Cigarettes contain several harmful chemicals that damage the body, diminishing its ability to adjust to the demands of exercise. The greatest effect of this damage is deprivation of oxygen, which is the principle underlying cause for diminished exercise performance.
Reduced Oxgyen Availability
Cigarettes produce a type of gas called carbon monoxide. Carbon monoxide can be dangerous to the body and even deadly if inhaled in large amounts. When this gas enters the body, it competes with oxygen to bind to hemoglobin on red blood cells. Hemoglobin is a type of protein responsible for carrying oxygen in red blood cells. Carbon monoxide has a higher affinity for hemoglobin than oxygen, meaning that it has a greater attraction to hemoglobin. Therefore, even in the presence of oxygen, carbon monoxide will preferentially bind to hemoglobin. Carbon dioxide also attenuates the release of oxygen from hemoglobin into the tissues, thereby diminishing oxygen levels even further. In addition to this, smoking damages the tiny air sacs called alveoli that fill with air as you breathe. When these sacs are destroyed, the volume of air that you take in with each breath, also called lung capacity, is reduced.
Increased Lung Resistance
Smoking induces several changes that result in narrowing of the bronchi, which are the long tube-like structures that carry air into the lungs. The most immediate change is bronchospasm, or constriction of the bronchi, which occurs within several seconds of smoke inhalation. The airways are further narrowed by inflammation created by the smoke. Irritants and harmful chemicals contained in smoke then stimulate the production of mucus by the lungs, which can block the airways as well. Normally, mucus is removed by small "finger-like" projections in the lungs known as cilia. Over time, smoking damages the cilia so that it is no longer able to remove these substances from the lung. To top this all off, cigarettes coat the alveoli in tar, thus interfering with the ability of the sacs to expand properly.
Effect on Exercise
As the level of oxygen in the blood drops, the body is unable to keep up with the demands of exercise and performance is diminished. This also results in symptoms such as shortness of breath, coughing, wheezing and fatigue that make it difficult to exercise. According to the Cleveland Clinic, smokers experience shortness of breath three times as frequently as nonsmokers.
Other Factors Related to Diminished Exercise Performance
Smoking not only affects your lungs, but your entire body. Smoking is also associated with increased heart rate, constriction of blood vessels, high blood pressure, diminished density of bone mass and reduced strength and flexibility of the muscles.
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