Table 3.
Heart rate variability results during the night after placebo or caffeine ingestion.
| Placebo | Caffeine | Effect Size (ES) | 95% CI for ES | |||||
|---|---|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | p | Lower | Upper | ||
| Mean R-R (ms) | 1151.5 | 114.4 | 1184.7 | 131.1 | 1.000 | −0.21 | −0.80 | 0.39 |
| SDNN (ms) | 40.4 | 7.2 | 36.5 | 6.7 | 0.102 | 0.56 | −0.58 | 0.58 |
| HR (bpm) | 52.4 | 5.7 | 51.2 | 6.1 | 1.000 | 0.58 | −0.01 | 0.87 |
| RMSSD (ms) | 27.1 | 4.1 | 26.9 | 4.0 | 0.715 | 0.11 | −0.48 | 0.70 |
| pNN50 (%) | 7.1 | 3.3 | 7.2 | 3.1 | 0.956 | −0.02 | −0.61 | 0.58 |
| LF (ms2) | 986.3 | 617.3 | 814.0 | 377.4 | 0.205 | 0.41 | −0.22 | 1.02 |
| HF (ms2) | 192.4 | 111.1 | 190.7 | 77.8 | 0.953 | 0.02 | −0.57 | 0.61 |
| TP (ms) | 1689.1 | 1094.3 | 1371.7 | 639.8 | 0.214 | 0.40 | −0.23 | 1.08 |
| LF/HF | 5.6 | 2.5 | 4.6 | 2.0 | 0.182 | 0.43 | −0.20 | 1.04 |
SD: standard deviation; SDNN: standard deviation of all normal N–N intervals; HR: mean heart rate; RMSSD: square root of the mean of the sum of the squared differences between adjacent normal R–R intervals; pNN50: percentage of differences between adjacent normal R–R intervals > 50 ms; TP: Total power; LF: low frequency; HF: high frequency (HF).