wk 7 - muscle movements

Question 1

what does the iliospoas do

Answer 1

hip flexor

Question 2

glute max/med

Answer 2

hip abductors

Question 3

bicep femoris

Answer 3

hip extensor, knee flexor

Question 4

rectus femoris

Answer 4

hip flexor, knee extensor

Question 5

gastrocnemius

Answer 5

knee flexor, ankle plantar flexor

Question 6

tibialis anterior, extensor digitorum longus, extensor hallucis longus

Answer 6

dorsiflexor

Question 7

soleus

Answer 7

ankle plantar flexor

Question 8

fibularis longus

Answer 8

plantar flexor, evertor of the foot

Question 9

muscle contracttion types

Answer 9

concentric- shortening against load
eccentric- lengthening under load
ismetric- maintaining constant legnth against load

Question 10

sites of common lesions affecting gait include

Answer 10

1. motor cortex (stroke, head injury)
2. UMN (spinal cord injury)
3. anterior horn cell (polio)
4. peripheral nerve (nerve injury)
   5.musle (muscle dystrophy)

Question 11

muscle fibre types

Answer 11

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

Question 12

what does EMG do?

Answer 12

EMG measures the electrical activity of a contracting
muscle (the muscle action potential at the motor unit)

Question 13

types of EMG electrodes? (2)

Answer 13

1. 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”
2. 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

Question 14

EMG parametres (5)

Answer 14

• 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)

Question 15

adductor longus

Answer 15

hip adductor

Question 16

understand power generation during the gait cycle

Question 17

discuss the role of individual muscles during the gait cycle

Question 18

reliability (ICC) what does it tell us

Answer 18

closer to 1 is the most reliable

above 0.9 is excellent
above 0.7 is good

Question 19

repeatability (RC) tells us what

Answer 19

the greater the change, the more clinically significant the findings are??????

Question 20

interpreting and understanding research paratmeters/ reliability/ repeatability - IN EXAM

Question 21

What can’t the EMG do and what do the signals depend on?

Answer 21

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)

Question 22

joint power analysis for EMG tells us what

Answer 22

power analysis can differentiate between eccentric, concentric loading of ankle plantarflexors

Question 23

joint moment for EMG tells us what

Answer 23

only tells us a simple version of joint moments occuring ???????

Question 24

understand what power analysis - in exam for research paper

Answer 24

eccentric followed by concentric movement. ankle plantarflexors and dorsiflexors

Question 25

what is power (formula, in joint terms, units)

Answer 25

p= force x velocity power (watts) = moment (Nm) x angular velocity (radians per second or degrees per second)

Question 26

power exchange during gait cycle and reference to type of muscle contractions

Answer 26

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

Question 27

during initial contact what power flow occurs in the limb

Answer 27

impact with the floor, absorbs the power of the limb, eccentric contraction (dorsifexors)

Question 28

during midstance what power flow occurs in the limb

Answer 28

flow reverses and leg power increases due to power generation at the ankle (plantar flexors)

Question 29

after toe off what power flow occurs

Answer 29

more power flows through the hip joint (hip flexors working during swing phase, hip extensors working after it)

Question 30

what happens in the ankle during loading response, midstance and terminal stance

Answer 30

Ankle dorsiflexors restrain foot slap eccentrically (power absorption) plantarfleors control forward momentum of the tibia eccentrically (power absorption) plantarflexors raise heel concentrically (power generation)

Question 31

at initial contact what muscles are involved and where is the ground reaction force located for the hip/knee/ankle

Answer 31

* 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

Question 32

loading response what muscles involved? + GRF

Answer 32

* 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

Question 33

midstance muscles involved + GRF

Answer 33

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

Question 34

terminal swing + GRF

Answer 34

* 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

Question 35

pre swing and initial swing + GRF

Answer 35

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

Question 36

terminal swing + GRF

Answer 36

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

Question 37

most muscle activity is active when?

Answer 37

active at the start and end of swing minimal activity in mid stance (switch off) accelerates and decelerate movements

Question 38

know your reference for degrees during gait

Answer 38

10% peak dorsiflexion terminal swing 60% knee flexion during swing etc