Around 10,000 liters of air pass into your lungs every day. Your respiratory rate at rest is about 10 to 15 breaths per minute. During exercise, oxygen consumption can increase from 250 to over 3,000 ml per minute. The well-being of all the cells in your body depends upon the efficiency of your respiratory processes. Airway constriction decreases your ability to move air into and out of your lungs, which poses a serious health threat.
Anatomy
Your airways are divided into upper and lower areas. Upper airways include the nose, mouth and larynx and trachea. The trachea divides into right and left bronchi, which serve as air conduits to the right and left lungs. The bronchi form a series of progressively smaller divisions that end at the alveoli, which are thin membranous sacs where blood in the capillaries pick up inhaled oxygen and unload carbon dioxide which is then exhaled. There are about 300 million alveoli in your lungs that have a combined area about the size of a tennis court. Increased metabolic demands of exercise require adequate lung functioning.
Physiology
When you exercise, the metabolic demands of muscle cells increase. To meet increased demand for energy, the muscle cells must increase glucose consumption. This process requires oxygen, so when you exercise, your brain receives a signal to increase respiration. The amount of air that can get into fine small alveolar sacs where the exchange of carbon dioxide for oxygen occurs, is determined by the extent to which the airways are open.
Pathology
According to William L. Cappiello, M.D., 90 percent of people with chronic asthma also have exercise induced asthma, or attacks that are triggered by exercise. Exercise-induced asthma is also more common in children, young adults and people with hay fever, allergies and eczema. Non-asthmatics can also have exercise induced asthma.
The process of warming and the addition of humidity to the inhaled air by the respiratory passages triggers an inflammatory reaction where potent broncho-constrictors are produced causing wheezing, coughing, shortness of breath or chest pain. Decreased glucose delivery causes muscles to use fat for energy. This results in the formation of lactic acid, which can cause muscle cramps.
Treatment
For treatment of exercise induced bronchial constriction, Dr. Cappiello recommends nasal breathing, use of a face mask, exercising in an area where the air is warm and moist, choosing exercises that do not avoid sustained exertion such as baseball and football, and avoidance of allergens and pollutants.
People with pure exercise induced asthma without any chronic inflammatory component as well as chronic asthmatics who have exercise induced asthma can reduce their symptoms by using warm-up and cool-down exercises. Those who have asthma with associated inflammatory changes can use an inhaler that causes the bronchial muscles to relax. MayoClinic.com details warm-up exercises that involve doing a slowed down version of your planned exercise activity for 5 to 10 minutes before actually engaging in the activity, such as walking slowly before increasing your speed.
References
- Lunguk.org; The Way Your Lungs Work; March 2011
- Houston Sports Medicine Foundation; Houston Health Alert: Exercise Induced Asthma; William L. Cappiello, M.D.
- Nuffield Dept.of Anaesthetics, University of Oxford; Update in Anesthesia;
- Mayo Clinic; Aerobic exercise: How to Warm up and Cool Down; 2011
- Health Central; Exercise's Effects on the Lungs; Harvey Simon, MD; 2011
