From the Journal of Sport and Health Science:
Therefore, promotion of adequate volumes and intensities of physical exercise (i.e., approximately 3 months of moderate-intensity aerobic exercise, with 2–3 sessions/week lasting not less than 30 min) represents an inexpensive and safe strategy for boosting BDNF (brain-derived neurotrophic factor) release that may preserve or restore cognitive function.
Taken together, the currently available data seemingly confirm the existence of a positive relationship between physical exercise and circulating BDNF levels, both in the short and long term, and also support the beneficial impact of training programs for amplifying the acute BDNF response.
Boomers Daily 