# Popular Science Monthly/Volume 71/December 1907/The Influence of Diet on Endurance and General Efficiency

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* THE INFLUENCE OF DIET ON ENDURANCE AND GENERAL EFFICIENCY
By Professor RUSSELL H. CHITTENDEN
SHEFFIELD SCIENTIFIC SCHOOL OF YALE UNIVERSITY
EXPERIMENTAL study of the physiological needs of the body for food has indicated that the real requirements of the system, especially for proteid foods, are far below the amounts called for by existing dietary standards, and still farther below the customary habits of the majority of mankind. The ability of the body to maintain a condition of physiological equilibrium, with a true nitrogen balance, etc., on a relatively small amount of nitrogenous food, would seemingly imply that the large surplus so generally consumed constitutes an entirely uncalled-for drain upon the system, as well as upon the pocket of the individual, and without any compensatory gain.
In our experimental study of this question, observations on many individuals have extended over such long periods of time that there is apparently perfect safety in the conclusion that the new dietary standards which aim to conform to the true needs of the body are perfectly adapted to maintain health, strength and vigor indefinitely. Further, the many data obtained in our experimental studies, reinforced by a multitude of personal experiences from all over the world, communicated to the writer, all lead to the view that there is great personal gain in the acquisition of dietary habits that tend toward moderation and simplicity. Renewed health, increased vigor, greater freedom from minor ailments, etc., are so frequently reported as the outcome of temperance in diet, that we are forced to the conclusion that the surplus of proteid food so commonly consumed—amounts far beyond what the physiological necessities of the body demand—is wholly unphysiological and in the long run detrimental to the best interests of the individual. There is seemingly sound philosophy in so changing the customs and habits of our daily life that they will conform more or less closely to our present understanding of the physiological requirements of the body.
It is certainly not presumptuous to assume that physiological experimentation can tell us definitely and concisely how much and what kinds of food are needed to supply the daily waste of tissue and to make good the loss of energy incidental to varying degrees of bodily ​activity. This we have sought to ascertain by our studies of the past five years, and confidence in our results is augmented by the fact that when living on a lower level of proteid consumption bodily strength and endurance are unquestionably increased; muscular fatigue and soreness as concomitants of severe or prolonged muscular effort diminish or are wholly wanting; thus raising the suggestion that under true physiological conditions the muscles of the body are capable of more prolonged effort, and with greater freedom from disagreeable after-effects than when the system is charged with an excess of nitrogenous and other waste incidental to large intakes of proteid food. In other words, consumption of proteid food in closer harmony with the true needs of the body is accompanied by a smoother and more efficient working of the bodily machinery; less friction and better results follow a daily diet in which excess is avoided and the intake made to correspond more closely with physiological requirements.
Those who are skeptical of the real value of a relatively low intake of proteid food frequently acquiesce in the general statement that as a physiological experiment it may be quite true that equilibrium, physical vigor, efficiency, etc., can be maintained by a smaller amount of proteid food, but they are inclined to the view that in the long run more abundant supplies of nutriment will be demanded in harmony with the ordinary customs of mankind. This is a reasonable objection, and one that time only can answer. It is quite possible—though not very probable—that an experiment of several years' duration even may fail to show certain deleterious effects which eventually may manifest themselves, assuming that the body does actually need more proteid food than our experimental results imply. This may be a purely theoretical objection, but it is one that is deserving of some consideration, since it is unquestionably true that there are many factors in the broad subject of nutrition not yet fully understood, and there are many phases of proteid metabolism not wholly clear. So far as any experimental evidence is concerned, however, there is nothing, in the writer's opinion, that can be construed as giving weight to this objection. Neither are there any observations bearing on the customs or habits of peoples or communities that can be adduced in favor of possible danger to the individual from a continued intake of proteid food in harmony with our experimental data; certainly none that is not equally susceptible of plausible explanation on some other ground.
As has been stated in another place, a daily intake of GO grams, or two ounces, of proteid is quite sufficient to meet the needs of a man of 70 kilograms body-weight, and this without increasing unduly the amount of non-nitrogenous food. In fact, for a man of the above weight doing an ordinary amount of work, the total calorific value of ​the daily food need not exceed 2,800 calories. As compared with the ordinary statements of the body's needs, this means a saving of one half in the amount of proteid food and about one fifth in the amount of non-nitrogenous food daily. That these smaller amounts of food are quite sufficient to meet the needs of the body is indicated by the condition of the subjects after many months of living at these lower levels. Especially noticeable, because at that time wholly unexpected, was the decided gain in bodily strength and endurance manifested by all the subjects of experiment. This gain was spoken of as gain in "total strength," but the element of endurance was incorporated therein, since the final product was a compound of the dynamometer tests of individual muscles and the number of times the individual could pull up and push up his body on the parallel bars. The natural interpretation of the results obtained was that the increased muscular efficiency was a direct or indirect result of the lowered proteid metabolism of the body. In other words, it might be reasoned that the smaller consumption of proteid food was a nearer approach to normal conditions, and as a result there was manifested an increased muscular efficiency. However this may be, bodily strength and endurance were certainly increased, and the question naturally arises, will this improved state of the body continue for any length of time under such conditions of diet? In other words, may we expect to find an improved physical condition of the body in following habits of life which seemingly accord more closely with true physiological needs, avoiding that excess of food intake that the common practises of mankind sanction?
One of the first subjects experimented with by the writer was Horace Fletcher, who in 1903 spent several months in our laboratory and was at the same time carefully tested by Dr. William G. Anderson, director of the Yale Gymnasium, as to his physical condition. For some five years Mr. Fletcher had practised a certain degree of abstinence in the taking of food with, as he believed, important economy, i. e., great gain in bodily and mental vigor and with marked improvement in his general health. He found that under his new method of living he was possessed of a peculiar fitness for work and with freedom from the ordinary fatigue incidental to extra physical exertion. In the laboratory observations made at that time, it was found that he was not metabolizing more than fifty grams of proteid per day, while at the same time his body was essentially in a condition of nitrogen equilibrium. Dr. Anderson, as the result of his observations on Mr. Fletcher, concluded that, considering his age, he had never seen an individual able to work in the gymnasium with fewer noticeable bad results, since he was able to do the work of trained athletes and not ​give marked evidences of over-exertion, although not in training. At the time these experiments were tried Mr. Fletcher weighed one hundred and fifty-seven and a half pounds, and was in his fifty-fourth year.
While, naturally, we have not been able to obtain daily records of the quantity of food taken by Mr. Fletcher during the past four years, observations made from time to time have confirmed his general statement that he lives essentially at this same low level of proteid metabolism. In June, 1907, Mr. Fletcher was again at New Haven for some weeks, thus giving us an opportunity to test his rate of nitrogen exchange and his physical condition. It was found that the amount of nitrogenous or proteid food consumed daily never exceeded sixty grams, and that his nitrogen metabolism averaged not far from seven grams per day. His body-weight was found to be one hundred and seventyseven and a half pounds. We thus had an opportunity of testing the physical endurance of a man who has for at least nine years practised a degree of physiological economy in nutrition, which means a daily consumption of proteid food in amount less than one half that called for by the ordinary dietary standards. It would seem reasonable to suppose that if a low nitrogen intake is destined eventually to prove detrimental to the individual, some sign of such deleterious effect would manifest itself during this period of time. If, on the other hand, consumption of proteid food in harmony with the lower dietary standards which the writer is disposed to advocate on the basis of his experimental results, is beneficial to the individual, then one might expect to find a continuance of the same physical vigor noted in the earlier observations on Mr. Fletcher, in spite of the fact that at this date the subject was nearly fifty-nine years of age.
Through the kindness of Dr. Anderson, of the Yale Gymnasium, Mr. Fletcher was subjected to a variety of tests, the outcome of which is best presented in the words of Dr. Anderson, as given to the writer in a report made under date of June 28, 1907.
On June 11, 1907, Mr. Fletcher again visited the Yale Gymnasium and underwent a test on Professor Fisher's dynamometer. This device is made to test the endurance of the calf muscles. (Soleus and gastrocnemius.) The subject makes a dead lift of a prescribed weight as many times as possible. In order to select a definite weight the subject first ascertains his strength on the Kellogg mercurial dynamometer by one strong, steady contraction of the muscles named—and then he finds his endurance by lifting three fourths of this weight on the Fisher dynamometer as many times as possible at two- or three-second internals. One leg only is used in the lift, and, as indicated, the right is usually chosen.
Mr. Fletcher's actual strength as indicated on the Kellogg machine was not quite 400 pounds, ascertained by three trials. In his endurance test on the Fisher machine he raised 300 pounds 3.50 times and then did not reach the limit of his power. Previous to this time Dr. Frank Born, the medical assistant at the gymnasium, had collected data from 18 Yale students, most of whom were trained athletes or gymnasts. The average record of these men was 87.4 lifts, the extremes being 33 and 175 lifts.
It will be noticed that Mr. Fletcher doubled the best record made previous to his feat and numerous subsequent tests have failed to increase the average ​of Mr. Fletcher's competitors. Mr. Fletcher informs me that he has done no training nor has he taken any strenuous exercise since February, 1907. On two occasions only during the past year he reports to have done hard work in emergencies; once while following Major General Wood in the Philippines in climbing a volcanic mountain through a tropical jungle on an island near Mindanao for nine hours; and once wading through deep snow in the Himalayan Mountains, some three miles one day and seven miles the next day, in about as many hours. This last emergency experience came through being caught in a blizzard near Murree, in northern India, at 8,500 feet elevation, on the way to the Vale of Kashmir. These two trials represented climatic extremes and Mr. Fletcher states that neither the heat nor the cold gave him discomfort, a significant fact in estimating physical condition.
Before the trial on the Fisher ergograph, the subject's pulse was normal (about 75); afterwards it ran 120 beats to the minute. Five minutes later it had fallen to 112. No later reading was taken that day. The hands did not tremble more than usual under resting conditions, as Mr. Fletcher was able to hold in either hand immediately after the test a glass brimming over with water without spilling a drop. The face was flushed, perspiration moderate, heart action regular and control of the right foot and leg vised in the test normal immediately following the feat. I consider this a remarkable showing for a man in his fifty-ninth year, 5 feet 6$^1$⁄$_2$ inches in height, weighing 177$^1$⁄$_2$ pounds and not in training.
In order to make a more thorough test of Mr. Fletcher's powers of endurance under varying degrees of physical strain he underwent on the 17th, 18th, 19th, 21st and 22d of June, 1907. the following:
1. Going up 32 steps of a spiral stairway at natural speed. 2. While in the lying position, raising the trunk to a vertical position a prescribed number of times and continuing as many more times, at will, as agreeable. 3. While standing with arms upraised to the full bending forward and downward, touching the floor with the fingers without bending the knees. 4. While holding two 25-pound iron dumb-bells, first flexing the elbows and then raising the weights to arm's length above the head. 5. A daily test on the Fisher dynamometer, not for endurance, but for measuring pulse acceleration. It became necessary to make a change in the character of the movements on the final day of the test on account of the chafed condition of the subject's skin, and we added: 6. "Running in place," with knee lifting forward and upwards to the extreme possible height. 7. Rapid extension of the arms upward, outward and downward. 8. Same as 7, but holding one-pound wooden bells in each hand.
Pulse readings were taken before and after each test, and in the following report the average pulse for each exercise is given:
After quickly climbing 32 spiral steps, five trials, the average pulse was 115.2 beats to the minute.
After trunk raising, five trials, 50, 60, 70, 100 and 100 times; the latter two trials in one day, five hours apart; average pulse, 115.2 beats.
After trunk bending, five trials, 60, 100, 150, 200 and 300 times; the latter two trials in one day, five hours apart; average pulse, 150 beats.
After lifting the 25-pound bells, five trials, 5, 5, 10, 10 and 10 times; average pulse, 138 beats.
After tests on the Fisher dynamometer, four trials, 50, 60, 60 and 60 times; average pulse, 120 beats.
After rapid arm work for three minutes, average pulse, 156 beats.
After similar work holding wooden bells (two minutes), average pulse, 156 beats.
After running in place as rapidly and as strenuously as possible for one minute, average pulse, 144 beats.
After each test the respiration and heart action, while active, were healthy, and, under such conditions, normal.
There was not the slightest evidence of soreness. stiffness or muscular fatigue either during or after the six days of the trials. The chafing of the skin was due to the rubbing of the "tights" worn while lying down and raising the trunk. Mr. Fletcher made no apparent effort to conceal any evidences of strain or overwork and did not show any. He informs me that he felt no distress whatever at any time.
Such a record of endurance as this, especially when made by a man fifty-nine years of age, can hardly fail to attract our attention. Further, when it is remembered that the subject of this test was not in training, the question naturally arises as to the cause of this phenomenal showing. Why a man of fifty-nine years of age, without training, should be able to far surpass the record for endurance made by young and vigorous athletes can only be surmised, but it certainly seems plausible to assume that the explanation is to be found in the careful dietary habits which this man has followed for the past nine years. In any event, it is fair to suppose that habits of life, leading to a relatively small intake of nitrogenous food, are not inimical to a general condition of physical efficiency and muscular endurance. We may go even farther and assume that the remarkable showing made by this subject is due directly to his temperate dietary habits. Mr. Fletcher would doubtless lay special stress upon his habit of thorough mastication and of abstaining from eating until the appetite strongly demanded food. This phase of the subject we need not discuss here. The main point is that this particular subject has during these nine years made a practise of consuming daily a quantity of proteid food not more than one half that demanded by ordinary dietary standards. In other words, his habits of living have been essentially in accord with the conclusions arrived at by our experimental studies bearing on the requirements of the body for proteid food.
We see in these results possible progressive muscular recuperation after middle life by means of diet alone. If a man by careful attention to his diet can show progressive gain in endurance and general efficiency after fifty without systematic training, it is a fact well worth knowing. In any event, the data afforded by this particular subject corroborate in striking fashion the conclusions arrived at by laboratory experimentation, and tend to confirm the view that there is perfect safety and probable gain to the body in a system of dietetics which approximates to true physiological requirements and avoids undue excess.
* ↑ See Chittenden: "Physiological Economy in Nutrition" and "The Nutrition of Man," Frederick A. Stokes Co., New York.
* ↑ "The Nutrition of Man," p. 272.
* ↑ "Physiological Economy in Nutrition," p. 259.
* ↑ See Popular Science Monthly, June, 1903, p. 127.