BDNF and Anxiety: Exercise can trigger the secretion of multiple hormones in the brain, such as brain-derived neurotrophic factor (BDNF, related to memory and information transmission), dopamine (DA, related to attention and satisfaction), norepinephrine (NE, related to complex emotions and motivational awakening), and serotonin (5-HT, which is related to depression, anxiety, impulsivity, and other emotions).