The purpose of this study was to investigate the effect of twelve weeks of aerobic training and eight weeks of training cessation on Heart Rate Variability (HRV). Ten healthy young men (Age: 21.7 +/- 2.2 years; Height: 179.2 +/- 6.9 cm; Mass 72.7 +/- 11.1 kg) completed an incremental test and a 60 degrees tilt test during which R-R intervals were recorded before (T0) and after (T12) 12 weeks of intensive training, and after 2, 4 and 8 weeks of training cessation (D2, D4 and D8, respectively). HRV was computed in time and frequency domains. Training resulted in a significant increase in estimated VO2max after T12 (p 0.05) to stabilize afterwards. LF + HF and LF were not different from T0 at D8 (p > 0.05). It was concluded that eight weeks of training cessation allow to reverse the cardiovascular autonomic adaptations induced by 12 weeks of intensive training in healthy young men.