BACKGROUND: The use of heart rate variability (HRV) in the management of sport training is a practice which tends to spread, especially in order to prevent the occurrence of fatigue states. OBJECTIVES: To estimate the HRV parameters obtained using a heart rate recording, according to different exercise impacts, and to make the link with the appearance of subjective fatigue. METHODS: Ten senior runners, aged 51+/-5 years, were each monitored over a period of 12 weeks in different conditions: (i) after a resting period, (ii) after a day with training, (iii) after a day of competition and (iv) after a rest day. They also completed three questionnaires, to assess fatigue (SFMS), profile of mood states (POMS) and quality of sleep. RESULTS: The HRV indices (heart rate, LF (n.u.), HF (n.u.) and LF/HF) were significantly altered with the competitive impact, shifting toward a sympathetic predominance. After rest and recovery nights, the LF (n.u.) increased significantly with the competitive impact (62.1+/-15.2 and 66.9+/-11.6 vs. 76.0+/-10.7; p<0.05 respectively) whereas the HF (n.u.) decreased significantly (37.9+/-15.2 and 33.1+/-11.6 vs. 24.0+/-10.7; p<0.05 respectively). Positive correlations were found between fatigue and frequency domain indices and between fatigue and training impact. CONCLUSION: Autonomic nervous system modulation-fatigue relationships were significant, suggesting the potential use of HRV in follow-up and control of training. Furthermore, the addition of questionnaires constitutes complementary tools that allow to achieve a greater relevance and accuracy of the athletes\' fitness and results.