THE PLACEBO EFFECT ON TIME TILL EXHAUSTION DURING CYCLE ERGOMETRY

Abstract

Aim: The present investigation aimed to explore the placebo effect of pre-exercise carbohydrate feeding via the ingestion a carbohydrate sports drink on short duration high intensity exercise. A secondary aim was to examine the effectiveness of the carbohydrate drink on short duration high intensity exercise. Methods: 8 subjects (3 males and 5 females, mean age ± SD = 21.1 ± 2.0 years, range = 18-25 years) completed the study. A randomised within-subjects repeated measures design was utilised to assess differences in: total performance duration, average heart rate, peak heart rate, RPE measured at minute two, five and immediately at the end of the exercise test. 30 minutes prior to exercise subjects were required to drink 250ml of either a carbohydrate drink, a non carbohydrate drink or a perceived 50/50 chance of receiving either drink (each subject unknowingly received the non carbohydrate drink for this condition). The experimental trials required subjects to continuously cycle until exhaustion on a cycle ergometer at a set cadence of 75RPM and at an intensity of 90% maximal power output. Results: A repeated measures ANOVA test revealed a significant difference in the total performance duration between the “told carbohydrate” condition compared to the “told non carbohydrate condition” (P=0.01), and very close to the accepted significance of <0.05 between the “told carbohydrate” and the “told 50/50” condition (P=0.06). No significant difference was observed between the “told 50/50” condition and the “told non carbohydrate” condition (P=0.97). No difference was observed been trials in the average heart rates (bpm), peak heart rates (bpm) and RPE measured at minute two, 5 and at the end of the test (all P=>0.05). Conclusion: The present study did not demonstrate a placebo effect of ingesting a 32g carbohydrate drink 30 minutes before high intensity short duration exercise. The present study did provide some indication of a possible performance enhancement from the actual ingestion of a 32g carbohydrate drink ingested 30 minutes before high intensity short duration exercise. The findings should however be treated with caution and further research should be undertaken addressing the limitations of the study before pre-exercise carbohydrate feeding or the placebo effects can be confirmed or rejected as a performance-enhancing aid in relation to high intensity short duration exercise.