Healthy, 21-35 year old, male and female volunteers were recruited from Touro University students, faculty and staff using a brochure, poster, e-mail or personal conversation. Each participant signed an informed consent form. Participants were allowed to participate in multiple experiments (in the experimental and control groups) at least 7 days after the last experiment.
Each subject's weight and height were measured before the procedure. Anthropometric measures were used in cardiac impedance analysis, and as descriptive statistics of the studied population. All cardiovascular parameters were recorded by using a non-invasive method. The disposable skin electrodes were used for impedance cardiography and a one-lead ECG.
The subjects were lying in the supine position and were asked to relax. All surface electrodes were connected to the computerized MP150 BIOPAC System for data recording. The duration of experimental protocol was about 30 minutes, and included three intervals: 10 minutes, pre-OMT rest phase (Rest); 8 to12 minutes (about 10 minutes) of the OMT/Sham (Manipulations); and 10 minutes post-OMT recovery phase (Recovery).
OMT and sham manipulations were administered by an osteopathic physician. The participants were told to lie supine with physician seated at the side of the table facing the participant. Cranial OMT included three techniques and was administered in the following sequence: occipital-atlantal decompression, occipital-mastoid joint, and compression of the fourth ventricle. Control subjects received the sham manipulative procedure or relaxed in supine position (non-touch control). The total duration of OMT controlled by an osteopathic physician and was about 10 minutes.
OMT and sham manipulations Occipital-atlantal decompression: Patient is in the supine position. The operator places the tip of a finger against the posterior tubercle of the atlas and holds that bone anteriorly, preventing it from moving posteriorly with the condyles as the patient nods or tips the head forward. This will release tension between the occipital condyles and the first cervical vertebrae.
Occipital-mastoid joint decompression: The occipital squama is gently moved forward and upward (anteriorly and superiorly) with the pads of the long finger, and the mastoid process of the temporal bone is lifted anterolaterally with the pads of the index fingers. This technique decompresses the jugular foramen, which the vagus nerve passes through.
Compression of the fourth ventricle: Manipulation is accomplished by having the operator's hands cupped to receive the lateral angles and supra-occiput on their thenar eminences. Gentle compression medially is maintained (generally 2 to 3 minutes) until tissue changes, such as a softening or increased motion, are noted in the supraoccipital area.
Sham: The osteopathic physician placed his hands on the skull of the subject and did not influence cranial motion. The sham manipulative procedure (SMP) was administered for 10 minutes.
All manipulations were administered by the osteopathic physician; experiments were conducted at Touro University Nevada. Data were collected by a non-invasive method using BIOPAC Systems, Inc. Equipment MP150 for data acquisition and analysis. The protocol consisted of three phases: rest before manipulations (10 min), manipulations (OMT) (approximately 10 min), and recovery after manipulations (10 min).
Data analysis Most cardiovascular response variables were measured at baseline, immediately after manipulation ("immediate response"), and at the end of protocol ("after rest"). The immediate responses and at the end of protocol were calculated on a percentage basis relative to baseline to control some individual variations.
The percent response variables were each analyzed in a three-way analysis of variance (ANOVA) which included time ("Immediate response", "after rest"), treatment (cranial manipulation, sham), and sex (male, female) as fixed effects. For significant interactions in the ANOVA, a Bonferroni post-hoc test was used to compare treatment effects within time, sex, or both. The type I error rate (alpha) was set at 0.05. The relationships among dependent variables were described with Spearman correlations between percent response variables within. Analyses were done in Rv3.5.1 (R Core Team 2018).
