| Kind of Exercise. | Work done in tons lifted 1 foot. |
| Walking 1 mile | 17·67 |
| Walking 2 miles | 35·34 |
| Walking 10 miles | 176·7 |
| Walking 20 miles | 353·4 |
| Walking 1 mile and carrying 60 lbs. | 24·75 |
| Walking 2 miles and carrying 60 lbs. | 49·5 |
| Walking 10 miles and carrying 60 lbs. | 247·5 |
| Walking 20 miles and carrying 60 lbs. | 495 |
From the above data something like a rough approximation may be formed of the daily amount of exercise requisite for a healthy male adult.
Since 500 tons lifted a foot is extremely hard work, the number of miles corresponding to this extreme amount of labour would, if persevered in, be objectionable.
Dr Parkes, regarding 300 tons lifted a foot as an average day’s work for a healthy man, thinks that walking exercise equivalent to half that amount should be taken daily.
This, or a 150 tons, represents a nine miles’ walk. He, however, qualifies the suggestion by adding “that, as there is much exertion taken in the ordinary business of life, this amount may be in many cases reduced;” and concludes by saying, “It is not possible to lay down rules to meet all cases, but probably every man with the above facts before him could fix the amount necessary for himself with tolerable accuracy.”
For muscular exercise to be safe and efficient, it must be taken under certain conditions and precautions. We have noticed the evil effects of immoderate bodily exertion on the heart. The lungs are no less seriously affected by an excessive indulgence in it, which shows itself in spitting of blood and in congestion of the pulmonary vessels. Congestion of the lungs brought on by overtaxed bodily strength very frequently causes the death of horses in the hunting field.
These facts, therefore, not only point to the importance of avoiding undue or extreme exertion,[293] but also to the necessity of ensuring the full and uncramped play of the respiratory organs during exercise, and the consequent removal of any impediment in the way of tight clothing that in any manner interferes with their freedom of exercise. Laboured respiration and sighing are indications of pulmonary congestion, and counsel temporary rest and abstention from exercise.
[293] “There must be proper intervals of rest, or the store of oxygen, and of the material in the muscles which is to be metamorphosed during contraction, cannot take place.”
—Parkes.
The great augmentation in the excretion of carbon which leaves the lungs in the form of carbonic anhydride during exercise has been already referred to. As this carbon is derived from the food, it follows that in the intervals of exercise an increase of carbonaceous diet is necessary. For this purpose physiologists prefer the fatty to the amylaceous varieties of diet. It has been already stated why at the same time the nitrogenous food must be increased during periods of great exertion. There seems little doubt that water is the best drink that can be taken during moderate as well as great exercise.... It is best taken in small quantities and frequently. Spirits are decidedly prejudicial, and indispose to bodily exertion. They are hurtful because they lessen the exhalation of carbonic anhydride from the lungs. Trainers never allow them, and but very little wine or beer.