Whether practitioners call it Muscle Response Testing (MRT), muscle monitoring or muscle feedback, the basic process is the same. Muscle testing is a painless procedure involving the practitioner applying gentle pressure to specific parts of the body (often arms and legs) to test the response of the underlying muscle. Many of the muscles can be tested standing, sitting or lying down. All muscles can be tested while the client wears a reasonable amount of clothing.
The particular part of the body involved is placed in a specific position, in order, as far as possible, to isolate the muscle that is being tested. The body normally uses several different muscles to perform any movement, so testing an individual muscle is not in practice usually possible, but kinesiologists work to isolate a muscle as best they can. The tested muscle will either easily be able to resist the pressure from the practitioner or will give way. Sometimes the muscle will not give way, but not hold either; it will be spongy. This is often because the client is trying to recruit other muscles. For example, when a weak leg muscle is being tested, the subject sometimes automatically tips their hips to engage other muscles and compensate for the weakness.
The kinesiologist uses this on/off response to gain information about what is happening and what is needed to restore balance. Because of the inter-relationship between muscles, meridians and body systems (see page 10), this information applies not only to the muscle being tested but more frequently is used to give valuable information about other imbalances within the body and the necessary procedures to correct them.
The pressure applied by the practitioner starts gently and gradually increases. If the practitioner suddenly applies the full pressure, the muscle is likely to give way and produce an inaccurate test. The Touch for Health manual advises using no more than 2 lbs of pressure, for no more than 2 seconds. Applying pressure for longer than this can fatigue the muscle so that it gives way. In practice, the amount of pressure used varies from practitioner to practitioner. Some kinesiologists use very light pressure, whereas others prefer firmer pressure. Sometimes the muscle will give way a little before responding. Some clients need to feel the pressure of the test before they respond. This is a reason for applying the pressure slowly as this gives the muscle a chance to react. The Touch for Health manual specifies that the muscle needs to lock within 2 inches of the starting position. If it locks after more movement, this suggests that other muscles are being recruited.
The kinesiologist will usually ask the client to ‘hold’ just before testing. At one time practitioners often used the word ‘resist’ rather than ‘hold’, but it became clear that the word ‘resist’ encouraged people to believe that if the muscle did not lock, they had failed in some way. Strong men are often astounded when their muscle weakens under the gentle testing pressure, but this is because the test is not a test for the strength of the muscle but is an indicator of some imbalance within the body.  Some kinesiologists (e.g. Three in One facilitators) will test both arms (or legs) simultaneously. They do so “to be sure there is agreement between the right and left hemispheres” (Tools of the Trade Book 1). 
Some kinesiologists also test the muscle both in extension and in contraction. Each muscle has a range of movement; testing in both these ways means that it is tested at both ends of the range. So, for example, the anterior deltoid (a front shoulder muscle) is tested when the arm is at about 30 degrees to the body and also when the arm is by the side of the body. This is seen as a way of accessing information from both hemispheres of the brain.