1 3 Eur J Appl Physiol DOI 10.1007/s00421-016-3456-1 ORIGINAL ARTICLE The effects of different aerobic exercise intensities on serum serotonin concentrations and their association with Stroop task performance: a randomized controlled trial Philipp Zimmer 1 · Christian Stritt 1 · Wilhelm Bloch 1 · Frank-Peter Schmidt 3 · Sven Thorsten Hübner 2 · Stephan Binnebößel 1 · Alexander Schenk 1 · Max Oberste 1 Received: 30 May 2016 / Accepted: 18 August 2016 © Springer-Verlag Berlin Heidelberg 2016 Results There was a significant (p = 0.022) difference between groups regarding serum Δ5-HT levels. Post hoc tests indicated significant (p = 0.013) higher 5-HT serum levels for the high-intensity group compared to the con- trol group while other groups did not differ significantly from each other. Serum Δ5-HT levels and exercise inten- sity were shown to be linearly associated through polyno- mial contrast analysis (p = 0.003). Furthermore, ANOVA revealed a significant difference for Stroop parameter read- ing (p = 0.030) and a tendency for reverse Stroop effect (p = 0.061). Correlation analysis showed that augmented 5-HT levels were associated with improved results in response inhibition. Conclusions This study indicates that intensive acute exer- cise increases serum 5-HT levels compared to a control group. These findings might be relevant for many other related research fields in exercise science, since 5-HT receptors are expressed on many different cell types includ- ing endothelia and immune cells. Abstract Purpose Acute exercise improves selective aspects of cog- nition such as executive functioning. Animal studies sug- gest that some effects are based on exercise-induced altera- tions in serotonin (5-HT) secretion. This study evaluates the impact of different aerobic exercise intensities on 5-HT serum levels as well as on executive functioning consider- ing 5-HT as a potential mediator. Methods 121 young adults (23.8 ± 3.6 years) were exam- ined in a randomized controlled trial including three exer- cise intervention (35 min) groups (low intensity, 45 % of the maximal heart rate (HR max ); moderate intensity, 65 % HR max ; high intensity, 85 % HR max ) and one con- trol group. 5-HT levels and response inhibition (measured by a computerized Stroop test) were assessed pre- and post-intervention. Communicated by Guido Ferretti. P. Zimmer and C. Stritt contributed equally to that work. * Philipp Zimmer p.zimmer@dshs-koeln.de Christian Stritt Christian.stritt@gmx.de Wilhelm Bloch w.bloch@dshs-koeln.de Frank-Peter Schmidt Dr.Schmidt@IMD-Berlin.de Sven Thorsten Hübner s.t.huebner@gmx.de Stephan Binnebößel stephan.binneboessel@gmx.de Alexander Schenk a.schenk@dshs-koeln.de Max Oberste m.oberste@dshs-koeln.de 1 Department of Molecular and Cellular Sport Medicine, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany 2 Department of Preventive and Rehabilitative Sport Medicine, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany 3 Hemostasiology and Pharmacology in the Hämostaseologicum Steglitz GmbH, Siemensstraße 27, 12247 Berlin, Germany