Men that did aerobic exercise (20-40 min.) had a 32% increase in BDNF (robustly triggers the growth of new neurons).
www.ncbi.nlm.nih.gov
This study also found that more intense and longer duration (40 min.) aerobic exercise increased the probability of an individual subject achieving a significant BDNF increase and in the integral (i.e. the volume of circulating BDNF).