When you’re active, your body. seeks more oxygen to bum the fuel it needs for extra energy. During heavy exercise, straining for that extra oxygen pushes your respiration rate from a resting rate of 12 or so breaths per minute to 35 to 45 (though rates of 60 to 75 have been recorded). Each inhalation pulls air into the lungs, where the oxygen moves into the bloodstream and is picked up by the hemoglobin in your red blood cells and delivered to body tissue and muscle, In exchange, carbon dioxide moves from the tissue into the bloodstream and then into the lungs; each exhalation expels some carbon dioxide (some remains in the blood). The brain’s breathing control center is most alert to the level of carbon dioxide in your blood; if the level is too high, your breathing rate is immediately stepped up, bringing in more oxygen and effecting a further exchange outpaces.
The lungs have no muscles their own, they’re squeezed, like bellows, by the diaphragm (a dome shaped muscle below the ib cage) and by muscles between the ribs. When you breathe in, the diaphragm contracts and flattens and at the same time the cage is pulled upward to enlarge the chest cavity, into which the lungs expand. Then, as the rib muscles and diaphragm relax, the rib cage and diaphragm return to their original places, forcing air out of the lungs.
Though we tend to think of our lungs as being empty, they are actually crammed with oxygen processing “equipment,” beginning with the bronchi, twin air passages that branch off the windpipe into a treelike network of smaller passages (bronchioles) and end in clusters of tiny thin walled air sacs called alveoli. Oxygen gets into the bloodstream by passing through the walls of millions of alveoli into the network of capillaries on their surface. Can you get a “second wind”?
For a few minutes into any bout of exercise, you may feel a little breathless and your muscles may hurt. Your body isn’t able to transfer enough oxygen quickly to the working muscles. Thus the muscles bum carbohydrates anaerobically (that is without oxygen), which steps up the output of lactic acid. Gradually there’s a kick over, and the muscles now bum fuel (carbohydrates and fats) aerobically. You seem to be back in stride this is what’s known as a second wind.
Getting your breath “back” this way seems to be linked to reaching. a point of equilibrium at which your respiratory and circulatory systems are able to keep pace with the intensity of your physical effort. The more you train, the sooner you reach this aerobic “steady state.”
Article extracted from this publication >> May 19, 1989
