1Charité - Universitätsmedizin Berlin Centrum für Schlaganfallforschung Berlin – CSB Berlin, Deutschland; 2Yerevan State Medical University Department of Cardiology, Clinic of General and Invasive Cardiology, University Clinical Hospital № 1 Yerevan, Armenien; 3Charité - Universitätsmedizin Berlin Department of Neurology and Center for Stroke Research Berlin Berlin, Deutschland; 4SMS-Sportmedizin Berlin Berlin, Deutschland; 5Berlin, Deutschland; 6Charité - Universitätsmedizin Berlin BIH Center für regenerative Therapien (BCRT) Berlin, Deutschland; 7Universitätsklinikum Würzburg Neurologische Klinik und Poliklinik Würzburg, Deutschland
Introduction Marathon running is a demanding physical burden requiring top physical condition and a high intensity training. Reduced parasympathetic and increased sympathetic activities have been observed in marathon participants. We hypothesized that a number of total marathon races is associated with cardiovascular autonomic modulation in non-professional endurance athletes.
Methods 105 non-professional marathon runners (mean age 49±6 years, BMI 23.2±2.1 kg/m², 25% female) were included in this prospective study. The Holter recordings during 6 hours of nocturnal sleep before and immediately after the marathon were analyzed. The first 5-miniute recordings of each hour were averaged and reported as a nocturnal autonomic tone. The presence of depressed HRV (heart rate variability) was defined by SDNN <100 ms (standard deviation of NN intervals) and HRV triangular index (HRV TI) <20 in athletes after the marathon race. HRV TI of 20 units after the marathon served as a cut point of cardiac autonomic modulation where the values ≤20 meant a reduced vagal tone.
Results HRV TI ≤20 was associated with a nocturnal heart rate (HR)>58 beats/min (bpm) (AUC 0.702, sensitivity 75.4%, specificity 61.4%, p<0001) in the present cohort. Therefore, the study participants were divided into two subgroups: “>58 bpm” (60% of the athletes) and “≤58 bpm”. Compared to the baseline, nocturnal HR increased by 12% in “>58 bpm” vs. 6% in “≤58 bpm” group (p=0.0017). No differences in LF (low frequency) and HF (high frequency) oscillations were observed between the subgroups before the marathon. However, significantly decreased vagal tone (reduced HF oscillations) (-36% vs. -14%, p=0.01) and increased sympathetic tone (increased LF) (9% vs. 5%, p=0.038) were observed in “>58 bpm” vs. “≤58 bpm” group.
Conclusion Increased nocturnal sympathetic tone was observed in non-professional marathon athletes immediately after the marathon race. Improved modulation of the nocturnal autonomic regulation with enhancement of vagal activity was observed in athletes who participated in marathons more frequently.