Effects of Training on Response of Cardiac Output to Muscular Exercise in Athletes

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Abstract
Results are reported of a study utilizing cardiac catheterization, various respiratory function tests, and (in one subject) a vigorous standardized exercise to investigate the cardio-respiratory effects of training on athletes. Observations were made on 3 long-distance runners. No differences attributable to training were seen in the way a trained or an untrained athlete meets the tissue demands for an increased supply of O2 during exercise up to levels requiring about 2 1 of O2 intake per minute. The possibility that the sedentary individual differs from the athlete, trained or untrained, was not eliminated in this study, but was made unlikely by comparison of our results with those previously reported in literature on normal individuals. Responses of both cardiac output and increased arterio-venous O2 difference to the increased need for O2 during exercise were defined and were found to be generally similar to those reported in previous studies. Pulmonary systolic, diastolic and mean pressures increased in response to all grades of exercise. Respiratory fluctuations of these pressures also increased during exercise. In both the trained and the untrained state there is an increased ventilatory efficiency in exercise compared with rest. Comparison of total excess O2 requirement of exercise and of O2 debt when one subject performed a standarized exercise in the untrained and again in the trained state showed no changes. An increased maximum breathing capacity occurs apparently as the result of training. The possibility was suggested that chronic inflow overload of the right ventricle might account, in part at least, for the incomplete right bundle branch system block sometimes seen in the ecg of athletes engaged in endurance sports.