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Table 1 Frequency domain power (ms 2 ) – (FFT spectrum) ECG data and HRV (heart rate variability) in study participants at night (02.00-04.00 am; n = 9)

From: Increased heart rate variability but no effect on blood pressure from 8 weeks of hatha yoga – a pilot study

  Before/Baseline After 8 weeks’ yoga P-value Effect size Confidence interval before Confidence interval after 8 weeks
LF [ms2] 1237.9 ± 1072.6 Md 852 1335.2 ± 989.1 Md 1346 0.82 0.10 412-2064 574-2097
HF [ms2] 560.7 ± 509.0 Md 454 689.2 ± 505.2 Md 666 0.50 0.27 169-953 300-1078
LF/HF ratio 2.5 ± 1.0 Md 2.2 2.4 ± 1.2 Md 2.3 0.36 0.10 1.7-3.3 1.5-3.3
LF n.u. 69.8 ± 7.9 Md 68.5 66.5 ± 13.1 Md 69.5 0.29 0.32 63.7-75.9 56.4-76.6
HF n.u. 30.2 ± 7.9 Md 31.5 33.5 ± 13.1 Md 30.5 0.29 0.32 24.1-36.3 23.4-43.6
  1. Data are expressed as means ± SD and, when stated, median.
  2. LF = Power in low frequency range (0.04-0.15 Hz). Some researchers believe this involves both sympathetic and parasympathetic modulation (sympathetic involves the blood vessels whereas parasympathetic involves the heart). LF measures withdrawal of vagal tone (Goldstein).
  3. HF = Power in high frequency range (0.15-0.4 Hz), indicates efferent vagal activity.
  4. LF/HF ratio = Ratio is correlated with sympatho-vagal balance.
  5. LF n.u = Represents the relative value of LF power component in proportion to the total power minus the VLF (very low frequency) component in normalized units (n.u).
  6. HF n.u. = Represents the relative value of HF power component in proportion to the total power minus the VLF (very low frequency) component.
  7. n.u. = normalized units.
  8. Confidence interval = 95%.
  9. Md = Median.