Frequency Analysis of Heart Rate Variability with Cold Water Intake

Heart Rate Variability (HRV) is the millisecond changes between heartbeats. Sympathetic and parasympathetic factors affect heart rhythm, which is regulated by the autonomic nervous system, the vagus nerve. Stimulating the vagus nerve with cold water intake changes the frequency distribution of HRV. Stimulation changes the HRV power spectrum of subjects compared to their resting state: while the low-frequency (LF) component ratio of the power spectrum decreases (from 34.6 to 28.9 percent), the high-frequency (HF) component ratio increases (21.4 to 30.3 percent). Repeated stimulation has an increased effect on HRV. The high-frequency component increases with repeated stimuli (31.4 percent). Vagus nerve stimulation also affects LF to HF power ratio, decreasing from 2.0 to 1.6. In summary, vagus nerve stimulation with cold water intake can change the HRV, and repeated stimulation strengthens this change.