Kovacs, E. M., Martin, A. M., & Brouns, F. (2002). The effect of ad libitum ingestion of a caffeinated carbohydrate-electrolyte solution on urinary caffeine concentration after 4 hours of endurance exercise. International Journal of Sports Medicine, 23, 237-241.

"The purpose of the present study was to examine the effect of ad libitum ingestion of a carbohydrate-electrolyte solution (CES) with 150 mg x L (-1) caffeine (CAF) on urinary CAF concentration after 4 h of endurance exercise. Fifty-eight healthy and well-trained male subjects ingested ad libitum a 7 % CES with 150 mg x L (-1) CAF during 4 h cycling at 50 % of maximal work capacity. Total fluid consumption (mean ± SE) was 2799 ± 72 mL and CAF intake was 420 ± 11 mg (5.7 ± 0.2 mg x kg (-1) body weight). The post-exercise urinary CAF concentration (4.53 ± 0.25 microg x mL (-1)) was below the doping level of the International Olympic Committee (12 microg x mL (-1)) in all subjects (range 1.20 - 10.84 microg x mL (-1)). A highly positive correlation was observed between CAF intake and post-exercise urinary CAF concentration (r = 0.68, p < 0.001). It is concluded that ad libitum ingestion of a CES with 150 mg x L (-1) CAF during 4 h cycling resulted in post-exercise urinary concentration below the doping level in all subjects".

Implication. The detection of post-exercise caffeine is no longer a problem since caffeine has been removed from the banned list. However, because of the international concern about athletes using caffeine pills as pre-competition "pep pills", it might reappear of the banned drugs list.

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