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Table 3 Time Domain Units – 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
RR mean [ms] 996.2 ± 105.4 Md 992.3 1019.8 ± 172.8 Md 1057.1 0.82 0.17 915-1077 887-1153
RR triangular index 16.3 ± 4.5 Md18.0 17.5 ± 5.8 Md 17.9 0.50 0.25 12.8-19.7 13.0-22.0
SDNN (stdRR) [ms] 85.6 ± 21.9 Md 83.4 92.7 ± 39.6 Md 95.6 0.57 0.24 68.7-102.5 62.2-123.2
NN50 count 868.4 ± 823.8 Md 731 1208.7 ± 810.0 Md 1497 0.13 0.44 234-1503 585-1832
pNN50 [%] 12.7 ± 12.5 Md 10.6 18.2 ± 13.3 Md 17.1 *0.035 0.45 3.1-22.3 8.0-28.4
RMSSD [ms] 42.1 ± 19.4 Md 41.0 47.6 ± 21.2 Md 50.2 0.30 0.29 27.2-57.0 31.3-63.9
  1. Data are expressed as means ± SD and, when stated, median. ms = milli seconds.
  2. * = P < 0.05 significant.
  3. NN = RR.
  4. RR triangular index = Total number of all NN intervals divided by the height of the histogram of all NN intervals measured on a discrete scale with bins of 7.8125 ms (1/128 s) [21].
  5. SDNN = the standard deviation of all NN intervals.
  6. NN50 count = Number of pairs of adjacent NN intervals differing by more than 50 ms in the entire recording. This is highly correlated with frequency domain measures and recognized to be strongly dependent on vagal tone.
  7. pNN50% = NN50 count divided by the total number of all NN intervals.
  8. RMSSD = the square root of the mean of the sum of the squares of differences between adjacent NN intervals.
  9. Confidence interval = 95%.
  10. Md = Median.