Muscle testing is also known as applied kinesiology (AK) or manual muscle testing (MMT). It is an alternative medicine practice that claims to effectively diagnose structural, muscular, chemical, and mental ailments. Applied kinesiology is not a part of the science of kinesiology, which is the study of the movement of the human body. The basic idea behind AK is similar to one of Sir Isaac Newton’s Laws of Motion, which states, “for every action in nature there is an equal and opposite reaction.” Applied kinesiology takes this concept and applies it to the human body. This means that any internal issues you may be experiencing would be accompanied by related muscle weakness.