Radioelectrocardiographic Changes during Strenuous Exercise in Normal Subjects

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Abstract
The effect of strenuous exercise (riding a stationary bicycle at 20 to 25 mph for 3 minutes) on the electrocardiogram was studied in 135 normal subjects, aged 17 to 64 years. Radioelectrocardiography was used to record the tracings during and after the period of exercise. The following electrocardiographic alterations during exercise were interpreted as representing a normal physiologic response; sinus tachycardia (100 per cent of the cases), increased P-wave amplitude (85 per cent), ST-segment depression of the junction type, 1 mm. or more (75 per cent), diminished (68 per cent) or increased (9 per cent) T-wave amplitude. A few ventricular premature beats were observed in only two subjects (1.4 per cent). All these changes were observed, although less frequently, in the period after exercise (1 minute after the cessation of exercise). According to criteria for abnormality described previously,23 34 of the 135 subjects (24.8 per cent) exhibited abnormal responses to the bicycle exercise test. Sixteen of the 34 "definitely" and "probably abnormal" responses (47 per cent) occurred only during the period of exercise, 12 were observed both during and after the exercise and six occurred only in the postexercise period. The incidence of abnormalities in the group of subjects in the age group 40 to 64 years was 37 per cent, while that in subjects in the age group 17 to 40 years was 22.5 per cent. A comparison between the Master two-step and the bicycle tests suggests that the latter may be more diagnostic for the detection of latent coronary artery disease and the evaluation of the state of physical fitness in subjects below the age of 40 years.