer, which is faster muscle because they all shorten at the same time

Question 54

what happens to contraction velocity when sarcomeres are added in series

Answer 54

greater contraction velocity

Question 55

what happens when you apply tension to muscle (fibronectin molecules 2)

Answer 55

these are attached to your satellite cells (membrane of muscle), applying tension of the muscle stimulates these which causes cell turnover and stimulates protein synthesis

Question 56

what can chronic stretching to do the pennation angle of the muscle and what does this do to muscle fibres

Answer 56

can decrease the pennation angle, leading to longer more parallel muscle fibres

Question 57

what does more parallel muscle fibres improve but slightly reduce

Answer 57

improves muscle extensibility but may slightly reduce force production, as force is typically maximised in more pennated muscles

Question 58

stretching will chronically and acutely increase ....

Answer 58

ROM in muscles that we can anatomically stretch - warming up fluids, inhibiting tonic muscle reflexes, increasing stretch tolerance

Question 59

stretching may plausibly reduce risk of ...

Answer 59

injury in hamstring muscles in sprinting athletes

Question 60

there is no evidence of reduced injury risk from stretching in ...

Answer 60

recreationally active people

Question 61

stretching may have other health benefits that are ...

Answer 61

more important than muscle injury

Question 62

who should stretch

Answer 62

- want to improve flexibility (general health) - athletes who require large ROM (e.g gymnasts, ice hockey goalies, dancers) - potentially beneficial to field athletes as protection for hamstring