FERRIS, L. T., J. S. WILLIAMS, and C.-L. SHEN. The Effect of Acute Exercise on Serum Brain-Derived Neurotrophic Factor Levels and Cognitive Function.Med. Sci. Sports Exerc., Vol. 39, No. 4, pp. 728–734, 2007. Brain-derived neurotrophic factor (BDNF)is one of a family of neurotrophic factors that participates in neuronal transmission, modulation and plasticity. Previous studies using animals have demonstrated that acute and chronic exercise leads to increases in BDNF in various brain regions. Purpose:To determine the effects of acute exercise on serum BDNF levels in humans, and to determine the relationship between exercise intensity and BDNF responses. Additionally, the relationship between changes in BDNF and cognitive function was examined.Methods:Fifteen subjects (25.4T1.01 yr; 11 male, 4 female) performed a graded exercise test (GXT) for the determination of V ˙O2maxand ventilatory threshold (VTh) on a cycle ergometer. On separate days, two subsequent 30-min endurance rides were performed at 20% below the VTh(VThj20) and at 10% above the VTh(VTh+ 10). Serum BDNF and cognitive function were determined before and after the GXT and endurance rides with an enzyme-linked immunosorbent assay (ELISA) and the Stroop tests, respectively.Results: The mean V˙O2maxwas 2805.8T164.3 mLImin j1(104.2T7.0% pred). BDNF values (pgImL j1) increased from baseline (PG0.05)after exercise at the VTh+ 10 (13%) and the GXT (30%). There was no significant change in BDNF from baseline after the VThj20. Changes in BDNF did not correlate with V˙O2maxduring the GXT, but they did correlate with changes in lactate (r= 0.57;PG0.05).Cognitive function scores improved after all exercise conditions, but they did not correlate with BDNF changes.Conclusion:BDNF levels in humans are significantly elevated in response to exercise, and the magnitude of increase is exercise intensity dependent. Given that BDNF can transit the blood–brain barrier in both directions, the intensity-dependent findings may aid in designing exercise prescriptions for maintaining or improving neurological health