The effect of ad libitum ingestion of a caffeinated carbohydrate-electrolyte solution on urinary caffeine concentration after 4 hours of endurance exercise

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 mug x mL(-1)) was below the doping level of the International Olympic Committee (12 mug x mL(-1)) in all subjects (range 1.20-10.84 mug 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.