RESULTS After kapalabhati, there was a significant reduction in high frequency power and an increase in low frequency power expressed in normalized units compared to the ‘pre’ value (P<0.01, paired ‘t’ test in both cases). This contributed to a significant increase in low frequency/high frequency power ratio (P<0.05, paired ‘t’ test, one tailed) following kapalabhati practice (Fig 1). Following nadisuddhi pranayama, there was no significant change, though a non-significant trend towards increase in high frequency power and low frequency power was observed (Fig 2). The baseline low frequency power value before nadisuddhi was higher than before kapalabhati (P<0.05).
TABLE 1: Heart rate variability spectral components measured pre and post high frequency (kapalabhati) and alternate nostril (nadisuddhi) breathing. Values are group mean ± SEM.
Fig.1: Sample records of heart rate variability spectrum made before (upper record) and after (lower record) kapalabhati in a single subject (VN/31/ M). The vertical axis gives the power values in BPMI2/ Hz. The two vertical dotted lines separate the three frequency components, viz very low frequency (VLF), low frequency (LF) and high frequency (HF). The arrows indicate the highest peak in each range. The present record shows an increase in low frequency power and a decrease in high frequency power following kapalabhati, even though the actual scales (on the vertical axis) are different for the two records.
Fig. 2: Sample records of heart rate variability spectrum made before (upper record) and after (lower record) nadisuddhi pranayama in a single subject (VN/31/M). The details of the records are the same as for Fig 1. The present record shows an increase in high frequency power as well as a smaller increase in low frequency power following nadisuddhi pranayama, even though the actual scales (on the vertical axis) are different for the two records.
However, the baseline high frequency power before nadisuddhi was lower than that before kapalabhati (P<0.05). The heart rate did not show a significant change after either practice. The group average values ± SEM are given in Table 1.