Twenty-four hour continuous ECG recordings in long-distance runners.

Twenty-four hour ambulatory ECG recordings were performed on 20 male long-distance runners, aged 19 to 28 years, during normal activities other than running. Average, maximum, and minimum waking heart rates, respectively, ranged from 58 to 108 (mean +/- SD, 73 +/- 15), 90 to 164 (120 +/- 19), and 34 to 53 (43 +/- 5) beats/min. Longest waking sinus pauses ranged from 1.35 to 2.55 (1.7 +/- 0.3) seconds. Average, maximum, and minimum sleeping heart rates, respectively, ranged from 38 to 58 (47 +/- 6), 69 to 114 (83 +/- 14), and 31 to 43 (36 +/- 3) beats/min. Longest sleeping sinus pauses ranged from 1.60 to 2.81 (2.0 +/- 0.3) seconds. All 20 runners had atrial premature beats, but only one (5 percent) had more than 100/24 hours. Fourteen runners (70 percent) had ventricular premature beats, but only two (10 percent) had more than 50/24 hours, and none had ventricular couplets or ventricular tachycardia. Eight runners (40 percent) had one or more episodes of type 1 second-degree atrioventricular (A-V) block. Compared with untrained males of similar age, the runners had slower heart rates (by approximately 10 beats/min), longer sinus pauses, and a higher prevalence of A-V block. Runners and untrained males did not differ with respect to prevalence of ventricular premature beats, R on T phenomenon, ventricular couplets, or ventricular tachycardia.