Assessing for strength and weakness is often best conducted in the community by reviewing function and ability.
However, in specialist centres Manual Muscle Testing (MMT) can be conducted around diagnosis (and in the undiagnosed patient to help with diagnosis) and used to monitor progression. For example, knowledge of whether the knee extensor muscles can move fully, extend against gravity or not, can guide advice on walking aids and orthotics.
Myometry – which is a method of assessing muscle strength using a dynamometer – may be used to gain more objective values and to identify asymmetry in patients. As a tool this is primarily used in clinical trials and would not be suitable for community use.
General method for MMT
- Explain or demonstrate movement to the patient.
- Ask the patient to perform the movement in the antigravity position.
- If unable to then check patient’s understanding, ROM available, weakness.
- Based on the limiting factor(s) either instruct and demonstrate again, decide if ROM is affecting performance or repeat the test using antigravity position.
- Resistance is given through full available range.
- In the case of a contracture limiting ROM, grades are given as stated in table below, for available range. Range limitation should be noted in the comments section.
- If uncertain as to what grade should be given, the lower option should be chosen.
- If general compliance is such a problem that the results do not give, in the assessors considered opinion, a true indicator of the patient’s ability, then this should be noted, and the results should not be included in the database. If specific muscle groups are a problem e.g., due to pain, please note this and do not include in any calculation of the MRC %.
- Equipment –a height adjustable plinth should be available.
- Clothing – ideally shorts and t-shirt. If not shorts, then tracksuit bottoms. Jeans may restrict movement – especially in very weak children.
- Watch for compensatory movements being used to produce an action – if uncertain, palpate the muscle group which should be prime movers. Be clear with positioning and stabilisation.
Table 1 – MMT Grading system
The above scale is based upon the modifications made to the original Medical Research Council 6- point scale by staff at the Hammersmith Hospital. Most physiotherapists who regularly use the muscle chart are familiar with this scale (or the expanded 16-point version).
A minus grade denotes loss of range. This is why 4- is not graded, as a grade of 4 is, by definition, full range.
The MRC percentage is to be calculated on the ‘whole’ score, rather than with the + and – grades. The ‘whole’ grades for each element of the scale are noted in column 2 of the above table.