Caffeine is a powerful stimulant that can enhance energy. It works by antagonizing (competing for) adenosine receptors. Adenosine is a molecule similar in structure to caffeine that causes sedation and relaxation. Caffeine prevents adenosine from binding to its receptors and promotes feelings of alertness. Research indicates the optimal dose of caffeine is 3-6mg per kilogram body weight 60 minutes before exercise with higher doses showing no additional benefits.