Caffeine but not acetaminophen increases 4-km cycling time-trial performance
Acetaminophen has been combined with caffeine for therapeutic purpose, but the effect of co-ingestion of acetaminophen and caffeine on exercise performance has not been investigated. The aim of this study was to determine the effect of isolated and combined ingestion of caffeine and acetaminophen on performance during a 4-km cycling time-trial. In a double-blind, crossover design, eleven men, accustomed to cycling recreationally, completed a 4-km cycling time-trial one hour after the ingestion of cellulose (PLA), acetaminophen (20 mg{middle dot}kg-1 body mass, ACT), caffeine (5 mg{middle dot}kg-1 body mass, CAF) or combined acetaminophen and caffeine (20 and 5 mg{middle dot}kg-1 body mass, respectively, ACTCAF). The perception of pain and rating of perceived exertion were recorded every 1-km, and electromyography and oxygen uptake were continually recorded and averaged each 1-km. Plasma lactate concentration was measured before and immediately after the trial. The time and mean power during the 4-km cycling time-trial was significantly improved (P < 0.05) in CAF (407.9 {+/-} 24.5 s, 241.4 {+/-} 16.1 W) compared to PLA (416.1 {+/-} 34.1 s, 234.1 {+/-} 19.2 W) and ACT (416.2 {+/-} 26.6 s, 235.8 {+/-} 19.7 W). However, there was no difference between ACTCAF (411.6 {+/-} 27.7 s, 238.7 {+/-} 18.7 W) and the other conditions (P > 0.05). The perception of pain, rating of perceived exertion, electromyography, oxygen uptake, and plasma lactate were similar across the conditions (P > 0.05). In conclusion, caffeine but not acetaminophen increases power output ultimately increasing performance during a 4-km cycling time-trial.