The impact of deep breathing and alternate nostril breathing on heart rate variability: a human physiology laboratory

An increase in the beat-to-beat variability of heart rate (HRV) is a robust marker of enhanced parasympathetic activity and of a calm and relaxed state. The purpose of this laboratory activity was to introduce the concept of HRV to our students, while having them address a novel question of whether two yogic breathing techniques, namely alternate nostril breathing (ANB) and standard deep breathing (DB), impact the SD of instantaneous heart rate (SDHR), a measure of HRV. Fifty-five undergraduates enrolled in a physiology course designed for nonscience majors were tasked with analyzing HR and SDHR from electrocardiograms recorded during normal breathing, DB, and ANB. A repeated-measures ANOVA showed that HR was significantly, albeit slightly, elevated from normal (74.5 ± 13.4 beats/min; means ± SD) during DB (76.5 ± 11.2 beats/min), but not during ANB (75.7 ± 10.1 beats/min). Analysis of SDHR showed significant differences between conditions (normal: 5.5 ± 2.1, DB: 8.6 ± 3.0, ANB: 7.8 ± 2.8 beats/min). The instructors further analyzed the same data set using more robust measures of HRV (SD of sequential N-N intervals, root mean square of successive differences, and high-frequency domain of HRV) to determine whether SDHR during a 2-min epoch is a sufficient measure for HRV in the undergraduate course setting. Statistical analysis for these measures showed a near identical pattern of magnitude and significance among the groups as SDHR. Our students developed a greater appreciation for the effects of breathing patterns on HRV and HR, using the simple measure of SDHR.