To determine the incidence of arrhythmias in long-distance runners, Holter ECG recordings were obtained of 20 healthy runners, aged 19-22, during 24-hour daily activities and training. Eleven runners (55%) had marked bradycardia (<40 beats/minute) and six runners (30%) had marked sinus arrhythmias defined as spontaneous changes in adjacent cycle lengths of 100% or more. Longest R-R interval ranged 1.23-3.16 seconds (1.83±0.48). Two runners (10%) had first-degree atrioventricular block and four (20%) had Wenckebach type second-degree atrioventricular block. Nineteen runners (95%) had supraventricular premature beats, but only one (5%) had more than 100/24 hours. One runner had supraventricular tachycardia of eight beats during training. Six runners (30%) had ventricular premature beats, but none had more than 50/24 hours. Three of six had ventricular premature beats only during training and one of them had couplets and multiform.

DESCENTE SPORTS SCIENCE Vol.6/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE