STUDIES IN EXERCISE PHYSIOLOGY

Publisher Website
Google Scholar
Abstract
I. Heart rates in the steady state of exercise lasting 45 min. depend on the intensity of the work but continue to rise slightly throughout the expt. Equations for this rise are given for 2 subjects in 24 expts. each. Significantly high correlations (0.969 [plus or minus] 0.013 and 0.955 [plus or minus] 0.020) are found between heart rate and work-load for the 2 subjects. Partial regression equations express the influence of training in lowering the heart rate during the work. II. Circulatory and respiratory responses of 3 [female] and 2 [male] subjects were studied in work expts. lasting 30 min. All functions except heart rate tend to reach a plateau at not later than 10 min. Equations are given for the regressions of heart rate, systolic pressure, diastolic pressure, pulse pressure and total ventilation on work-load in 2 [female] subjects. Curvilinear relations in these functions precluded the calculation of these values for the 2 [female] subjects. Comparison of the responses of [male] and 2 on an equal wt. basis shows significant differences only in heart rate and respiratory rate which are higher in the latter. III. The circulatory, respiratory and metabolic responses of subjects to a periodically increasing work-load on a bicycle ergometer were studied. All expts. were continued uninterruptedly until the subject was forced to quit from exhaustion. Heart rate, total ventilation, O2 consumption, and R.Q. increase with work-load in approx. linear fashion. The slope of the regression line and the ultimate level reached are individual variables. The behavior of these functions at the approach of exhaustion is detd. by comparing trends throughout the range of workloads to the trend at the uppermost step at which exhaustion occurs. The exhaustion trends of metabolic and circulatory functions are lacking in uniformity; total ventilation, on the other hand, most often becomes excessive. The alveolar pCO2 and % CO2 in expired air both increase in the transition from rest to work, remain on a fluctuating plateau throughout most of the work range and decline sharply at exhaustion. These variables and the ventilation most reliably signal the onset of exhaustion. The efficiency and the magnitude of O2 consumption at the crest-load determine total work capacity. The step-up expt. helps to identify the physiological factors underlying individual physical capacity for sustained exercise.

This publication has 5 references indexed in Scilit: