The invention relates to the use of a device to analyze heart rate variability to determine changes of the physiological state of a test subject due to a change of a magnetic field acting on the test subject, comprising the analysis of the heart rate variability of the test subject before and after the change of the acting magnetic field. A corresponding method comprises the steps of: analyzing the heart rate variability of the test subject making changes to the magnetic field acting on the test subject analyzing the heart rate variability of the test subject again and evaluating a change of the physiological state of the test subject based on the change of the heart rate variability between the measurement before and after the magnetic field change.
