This approach was used by these investigators in a pilot study (n=9 healthy, adult volunteers, 3 females and 6 males) which showed that the LF/HF ratio changed from a mean of 1.75+1.40 (mean+SD) in the horizontal position to a mean of 6.00+1.20 in the 50-degree head-up position. This change reflects an increase in sympathetic tone. Mean heart rate in these subjects increased from 61+7 bpm to 78+2 bpm in the head-up position. The subjects then were treated in the 50-degree head-up position with an OMT procedure, cervical myofascial release, which is thought to increase vagal tone. After the procedure was applied, the LF/HF ratio decreased back down to 1.75+1.58, even though the subjects were still in the head-up position. These data support the initial hypothesis that specific OMT procedures can modulate vagal tone, and also provide information relating to the significance of the LF/HF change. That is, the application of OMT reversed the increase in the ratio that occurs in the 50-degree head-up position.