People will only workout within their respiratory limits, the body gets uncomfortable, the brain shuts down, the muscles fatigue. If you train the respiratory breathing system you improve your aerobic capacity thereby moving further and moving faster. Aerobic metabolism is up to 15 times more efficient than anaerobic metabolism.
“Blood doping’ refers to any illicit method of boosting an athlete’s red blood-cell supply in advance of competition. The typical adult male’s hematocrit–the percentage of his blood that is composed of red blood cells–hovers around 45. Since red blood cells carry oxygen through the bloodstream, increasing the number of them allows an athlete’s blood to deliver oxygen to muscles more efficiently, reducing fatigue and giving the athlete an edge. Endurance athletes often train at high altitude for precisely this reason. The lower air pressure and diminished atmospheric oxygen at altitude spur the body to generate extra red blood cells, and can bump the hematocrit up two or three (non-illicit) percentage points.