The aim of this study was to determine the effect of caffeine ingestion on simple reaction time, mood states, and maximal anaerobic power measured in the morning on elite judoists. Our results showed a decrease in simple reaction time, changes in mood states caused by the increase of the anxiety and the vigor, and a significant increase of PP and MP. However, FI is unaffected by caffeine ingestion.
Although, Ruijter et al 
showed no-significant caffeine effect, the present study’ results are consistent with previous studies that showed a significant decrease in the simple reaction time 60 min after ingestion of caffeine [8, 9, 27]
. Latini et al 
explain the decrease of the simple reaction time induced by the ingestion of caffeine by its role as a molecule necessary for the transfer of messages from one neuron to another.
Concerning the effect of caffeine on mood states, previous studies suggest that the dose of caffeine is a determinant factor [29, 30]
. Indeed, Hasenfratz et al 
showed that low doses of caffeine improve positive mood, while higher doses result in the creation of negative mood. Likewise, Griffiths et al 
showed that 300 mg of caffeine was able to create a positive mood states. For the present study's caffeine dose, our results are on line with those of Kawachi et al 
who revealed that ingestion of caffeine contributes to a higher negative mood in the morning. This higher negative mood state could be explained by the caffeine dose (i.e. 5 mg/kg).
The effect of caffeine on anxiety has been the subject of several studies [32, 33]
. Loke et al. 
revealed that the increase in anxiety is in relation with the high doses of caffeine (3 or 6 mg / kg). In with our findings, Sicard et al 
observed an increase in anxiety after the ingestion of 600 mg of caffeine. In the same way, Green and Suls 
found an increase in anxiety following the consumption of 125 mg of caffeine. Likewise, consistent with previous works, the present study's results showed an increase of vigor after caffeine ingestion [37, 38]
For lower-limb muscle power, the present study's results showed an increase in PP and PM in the morning after ingestion of caffeine in trained subjects. However, the FI was unaffected by caffeine ingestion.
These results are in line with those of Kang et al 
that revealed a significant increase in PP and PM during a Wingate test in trained subjects following the ingestion of 5mg/kg [12, 40, 41]
. Anselm et al 
found a 7% increase in maximal anaerobic power with untrained subjects during a single 6-s sprint following consumption of 250 mg of caffeine. However, Williams et al 
found no benefit from caffeine (7 mg/kg) during maximal exercise (15-s) for peak power, total power, and fatigue index with untrained subjects. Although Williams et al 
failed to find improved performance during a 15-s Wingate test; results indicate that caffeine is beneficial for trained and untrained subjects when bouts are 4–6 seconds in duration, which may more closely mimic the time frame associated with high-intensity sports 
However, other studies showed no effect of caffeine on anaerobic performance in untrained subjects 
. They found that caffeine had no effect on electromyogram (EMG) activity. Moreover, Williams et al 
failed to find an effect of caffeine ingestion on EMG signalling during maximal and submaximal isometric hand grip contraction indicating that neuromuscular proprieties of the muscle are not affected by the caffeine ingestion. Nevertheless, the present study's results cannot be compared with those studies because our participants are trained subjects. Alternatively, differences in training status could explain these discrepancies, as it has been speculated that caffeine may provide a greater ergogenic benefit in trained subjects 
In support of these possible mechanistic effects of caffeine, Lopes et al 
reported that caffeine had a direct effect on skeletal muscle contractile properties. Similarly, Tarnopolsky 
reported that caffeine delayed the fatigue in human muscle during low-frequency stimulation, demonstrating an impact of caffeine on excitation-contraction coupling.
Of the mechanisms purported to explain the beneficial effects of caffeine ingestion, recent findings support a CNS response mediated by antagonism of adenosine receptors leading to increases in neurotransmitter release, motor unit firing rates, and dopaminergic transmission 
. Although further research is required to clarify the relative contribution made by each of these processes to various activities and to confirm or refute the possibility of an intramuscular mechanism of action 
, Kalmar and Cafarelli
reported higher maximal voluntary contraction and greater ability to activate the vastus lateralis motor unit pool with caffeine compared to placebo.
Consistent with Graham et al 
our results showed an ergogenic effect of caffeine. Numerous factors can explain the ergogenic effect of caffeine. Caffeine ingestion has been shown to reduce the sensation of pain induced by exercise 
, enhance excitation-contraction coupling 
, and stimulate the CNS 
by altering motor unit recruitment and perceptions of fatigue via antagonism of the adenosine receptor. These mechanisms seem to offer sparse insight into the influence of caffeine on anaerobic performance.