Half an hour’s exercise a day cuts the risks of catching colds in half, a new trial suggests. Brisk walking is all that is needed, and the longer that you continue to exercise daily the greater the (26) . The trial (27) 115 older women from Seattle, Washington state. All were sedentary and either (28) or obese. For a year they were asked either to exercise daily or take part in a 45-minute stretching class once a week. The women were (29) . allocated to one or other of these groups, and every quarter were asked to fill in questionnaires asking them whether they had suffered colds or other upper respiratory (30) in the previous three months. The results show that the daily exercise group had only half as many colds as the weekly stretch-class group. "This adds another good reason to put exercise on your to-do list," said Cornelia Ulrich, an (31) member of the Fred Hutchinson Cancer Research center’s public health sciences (32) in Seattle. But (33) was the key. Other studies had shown that excessive exercise could increase the risk of colds. (34) . The exercise group was asked to do 45 minutes of exercise a day, five days a week, but managed only 30 minutes, mainly brisk walking. (35) . "The enhanced immunity was strongest in the final quarter of the year," Dr. Ulrich said. " (36) ".
【参考答案】
This suggests that,when it comes to preventing colds,it’s im......