Muscle Strength Assessment by Physiotherapy
We depend on our muscles to allow us to do all the functional activities we want to perform, from walking to climbing stairs to typing and doing precise work. Our muscles can deliver huge amounts of power and endurance as well as highly co-ordinated and skilled manipulations. Loss of feeling may be more important in a limb but loss of sufficient muscle power compromises our independence particularly as we get older and find difficulty performing routine actions for ourselves. Muscle power can be reduced by a large number of causes including not using them when ill and forced to rest, pain from injury or operations, stroke or other neurological condition, disease and illness. The assessment and treatment of muscle weakness is a routine skill in physiotherapy.
Physiotherapists rate muscle power by using the five step Oxford Scale to record the assessment and progress of treatment. It is important to know the muscle and tendon anatomy well as well as the movement actions the muscles perform so that the joint can be positioned best to allow muscle function to be apparent. The physiotherapist will often palpate over the tendon and over the muscle belly to feel any activity that may not be visually very obvious. Ratings are recorded in the form 1/5 or 5/5, with a + or a " sign used to indicate greater or lesser power but not sufficient to give the muscle an entire grade lower or higher on the scale.
If there is no muscle activity, either visible or with the physiotherapist feeling the tendon and muscle belly after several attempts by the patient to perform the muscle action then the muscle is graded as zero. A small muscle contraction such as a twitch, without any joint movement, is rated as one. When the muscle can do its joint action but without the force of gravity resisting the movement then this is graded as two, but the joint needs to be in the right position for correct testing. If the muscle can perform its typical action against the force of gravity then it is rated as three. An example is bending the elbow whilst standing up, where the biceps is working against gravity.
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.
Grade three out of five for the shoulder muscles might be the ability to lift the arm above the head, but if this cannot be easily done or to full range then the muscle can be graded as three minus to indicate its inability to be fully grade three. If the physiotherapist can resist the muscle firmly but it still doesn't seem to be strong enough for a five, then the rating can be four plus. Physiotherapists go through all the muscles to be tested and rate them all on a muscle testing chart as a record of the muscle strength, which can be retested over time to chart recovery.
Physiotherapists begin muscle strengthening techniques in a position where gravity is eliminated, allowing a weak muscle to be repetitively exercised. As the patient's ability increases they can perform more functional activities of daily life which strengthens the muscles in a co-ordinated way which reflects normality. Next, resistance against muscle action is increased as muscle strength improves in response to the level of intensity of resistance and not just repetition. High intensity causes muscle fibre breakdown which repairs with increased size and power until the next intensity workout repeats the process. Progression is then moved to functional exercise with bodyweight resistance as dynamic movement is more useful.