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