Lecture 6 : Flexibility Training Flashcards
(46 cards)
when we stretch we are attempting to alter … .
attempting to alter muscle tone
muscle spindles generate tone by …
activating the stretch reflex
explain the stretch reflex
afferent neurons carry the dynamic signal to spinal cord
efferent signal from the cord (via alpha motor neuron) comes via efferent neurons to muscle fibres
causing sudden contraction of the muscle
how do muscles maintain tone ? (sustained stretch of muscle stimulates a different type of afferent neuron)
stimulates nuclear chain fibres and type II afferents carry the signal to the cord
efferent signal travels to muscle
how is the contraction caused by efferent signals different when it is from a sustained stretch (and what does this mean)
there will be asynchronous contraction of muscle fibres meaning motor units not discharging all togther)
this results in mild sustained contraction of these fibres as long as it is stretched
what happens to golgi tendon in sustained stretch (golgi threshold)
golgi threshold : a more intense stretch will trigger a stronger reflex contraction
what happens to golgi tendon in sustained stretch where the golgi threshold is passed (what is this known as) (this is a protective mechanism but research suggests its not the mechanism related to acute responses of stretching)
after crossing threshold, contraction stops and the muscle relaxes
this is known as the ‘inverse stretch reflex’ and is mediated by the golgi tendon organ present in the fascicles of a tendon
what does the research say about golgi threshold triggering autogenic inhibition
it seems like a logical mechanism - however current research suggests it may be unlikely
what does the current research say the likely mechanism that causes us to relax after holding a stretch ???
superspinal
suggesting that brain is modulating the descending drive which is having an effect on persistent inward currents
this changes the excitability of the spinal reflex
current research suggests that what happens to persistent inward current from static stretching (and what does this depend on)
static stretching decreases persistent inward current which decreases the excitability of the motor neuron
this will depend on the intensity and duration of the stretching
why do researchers not think that autogenic inhibition from golgi tendon threshold is the primary mechanism
because if it was, it wouldn’t last long enough so it wouldn’t explain some of the performance determinants that we see after a stretch
how does stretching increase ROM acutely
- changing excitation, physiological mechanisms
- decreasing viscosity of tissue
is the elasticity of the tissue changing in chronic stretching ?
no its the tonus and how we modulate muscle tone in the muscle not the elasticity of the tissue
tendon modulates force from …
from the muscle to the bones and back again
the muscle tendon unit can control the rate of …… or the rate that …
rate of elongation of the muscle or the rate that force is distributed to the muscle
when is the muscle tendon unit under the highest amount of load when you are landing on the ground and why
when you have fully touched down but not at rest
because the tendon is under full stretch muscle is under full contraction
is power negative or positive in muscle tendon unit when you have fully touched down landing but not at rest
negative meaning energy is being absorbed, energy moving from the tendon to the muscle
at rest after landing what happens to energy in the tendon
energy stored in the tendon is returned to the muscle
at what point of landing might we see the effect of muscle tendon viscosity or stiffness and what does that modulate
when at rest in the transfer of energy from tendon to muscle
it can modulate how fast we transfer the energy
when we lower viscosity what happens to resistance and hysteresis
lower the resistance and decrease hysteresis
after long term stretching what happens to the unloading curve of the hysteresis curve (what does this mean for energy and the tendon)
less energy is lost, the unloading curve shifts to the left, the tendon is stiffer during the unloading phase
muscle tendon injuries probably have very little to do with ROM and more to do with ..
energy return and timing of energy return
what is proprioceptive neuromuscular facilitation stretches
engage the muscle in an active contraction prior to stretching
what is the traditional thinking about proprioceptive neuromuscular facilitation (PNF) stretching and is this still correct
they thought that you could relax one muscle in order to increase range of motion of another group
THIS IS WRONG
