title: Training-related modulations of the autonomic nervous system in endurance athletes: is female gender cardioprotective?
abstract: The risk of sudden death is increased in athletes with a male predominance. Regular physical activity increases vagal tone, and may protect against exercise-induced ventricular arrhythmias. We investigated training-related modulations of the autonomic nervous system in female and male endurance athletes. Runners of a 10-mile race were invited. Of 873 applicants, 68 female and 70 male athletes were randomly selected and stratified according to their average weekly training hours in a low (≤4 h) and high (>4 h) volume training group. Analysis of heart rate variability was performed over 24 h. Spectral components (high frequency [HF] and low frequency [LF] power in normalized units) were analyzed for hourly 5 min segments and averaged for day- and nighttime. One hundred and fourteen athletes (50 % female, mean age 42 ± 7 years) were included. No significant gender difference was observed for training volume and 10-mile race time. Over the 24-h period, female athletes exhibited a higher HF and lower LF power for each hourly time-point. Female gender and endurance training hours were independent predictors of a higher HF and lower LF power. In female athletes, higher training hours were associated with a higher HF and lower LF power during nighttime. In male athletes, the same was true during daytime. In conclusion, female and male athletes showed a different circadian pattern of the training-related increase in markers of vagal tone. For a comparable amount of training volume, female athletes maintained their higher markers of vagal tone, possibly indicating a superior protection against exercise-induced ventricular arrhythmias.
authors.affiliation: Division of Cardiovascular Prevention, Rehabilitation and Sports Cardiology, University Clinic for Cardiology, Inselspital, University Hospital and University of Bern, 3010 Bern, Switzerland.
authors.forename: Monika
authors.initials: M
authors.lastname: Fürholz
authors.forename: Thomas
authors.initials: T
authors.lastname: Radtke
authors.forename: Laurent
authors.initials: L
authors.lastname: Roten
authors.forename: Hildegard
authors.initials: H
authors.lastname: Tanner
authors.forename: Ilca
authors.initials: I
authors.lastname: Wilhelm
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Schmid
authors.forename: Hugo
authors.initials: H
authors.lastname: Saner
authors.forename: Matthias
authors.initials: M
authors.lastname: Wilhelm
mesh_terms: D000328:Adult; D001145:Arrhythmias, Cardiac / Q000209:etiology* / Q000503:physiopathology; D056352:Athletes; D001341:Autonomic Nervous System / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology; D015716:Electrocardiography, Ambulatory; D015444:Exercise; D005260:Female; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology