Moods, say the experts, are emotions that tend to become fixed, influencing one’s outlook for hours, days or even weeks. That’s great if your mood is a pleasant one, but a problem if you are sad, anxious, angry or simply lonely. Perhaps the best way to deal with such moods is to talk them out: sometimes, though, there is no one to listen. Modern pharmacology ( 药物学 )offers an abundance of tranquilizers ( 镇静剂 ) , antidepressants and antianxiety drugs. What many people don’t realize, however, is that scientists have discovered the effectiveness of several non-drug approaches to make you loose from an unwanted mood. These can be just as useful as drugs, and have the added benefit of being non-poisonous. So next time you feel out of sorts, don’t head for the drug-store, try the following approach. Of all the mood-altering self-help techniques, aerobic ( 增氧健体的 )exercise seems to be the most efficient cure for a bad mood. “If you could keep the exercise, you’d be in high spirits.” Says Kathryn Lance, author of Running for Health and Beauty. Researchers have explained biochemical and various other changes that make exercise compared favorably to drugs as a mood-raiser. Physical exertion such as housework, however, does little. The key is aerobic exercise----running, cycling, walking, swimming or other repetitive and so tamed activities that boost the heart rate, increase circulation and improve the body’s utilization of oxygen. Do them for at least 20 minutes a session, three or five times a week.