Effects of caffeine on exercise performance in sedentary females

The purpose of the study was to examine the effect of caffeine ingestion on total work, average power, oxygen consumption (VO2), respiratory exchange ratio (RER), ratings of perceived exertion (RPE), heart rate (HR) and energy expenditure (kJ) during stationary cycling at a standardised power output, as well as during a set time period where participants were required to cycle as fast as they could. Ten healthy, sedentary, female, non- regular caffeine users completed 15 min of stationary cycling at a standardised power output equating to 65% HRmax (Phase A), followed by 10 min of stationary cycling where they were required to cycled as fast as they could (Phase B) after ingesting 6.0 mg·kg(-1) of caffeine or placebo 60 min prior to exercise. VO2 and energy expenditure were significantly higher at the end of Phase A (p = 0.008 and p = 0.011, respectively). All other variables examined in Phase A were similar between trials. In Phase B, there were no significant differences found for any variable assessed. While caffeine ingestion resulted in significant increases in VO2 and energy expenditure during steady-state exercise, it did not improve cycling performance during a 10 min trial where participants were required to cycle as fast as they could. Key pointsA 6.0 mg·kg(-1) dose of caffeine did not improve work done (J·kg(-1)) or mean power (W) during 10 min of self-paced stationery cycling in sedentary female participants.A 6.0 mg·kg(-1) dose of caffeine significantly increased VO2 and energy expenditure (kJ) during 15 min of steady-state stationery cycling in sedentary female participants.A 6.0 mg·kg(-1) dose of caffeine did not significantly affect RPE, RER or HR during 15 min of steady-state cycling or 10 min of cycling performed as fast as the participant could achieve, when compared to placebo, in sedentary female participants.