Blood samples were allowed to clot at room temperature after which they were centrifuged at 2000 rpm for 20 minutes with subsequently decanted serum samples frozen at 20C until analysed for caffeine and primary metabolite content using high-performance liquid chromatography (HPLC). After Trial 4 subjects were asked if they could distinguish between the
two supplements and if so to identify the basis of that decision. Nine subjects correctly identified the caffeine trial post hoc. Common explanatory characteristics were terms such as ‘energised’, ‘boosted’, and ‘fidgety’.