2016年12月英语四级阅读200篇：生活中三种疲劳
Three Kinds of Fatigue
Fatigue is one of the most common complaints brought to doctors, friends, and relatives. You'd think in this era of labor-saving devices and convenient transportation that few people would have reason to be so tired. But probably more people complain of fatigue today than in the days when hay was baled by hand and laundry scrubbed on a washboard.
The causes of modern-day fatigue are diverse and only rarely related to excessive physical exertion. The relatively few people who do heavy labor all day long almost never complain about being tired, perhaps because they expect to be. Today, physicians report, tiredness is more likely a consequence of under-exertion than of wearing yourself down with over-activity. In fact, increased physical activity is often prescribed as a cure for lowering energy.
Physical. This is the well-known result of overworking your muscles to the point where metabolic (新成代谢的) waste products—carbon dioxide and lactic acid (乳酸)—accumulate in our blood and reduce your strength. Your muscles can't continue to work efficiently in a bath of these chemicals. Physical fatigue is usually a pleasant tiredness, such as that which you might experience after playing a hard set of tennis, chopping wood, or climbing a mountain. The cure is simple and fast: You rest, giving your body a chance to get rid of accumulated wastes and restore muscle fuel.
Pathological (病理的). Here fatigue is a warning sign or consequence of some underlying physical disorder, perhaps the common cold or flu or something more serious like diabetes or cancer. Usually other symptoms besides fatigue are present that suggest the true cause.
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