Lecture 8 - Constraints on Movement

Question 1

How is movement constrained by physical means?

Answer 1

Adding mass to ankle/wrist leads to increased movement/magnitude in all: ankle = increase in arms, wrist = increase in other arm

Question 2

What are the primary and secondary effects of neuromuscular disorders?

Answer 2

Created through a lesion in the descending pathway that results in primary/secondary effects and constrains movement
Primary = direct result of lesion –> paresis and spasticity
Secondary = indirect result of lesion –> structural and functional changes to joints/muscles

Question 3

What is paresis?

Answer 3

Weakness, inability to produce normal levels of force

Reduced voluntary motor unit recruitment and inability to recruit motor units to generate torque

Question 4

What is spasticity?

Answer 4

velocity-dependent exaggerated tendon-jerks in response to passive stretch. Increased hyperexcitability of stretch reflex
Increased alpha-motoneuron excitability

Question 5

What are the 4 coordination problems

Answer 5

Activation/Sequencing –> change in synergies, co-activation
Timing –> reaction time increase, increased movement time, trouble terminating movement
Scaling –> inappropriate force production, difficulties assessing distance

Question 6

What are the secondary effects?

Answer 6

Contractures –> permanent shortening of the muscle
muscle atrophy
change in muscle fibre type
degenerative joint disease

Question 7

What is a stroke?

Answer 7

Restricted blood flow to the brain causing cell damage

Characterized through paralysis or paresis of opposite side of lesion

Question 8

What are some of the impairments due to stroke?

Answer 8

decrease in fast-twitch fibres
decrease in motor units
decreased firing frequency
increased noise
slower motor conduction velocity
impaired standing balance

Question 9

What are the statistics for stroke?

Answer 9

50% fall, 50% of falls due to walking, 50% can walk independently after 1 month, 90% can walk independently after 3 months

Question 10

What are the results of impaired balance?

Answer 10

more falls
delayed postural reflexes –> evidence through EMG graph
Abnormal sequencing of muscle activity
ankle torque in paretic side reduced

Question 11

Describe the upper extremities following a stroke and the theory behind constraint-induced therapy

Answer 11

Upper extremities permanently flexed, inability to generate torque, prolonged time to generate torque
Lowing sensory/motor use in one side leads to learned non-use. Try to prevent this. constrain the non-paretic limb (in splint and sling), force body to use paretic limb, combine with intensive paretic limb physical therapy (6hrs/day)
See improvements in plasticity, motor performance, motor limb strength, see retention effects too
First performed on monkeys following induced lesion

Question 12

What is the evidence for increased plasticity?

Answer 12

Measure brain plasticity through TMS
See larger area that produces stimulus to muscle when stimulated by TMS (motor output area)
See that larger potentials generated (motor evoked potential)

Question 13

Describe the exercise interventions designed by Marigold

Answer 13

Weightshifting/stretching (tai chi, standing from floor) group vs agility group (stepping, sit to stand, line walking)
Agility group has greater retention, faster relexes in paretic limb, better functional mobility (timed up and go)
Fewer falls, fewer falls after training

Question 14

Describe Parkinson’s disease

Answer 14

slow progressive hypokinetic movement disorder
caused by impairment of neurons in substantia nigra
Lose ability to produce dopamine (coordination)

Question 15

What are the 4 major effects of Parkinsons

Answer 15

Resting tremor –> first manifestation, pill-rolling
rigidity of trunk/core –> resistance to passive movement, not velocity dependent, can be cogwheel or leadpipe
bradykinesia (slowness of movement) –> problems initiating and executing motor act
poor balance –> shuffling gait, turning en bloc (lots of small steps), decreased arm swing

Question 16

Describe the gait effects of Parkinsons and how these can be resolved

Answer 16

gait freezing (akinesia), inability to move feet in tight spaces or initiating gait
Use lines, music, improve optic flow, have targets
Effect best if you can see lower limbs

Question 17

Describe the different types of spinal cord injuries

Answer 17

Complete –> loss of all movement/ sensation, both sides equally affected
Incomplete –> may affect one side more than the other, some sensation of movement in unmoveable limbs
Paraplegia –> loss of sensation/movement in legs and part of trunk
Quadriplegia –> loss of sensation/movement below neck

Question 18

Describe the relationship between spasticity and SCI

Answer 18

exaggeration of normal reflex

Lack of range of motion exercises means that spasticity triggered even for small movements, less flexibillty

Question 19

How can SCI be rehabilitated (contemporary and modern)

Answer 19

Traditional –> bodyweight supported treadmill
still have CPGs to produce movement, improves walking function, can try to regenerate circuitry in ascending pathways. Doesn’t regrow descending pathways because you don’t need full body control
Modern –> overground training occurs in mice. Supports bodyweight against gravity, does not provide any forward locomotion assistance
Leads to initiation of locomotion, can go up stairs and over obstacles –> actively initiate locomotion and engage cortical neurons, remodel descending pathways
both method leads to ability to initiate full weight-bearing locomotion