Table 1.
Mean power, fatigue index, blood lactate concentration and self‐reported fatigue and muscle strength during a 15‐s Wingate test with the administration of 3 mg kg−1 of caffeine or a placebo in 3 different phases of the menstrual cycle
| Variable (units) | Early follicular | Preovulatory | Mid‐luteal | Main effect | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Placebo | Caffeine | d | Placebo | Caffeine | d | Placebo | Caffeine | d | Substance | Cycle | Interaction | |
| Peak power (W/kg) | 8.6 ± 0.8 | 8.9 ± 0.9* | 0.45 | 8.6 ± 0.9 | 8.9 ± 0.9* | 0.23 | 8.6 ± 0.8 | 8.9 ± 0.8* | 0.52 | <0.01 | 0.69 | 0.37 |
| Mean power (W/kg) | 7.8 ± 0.8 | 7.9 ± 0.7* | 0.20 | 7.8 ± 0.9 | 8.0 ± 0.8* | 0.25 | 8.0 ± 0.7 | 8.2 ± 0.7* | 0.37 | <0.01 | 0.14 | 0.05 |
| Fatigue index (%) | 25.8 ± 6.6 | 27.5 ± 10.4 | 0.27 | 26.0 ± 10.0 | 26.3 ± 7.5 | 0.04 | 25.4 ± 10.7 | 25.6 ± 7.1 | 0.02 | 0.15 | 0.23 | 0.31 |
| Blood lactate concentration (mmol/L) | 10.0 ± 2.6 | 11.7 ± 4.1* | 0.68 | 10.9 ± 3.6 | 11.9 ± 2.6 | 0.47 | 10.8 ± 3.4 | 11.9 ± 4.5 | 0.41 | 0.04 | 0.58 | 0.80 |
| Borg scale (a.u) | 19 ± 1 | 19 ± 1 | 0.24 | 19 ± 1 | 19 ± 1 | −0.37 | 19 ± 1 | 19 ± 1 | −0.14 | 0.58 | 0.45 | 0.12 |
| Perceived muscle power (a.u) | 8.3 ± 1.0 | 8.9 ± 1.1 | 0.79 | 8.9 ± 1.0 | 8.8 ± 0.8 | −0.24 | 8.7 ± 1.3 | 8.6 ± 1.0 | −0.15 | 0.77 | 0.59 | 0.25 |
(*) Caffeine different from placebo within the same menstrual cycle phase at P < .05. a.u. = arbitrary units.