Have you ever heard about Polar Bear(北极熊)Club in New York? These “Polar Bears” are people who meet 1 in the winter to swim in freezing cold water．The members of the Polar Bear Club are above the age of 60．Members must satisfy two requirements．First, they must get along well with everyone else in the group; this is very 2 because there are so many different kinds of people in the club．Polar Bears must also agree to swim outdoors at least twice a month from November through February．
Doctors don't 3 the medical effects of cold-water swimming．Some think that the body's temperature drops so low in cold-water swimming that finally the heart stops．But other doctors think differently．They point out that there is more danger of a heart attack during 4 swimming because the difference between the air temperature and the water temperature is much greater in summer than in winter．
The Polar Bears themselves are satisfied with the advantages of cold-water swimming．They say that their favourite form of exercise is very good for the circulatory system(循环系统)because it makes the blood move fast to keep the body warm．Cold-water swimmers usually turn bright red after a few minutes in the water．A person who turns blue probably has a very 5 circulatory system and could not try cold-water swimming．
The Polar Bears love to swim all the year round．They find it fun and relaxing．As one 70-year-old woman says, “When I go into the water, I throw my 6 into the ocean and let the water carry them away．When I get out of the water, I feel happy again．”