Exercise has many known benefits, from improving strength and flexibility to helping cardiovascular fitness. One important component of cardiovascular fitness that is improved by participation in a regular exercise program is respiratory health. The human respiratory system and exercise are linked in that exercise strengthens the body’s ability to efficiently utilize oxygen, a gas that makes its way into the bloodstream via exchange with carbon dioxide in the lungs.
Composed of the airways — the breathing passages, the nasal cavity and mouth, the pharynx or throat, and the trachea or windpipe — and the lungs, the respiratory system is responsible for removing oxygen from inhaled air while expelling carbon dioxide from the body via exhaled air. Oxygen is vital to a number of important bodily processes, particularly cellular metabolism, while carbon dioxide is a waste product of these processes. The respiratory system works in conjunction with the cardiovascular system to deliver oxygen via blood to the body’s tissues and return carbon dioxide from the tissues to the lungs for elimination from the body.
How the respiratory system and exercise are connected cannot be explained without an explanation of cardiovascular system function. The heart pumps to circulate blood that has received oxygen in the lungs throughout the body while also cycling deoxygenated blood, or blood that has deposited oxygen and returned with carbon dioxide, back to the lungs. Once back in the lungs, the blood takes up a certain percentage of the oxygen available in a given volume of inhaled air. This oxygen extraction occurs within the alveoli, tiny sacs in the lungs that are permeated by capillaries; the capillaries feed larger blood vessels that briefly carry the oxygenated blood back to the heart, which then pumps it out into the body.
Exercise improves not only the volume of oxygen that can be extracted from air in the lungs, but the amount of oxygen that can be delivered by the cardiovascular system to the body’s tissues and the amount those tissues consume. Cardiovascular training enables an individual to take up a larger volume of oxygen in a given volume of blood, which means that the heart can meet the body’s oxygen needs with a smaller output of blood pumped out of the heart, expressed as a lower heart rate in beats per minute. It also contributes to an increased number of red blood cells, which contain a protein called hemoglobin to which oxygen attaches in order to be transported throughout the body. More red blood cells means more oxygen that can be delivered to the tissues in a given volume of blood.
Another link between the respiratory system and exercise is the effect of carbon dioxide on the blood vessels. During exercise, cellular metabolism increases, meaning simply that an increased amount of oxygen must be consumed to meet the body’s energy needs, and therefore that an increased amount of carbon dioxide is expelled compared to resting levels. This increased presence of carbon dioxide in the blood vessels causes them to dilate, or expand in diameter. As a result of this vasodilation, a larger volume of blood and therefore oxygen can get to the tissues that demand it. This means that fit individuals will enjoy one more benefit of this positive relationship between the respiratory system and exercise: not only a lower resting heart rate, but a slower breathing rate as their body becomes increasingly efficient at taking up and consuming oxygen.