Effects of 21 half-marathon in 21 days on autonomic nervous system and psychological parameters : a case report

Aim. Heart Rate Variability (HRV) measurement is a non-invasive method used to investigate the Autonomic Nervous System (ANS) responsiveness in healthy as well as patients. Even if consequences of a short term training period on ANS is well ancknoledged, the long-term (>15 days) effect of repeated submaximal exercise remains elusive. We investigated the cardiac ANS adaptation to 21 consecutive half-marathons and its possible relationships with psychological fatigue. Methods. A 42 yrs old woman (BMI: 19.8; VO2max: 45,9 ml/kg/min), voluntarily performed 21 half-marathons in 21 consecutive days. Every morning, after awakening, heart rate (HR) for 10 min on a beat-to-beat basis (RR series) in supine position. RR series spectral powers, indexes of vagal (HFnu; 0.15-0.40 Hz), mixed para- and sympathetic tone (LFnu; 0.04-0.15 Hz) and sympatho-vagal balance (LF/HF ratio), were derived. A 32-item profile of mood states (POMS) questionnaire and Session RPE (mins x RPE 10 points scale) were daily collected. Results. Running time did not change significantly (1h54’55’’± 4’55’’; p=0.44, r=-0.18). Number of consecutive running days (NcRD) negatively linearly correlated with HR rest (p<0.001, r=-0.7) and LogLF/HF (p<0.01, r=0.64), and positively with LogHF Power (n.u.) (p<0.01, r=0.62). NcRD did not linearly correlated with LogLF Power (n.u.) (p<0.01, r2=0.55). NcRD negatively linearly correlated with the Energy Index (EI) (p<0.0001, r=-0.87). NcRD positively correlated with session-RPE (p<0.01, r=0.62), whose scores ranged between 0.3 and 5. A positive correlation between LogLF/HF ratio and EI (p<0.01, r=0.61) and a negative correlation between LogHF Power (n.u.) (p<0.01, r=-0.61) were found. There were no correlations between EI (vigor-fatigue) and LogLF Power (n.u.). Conclusions. Twenty-one consecutive half-marathons at sub-maximal intensity led to a continuous improvement of cardio-vagal control and sympatho-vagal balance, without a clear plateau. This suggests a training effect, that could be extended further. The EI increase seemed to reveal an accumulation of psychological fatigue, probably due to lack of recovery days and monotony of training. Therefore, long-term daily repetitions of sub-maximal exercise seems to improve cardio-vagal tone, but to induce also a psychological fatigue accumulation, which could demotivate the atlete in continuing the training. References 1. Aubert AE et al.(2003) Heart Rate Varibility in Athletes. Sports Med.;33(12):889-919.