Heart rate variability (HRV) is a noninvasive measurement developed over the past two decades to determine the balance of the autonomic nervous system. This observational study was designed to determine whether the time that students spent in the chiropractic training program and the associated care that they had received had any effect on the activity of their autonomic nervous systems as measured by HRV analysis. Twenty-seven students, 22 to 49 years old, participated in the study. HRV was measured four times within a 12-month period. The first three measurements were made within the first three months of the academic period, and the fourth reading was taken after the 12-month period. The mean heart rate decreased from 80±9 (Mean ± SD), 81±12, and 83±10 beats per minute in the first three tests to 73±10 beats per minute in the fourth test (p<0.05). The mean high frequency component that represents parasympathetic activity increased from 95, 121, and 67 Hz2 in the first three measurements to 218 Hz2 in the fourth measurement. The low frequency component that represents sympathetic stimulation (along with some parasympathetic activity) showed dominant pattern in all four readings, with mean components of 522, 592, 487 , and 676 Hz2 (p>0.05). Sympathetic stimulation increased slightly in the fourth reading compared with the first three measurements but did not reach a statistical significance.
In the-first year chiropractic students, sympathetic activity was greater than parasympathetic activity. A significant decrease in heart rate and increase in parasympathetic activity was noted one year later with varying chiropractic care. HRV used in the study appeared to be a useful measurement of sympathetic and parasympathetic balance.
Author Keywords: Heart rate variability, Chiropractic, Autonomic Nervous System
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