Exercise in the City.
From the standpoint of coaches and athletes, carbon monoxide is the most important of the primary pollutants. The principle source of carbon monoxide is automotive exhaust. Carbon monoxide exerts its effect by binding to and blocking the oxygen-binding sites on hemoglobin in the red blood cells [forming the molecule HbCO]. Hemoglobin has an affinity for carbon monoxide that is times greater than its affinity for oxygen.. This means that increased levels of carbon monoxide in the blood compromise both the transport of oxygen in the blood, and the extraction of oxygen to the tissues.. The immediate impact of this on exercise performance is that as the concentration of HbCO in the blood increases, there is a decrement in maximum oxygen consumption. [and a decrease] in maximal exercise time.
Airborne contaminants represent environmental stressors that primarily affect the respiratory and cardiovascular systems. However, air pollutants also may cause inflammation and may increase the levels of blood-borne immune factors. It is not valid to categorize the effects of carbon monoxide, ozone, sulfur dioxide, nitrogen dioxide, and peroxyacetyl nitrate as one environmental stressor because they each affect health and performance via unique mechanisms and to a different degree. Although we cannot selectively filter air pollutants, this chapter presents techniques to reduce the effects of contaminants on exercise performance and health. High-risk individuals, such as those with asthma, also are identified.
Pollution: A Modern Environmental Stressor.
As described in the preface of this book, earth's environment can be extreme in many ways. Environmental features, including temperature, pressure, wind speed, and moisture, represent stressors that challenge survival and diminish performance. Although adequate adaptive responses occur acclimatization in response to repeated exposures to different stressors, one aspect of our environment seems to have outpaced our hereditary capabilities: air pollution. The ocean of air that surrounds us has changed so rapidly in the last century, especially due to the internal combustion engine, that it presents a new challenge to our adaptive potentials. Because research involving individual pollutants is in its infancy, we are still learning simple facts regarding the impact of air quality on exercise and work performance. The details below verify that the effects of each pollutant are distinctive, and that each should be viewed as a unique stressor that the body may, or may not, be genetically equipped to deal with.
In contrast to heat and humidity, which affect virtually all organs in the body, air pollutants affect few body systems directly figure Despite this difference, weather fronts that contain heat and humidity may act to magnify the effects of air pollution on health and physical performance. Figurepage illustrates this connection. Panel A shows normal atmospheric conditions, in which the air above the earth gets colder as altitude increases. This decrease in temperature amounts to a decrease of approximately. C .F for every increase in altitude. In these conditions, the pollutants, which are relatively warm, rise through the layers of denser, cold air. Panel B shows the conditions of a thermal inversion, during which a layer of warm or hot air is sandwiched between two layers of colder air. Such a warm air layer may be very stable and persist for several days, until a different weather front arrives and the thermal inversion is disrupted. The warm air layer forms a ceiling that traps the.
Upward movement of airborne pollutants, causing them to move horizontally beneath the thermal inversion. The combined factors of an environmental trap and a source of pollution are common to almost all locations where there is an accumulation of atmospheric pollution that negatively affects health and exercise performance.
It even is possible that the geographic location of a city causes it to be an environmental trap. Denver, Colorado, for example, sits at the bottom of a large bowl-like basin on the eastern edge of the Rocky Mountains. This basin forms an ideal collecting trap for the industrial and automotive pollutants generated in that area. Thus, anyone who lives, works, or competes in a geographic area such as Denver may be affected by atmospheric contaminants.