Assessment of Muscle Strength

Question 1

causes of muscle weakness

Answer 1

Lesion or pathology affecting the nerve which innervates the muscle

2. Any lesion, injury or pathology of the muscle tissue
3. Disuse
4. Immobilisation

Question 2

example of upper motor neuron lesion CNS

Answer 2

stroke

Question 3

example of lower motor neuron lesion PNS

Answer 3

peripheral nerve lesion

Question 4

effects of immobilisation on muscle

Answer 4

Decrease;
Muscle fibre size
Size and number of mitochondria
total muscle weight
Stores of glycogen and ATP
Protein synthesis
Muscle tension produced 
all leading to atrophy

Question 5

Strength

Answer 5

• Ability to generate force
• Capacity to exert force
• Ability to do work against resistance

Question 6

factors of strength to make movement

Answer 6

Combined contractile forces of the muscles causing movement
• The ability to co-ordinate the agonists, antagonists and
stabiliser muscles
• The mechanical advantages of the levers

Question 7

assessment of strength

Answer 7

cross sectional area - CT/MRI/ Tape measure
manual muscle testing - Oxford scale how much force a muscle can make
Objective measurement - isokinetics - endurance how long can you maintain force/strain gauge, dynamometry
functional assessment - 1RM

Question 8

Use of assessing cross sectional area

Answer 8

detect muscular atrophy
MEASURED WHHEN MUSCLE IS RELAXED
predictor of mortality in some diseases e.g. COPD

Question 9

Manual Muscle Testing - MMT 0

Answer 9

No contraction

Question 10

MMT 1

Answer 10

Flicker or trace of contraction

Question 11

MMT 2

Answer 11

Full range of active movement with gravity eliminated

Question 12

MMT 3

Answer 12

Full range of active movement against gravity

Question 13

MMT 4

Answer 13

Full range of active movement against gravity and resistance

Question 14

MMT 5

Answer 14

Normal

Question 15

Where would you position your hands to

examine the strength of the bicep muscle?

Answer 15

wrist and back of elbow

Question 16

principles of manual resistance

Answer 16

1. Stabilise the proximal segment (non-moving part, muscle origin)
2. Resist the distal (moving) segment
3. Give yourself mechanical advantage: consider the length of the lever and where your resistance is coming from
4. Respond to the patient’s effort: increase your resistance gradually

Question 17

Assessment of Strength of Deltoid Muscle

Answer 17

shoulder abduction and pressing against elbow and put hand on opposite shoulder.

Question 18

limits of oxford scale

Answer 18

Grade 4 is not sensitive to change in strength (amount of resistance is not measured)
Grade 5 (“normal strength”) is subjective

Question 19

reason to use oxford scale

Answer 19

1. Quick
2. No equipment needed
3. Allows assessor to get a “feel” for the muscle and observe
   movement through range
4. Sensitive from grade 0 to the start point of grade 4
5. Assessor can adjust resistance intuitively (for example, in
   trying to reproduce pain)
6. Useful as a screening tool for strength deficits

Question 20

benefits of using handheld dynamometry

Answer 20

Suitable for assessing strength of individuals who score Grade 4 or 5 on the Oxford Scale
• More sensitive than MMT
• Allows measurement of Maximal Isometric
Torque = Maximum Voluntary Isometric Contraction (MVIC)

Question 21

limitations of dynamometry

Answer 21

Requires training
• If patient is very strong the tester may not be able to fully resist the patient’s effort (needs to be a “break” test)
• Isometric testing only

Question 22

purpose of hand grip dynamometry

Answer 22

Useful predictor of physical function in aging adults

• Hand grip is fundamental to ADLs

Question 23

advantages of strain gauges

Answer 23

• Sensitive
• Objective
• Reliable
• Can assess a large number of muscles

Question 24

disadvantages of strain gauges

Answer 24

Time consuming
• Requires training
• Only measures isometric force

Question 25

benefits of isokinetic evaluation

Answer 25

Mechanical measurement of muscle performance • Objective • Quantitative • Isometric / concentric / eccentric • Muscle works at constant velocity: Isokinetic • Resistance is variable depending on muscle ability to generate force & to keep pace with selected speed

Question 26

positive of isokinetic testing

Answer 26

* Objective, sensitive, accurate * Controls for speed * Calculates agonist: antagonist ratios * Tests isometric, concentric and eccentric strength

Question 27

negatives of isokinetic testing

Answer 27

* Isokinetic machines are expensive and bulky * Takes a long time to test * Limited to a small number of muscle groups * Open-chain movement only * Not very functional

Question 28

1 repetition maximum - 1R,

Answer 28

the maximal weight that can be lifted once using a proper lifting technique.

Question 29

why use 1RM

Answer 29

1. Allows dynamic movement (concentric and eccentric) 2. Functional and meaningful 3. No expensive equipment 4. Specific to exercise prescription 5. Research shows it to be very reliable (Grgic et al, 2020) 6. Motivating for patient

Question 30

Calculating 1 RM

Answer 30

determining the maximum weight that the patient can lift, without failure or compensatory body movements, with good technique. (If you do this, try to get to the 1-RM within 5 attempts.)

Question 31

Functional strength testing

Answer 31

Performance of a compound movement, such as sit to stand, heel raise, pull up or push up

Question 32

functional strength testing detects

Answer 32

• Speed of performance (= POWER) • Absolute repetition number (concentric / eccentric) (= ENDURANCE) • Sustained maximal duration trials (isometric) (= ENDURANCE)

Question 33

endurance

Answer 33

Ability to undergo prolonged activity or to resist stresses set up as a result of prolonged activity

Question 34

muscular endurance

Answer 34

The ability of a muscle to sustain an isometric contraction or to continue a dynamic contraction

Question 35

cardiovascular endurance

Answer 35

The capacity of the individual to maintain strenuous activity of a number of muscle groups or of the whole body for a prolonged period

Question 36

fatigue

Answer 36

Subjective feeling of discomfort, tiredness • Increased perception of effort • Decrease in maximal power produced by a muscle

Question 37

What is the relationship of fatigue to task failure in PNS?

Answer 37

Impairment of physiological processes that enable contractile proteins to generate a force Accumulation of metabolic by-products (H+, Pi, AMP) ATP used faster than it can be provided

Question 38

What is the relationship of fatigue to task failure in CNS?

Answer 38

Mechanisms in the CNS which result in decreased voluntary activation • The “central governor theory”