Building endurance without extensive mileage can be achieved by increasing capillary beds within muscles to improve oxygen utilization, muscle endurance, and brain metabolism.

“And that's because there are these other forms of endurance that can build up, for instance, the capillary beds within the muscles. Building up the capillary beds within the muscles will allow more oxygen utilization within the muscles, and thereby will increase your endurance both of the muscles, but also will improve brain metabolism and the way that the heart functions, so cardiovascular function.”