Author(s): WEIPPERT, M., BEHRENS, M., GUBE, M., MORITZ, J., STRÜBEN, M., MAU-MÖLLER, A., BRUHN, S., Institution: UNIVERSITY OF ROSTOCK, Country: GERMANY, Abstract-ID: 1911

INTRODUCTION:
Sustained cognitive activities (SCA) can lead to perceived fatigue and impair subsequent exercise motivation and endurance performance. Elite athletes as well as habitual exercisers regularly consume caffeinated beverages before exercise to boost mood, motivation and performance during states of perceived fatigue. However, it is not clear whether the potential positive outcomes are caused by positive “side-effects” (conditioned or expected increase in affect, mood motivation etc.) or the pharmacological effect of caffeine itself. Also, the performance enhancing effects seem to be larger in trained athletes. Here, we tested, whether caffeine has an effect on exercise behaviour (i. e., running/ walking distance during 30 min of self-paced exercise) after SCA in a placebo-controlled randomized cross-over trial in untrained subjects.
METHODS:
Therefore, 20 untrained male and female participants (10/10) completed two 60 min Stroop-tests (SCA) after reading the current physical activity guidelines of the American College of Sports Medicine in a weekly interval. After 30 min of SCA they ingested a pill with either 6 mg/kg bodyweight caffeine or a placebo (maize flour) and proceeded for another 30 min. Following the SCA, the participants completed a treadmill run or walk at self-selected speed. Covered distance was compared between conditions, while controlling for habitual caffeine consumption (HCC) as well as for a potential placebo effect (i. e., participant´s expectation of the content of the ingested pill, PE) using an analysis of covariance (ANCOVA, IBM SPSS Statistics 29.0).
RESULTS:
The ANCOVA revealed significant and large interaction effects of condition × HCC (F(1,17) = 9.330, p = 0.007, ηp² = 0.354) and condition × PE (F(1,17) = 6.698, p = 0.019, ηp² = 0.282). Only after controlling for these covariates, condition had a significant and large effect on covered distance (F(1,17) = 6.089, p = 0.025, ηp² = 0.264), with higher values in the caffeine condition.
CONCLUSION:
HCC and the individual expectation may bias potential effects of caffeine on endurance performance after SCA. Both aspects have to be considered when evaluating a potential performance enhancing effect of caffeine after SCA, also in placebo-controlled experiments. Incorporating experimental designs that consider placebo-/nocebo-effects may better elucidate the performance enhancing effects of caffeine and potential mechanisms affecting exercise behaviour after SCA (Beedie et al. 2020).