This study intends to examine how three different OMM techniques, sub-occipital release, rib-raising, and stellate ganglion release, impact autonomic nervous system tone. Subjects will be randomly assigned to one of four cohort groups, receiving either sub-occipital release, rib-raising, stellate ganglion release or all three treatment techniques. A shift towards sympathetic tone will be induced in all subjects using a tilted-to-seated-position test (Tilt-Seated Position test) and cognitive challenge test, consisting of computerized questions that become progressively more difficult, and which subjects are asked to answer as quickly and accurately as possible. These stress tests will be induced twice, once without any OMM treatment and a second time with the designated OMM treatment(s). The sympathetic-dependent response to orthostatic change and cognitive challenges will be determined by Fourier analysis of heart rate variability, recorded using an EKG attached to each subject.