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(Circulation. 2002;105:2719.)
© 2002 American Heart Association, Inc.

Clinical Investigation and Reports

Conversion From Vagal to Sympathetic Predominance With Strenuous Training in High-Performance World Class Athletes

Ferdinando Iellamo, MD; Jacopo M. Legramante, MD; Fabio Pigozzi, MD; Antonio Spataro, MD; Guido Norbiato, MD; Daniela Lucini, PhD, MD; Massimo Pagani, MD

From the Dipartimento di Medicina Interna-Centro di Riabilitazione Cardiologica S. Raffaele (F.I., J.M.L.), Università di Roma Tor Vergata; Istituto Universitario di Scienze Motorie-Roma (F.P.); Federazione Italiana Canottaggio (A.S.); Dipartimento Endocrinologia Ospedale L. Sacco Milano (G.N.); and Centro di Terapia Neurovegetativa (D.L., M.P.), Polo L. Sacco-Università di Milano, Italy.

Correspondence to Ferdinando Iellamo, MD, Dipartimento di Medicina Interna, Università di Roma Tor Vergata, Via O. Raimondo, 8, 00173, Roma, Italy. E-mail iellamo{at}med.uniroma2.it

Background— Benefits of moderate endurance training include increases in parasympathetic activity and baroreflex sensitivity (BRS) and a relative decrease in sympathetic tone. However, the effect of very intensive training load on neural cardiovascular regulation is not known. We tested the hypothesis that strenuous endurance training, like in high-performance athletes, would enhance sympathetic activation and reduce vagal inhibition.

Methods and Results— We studied the entire Italian junior national team of rowing (n=7) at increasing training loads up to 75% and 100% of maximum, the latter 20 days before the Rowing World Championship. Autoregressive power spectral analysis was used to investigate RR interval and blood pressure (BP) variabilities. BRS was assessed by the sequences method. Increasing training load up to 75% of maximum was associated with a progressive resting bradycardia and increased indexes of cardiac vagal modulation and BRS. However, at 100% training load these effects were reversed, with increases in resting heart rate, diastolic BP, low-frequency RR interval, and BP variabilities and decreases in high-frequency RR variability and BRS. Three athletes later won medals in the World Championship.

Conclusions— This study indicates that very intensive endurance training shifted the cardiovascular autonomic modulation from a parasympathetic toward a sympathetic predominance. This finding should be interpreted within the context of the substantial role played by the sympathetic nervous system in increasing cardiovascular performance at peak training. Whether the altered BP and autonomic function shown in this study might be in time hazardous to human cardiovascular system remains to be established.

Key Words: exercise • nervous system, autonomic • reflex

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