Heart rate variability changes during high frequency yoga breathingand breath awareness

Thirty-eight male volunteers with group average age ± S.D., 23.3 ± 4.4 years were each assessed on two separate days in two sessions, (i) HFYB and (ii) breath awareness. Each session was for 35 minutes, with 3 periods, i.e., pre (5 minutes), during HFYB or breath awareness (15 minutes) and post (5 minutes).There was a significant decrease in NN50, pNN50 and the mean RR interval during and after HFYB and after breath awareness, compared to the respective 'pre' values (p < 0.05) (repeated measures ANOVA followed by post-hoc analysis). The LF power increased and HF power decreased during and after breath awareness and LF/HF ratio increased after breath awareness (p < 0.05).The results suggest that there was reduced parasympathetic modulation during and after HFYB and increased sympathetic modulation with reduced parasympathetic modulation during and after breath awareness.Yoga practice places particular emphasis on voluntary breath regulation, as this is traditionally believed to influence brain functions [1]. In yoga practice there are several ways in which a practitioner may voluntarily modify their respiration, which includes changing the rate, depth, and breathing through the mouth, among other methods [2].Modifying the rate of breathing is the basis for a particular technique called kapalabhati, which is a high frequency yoga breathing technique (with a breath rate of 1.0 to 2.0 Hz) [3].This high frequency yoga breathing (HFYB) technique could be expected to alter cardiac functioning, and indeed this was seen in a study on twenty-four volunteers who practiced the technique at the rate of 2.0 Hz for 15 minutes, analyzed as three, five minute periods [4]. A 0.1 Hz rhythm was present in the record of R-R intervals and the blood pressure during the HFYB. The results were taken to support the hypothesis about the integrative role of cardiovascular and respiratory rhythms when the respiratory frequency is altered. The same authors further assessed the effects of the HFY