THE PHYSIOLOGY OF EXERCISE.
Messrs. Editors:
WHILE all must agree with Professor Richards as to the importance of physical exercise to the brain-worker, there are some points in his article on "The Influence of Exercise upon Health," in the "Monthly" for July, 1886, requiring comment.
On page 328 he says: "When we use our muscles, their contractile force upon the blood-vessels helps the blood along its channels, and thus takes a little labor from the propelling heart. It beats faster, but with less effort."
It is admitted that contracting muscles by their lateral pressure promote the flow of blood through the veins; but the work of the heart is not lessened thereby, because the force of the heart-beat is not expended in propelling the blood through the veins, but (according to Foster) in expanding the elastic arteries and overcoming the friction between the blood and the walls of the arteries and capillaries. This friction is called the peripheral resistance. Now, whatever diminishes the caliber of the terminal arteries and capillaries increases the peripheral resistance; and, if the contracting muscles have any effect upon these vessels, it is to lessen their caliber and so increase the peripheral resistance, thus throwing more work upon the heart.
The heart beats faster, but does it beat with less effort? Du Bois-Reymond ("The Physiology of Exercise," "Popular Science Monthly," July, 1882) says: "Under continuous severe exertions, as in mountain-climbing and long walks, the heart begins to beat faster and more strongly; because, according to Traube, it is stimulated by excess of carbonic acid formed in the laboring muscles; according to Johann Müller, because it participates in a by-motion."
How is it, if muscular exercise lessens the work of the heart, that excessive and long-continued muscular exertion causes hypertrophy and even valvular disease of that organ? Yet such is the case, according to such eminent authorities on medical matters as Drs. Da Costa, A. L. Loomis, the late Austin Flint, and others. This is a matter of great importance from a medical stand-point, for, if muscular exercise lessens the work of the heart, our medical writers have all gone wrong in saying that the most essential item in the treatment of a diseased and overtaxed heart is rest.
Again, the professor quotes Maudsley as follows: "By one organic element of the body the blood is purified from the waste matter of a higher element, which would be poisonous to it." This is undoubtedly true. The lungs, kidneys, and other excreting organs certainly do eliminate materials which would be poisonous to other organs. But Professor Richards applies this remark to the muscular and nervous systems, which, I think, he is not warranted in doing, as I shall endeavor to show.
He says (page 332, July "Monthly"): "A tired brain and quivering nerves may not be more wearied by physical exercise, but may be refreshed by it. This refreshment may result from two processes: First, by drawing the excessive blood-supply from the before active organs; and, secondly, by purifying the blood so that it may be ready to properly nourish the brain."
In the first place, it is not the excessive blood-supply that makes the brain tired, the increase of blood being caused by the increased demand of the functionally active organs. In the second place, contracting muscles, as the result of the chemical changes that take place in their substance, form lactic acid, keratin, and carbonic acid. The last, according to M. Foster ("Text-Book of Physiology"), acts upon the central nervous system as a narcotic poison. The brain forms keratin during functional activity. Now, since one product of muscular action is a narcotic poison, and another is a waste product of the brain, it is inconceivable how the blood is purified and better fitted to nourish the brain.
If, as Professor Foster says, "the fatigue of which, after prolonged and unusual exertion, we are conscious in our own bodies arises chiefly from an exhaustion of the central nervous system concerned in the production of voluntary impulses," then Professor Richards's statement, that the time for exercise is when the brain is tired and one feels inclined to rest and to forego exercise, is open to question. May it not be that the indisposition to take active exercise when fatigued by brain-work is rather conservative, just as is the natural tendency to rest after a full meal during the process of digestion?Respectfully,
| A. B. Rosenberry, M. D. |
| Sheboygan Falls, Wisconsin, July 8, 1886. |
A CURIOUS OPTICAL PHENOMENON.
Messrs. Editors:
A strange phenomenon was observed here at a few minutes before sunset yesterday evening. A heavy storm had come up
