Kinesiology, or Muscle testing (checking) as an indicator for bodily function and information was developed by Dr. George Goodhart in 1964 from the work of H. Kendall and F. Kendall. With the proper intention and procedure, it is a very accurate way to assess the body’s wisdom about itself.
Muscle checking is usually done using the anterior deltoid muscle which is held out at a 45 or 90 degree angle from the body and is challenged by applying approximately 2 pounds of pressure to the forearm. The mechanism by which we hold up the arm is well understood. Physiologically it works through the intricate structure of the muscle fibers that utilize a feedback system of communication with the nervous system. All muscles constantly report their position and degree of stretch to the Central Nervous System via sensory nerves from the spindle fibers (the stretch sensing devices) within the muscles themselves. That’s the feedback system. In addition, the intention to hold up the arm comes from the Central Nervous System and activates specific motor nerves which in turn activate muscle fibers to hold up the arm. Additionally, there are nerves from the Central Nervous System to the spindle fibers to set sensitivity to stretch so that the arm can maintain its position. That’s the feedback system. Each muscle (like the deltoid) is made up of hundreds of muscle fibers, each communicating through the spindle fibers to facilitate this feedback system.
Spindle fibers are unique sensory structures among the muscle fibers that not only provide information to the Central nervous System by means of l- and ll- afferents, but also receive information by many of the gamma-efferents. There are up to 13 nerve fibers to and from each muscle spindle. This information provides the Central Nervous System with the options on how to influence the specific sensitivity of the muscle spindle that will in turn affect what the muscle does (whether it contracts or relaxes to move the arm in a specific way). The Central Nervous System sets the sensitivity of the muscle spindle by the way of the nuclear bag and nuclear chain fibers which allow the arm to maintain its held position until a new intention is set. In other words, if the arm starts to release it’s hold and the muscles stretch even a bit, spindle fibers send that message to the CNS which feeds forward a message to reset the sensitivity and contract the muscle fibers in order to hold the position of the arm.
We can tap into the body’s information system through this intricate feedback system by setting a specific intention and then muscle checking. With muscle checking, the muscle becomes a transducer for the innate patterns that are difficult to access directly. The intention becomes the key factor to input into the spindle fiber, adjusting its sensitivity, like a gauge or meter.