Backshouse, S. H., Bishop, N. C., Biddle, S. J., & Williams, C. (2006). Caffeine ingestion prior to prolonged cycling can enhance positive affect and reduce perceived exertion. Medicine and Science in Sports and Exercise, 38(5), Supplement abstract 1537.

This investigation determined the effect of ingesting caffeine (6 mg/kgBM) versus a placebo one hour before cycling at 70% VO2max for 90 minutes on affect and rating of perceived exertion. Male endurance-trained athletes (N = 12) cycled for 90 minutes at 70% VO2max on two occasions, separated by one week. On one occasion, Ss ingested 6 mg/kgBM of caffeine combined with 3ml/kgBM of low-calorie lemon concentrate. On the other occasion, just 3 ml/kgBM of the concentrate consumed one hour before the onset of exercise served as the placebo condition . The Feeling Scale (a measure of pleasure-displeasure anchored by ‘very good’ and ‘very bad’) and Borg's Rating of Perceived Exertion Scale were administered at regular intervals during the protocol.

Exercise intensity was the same in both trials, as evidenced by values for oxygen uptake, %VO2max, and heart rate. An interaction effect was noted for the Feeling Scale , with Ss reporting higher feelings of pleasure during exercise in the caffeine trial when compared to the placebo trial. An overall condition effect was found for rating of perceived exertion, with higher values in the placebo trial when compared to the caffeine trial. A linear response over time was observed for the RPE, whereas the responses on the FS scale decreased in a quadratic fashion.

Implication. Caffeine ingestion one hour prior to exercise induced reliable changes in affect, with participants in the placebo condition reporting significantly less pleasure than those in the caffeine condition as cycling progressed. Consistent with previous research, perceptions of exertion were reduced following caffeine ingestion. Caffeine ingestion enhances the psychological component of exertion.

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