Effect of caffeine on RPE and perceptions of pain, arousal, and pleasure/displeasure during a cycling time trial in endurance trained and active men.Physiol Behav. 2012 May 15; 106(2):211-7.PB
Caffeine has been reported to alter perceptions of exertion, muscle pain, and mood, yet the majority of existing data were obtained in resting volunteers or during steady-state exercise. The primary aim of this study was to examine the effects of caffeine on rating of perceived exertion (RPE) and perceptions of leg pain, arousal, and pleasure/displeasure during a simulated cycling time trial. Endurance-trained (n=8, VO(2)max=57.5±3.9 mL/kg/min) and active (n=8, VO(2)max=46.5±6.3 mL/kg/min) men initially completed two familiarization trials separated by at least 48 h. Over the next three trials, they completed a 10 km time trial preceded by ingestion of drinks containing caffeine (5 mg/kg ingested on 2 separate days) or placebo. Treatments were ingested using a single-blind, crossover design, and participants were deceived as to the content of all drinks. During exercise, RPE (6-20 scale), leg pain (0-10 scale), arousal (Felt Arousal Scale), and pleasure/displeasure (Feeling Scale) were recorded using various categorical scales. Repeated measures analysis of variance was used to assess differences in all variables across time and treatments, with fitness level used as a between-subjects variable. Pleasure/displeasure was altered (p<0.05, partial eta-squared (η(2))=0.23) with caffeine compared to placebo, although leg pain, RPE, and arousal were similar (p>0.05) across treatments. Caffeine increased (p<0.05, η(2)=0.27) cycling performance by 0.3-2.0% versus placebo, with no effect (p>0.05) of fitness level. Only in trained men; however, was there a significant caffeine-mediated improvement in cycling performance, which was consequent with diminished mood in trained and improved mood in active individuals.