Observations on the adjustment of the human body to muscular work

Abstract

Introduction .—It has long been known that the dyspnœa produced by strenuous exercise, such as running or rowing, disappears if the work is continued and is replaced by a sense of great relief, the so-called “second wind.” A certain time is necessary for the adjustment or accommodation which produces this sensation; short-distance runners do not experience it, but those who are accustomed to long runs over the same course can predict at which lap or point they will obtain the relief of second wind. There are also individual differences; in some men the sensation is very definite, in others so indefinite that it is unrecognised. The observations of Cook and Pembrey showed that during dyspnœa the percentage of carbon dioxide in the alveolar air was raised above the resting value and the respiratory quotient was unity or above unity, but daring the hyperpnœa following the onset of second wind the percentage of carbon dioxide and the respiratory quotient fell; the amount of air breathed per minute was less during hyperpnœa than during dyspnœa; the rectal temperature showed a rise of about 1° F. during second wind, and as a rule there was a close association between the onset of sweating and second wind. Carbon dioxide appeared to be the chief factor in the adjustment of the respiratory and circulatory systems to the demands of the muscles for an adequate supply of blood.

The peripheral vascular response to severe exercise in untethered dogs before and after complete heart block

“…The early experimental basis for this concept was derived from studies in humans, observing altered renal function, i.e., proteinuria and oliguria with exercise and indicating that renal arterial vasoconstriction occurred (19,20). Exteriorized colons were observed to blanch during exercise and spleens of dogs were observed to decrease in size, suggesting splanchnic vasoconstriction (21,22).…”

The effects of exercise on the vascular conditions in the spleen and the colon

“…Effect of more protracted exercise than shown in Fig. 5 (3), who brought forward evidence to show that on severe exercise there was considerable constriction in the renal vessels, it seemed desirable to carry out our own experiments over much longer periods of time. Betsy was therefore trained to follow a bicycle, after which the following experiments were carried out at the Cambridge Field Laboratories.…”

The influence of exercise on the inorganic phosphates of the blood and urine

“…respectively of the normal rate. This leaves out of account the fall in rate observed in all cases during the actal running, which has been noted by many observers and put down to the effect of vasoconstriction (15). Only one complete experiment was done on sulphates, and this gave a value of 116 p.c.…”