The effects of three carbohydrate electrolyte solutions (CES) containing different amounts of caffeine on cognitive function and the combined effects of these drinks and exercise on cognitive functions were investigated in a double-blind, cross-over study On five separate occasions, fifteen endurance trained male athletes (23.3 years) received water placebo, CES placebo (68.8 g/l), and three CES drinks containing low, medium and high dosages of caffeine (150, 225 and 320 mg/l). Each occasion, 8 ml/kg of the drink was consumed before - and 6 ml/kg of the drink was consumed during an all-out 1 hour time trial on a bicycle ergometer, Cognitive (attentional, psychomotor, and memory) tests were carried out immediately before and immediately after exercise. Before exercise, long term memory was improved by CES plus low dose caffeine compared to both placebos. Immediately after exercise, all cognitive functions were improved by CES plus low- and medium-dose caffeine compared to placebo. These results comprise the first practical demonstration of the cognition improving effects of low amounts of caffeine in CES after strenuous physical exercise.
Hogervorst, E., Riedel, W. J., Kovacs, E. M. R., Brouns, F. J. P. H., & Jolles, J. (1999). Caffeine improves cognitive performance after strenuous physical exercise. International Journal of Sports Medicine, 20(6), 354-361. https://doi.org/10.1055/s-2007-971144