The precordial electrocardiogram during and after strenuous exercise

Forty-nine apparently healthy, physically active middle-aged men were selected for progressive exercise on a treadmill in an attempt to achieve a near-maximal or maximal effort. Electrocardiographic recordings during and after exercise were made utilizing the earensiform-precordial (EEP) electrode lead system. In 20 per cent of the men a sagging, downwardsloping S-T segment depression of 0.5 mm. or greater developed; in most of these men it was recorded both during and after exercise. In an additional 24 per cent, electrocardiograms showed horizontal flattening of the S-T segment, observed in most of these men only during the exercise. These responses of the S-T segment were more frequent in men with one or more coronary risk factors (e.g., hypercholesterolemia, heavy cigarette smoking, overweight) than in men with none of these. Short runs of premature ventricular beats in 2 men antedated a sagging, downward-sloping S-T segment response. Further long term studies of large populations are needed to determine whether or not the usual standards of normal and abnormal electrocardiographic response after moderate exercise can be applied to the electrocardiogram during and after near-maximal and maximal exercise.