The experimental trials were performed 10 min after ingesting CP ( 21.6 g of carbohydrate , 0 mg caffeine ) or CC ( 21.6 g carbohydrate , 100 mg caffeine ) , and heart rate ( HR ) , oxygen consumption ( VO2 ) , carbon dioxide production , minute ventilation ( VE ) , respiratory-exchange ratio ( RER ) , rating of perceived exertion ( RPE ) , gastrointestinal discomfort ( GI ) , and thirst perception ( Thirst ) were recorded every 200 m. Blood lactate [ La - ] was recorded immediately before and after exercise .