Finally, we have rates obtained immediately prior to, during, and after walking. Inasmuch as the subjects during the walking experiments were confined inside an air-tight metal box, it was impracticable to use the ordinary methods of graphic registration to determine the respiration rate. Recourse was thus had to the special technique outlined on page 130 of this report. Although in a preliminary test it was possible so to adjust the technique for the individual subjects as to obtain most satisfactory records, in the actual experiments we were able to adjust the subject for only a moment, and the experiment was then immediately begun without opportunity for subsequent adjustment. As a result, much to our regret, a considerable number of the records are illegible. This frequently happened with the records of a particular subject, indicating that the difficulty was in the adjustment for that especial man.

The respiration rate is commonly recorded in respirations per minute, and we have followed this custom in presenting the previous data. In the records with the treadmill chamber, however, we were unable to count the number of respirations, as was possible from the graphic records obtained from the pneumograph around the chest in the experiments with the respiratory-valve apparatus, or to record the rise and fall of a spirometer as in the experiments with the portable respiration apparatus. It was necessary to depend here upon short photographic records; consequently the actual number of respiration cycles counted was, at times, rather few and the few records had to be multiplied to bring them to the per minute basis. While the pulse-rate may be advantageously counted for 30 seconds or even as low as 20 seconds, and raised to values per minute without serious error, it is a legitimate question as to whether or not it is possible to count 4, 5, or even less respiratory cycles, determine the length of time photographically to 0.01 part of a second, and then raise this to a rate per minute on the assumption that the regularity of breathing would be the same throughout the rest of the minute. In lieu of longer records it has been necessary to do this. The results obtained by the photographic method are therefore recorded only to whole numbers in table 110, in which the values are given for the respiration rate with the subject standing before walking and those found 1, 6, 12, 24, and 26 minutes after the walking began. A few records taken at other intervals are given in footnotes. Finally, a few values are recorded 22 minutes. 25.

Table 110. - Respiration Rate Before, During, And After 24 Minutes Of Level Walking On A Treadmill - Squads A And B

1 The respiration rates for January 28 and February 3 were recorded during the first minute. 2The respiration rate of Gul after he had walked 4 minutes was 21; after 8 minutes, 27; after 14 minutes, 23; after 16 minutes, 22; after 18 minutes, 24; after 20 minutes, 22; after 22 minutes, 23. 3 The respiration rate of Vea after he had walked 2 minutes was 23; after 4 minutes, 22; after 10 minutes, 24; after 14 minutes, 24; after 18 minutes, 24; after 20 minutes, 24; after in the last column which were obtained with the subject standing after walking ceased. The actual number of respiratory cycles counted were usually not far from 6 to 9, but occasionally there were no more than 4 and rarely but 2. Special attention will be called to those values lower than 4 in discussing the table, particularly if the count seems in any sense abnormal, for it is obvious that these few respiratory cycles should not be accorded the significance of the longer counts.

The most important point in studying the respiration rate under these conditions is the transition from the standing position to walking. With practically all of these subjects we have the standing respiration rate which was determined in connection with the experiments on the portable respiration apparatus. It seemed best, however, to attempt to obtain the standing respiration rate immediately prior to the beginning of the walking on the treadmill and under the same conditions. Unfortunately, owing to difficulty of instrumental adjustment, but few of these values could be obtained (see first column of table). While from the standpoint of a study of the respiration rate this is of course a serious omission, the exigencies of experimentation demanded that the walking begin immediately. On the other hand, when legible records were obtained, the rates after 1, 6,12, 24, and 26 minutes show clearly the influence of the continued walking upon the respiratory rhythm.

The respiration in this chamber was not under strictly normal conditions, for after the first minute the percentage of carbon dioxide in the air inside the chamber was perceptibly higher than that of the room air. In the first 2\ minutes that the subject walked on the treadmill the cover of the respiration chamber was not closed down (see p. 132)1; hence the respiration rate recorded for the first minute was obtained under normal conditions. The subsequent records, and particularly those for the twenty-fourth minute, were obtained with the subject breathing air in which the percentage of carbon dioxide was gradually increasing; rarely, however, did it exceed 0.9 per cent; the average proportion was not far from 0.6 to 0.7 per cent. The relatively few records obtained after 26 minutes of walking were secured when the subject was still walking upon the treadmill, but the cover of the respiration apparatus had been raised and he was breathing essentially normal, outdoor air.

With these preliminary statements regarding the actual conditions obtaining during the experiment, the data in the table may be analyzed.

The observations were first made for Squad B on January 6,1918. Such records as were obtained were for the most part unsatisfactory. In the three cases in which standing records were obtained, the effect of walking was, in the case of How and Sch, to raise the rate from 18 to 24 at the end of 1 and 6 minutes, respectively, while with Sne the prewalking respiration rate of 25 fell immediately after the beginning of walking to 22 and continued at 23 for the remainder of the test, a condition exactly opposite that reported with Sch. While the data are too few for generalization as to the change from the standing position to walking, the successive records obtained during walking are fairly numerous and show that there was no tendency for the respiration rate either to decrease or to increase as the test proceeded, although there were slight variations. On January 6 the respiration rate with the subject standing after walking was not obtained for any of the men.

1On January 6 the cover was lowered directly after the subject entered the chamber.