Abstract
The purpose of this study was to examine the ergogenic effect of caffeine ingestion on the diurnal fluctuations of mood states, simple reaction time, and muscle power during the Wingate test. Twelve elite judoists (age: 21.1 ± 1.2 years; body mass: 83.8 ± 8.2 kg; height: 1.8 ± 0.6 m), participated in the present study. Mood states and simple reaction time, and peak and mean powers (P
peak
, P
mean
) during the Wingate test were measured during four separate sessions in a randomized design: at 07:00 and 17:00 h after placebo or caffeine ingestion (i.e. 5 mg/kg). The results of the present study revealed an increase in the anxiety, vigor, and fatigue and a decrease in the simple reaction time after the caffeine compared to the placebo ingestion at 07:00 and 17:00 h. Moreover, the results indicated that the diurnal variation of P
peak
and P
mean
was reduced after the ingestion of the caffeine in comparison with the control session by an increased performance only at 07:00 h (p < 0.05). In conclusion, caffeine ingestion is recommended in the morning to minimize the diurnal fluctuations of short-term maximal performance.