Muscle strength

Question 1

muscle strength structural

3

Answer 1

1. size - cross sectional area
2. density of muscle fibres per unit area
3. efficiency of mechanical leverage over joints

Question 2

muscle strength-

biomechanical

1

Answer 2

visco-elastic properties- tissues absorb energy during stretch which increase force of contraction

Question 3

muscle strength

neural factors

3

Answer 3

1. number of motor units recruited
2. frequency of motor unit recruitment
3. efficiency of synergistic coordination

Question 4

functional factors

Answer 4

• initial length of the muscle
• postural and joint stability

Question 5

3

reason for abnormal motor output

Answer 5

1. under-active agonist
   muscle weakness
   secondary disuse atrophy
2. over-active antagonist
   increased tone and spasticity
3. shortened antagonist
   secondary biomechanical changes

Question 6

4

weakness

Answer 6

power insufficiency
low tone (hypotonia / flaccidity)

Question 7

5

tightness

Answer 7

increased tone
(hypertonia / spasticity / rigidity)
shortening – insufficient length in opposing muscle

Question 8

1° weakness: decreased cortical output

Answer 8

• reduced inputs on spinal motor neurone pool
• reduction in number and frequency motor unit recruitment
  1. reduced efficiency of muscle contraction
  2. slowness of movment
  3. fatigue
  4. disorganised motor control

Question 9

2° weakness: immobility- disuse atrophy and stiffness

Answer 9

1. reduction in cross-sectional area
2. reduction in density of muscle fibres
3. reduction in number of motor units
4. quads atrophy after only 3 days, 30% in one month
5. immobility- shortening of opposing muscle groups
6. increased resistance to contraction in agonists

Question 10

pre CNS pathology weakness

Answer 10

ageing
sedentry lifestyles
other pathologies (OA, RA, diabetes)

Question 11

testing full rom

Answer 11

outer- full stretch
mid- mid to outer and mid to inner
inner- fully shortened

Often patients with neurological conditions have weakness in a certain point in the range – you would not pick this up if you only tested isometrically.

Question 12

oxford grading scale

Answer 12

• 0- absent voluntary contraction
• 1- feeble flicker contractions that are unable to move a joint
• 2- movement with gravity eliminated
• 3- movement against gravity
• 4- movement against partial resistance
• 5- full strength

Question 13

centeral processing

Answer 13

recieves info from periphery, interprets it and sends commands to motor systems

Question 14

peripheral input

Answer 14

• visual
• vestibular (inner ear)
• somatosensory (input from joint and muscle receptors
• auditory (hearing)

Question 15

UMN Lesion

Answer 15

any damage to the motor neurons above the nuclei of cranial nerves or the anterior horn cells of the spinal cord

Question 16

motor aspects of drinking
5 point order

Answer 16

• appropriate activation of the muscles of the shoulder, elbow & wrist
  1. reaching
  2. forward transfer
  3. drinking
  4. backwards transfer
  5. initial returning phase

Question 17

UMN characteristics

Answer 17

• weakness/atrophy
• hypertonia
• hyperrreflexia
• spasticity
• • babinski

Question 18

LMN characteristics

Answer 18

• flaccid
• hypotonic
• hyporeflexic
• denervation atrophy
• -ive babinski

Question 19

distribution of muscle weakness

Answer 19

• dependent on site and extent of lesion
• distal>promimal = glove and stockings (andrews and Bohannon 2000)

Question 20

effect of muscle length on weakness

Answer 20

• greater weakness found at shorter lengths (inner range) after stroke (Ada et al 2003)

Question 21

strongest position for a muscle

Answer 21

normally mid range, where myosin/actin overlap is maximum