The effect of a caffeinated mouth-rinse on endurance cycling time-trial performance

The purpose of this study was to investigate if acute caffeine exposure via mouth-rinse improved endurance cycling time-trial performance in well-trained cyclists. It was hypothesized that caffeine exposure at the mouth would enhance endurance cycling time-trial performance. Ten well-trained male cyclists (mean ± SD: 32.9 ± 7.5 years, 74.7 ± 5.3 kg, 176.8 ± 5.1cm, VO₂peak = 59.8 ± 3.5 ml·kg⁻¹·min⁻¹) completed two experimental time-trials following 24 hr of dietary and exercise standardization. A randomized, double-blind, placebo-controlled, cross-over design was employed whereby cyclists completed a time-trial in the fastest time possible, which was equivalent work to cycling at 75% of peak aerobic power output for 60 min. Cyclists were administered 25 ml mouth-rinses for 10 s containing either placebo or 35 mg of anhydrous caffeine eight times throughout the time-trial. Perceptual and physiological variables were recorded throughout. No significant improvement in time-trial performance was observed with caffeine (3918 ± 243 s) compared with placebo mouth-rinse (3940 ± 227 s). No elevation in plasma caffeine was detected due to the mouth-rinse conditions. Caffeine mouth-rinse had no significant effect on rating of perceived exertion, heart rate, rate of oxygen consumption or blood lactate concentration. Eight exposures of a 35 mg dose of caffeine at the buccal cavity for 10s does not significantly enhance endurance cycling time-trial performance, nor does it elevate plasma caffeine concentration.