To reach an optimal level of performance, athlete's training programs include intense workout periods mixed with short cycles of relative rest. Several researches on resistance activities have used heart rate variability (HRV) to establish the effects of training on cardiovascular parameters controlled by the autonomic nervous system (ANS), HRV use in the management of training has become popular especially for its ability to prevent fatigue. However, few studies have been published about these effects on team sports like football. PURPOSE: To assess the effects of training on the autonomic control of the heart rate on a group of soccer players during a 4 month period of preparation and competition. METHODS: A spectral analysis of the HRV was performed in 12 professional soccer players (25,10 ± 3,63 years; 1,79 ± 0,6 m high; 77,9 ± 6,98 kg weight) during a resting period of 13 minutes, in supine (SP) and standing (ST) position. All measurements were made in the morning hours to avoid physiological variations. The tests were taken on the first day and day 45 of preparatory period and also during competition on days 90 and 120. The low frequency (LF), high frequency (HF) and LF/HF index was obtained. The values obtained were compared using a Wilcoxon Test. RESULTS: The heart rate (HR) decreased on ST at day 45 compare to day 1 (64,5±1,9 vs. 74,6±1,9; p<0,01). HR on SP decreased from day one to day 45(56,75±2,1 vs. 48,3±1,4; p<0.05), also in day 90 (48,25±1,3; p<0.01) and day 120 (45,83±1,4; p<0.01). The LF-SP on day 45 improved compared to day 1(3033±486 vs. 1905±287; p<0.01), it also improved on day 90 (2984±363; p<0.01). LF-ST improved on day 90 compared to day 1(3508±382 vs. 2605±311; p<0.05), it also improved in day 120 (3579±240; p<0.05). The HF-SP improved on day 90 compared to day 1 (3033±232 vs. 2017±278; p<0.01), as well as in day 120 (3090±306; p<0.05). The LF/HF index ST improved on day 90 compared to day 1 (3,98±0,32 vs. 2,79±0,17; p<0.01). CONCLUSION: The decrease of HR at the end of preparatory period might be explained by an improvement in parasympathetic modulation (improvement of HF-SP) and could account as a training benefit. The HF-SP and LF-ST activity did not change throughout the competitive season. The patterns observed in this study could be used as reference for individual or group training control.