The muscle selected to be used as a general tool to communicate with the Client's subconscious. Any Indicator Change, should not be confused with the muscle-organ-meridian relationship. When a muscle is used as an Indicator Muscle, it's responses are those of the subconscious rather than those of the related meridian. 

A muscle, to be used as an Indicator Muscle, must be in a balanced state and be able to weaken when stimulated with spindle cells, magnets, or verbal questions, and then be able to reinforce when stimulated in the opposite way by spindle cells, magnets, or verbal questions. Any Muscle can be used as an Indicator Muscle.

Some practitioners always start with a 14 muscle balance, testing one muscle per meridian, but some practitioners only use one or two muscles in a session. This is because the muscle is being used as an indicator muscle. It is not being solely tested to establish its physical integrity or even the state of its related meridian but is being used to gain a range of other information about the whole system, such as supplement needs, chakra imbalances, neurotransmitter problems, psychological issues, past traumatic events, etc. 

Because indicator muscles are repeatedly tested during a session, some muscles are more appropriate than others. Three In One recommends the anterior deltoid or the pectoralis major clavicular, whereas Health Kinesiology practitioners tend to use the  brachioradialis. Whichever muscle is chosen, it needs to be a naturally strong muscle that is easy for the client to hold in position and that is not injured in any way.

Normally, before the real work begins, pre-checks are run to make sure that this indicator muscle is functioning properly.

Some kinesiologies that use Verbal Questioning and Yes and No Questioning use the indicator muscle to show an answer to a yes/no question  – a locked response means ‘yes’ and an unlocked or weak response means ‘no’. So, for example if the query was whether the client would benefit from taking a vitamin C supplement a kinesiologist who uses verbal questioning would ask a question and test the muscle. The question could be phrased in various ways, but could be, for example: Would it be beneficial to take a vitamin C supplement? A locked response indicates that the person should take the supplement (yes), an unlocked response indicates that the client would not benefit from this supplement (no).

See also Specific Indicator Muscle, Indicator Change and Muscle Change.