wk 7 - muscle movements Flashcards
what does the iliospoas do
hip flexor
glute max/med
hip abductors
bicep femoris
hip extensor, knee flexor
rectus femoris
hip flexor, knee extensor
gastrocnemius
knee flexor, ankle plantar flexor
tibialis anterior, extensor digitorum longus, extensor hallucis longus
dorsiflexor
soleus
ankle plantar flexor
fibularis longus
plantar flexor, evertor of the foot
muscle contracttion types
concentric- shortening against load
eccentric- lengthening under load
ismetric- maintaining constant legnth against load
sites of common lesions affecting gait include
- motor cortex (stroke, head injury)
- UMN (spinal cord injury)
- anterior horn cell (polio)
- peripheral nerve (nerve injury)
5.musle (muscle dystrophy)
muscle fibre types
Type I (slow twitch)
* Low to moderate force over long periods
* Aerobic metabolism
* Fatigue resistant
- Type IIB (fast twitch)
- Higher forces generated
- Glycolytic metabolism
- Easily fatigued
- Type IIA
- Properties intermediate between Type I and Type IIB
what does EMG do?
EMG measures the electrical activity of a contracting
muscle (the muscle action potential at the motor unit)
types of EMG electrodes? (2)
- surface electrodes
fixed to the skin overlying the
muscle
* Can pick up muscle action
potentials from many (superficial)
motor units
* Not appropriate for deep
muscles
* Interference from adjacent
muscles (“cross-talk” - fine wire electrodes
inserted into the muscle belly using a needle
can be painful/invasive
signal comes from small region of a muscle so correct placement is crucial
EMG parametres (5)
- Peak activity (magnitude usually expressed as %MVC)
- Time to peak (seconds)
- Average activity (magnitude usually expressed as %MVC)
- Onset/offset times (% gait cycle)
- Duration of muscle activity (% gait cycle)
adductor longus
hip adductor
understand power generation during the gait cycle
discuss the role of individual muscles during the gait cycle
reliability (ICC) what does it tell us
closer to 1 is the most reliable
above 0.9 is excellent
above 0.7 is good
repeatability (RC) tells us what
the greater the change, the more clinically significant the findings are??????
interpreting and understanding research paratmeters/ reliability/ repeatability - IN EXAM
What can’t the EMG do and what do the signals depend on?
cannot differentiate between concentric, eccentric and isometric contractions but tells us when the muscle switches on and switches off (muscle activity)
EMG signal depends on length-tension relationship of muscle.
EMG activity does not affect force output. higher EMG activity does not mean the force production has increased (not linear)
joint power analysis for EMG tells us what
power analysis can differentiate between eccentric, concentric loading of ankle plantarflexors
joint moment for EMG tells us what
only tells us a simple version of joint moments occuring ???????
understand what power analysis - in exam for research paper
eccentric followed by concentric movement. ankle plantarflexors and dorsiflexors
what is power (formula, in joint terms, units)
p= force x velocity
power (watts) = moment (Nm) x angular velocity (radians per second or degrees per second)
power exchange during gait cycle and reference to type of muscle contractions
kinetic and potential energy
power exchanges take place across the hip, knee and ankle joints throughout the gait cycle (swapping between kinetic energy and potential energy-stored)`
-concentric muscle contraction: power is generated
-eccentric: absorbs power
-isometric: no power exchange takes place
same occurs with ligaments not just muscles
during initial contact what power flow occurs in the limb
impact with the floor, absorbs the power of the limb, eccentric contraction (dorsifexors)
during midstance what power flow occurs in the limb
flow reverses and leg power increases due to power generation at the ankle (plantar flexors)
after toe off what power flow occurs
more power flows through the hip joint (hip flexors working during swing phase, hip extensors working after it)
what happens in the ankle during loading response, midstance and terminal stance
Ankle dorsiflexors restrain foot slap eccentrically (power absorption)
plantarfleors control forward momentum of the tibia eccentrically (power absorption)
plantarflexors raise heel concentrically (power generation)
at initial contact what muscles are involved and where is the ground reaction force located for the hip/knee/ankle
- Simultaneous activity of knee extensors
and flexors
– stabilise and position knee - Hip extensors decelerate thigh (glute max)
– drives knee extension - Tibialis anterior eccentric contraction
– eases foot to floor
– prevents foot slap
GRF anterior to hip, posterior to knee and ankle
loading response what muscles involved? + GRF
- Weight acceptance
– controlled collapse
– knee spring (quads & vasti) - tiny bit of Ankle plantarfexion (eccentric)
– allows CoP to move forward
– shifts reaction force of body anterior at
the knee
– thus aids knee extension - Gluteus medius contracts (isometric)
– stabilises pelvis (frontal plane)
GRF: anterior to hip, posterior to knee, anterior to ankle
midstance muscles involved + GRF
Controlled lengthening of soleus
– keeps foot/forefoot “pressed’ to ground
– allowing shank to lean forward
- Minimal muscle activity
– body is “falling” forward
– has momentum and kinetic energy
GRF: posterior to hip, anterior to knee and ankle
terminal swing + GRF
- Ankle plantarflexors
– concentric contraction
– accelerates body forward
(This burst of activity is responsible for
most of the power generation which
occurs in walking) - Iliopsoas
– Small burst of activity
– Leads unloading process of pre-swing
GRF: posterior to hip, anterior to knee, anterior to ankle
pre swing and initial swing + GRF
Hip flexors (iliopsoas & rectus femoris)
– concentric contraction
– starts to lift femur
– starts to swing limb forward
- Limb is like a passive pendulum
– pendulum swing is regulated by the
way the limb is flexed (moment of
inertia) - Tibialis anterior gives foot ground clearance
GRF: posterior to hip, posterior to knee, anterior to ankle
terminal swing + GRF
Hamstring contraction
– eccentric and/or isometric
– controlled slowing of shank
– energy transfer to hip & pelvis
- Ankle
– Tibialis anterior changes to eccentric
contraction
– Foot finely adjusted in preparation for
initial contact
GRF: anterior to hip, posterior to knee and ankle
most muscle activity is active when?
active at the start and end of swing
minimal activity in mid stance (switch off)
accelerates and decelerate movements
know your reference for degrees during gait
10% peak dorsiflexion terminal swing
60% knee flexion during swing
etc
