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回答题：Walking-like swimming，Bicycling and running--is an aerobic exercise，(31)_____builds the capacity for energy output and physical endurance by increasing the supply of oxygen to skin and muscles．Such exercises may be a primary factor in the(32)_____of heart and circulatory disease．
As probably the least strenuous，safest aerobic activity，walking is the(33)_____acceptable exercise for the largest number of people．Walking(34)_____comfortable speed improves the efficiency of the cardiorespi ratory system(35)_____stimulating the lungs and heart，But at a more gradual rate(36)_____most other forms of exercise．
In one test，a group of men 40 to 57 years of age，(37)——at a fast pace for 40 minutes four days a week，showed improvement(38)_____to men the salve age on a 30 minute，three-day-a-week jogging program in the sanle period．Their resting heart rate and body fat decreased(39)_____．These changes suggest (40)_____of the impoaant--even vital--benefits walking can(41)_____about．
Walking(42)______bums calories．It takes 3，500 calories to gain or(43)______0ne pound．Since a one-hour walk at a moderate pace will(44)______up 300 to 360 calories．By walking one hour every Other day，you aan bum up a pound-and-a-half monthly，or 18 pounds(45)______providing there is no change in your intake of food．To(46)______weight faster，walk art hour every day and bum up 3 pounds a month，or 36 pounds a year．
(47)______your age，right flOW is the time to give your physical well—being as much thought as you (48)______to pensions or insuranCe．Walking is a vital defense(49)______the ravages of degenerative diseases and aging．It is nature’s(50)______of giving you a tuneup．
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