The confidence given to the LF/HF ratio accurately reflecting autonomic balance is significantly influenced by experimental design. A tilt protocol involving postural change from horizontal to upright can be used to calibrate the change in the LF/HF ratio which occurs between the two positions and thus set a physiological range for sympathetic and vagal modulation of heart rate. An experimental procedure then can be implemented where comparisons are made of the changes in the LF/HF ratios that occur when the body is shifted from the horizontal to the upright position under conditions with application of an intervention versus without the intervention. In this manner, an experimentally mediated change in LF/HF ratio (i.e., with intervention) can be calibrated against a physiologically relevant change in ratio (i.e., without intervention).