Electrophysiologic Study of Exhaustive Exercise

Background: Exhaustive exercise is well known to pose a variety ofhealth hazards, such as sudden cardiac death reported in ultra-marathon runners.Depressed parasympathetic tone is associated with increased risk of suddencardiac death, thus parasympathetic withdrawal in post-exercise phase may be ahigh risk period for sudden death. To date, the effect on cardiacelectrophysiology after exhaustive strenuous exercise has not been described.The aim of this study was to evaluate the impact of severe exhaustive exerciseon cardiac electrophysiology.Methods: The subjects in ranger training were invited to participatein this prospective study. The parameters measured consisted of PR interval, QRSduration, and macro T wave alternans as well as corrected QT, QTc dispersion,Tpeak –Tend interval and Tpeak –Tend dispersion.Results: The study group consisted of 40 consecutive male rangers whocompleted training and the control group (22 healthy age and height matched malesubjects). In regard to electrocardiographic criteria, no differences were foundbetween rangers before and after training program. In respect of therepolarization markers, there were no significant differences between therangers before and after training program.