Interval training in elderly men increases both heart rate variability and baroreflex activity

Aims Autonomic nervous system activity decreases continuously with age and appears to be a powerful predictor of disease and death. Attempts are thus made to reactivate autonomic drive with the intent of improving health. Methods We assessed maximal oxygen consumption (VO2max), auto-nomic nervous system activity by heart rate variability (HRV) analysis and spontaneous cardiac baroreflex activity (SBR) in eleven elderly men (73.5 +/- 4.2 years) before and after a 14-week program of intensive cycloergometer interval training. The standard HRV indices were calculated using time domain (mean RR, PNN50, RMSSD, SDNN, SDANN and SDNNIDX), and Fourier transform (total power, ULF, VLF, LF, LFnu, HF, HFnu and LF/HF) analyses of 24-hour, daytime and nighttime Holter recordings. The SBR was calculated from 15-minute recordings of spontaneous blood pressure and RR interval variations using the sequence (slope, slSBR) and cross-spectral (alpha SBRHF and alpha SBRLF) methods. Results After the training period, VO2max increased by 18.6% (26.8 +/- 4.4 to 31.8 +/- 5.2 ml(.)kg(-1.)min(-1), p < 0.01). The nocturnal parasympathetic indices of HRV increased (PNN50: 3.05 +/- 2.21 to 5.00 +/- 2.87%, RMSSD: 29.1 +/- 7.6 to 38.8 +/- 10.9 ms, HF: 117 +/- 54 to 194 +/- 116 ms(2)/Hz, all p < 0.05) as did the SBR indices (sISBR: 7.0 +/- 1.8 to 9.8 +/- 2.1 ms(.)mmHg(-1), p < 0.01; alpha SBRHF: 6.9 +/- 2.2 to 10.5 +/- 3.7 ms(.)mmHg(-1), p < 0.05; alpha SBRLF: 5.3 +/- 2.3 to 6.9 +/- 3.1 ms(.)mmHg(-1),p = 0.22). Conclusion Intensive endurance training in elderly men enhanced parasympathetic parameters of HRV and, interestingly, of SBR. Physiological mechanisms and long-term clinical effects on health status should be further investigated.