Table 1.
Frequency domain power (ms2) – (FFT spectrum) ECG data and HRV (heart rate variability) in study participants at night (02.00-04.00 am; n = 9)
| 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 |
Data are expressed as means ± SD and, when stated, median.
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).
HF = Power in high frequency range (0.15-0.4 Hz), indicates efferent vagal activity.
LF/HF ratio = Ratio is correlated with sympatho-vagal balance.
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).
HF n.u. = Represents the relative value of HF power component in proportion to the total power minus the VLF (very low frequency) component.
n.u. = normalized units.
Confidence interval = 95%.
Md = Median.