Let me be first to mention link between amount of endurance activity and serum level of brain-derived neurotrophic factor (BDNF). NIH is down for me, at least,

Let me be first to mention link between amount of endurance activity and serum level of brain-derived neurotrophic factor (BDNF). NIH is down for me, at least, so all I can offer is for you to google it and around it, it may change your life. The longer you train, the higher elevation is. On the other hand, the longer one trains, the longer fitness stays. (by the way, walking 35 km per week in average has been shown as stopping of brain mass decline in some important parts of brain, related to internal organ regulation, learning, higher order functions and long term memory) Thus, nothing surprising here.