Abstract des Autors

Many sport-cardiologists attribute the low heart rate typical of athletes to a relative vagal activity with an important sympathetic activity withdrawal, without substantial modifications of the vagal component. New methods of heart-rate spontaneous variability analysis have been improved in the last years, which can provide non-invasive evaluations of sympathetic and parasympathetic neural regulatory activity. The first studies on athletes show an increase in all the spectral components in the well-trained, including the low frequency (LF) peak, expression of sympathetic activity. The aim of the study is to verify, using a Holter reading equipped with a spectral analyzer and Fast-Fourier transformed, the daily rhythm of spectral parameters in athletes and the differences with sedentary men. The authors have studied 44 male (22 endrurance athletes and 22 sedentary men of comparable mean age) with a 24-hour Holter recording, at least 36 hours after the last training. In the time-domain athletes show a higher main R-R interval (953+/-104 vs 785+/-90 msec; p<0.001) and a heart-rate variability significantly increased (with SD 216+/-48 vs 160+/-41 msec; p<0.001). In the frequency-domain have been evaluated the total spectral density (TP), the low-frequency peak (LF) included between 0.04 and 0.15 HZ, and the high-frequency peak (HF), included between 0.15 and 0.4 Hz, with density expressed in millisecond (mec). The LF/HF relation is considered a good indicator of the sympathetic-parasympathetic balance. The data have been obtained for time-windows and daily bands have been made for each parameter. The absolute values of TP, LF and HF, show a nightly increase and the bands related to the two groups studied show a parallel course, but the group of athletes is characterized by higher values, both for HF and for LF. The LF/HF ratio, used as expression of the sympathetic parasympathetic balance, allows us to make clear a daily rhythm also in athletes, which show a LF/HF ratio significantly reduced in the diurnal hours, while during the night the values are similar. Also this way of analysis shows a global increase in neurovegetative modulation for well-trained athletes, with high values both in LF and in HF peaks, which present however a normal daily rhythm. In such a global increase of modulation, a parasympathetic prevalence is still present, at least during daylight, expressed by a significantly reduce LF/HF ratio. Verf.-Referat