High-intensity interval training near or exceeding VO2 max increases heart stroke volume and capillary beds in the brain, improving cognitive function.

“If you are breathing hard and your heart is beating hard, so this would be certainly in the high-intensity anaerobic and aerobic conditioning because you're getting up near your VO2 max in high-intensity aerobic conditioning and you're exceeding your VO2 max in high-intensity anaerobic conditioning, what's going to happen is as, of course, your heart beats faster, your blood is going to be circulating faster in principle. Oxygen utilization in muscles is going to go up, and over time, not long, very quickly what will happen when those capillary beds start to expand, in addition, because of the amount of blood that's being returned to the heart when you engage in these really intense bouts of effort repeatedly, the amount of blood being returned to the heart actually causes an eccentric loading of one of the muscular walls of the heart.”