Table 1.
Changes in heart rate and heart rate variability (HF, LF, and LF/HF) of the participants at different test times (R−2, R11, R20, R32, R40, and R+8), under the spatial working memory 2-back task (expressed as mean ± SE)
| Time points
|
||||||
|---|---|---|---|---|---|---|
| R−2
|
R11
|
R20
|
R32
|
R40
|
R+8
|
|
| M (SE) | M (SE) | M (SE) | M (SE) | M (SE) | M (SE) | |
| Heart rate (bpm) | 71.92 (4.28) | 70.23 (3.63) | 68.50 (2.21) | 70.64 (2.22) | 74.48 (2.12) | 72.26 (3.15) |
| Low frequency (nu) | 45.47 (0.34) | 45.48 (0.50) | 45.60 (0.25) | 45.53 (0.17) | 45.71 (0.38) | 45.41 (0.10) |
| High frequency (nu) | 54.53 (0.34) | 54.52 (0.50) | 54.40 (0.25) | 54.47 (0.17) | 55.29 (0.38) | 55.59 (0.10) |
| LF/HF | 0.84 (0.01) | 0.84 (0.02) | 0.84 (0.01) | 0.84 (0.01) | 0.84 (0.01) | 0.83 (0.01) |
Note: The high-frequency and low-frequency data that are shown in table 1 were normalized and their units are ‘nu’.
Abbreviations: HDBR, head-down bed rest; HF, high frequency of heart rate variability; LF, low frequency of heart rate variability; R−2, 2 days before the HDBR; R11, day 11 of HDBR; R20, day 20 of HDBR; R32, day 32 of HDBR; R40, day 40 of HDBR; R+8, 8 days after the HDBR; SE, standard error of the mean.