The study aimed to determine the effects of methylliberine and theacrine on reaction time, vigilance, and marksmanship performance in tactical athletes. Participants were randomly assigned to consume either methylliberine, theacrine, or a placebo before completing a battery of tests. The results showed that methylliberine and theacrine improved reaction time and vigilance without increasing blood pressure or causing jitteriness, suggesting they may be a useful alternative to caffeine for tactical performance.