Cardiovascular autonomic control in endurance-trained and sedentary young women

This study aimed to investigate whether endurance-trained (ET) female athletes demonstrate differences in cardiovascular autonomic control compared with sedentary controls. Eighteen healthy eumenorrhoeic subjects, nine trained (22.4 +/- 3 years) and nine sedentary (21.0 +/- 1 years), volunteered for the study. Heart rate variability (HRV) and cardiovagal baroreflex sensitivity (BRS) measures were adopted to assess cardiac autonomic control. HRV was recorded for 30 min under both controlled (0.25 Hz) and spontaneous breathing conditions. Cardiovagal BRS was assessed using the Valsalva manoeuvre. Analysis of the HRV showed a longer R-R interval (1089 +/- 114 ms versus 865 +/- 100 ms; P<0.001) in the trained subject but only in the spontaneous breathing condition. Conversely, athletes exhibited higher normalized low frequency (LFnu, 44.2 +/- 8.5% versus 29.5 +/- 6.8%; P<0.001) and lower normalized high frequency (HFnu, 55.8 +/- 8.5% versus 69.9 +/- 7.7%; P<0.01) only during the controlled breathing condition, consequently the LF/HF ratio was also higher in the trained group in the same condition (0.83 +/- 0.3 versus 0.47 +/- 0.1, P<0.01). BRS was significantly lower in the ET group (7.95 +/- 4.0 ms mmHg(-1) versus 13.00 +/- 4.4 ms mmHg(-1), P<0.05). Further studies are necessary to elucidate the potential role of training and altered hormonal profile in the genesis of the observed differences in cardiovascular autonomic control between highly trained and sedentary control female subjects.