Respiration & Exercise

According to the British Lung Foundation, a healthy individual's average respiratory rate is about 15 breaths per minute. During exercise, your respiratory rate increases. Elite endurance athletes can be expected to have a respiratory rate of 40 to 60 breaths per minute, which translates into the consumption of 100L to 150L of air, from which about 5L of oxygen will be extracted per minute. The BLF states that even for less highly trained individuals, you'll still need to double your lung intake to meet the oxygen demands of vigorous and sustained aerobic activity.

Function

The principal physiological function of your pulmonary system is to serve as an intermediary between your body and the environment so that gas exchange can occur, states Brian B. Parr, assistant professor at the University of South Carolina-Aiken. Your lungs replace oxygen, remove carbon dioxide and help regulate your body's acid-base balance. According to Parr, your body's ability to maintain this acid-base balance during exercise is one of the respiratory system's most important functions.

Anatomy

The principal anatomical components of your respiratory system, according the Children's Hospital of Wisconsin, include your nose and nasal cavities, pharynx, larynx, trachea and bronchial tree, and lungs--including the "alveoli" or air sacs where gas exchange takes place. Parr sums up the components of your respiratory system by stating, "Anatomically, the pulmonary system consists of a group of passages that filter air and transport it into the lungs. where gas exchange occurs."

Muscles Involved

The muscles that assist your respiration at rest and during exercise are separated into two categories--muscles of inspiration and muscles of expiration. Your muscles of inspiration include your sternocleidomastoid, scalenes, external and internal intercostals and diaphragm. These muscles, when working in concert, lift the ribs outward and allow the diaphragm to descend. Your lung volume increases, and gas exchange occurs. Your muscles of expiration include your internal intercostals, external and internal abdominal obliques, transversus abdominis and rectus abdominis. Collectively, these muscles pull your ribcage downward and help decrease lung volume.

Misconceptions

It was once believed that your respiratory muscles could not fatigue with exercise. According to Parr, current evidence suggests that respiratory muscle fatigue does occur with exercise, especially with bouts of aerobic exercise lasting longer than two hours and with high-intensity--90 to 100 percent VO2 max--exercise. Par said that, like other skeletal muscles and despite its relative thinness, your abdominal diaphragm can adapt to training. With aerobic training, the cellular processes of your diaphragm become more efficient and you experience an overall reduced work of breathing.

Considerations

John Douillard, a Boulder, Colorado-based chiropractor and author of "Body, Mind and Sport," believes your body is designed to breathe through the nose, "except in extraordinary circumstances when access to nasal air is insufficient." In his book, Douillard argues that nose breathing is your best choice for optimal respiration during both rest and exercise. He states that "when air enters the body through the nose, it does so in a more refined, rarefied stream," which allows it to more easily access your lung's blood-rich lower lobes while diminishing stress on your heart. Air breathed in through your mouth reaches only your lung's middle and upper lobes and contributes to an elevated heart rate and a shorter amount of time that gas exchange can occur in the lungs.