Exercise
Whether or not exercise adds to the length of life, it is common experience that a certain amount of regular exercise -(51) health and contributes a feeling of well-being. Furthermore, exerise _(52) involves play and recreation(娱乐), and relieves nervous tension and mental fatigue in so _(53) is not only pleasant but beneficial.
How much and what kind of exercise one should _(54) merits careful consideration The growing child and the normal young man and young woman thrill(兴奋) with the strenuousc剧烈的) sports. They fatigue to the _(55) of exhaustion but recover promptly with a period of rest. But not so with those of middle age and beyond. For them moderation is _(56) vital importance.
Just how much exercise a person of a given age can safely take is a question hard to (57). Individual variability is too great to permit of generalization A game of tennis may be perfectly safe for one person of forty but folly (愚蠢) for another. The sage _(58) for exercise depends on the condition of the heart, the condition of the muscles, the _(59) of exercise, and the reg- ularity with which it is taken. Two general suggestions, however, will _(60) as sound advice for anyone. The first is that the _ _(61) of the heart and general health should be determined pe- riodically by careful, thorough physical examinations. The other is that exercise should be (62) below the point of physical exhaustion.
What type of exercise one should _(63) depends upon one's physical condition. Young people can safely enjoy competitive sports, but most older persons do better to limit themselves to less strenuous (64). Walking, swimming, skating are among the sports that one can enjoy and safely _ (65) in throughout life. Regularity is important if one is to get the most enjoyment and benefit out of exercise.
51

A. improves
B. damages
C. enjoys
D. provides