Caffeinated energy drinks have gained popularity in recent years. Caffeine has been shown to increase short-term muscle endurance and power output. PURPOSE: To determine the effects of a caffeinated energy drink on upper body muscle endurance and repeated Wingate cycle performance in young males and females. METHODS: Healthy young adults (n=15, 11 male, 4 female, ∼21yrs) participated in a cross-over design where they were randomized to supplement with a caffeinated energy drink (2mg/kg body mass caffeine) or isoenergetic, isovolumetric, non-caffeinated placebo, separated by ∼7 days. Muscular endurance (bench press) was assessed by the maximum number of repetitions over 3 sets (separated by 1-min rest intervals) at an intensity corresponding to 70% baseline 1-repetition maximum (1-RM). Three 30s Wingate cycling tests (load=0.075kp/kg body mass), with 2 minutes recovery between each, were used to assess peak power and average power output. RESULTS: The caffeinated energy drink significantly increased total bench press repetitions over 3 sets (caffeine= 34±9 vs. placebo = 32±8; p<0.05), with no greater effect on peak or average power (caffeine=701±124W vs. placebo=700±132W; caffeine=479±74Wvs. placebo=471±74W). CONCLUSION: The caffeine containing energy drink significantly increased upper body muscle endurance, but had no effect on anaerobic peak or average power in young healthy adults. Supported by Red Bull Canada.