Table 1.
Ventilatory equivalent for oxygen (O2) and for carbon dioxide (CO2) at the second ventilatory threshold (VT2) during a cycling ramp test with the administration of 3 mg of caffeine per kg of body mass per day or a placebo for twenty consecutive days.
| Ventilatory Equivalent of O2 at VT2 | Ventilatory Equivalent of CO2 at VT2 | |||||
|---|---|---|---|---|---|---|
| Day | Placebo | Caffeine | Effect Size (±95% CI) | Placebo | Caffeine | Effect Size (±95% CI) |
| 0 | 28.2 ± 3.2 | 29.9 ± 3.5 | 0.5 (−0.2/1.1) | 24.4 ± 2.1 | 25.8 ± 2.2 | 0.4 (−0.1/1.0) |
| 1 | 29.8 ± 4.8 | 30.6 ± 3.9 | 0.2 (−0.4/0.7) | 25.1 ± 2.6 | 27.2 ± 3.7 * | 0.7 (0.2/1.2) |
| 4 | 29.0 ± 2.5 | 32.8 ± 4.1 * | 1.3 (0.5/2.1) | 25.1 ± 2.0 | 26.0 ± 2.4 | 0.4 (−0.3/1.1) |
| 6 | 28.1 ± 2.4 | 30.6 ± 2.4 * | 0.9 (0.3/1.4) | 25.7 ± 1.9 | 26.6 ± 2.7 | 0.4 (−0.3/1.1) |
| 8 | 28.6 ± 1.8 | 30.6 ± 4.5 | 0.9 (−0.2/2.1) | 25.0 ± 1.4 | 26.0 ± 2.4 | 0.6 (−0.4/1.6) |
| 11 | 28.3 ± 2.3 | 29.3 ± 2.8 | 0.4 (0.0/0.7) | 25.1 ± 1.9 | 25.4 ± 1.5 | 0.1 (−0.5/0.8) |
| 13 | 28.2 ± 2.2 | 30.5 ± 2.6 * | 0.9 (0.5/1.3) | 25.7 ± 1.5 | 26.6 ± 1.7 | 0.5 (−0.1/1.1) |
| 15 | 28.0 ± 3.1 | 30.9 ± 2.5 * | 0.8 (0.2/1.4) | 26.5 ± 2.6 | 26.7 ± 2.1 | 0.1 (−0.2/0.4) |
| 18 | 29.9 ± 2.8 | 32.2 ± 3.8 | 0.7 (−0.1/1.4) | 25.8 ± 2.0 | 26.0 ± 2.5 | 0.0 (−0.4/0.4) |
| 20 | 29.0 ± 3.7 | 31.2 ± 3.4 | 0.6 (−0.2/1.1) | 26.4 ± 2.2 † | 26.2 ± 2.0 | 0.1 (−0.7/0.6) |
CI = confidence interval; (*) the value in the caffeine trial was different to the value in the placebo trial within the same day of intervention (p < 0.05). The effect size was calculated in all caffeine–placebo comparisons within the same day of intervention.