The Medical Research Council Muscle Power Test
Previous TopicIntroduction to the Medical Research Council muscle power test
When assessing the strength of individual movements, the Medical Research Council (MRC) muscle power test should be used.
The MRC muscle power test involves testing muscle strength against the examiner’s resistance and grading the strength from 0-5 accordingly.
0: No contraction
1: Flicker of trace of contraction
2: Active movement with gravity eliminated
3: Active movement against gravity
4: Active movement against gravity and resistance
5: Normal power
For grades 0-2 you will need to test muscle strength in a ‘gravity-eliminated’ position. This means that the person does not have to move their body part against the weight of gravity.
The MRC muscle power test does not require any equipment.
Grade 0
Muscle tested in gravity eliminated position.
For grade 0 out of 5, it is not possible to see or feel a contraction in the muscle being tested and no movement will be produced
Grade 1
Muscle tested in gravity eliminated position.
For grade 1 out of 5, it is possible to see or feel a small or light contraction of the muscle. The contraction is not strong enough to produce movement.Grade 2
Muscle tested in gravity eliminated position.
It is possible to see and feel a muscle contraction. Movement will be produced in a gravity eliminated position through full range of movement.
You may support the body part being moved during the movement but try not to assist the movement if possible.Example of grade 2/5 muscle strength
Grade 3
Muscle tested against gravity.
It is possible to see and feel a muscle contraction and movement will be produced against gravity through full range of movement.
Example of grade 3/5 muscle strength
Grade 4
Muscle tested against gravity.
It is possible to see and feel a muscle contraction. Movement will be produced against gravity plus some resistance added by the clinician through full range of movement.
Example of grade 4/5 muscle strength
Grade 5
Muscle tested against gravity
It is possible to see and feel a muscle contraction. Movement will be produced against gravity plus full resistance added by the clinician through full range of movement.
Example of grade 5/5 muscle strength
Question
Gravity is important when assessing muscle strength because to move a body part against gravity requires more strength than moving a body part ‘with gravity’ or with ‘gravity eliminated’.
When trying to work out what position to test a person’s muscle strength in, generally, if the person is having to lift the body part up towards the sky, this is considered ‘against gravity’.
Which of the following movements is being performed in a ‘gravity eliminated’ position?
- a. Video one
- b. Video two
If you selected video b, you are correct.
In a side-lying position, the person will not have to lift their lower leg against the weight of gravity, instead they will be extending it horizontally, where gravity is eliminated throughout the entire range of motion.
Which of the following movements is being performed in an ‘against gravity’ position?
- a. Lying facing the sky and sliding leg out to the side
- b. Lying in side lying and lifting the top leg towards the sky
- c. Lying in side lying and bending the knee so the foot comes towards the buttock
If you selected video b, you are correct.
This movement is being performed ‘against gravity’ as gravity is pushing down against the leg which is being lifted up.
The MRC muscle power test can be used to assess most individual movements in the body.
Unfortunately, the MRC muscle power test is NOT as useful for assessing functional movements, where multiple movements across different body parts are required at once.
We will discuss how to assess functional strength in the next topic.General guidelines for assessing the strength of individual movements using the MRC Muscle Power Test
- Remember to take care of your own health when assessing muscle strength. Protect your back by keeping your arms close to your body when assessing strength and by not bending or reaching when assessing strength
- Where possible, test all movements using the same arm. This makes it easier to compare opposite sides
- Make sure the person is comfortable before testing
- When testing muscles in a person’s arm or leg, always test the opposite side first to give a baseline to compare to
- If the person experiences a moderate or severe pain increase during an assessment, stop that movement. Assess in a different way by observing, palpating and assessing range of motion
Question
It is important to assess the opposite side of the body so that you can compare the strength of the impaired side with the ‘normal’ side.
- a. True
- b. False
If you selected a, you are correct.
If the strength of the opposite side is ‘normal’ for the person, it will give you a ‘baseline’ grade of strength and allows you to compare the strength differences between the impaired or injured side and the ‘normal’ side.
Where to begin muscle testing
When testing muscle strength, it is not necessary to test each movement from grade 0-5.
First decide which position to test a muscle
- Gravity eliminated (up to grade 2)
OR
- Against gravity (grade 3 and above)
Question
Which of the following can give you information about whether to start assessing muscle strength in a gravity eliminated or against gravity position?
Select all that apply.
- a. What the person tells you during the assessment interview
- b. What you observe as the person arrives and during the assessment interview
- c. The person’s available joint mobility during range of motion assessment
All are correct.
The subjective assessment, your observations and assessment of range of motion can all give you information about where to start assessing muscle strength.
If you have not observed the person move the body part being assessed, or the person/family has told you they have difficulty moving that body part, where would you start the muscle testing assessment?
- a. Test against gravity
- b. Test in a gravity eliminated position
If you selected b, you are correct.
If you have not observed the person moving, or they have difficulty moving, start with testing grade 2 muscle strength in a gravity eliminated position with no added resistance.
If you observe the person moving the body part against gravity, when assessing, you should start by asking them to perform a movement in a gravity eliminated position first.
- a. True
- b. False
If you selected b, you are correct.
If the person can move their body against gravity, start by assessing grade 3 muscle strength against gravity.
How to decide whether to test a higher or lower grade
If the person is able to achieve grade of movement being tested: Assess the next higher grade of muscle strength.
If the person is unable to achieve the grade of movement being tested: Assess the grade below.
You should keep assessing muscle strength for each movement until the person has achieved the highest grade possible for each movement.Fatigue when assessing muscle strength
Be aware of fatigue when assessing muscle strength, you should allow a short amount of time (at least 5-10 seconds) before re-assessing the same movement, especially if the person has reduced strength (i.e. below 5/5 strength). Question
Remember Julie?
Julie loves playing badminton with her friends, however she has had to stop playing recently due to the pain and stiffness caused by osteoarthritis in both of her knees.
Julie has come into the clinic for assistance in managing her knee osteoarthritis. Her main goal is to be able to return to playing badminton.
When assessing Julie’s knee extension strength, you have observed her walk in to your clinic room with an expression of discomfort on her face and you notice she does not seem comfortable putting weight through her left leg.
Based on the information above, what position would you start assessing Julie’s knee strength in?
- a. In a gravity eliminated position
- b. In a position against gravity
- c. In a position against gravity and resistance
- d. None of the above
If you selected b, you are correct.
You have seen that Julie can perform knee extension against gravity (when walking), meaning that she has at least 3/5 knee extension strength, so this would be appropriate position to begin assessment in.
If you assessed Julie’s knee extension strength against gravity without resistance and she was able to achieve this movement, should that be the end of your assessment of Julie’s knee extension strength?
- a. Yes, Julie’s knee extension strength should be recorded as 3/5
- b. Yes, Julie’s knee extension strength should be recorded as 4/5
- c. No, next you should assess Julie’s knee extension strength against your resistance
- d. No, next you should assess Julie’s knee extension strength with gravity eliminated
If you selected c, you are correct.
To fully assess Julie’s knee extension strength you must assess the movement against resistance.
How would you record Julie’s knee extension if she is able to perform the movement against some resistance but not full resistance?
- a. 0
- b. 1
- c. 2
- d. 3
- e. 4
- f. 5
If you selected e, you are correct.
If Julie is able to perform the movement against some resistance, her knee extension strength should be recorded as 4/5. If she is able to perform the movement against full resistance, her knee extension strength should be recorded as 5/5.
Question
Remember Farah?
Farah is a university student studying engineering. Farah fractured her wrist after a fall.
Farah has come to your clinic for a rehabilitation program for her wrist before she returns to university after the holidays.
Farah needs to be able to write and type with her fractured wrist for university.
During the subjective assessment, Farah is holding her wrist by her side and you do not observe her moving it. She explains that she finds it painful to move her wrist in any direction.
What position should you begin to test Farah’s wrist extension strength in?
- a. You should ask her to perform the movement against gravity
- b. You should ask Farah to perform the movement in a gravity eliminated position.
- c. You should ask her to perform the movement against gravity and resistance
If you selected b, you are correct.
As you have not seen Farah perform wrist extension and she has indicated that it is painful to move her wrist in all directions, assessing in a gravity eliminated position first would be appropriate.
