Introduction: Resting heart (pulse) rate (PR) is an autonomic marker that may be useful in subluxation-centered chiropractic practice. The present study investigated the change in PR following chiropractic adjustment of C1 subluxation.
Methods: A convenience sample of 23 chiropractic students was examined on three visits; two pre-adjustment visits and one post-adjustment visit. The outcome variable was the PR difference between the second pre-intervention visit and the post-intervention visit using the paired t-test. Since PR changes may be different between genders, subgroup analysis by gender was also performed.
Results: A decrease in post-intervention PR from pre-intervention PR was observed but was not statistically significant (mean reduction of 2.7 beats per minute [BPM]; p = 0.243). However, a statistically significant reduction in PR was observed, with a large effect size for males (n = 12; mean reduction = 8.0 BPM, p = 0.014, ES = 0.74). Proportion-wise, five of the 11 females (45.5%) showed a PR that either decreased (n = 4; 36.4%) or was unchanged (n = 1) following adjustment, compared to the remaining six (54.5%) whose PR increased following their adjustment. Eleven of the 12 males (91.7%) showed a PR that either decreased (n = 9; 75%) or stayed the same (n = 2) following adjustment compared to one (8.3%) whose PR increased following his adjustment.
Discussion: It is not clear why a greater percent of males showed PR decreases following their adjustment compared to females. Still, it is noteworthy that more than a third of the females in this preliminary study showed success (a reduced PR) following their adjustment. Increases in PR on the post-adjustment visit, whether female or male, could be due to circumstances such as an incorrect subluxation listing (resulting in adjustment from the wrong side). Further research with different chiropractic procedures may reveal greater success in PR decreases following their chiropractic care.
Conclusion: In this preliminary study, a statistically significant decrease in pulse rate was observed for males following adjustment of C1 subluxation. More than a third of females showed a decrease in pulse rate following their adjustment while three-fourths of males showed pulse rate decreases following their adjustment.