WEEK 3 Flashcards
define torque
torque is force x momentum arm which is rotational or angular
define a moment arm
perpendicular, distance arm between the line of action of the force to the axis of rotation
define a moment arm for skeletal muscle
the distance from the joint axis of rotation to the muscles force vector
what happens to the moment arm when there is damage to the spinal cord at a cervical level ( x2)
- loss of function
- loss of balance of the wrist:
= flexed
what happens to the moment arm after a tendon transfer occurs from spinal cord damage. ( x2)
- increased wrist extension moment arm
- increased wrist extension strength
define a concentric contraction
concentric contractions is when a muscle shortens and produces force
define eccentric contractions
an eccentric contraction is when a muscle lengthens while producing force
define isometric contraction
an isometric contraction is when a muscle length is unchanged while producing force
define an agonist
a muscle which when it contracts it performs the desired action
define anatagonist
an antagonist muscle is a muscle which when it contracts it performs the opposite of the desired action
define a prime mover
a muscle that contributes considerably to a movement
define assistant movers
an assistant mover is a muscle which contributes to a movement but not considerably.
what are the 2 key principles of two joint muscles
1) when a muscle contracts and shortens it WANTS to produce all of its desired actions
2) just because a particular action is present does not mean that all muscles that contribute to that joint action will be active.
describe stabilisation energy x2
1- when a muscle contracts and shortens it WANTS to produce ALL of its actions
2- what a muscle can do is not an indication of what it will do
define stabilisation
a stabiliser is a muscle that acts isometrically or quasi- isometrically to prevent unwanted movement of a joint
define HELP synergy
when muscles with a common action and opposing actions cancel out their opposing actions to produce the common action
define TRUE synergy
one or more actions of a muscle is opposed by a muscle which doesn’t contribute to the observed movement, to allow for the observed movement to occur
helping synergy: what muscles are involved helping medial rotation and lateral rotation
medial:
- semitendinosus
- semimembranosus
lateral:
- biceps femoris LH
- biceps femoris SH
what are the 4 steps for muscle contraction to occur
1) the brain receives the message
2) this is then transferred to the spinal cord
3) then the neural drive goes to the muscle
4) muscle contraction occurs
what is the order of the muscle components (x5)
- muscle belly
- muscle fascicle
- muscle fibre
- myofibril
- sacromere
describe motor units and force production (x2)
- increase force means that increases the size of units
- increased force is the increased rate of AP discharge
describe the size principle
increased force means there is increased number of motor neurone
break down the word electromyography
electro= electrical activity
myo= muscle
graphy= measure
define electromyography
a measure of a movement.
describe bi polar electrodes ( x2)
- subtracting the signal between electrodes eliminates majority of the noise
- amplified signal= potential difference between two recording electrodes
what are the 3 factors that affect EMG and describe them
1) number of active motor units= increase motor unit recruitment therefore increasing EMG.
2) motor unit firing rates= increased firing rate means increased increased EMG
3) motor unit synchrony= increased synchrony means increased EMG
what is the first step to collecting electromyography data
1) skin preparation
- this means shave to remove hair
- abrade- remove the hair and excess
- apply alcohol wipe to sterilise the site
purpose= to reduce the skin resistance and therefore allow greater amplitude and frequency of EMG
what are the 5 processes of electromyography
1) remove offset= centre data to zero
2) high pass filter= remove the motion artefact
3) rectify= converts data to absolute value
4) smoothing= typically with low pass filter
5) normalisation= facilitates comparison of singles
what are the limitations of EMG (x2)
1- surface is limited to larger, superficial muscles
2- pick up nodes tend to exceed the intended muscle size
