填空题 Walking—like swimming, bicycling and running—is an aerobic exercise,{{U}} {{U}} 1 {{/U}} {{/U}}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{{U}} {{U}} 2 {{/U}} {{/U}}of heart and circulatory disease.
As probably the least strenuous, safest aerobic activity, walking is the{{U}} {{U}} 3 {{/U}} {{/U}}acceptable exercise for the largest number of people. Walking{{U}} {{U}} 4 {{/U}} {{/U}}comfortable speed improves the efficiency of the cardiorespiratory system{{U}} {{U}} 5 {{/U}} {{/U}}stimulating the lungs and heart, but at a more gradual rate{{U}} {{U}} 6 {{/U}} {{/U}}most other forms of exercise.
In one test, a group of men 40 to 57 years of age,{{U}} {{U}} 7 {{/U}} {{/U}}at a fast pace for 40 minutes four days a week, showed improvement{{U}} {{U}} 8 {{/U}} {{/U}}to men the same age on a 30 minute, three-day-a-week jogging program in the same period. Their resting heart rate and body fat decreased{{U}} {{U}} 9 {{/U}} {{/U}}. These changes suggest{{U}} {{U}} 10 {{/U}} {{/U}}of the important—even vital—benefits walking can{{U}} {{U}} 11 {{/U}} {{/U}}about.
Walking{{U}} {{U}} 12 {{/U}} {{/U}}burns calories. It takes 3,500 calories to gain or{{U}} {{U}} 13 {{/U}} {{/U}}one pound. Since a one-hour walk at a moderate pace will{{U}} {{U}} 14 {{/U}} {{/U}}up 300 to 360 calories. By walking one hour every other day, you can burn up a pound-and-a-half monthly, or 18 pounds{{U}} {{U}} 15 {{/U}} {{/U}}providing there is no change in your intake of food. To{{U}} {{U}} 16 {{/U}} {{/U}}weight faster, walk an hour every day and burn up 3 pounds a month, or 36 pounds a year.
{{U}} {{U}} 17 {{/U}} {{/U}}your age, right now is the time to give your physical well being as much thought as you {{U}} {{U}} 18 {{/U}} {{/U}}to pensions or insurance. Walking is a vital defense{{U}} {{U}} 19 {{/U}} {{/U}}the ravages of degenerative diseases and aging. It is nature's{{U}} {{U}} 20 {{/U}} {{/U}}of giving you a tuneup.