This repair is really a renovation of the structure. Rest and work are relative terms, directly opposed to each other. Work quickens the pulse and the respiration, while rest slows both. During sleep the voluntary muscles are relaxed, and those of organic life work with less energy. The pulse and the respiration are less frequent, and the temperature lower than when awake. Hence sleep, "tired Nature's sweet restorer," may be regarded as a complete rest.
The periods of rest should vary with the kind of exercise. Thus exercise which produces breathlessness requires frequent but short rests. The trained runner, finding his respiration embarrassed, stops a moment to regain his breath. Exercises of endurance cause fatigue less quickly than those of speed, but require longer rest. Thus a man not used to long distances may walk a number of hours without stopping, but while fatigue is slow to result, it is also slow to disappear. Hence a lengthy period of rest is necessary before he is able to renew his journey.
88. Amount of Physical Exercise Required. The amount of physical exercise that can be safely performed by each person, is a most important and practical question. No rule can be laid down, for what one person bears well, may prove very injurious to another. To a certain extent, each must be guided by his own judgment. If, after taking exercise, we feel fatigued and irritable, are subject to headache and sleeplessness, or find it difficult to apply the mind to its work, it is plain that we have been taxing our strength unduly, and the warnings should be heeded.
Age is an important factor in the problem, as a young man may do with ease and safety, what might be injurious to an older person. In youth, when the body is making its most active development, the judicious use of games, sports, and gymnastics is most beneficial. In advanced life, both the power and the inclination for exercise fail, but even then effort should be made to take a certain reasonable amount of exercise.
Abundant evidence shows that physical development is most active from thirteen to seventeen years of age; this manifests itself clearly by increase in weight. Hence this period of life is of great consequence. If at this age a boy or girl is subjected to undue physical strain, the development may suffer, the growth be retarded, and the foundation laid for future ill health.
Fig. 43.--Student exercising in the School Gymnasium on the Rowing Machine. (From a photograph.)
The proper amount of exercise must vary greatly with circumstances. It may be laid down as a fairly safe rule, that a person of average height and weight, engaged in study or in any indoor or sedentary occupation, should take an amount of exercise equivalent to walking five or six miles a day. Growing children, as a rule, take more exercise than this, while most men working indoors take far less, and many women take less exercise than men. Exercise may be varied in many ways, the more the better; but for the most part it should always be taken in the open air.
89. Time for Exercise. It is not prudent to do hard work or take severe exercise, just before or just after a full meal. The best time is one or two hours after a meal. Vigorous exercise while the stomach is busily digesting food, may prove injurious, and is apt to result sooner or later in dyspepsia. On the other hand, severe exercise should not be taken on an empty stomach. Those who do much work or study before breakfast, should first take a light lunch, just enough to prevent any faint feeling. With this precaution, there is no better time for moderate exercise than the early morning.
In the case of children, physical exercises should not be undertaken when they are overtired or hungry. Neither is it judicious for adults to take vigorous exercise in the evening, after a long and arduous day's work.
90. Walking, Running, and Jumping. Walking is generally regarded as the simplest and most convenient mode of taking exercise. Man is essentially a walking animal. When taken with a special object in view, it is the best and most pleasant of all physical activities. It is suited for individuals of all ages and occupations, and for residents of every climate. The child, the athlete, and the aged are all able to indulge in this simple and effective means of keeping the body in health.
In walking, the muscles of the entire body are brought into action, and the movements of breathing and the circulation of the blood are increased. The body should be erect, the chest thrown out, the head and shoulders held back, and the stride long and elastic. It is an excellent custom to add to the usefulness of this fine exercise, by deep, voluntary inhalations of pure air.
Running is an excellent exercise for children and young people, but should be sparingly indulged in after the age of thirty-five. If it be accompanied with a feeling of faintness, breathlessness, and palpitation of the heart, the exercise is too severe, and its continuance may do serious harm. Running as an exercise is beneficial to those who have kept themselves in practice and in sound condition. It brings into play nearly every muscle of the body, and thus serves to develop the power of endurance, as well as strength and capacity for rapid movement.
Jumping may well be left to boys and young men under twenty, but skipping with a rope, allied to jumping, is an admirable and beneficial form of exercise. It brings into action many muscles without putting undue strain upon any particular group.
91. Skating, Swimming, and Rowing. Skating is a delightful and invigorating exercise. It calls into play a great variety of muscles, and is admirably adapted for almost all ages. It strengthens the ankles and helps give an easy and graceful carriage to the body. Skating is especially valuable, as it can be enjoyed when other out-door exercises are not convenient.
Every child above ten years of age should be taught to swim. The art, once mastered, is never forgotten. It calls into use a wide combination of muscles. This accomplishment, so easily learned, should be a part of our education, as well as baseball or bicycling, as it may chance to any one to save his own life or that of a companion.
In many respects rowing is one of the most perfect exercises at our command. It expands the chest, strengthens the body, and gives tone to the muscles of the abdomen. It is very suitable for girls and women, as no other exercise is so well adapted to remedy the muscular defects so marked in their sex. Even elderly persons can row day after day without difficulty. The degree of muscular effort required, can be regulated so that those with weak hearts and weak lungs can adjust themselves to the exercise.
92. Bicycling as an Exercise. The bicycle as a means of taking exercise has come into popular use with remarkable rapidity. Sharp competition bids fair to make the wheel more popular and less expensive than ever. Its phenomenal use by persons of all ages and in all stations of life, is proof of the enthusiasm with which this athletic exercise is employed by women as well as by men.
Mechanical skill has removed most of the risks to health and person which once existed. A good machine, used by its owner with judgment, is the most convenient, the safest, and the least expensive means of traveling for pleasure or exercise. It is doing more than any other form of exercise to improve the bodily condition of thousands whose occupations confine them all day to sedentary work. Dependent upon no one but himself, the cyclist has his means of exercise always at hand. No preparation is necessary to take a spin of ten miles or so on the road, during a summer evening or before breakfast.
Bicycling brings into active use the muscles of the legs as well as those of the trunk and arms. It seems to benefit those who suffer from dyspepsia, constipation, and functional disorders of the liver.
A special caution must be used against overdoing in cycling, for the temptation by rivalry, making a record, by social competition on the road, is stronger in this form of exercise than in any other, especially for young folks. Many cases have occurred of permanent injury,