Exercise electrocardiography of health black children.

Exercise electrocardiography was performed on 170 healthy black children 7 to 14 years of age in order to determine the normal childhood electrocardiographic response to exercise. R-wave amplitude decreased from 27 +/- 8 (SD) to 22 +/- 8 mm (P less than .01) and the S-wave amplitude increased from 6.9 +/- 4.4 to 7.8 +/- 5 mm (P less than .01), indicating a shift of the mean QRS vector to the right at maximum exercise. J-point depression of 1.0 mm or greater was observed in 2.3% of children at maximum exercise, using the PR isoelectric line. ST-segment slope increased from 1.5 +/- 0.7 to 4.3 +/- 1.5 mV/sec at maximum. T-wave duration decreased with exercise and T-wave amplitude initially decreased with mild exercise but exceeded resting values at maximum exercise. No dysrhythmias were observed during or after the exercise study.