The ANS of a subject is continuously monitored to obtain the sympathetic nervous system (SNS) and parasympathetic nervous system (PSNS) components of the autonomous nervous system while an external stimulus is applied to the subject having a frequency that sweeps across a frequency band. The stimulus may be a vibration, flickering light or sound. The ANS is determined to have entered into a state of homeostasis when the SNS component equals the PSNS component. The value of frequency that corresponds to the state of homeostasis is selected as the fundamental frequency of the subject for use in subsequent treatment protocols.