METHODS: Prior to data collection IRB approval was obtained from the New York Chiropractic College Institutional Review Board. Subjects (n=22) were seen in the autonomic laboratory on 4 separate occasions over a two-week period. On each visit, after obtaining baseline data a heightened cardiovascular-sympathetic response was evoked using the cold pressor test as the noxious stimulus. During the first visit subjects performed a cold pressor test. During the second, third and fourth visits, in a randomized order, subjects received a high velocity low amplitude spinal manipulative thrust to their upper thoracic spine either during or immediately preceding the cold pressor or repeated the cold pressor test without SMT. Power spectral analysis was performed on beat-to-beat R-R intervals (RRIHF) and continuous systolic blood pressure (SBPLF). Baroreceptor sensitivity was calculated . A Condition x Time repeated measures ANOVA was applied and using paired t-tests, post-hoc analyses were three pairwise comparisons among the three conditions.
RESULTS: Post-hoc comparisons detected significant differences for RRIHF, SBPLF and baroreceptor sensitivity between cold pressor and spinal manipulation prior to cold pressor conditions during the pressor test (26.8 „b 12.9 vs. 38 „b 14.5 msec2/Hz; 66.5 „b 16.1 vs. 55.4 „b 18.1 mmHg2/Hz; and 1.14 „b 0.78 vs. 1.02 „b 0.77 mmHg, respectively; p<0.01).
DISCUSSION: Our data suggest that SMT applied prior to a somato-autonomic provocation significantly reduced the sympathetic vasomotor response and attenuated cardiac vagal withdrawal.
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