Muscle Strength Assessment – Physiotherapy
Muscle strength is very important for all of our functional activities, from heavy work such as climbing stairs or a hill to fine work such as sewing or typing on a keyboard. While losing feeling in a part of the body can be more disabling, losing muscle power always has consequences for our function and our independence, especially as we get much older when our power levels decline anyhow. We may lose muscle power for a wide variety of reasons: disuse; pain; injury; disease or neurological illness. Physiotherapists are skilled at the assessment of muscle power and in progressive strengthening techniques to restore power within the patient’s capacity.
The Oxford Scale is the rating system used by physiotherapists for the assessment and recording of muscle power when required. Knowledge of muscle anatomy is vital so that the joint can be positioned correctly and the tendon and muscle palpated so whether there is any muscle action can be judged. The muscle is rated on the Oxford Scale from one to five and written down as 2/5 or 4/5, at times with a plus or minus sign to show the muscle has more or less strength but not enough to go down or up the scale. The physiotherapist ensures the joint is in the optimal position to enable the muscle to function easily and for easy visualisation of the tendon and muscle.
The physiotherapist will ensure the joint is positioned best for good visibility of the muscle, easy manual palpation of the tendon and muscle belly and the correct alignment for the expected strength of the muscle. Palpating the tendon and muscle, the physiotherapist will ask the patient to perform the muscle action desired, feeling for any contraction or movement. If there is none then the score is 0/5 and 1/5 if there is a just discernable contraction or a twitch, without apparent joint movement. If the joint can be moved through its whole motion but only without gravity resisting then the grade is 2/5, for which the joint needs careful positioning. 3/5 grade would be recorded when the joint can be moved through its range against gravity, an example being straightening the knee from bent in sitting.
Grade 4 means that the muscle can move the joint through range both against gravity and against resistance such as a weight or the physiotherapist’s manual resistance. The amount of resistance is not stated but has to be judged as reasonable for the age, weight, health and normal status of the patient. Grade 5 muscle power is normal power, but this again is a judgment for the patient as a young rugby player will have much greater normal power than an elderly lady, although both might be Grade 5. Some parts of the body cannot have their strength tested manually as the muscles are too strong for the hands to resist appropriately. Bodyweight will need to be the resistance here.
If the patient lifts their arm up above their head but finds it difficult to do and cannot quite get the arm fully up then the physiotherapist might record this as 3- as the grade is not fully three but it is too strong for grade 2. If some resistance can be applied by the physiotherapist but the muscle still does not seem to be of fully normal strength then the rating cannot be a 5, but rather a 4+. A muscle testing chart is used to record the physiotherapist’s testing and can be used to chart progress in muscle power over time.
Muscle strengthening begins with encouraging muscle activity with gravity counterbalanced if the muscle is weak. Once a functional level of muscle activity is reached the patient can be encouraged to perform normal daily activities to power up their muscles. At a higher level resistance must be added as it is the intensity of work which develops muscle strength. This causes a breakdown of muscle fibres which regenerate with increased strength, a cycle which can be repeated with increased levels of applied intensity of resistance. Once simple resistance has been managed, the patient is taught to perform dynamic exercises using their bodyweight as this is the ultimate expression of muscle strength.