This technique can be used to test food (allergy) responses, emotions, internal conflicts, and to some extent has been used as a supplementary test for internal organs.   

Muscle testing can be done as a two-person test using an outstretched arm. A control test is performed, asking the recipient (with outreached arm) to 'resist pressure' as the tester pushes the arm firmly yet gently downward.  The recipient is then given a sample (of the substance being tested) to hold in the other hand, or asked to focus on a topic, and the same pressure is applied again.  The difference is noted, with a change in the muscle strength during the test indicating a conflict, weakness, or resistance.   The generally accepted idea behind muscle testing is that the response or results come from the superconscious (non-ego, non-conscious) self.

Muscle testing can be used by the individual using one or both hands. The one handed method can be as simple as a snap of the fingers.  Testing can be used to test food sensitivities without consumption, be used as an aid in selecting one product over another, or even for determining a percentage or count.

The energy-release technique known as "EFT" uses muscle testing to aid determining the appropriate treatment phrases and effectiveness of the treatment.  Other modalities use muscle testing to help determine a modality or method to use, or area of the body needing focus.