Lars Brechtel

Heart Rate Variability, Blood Pressure Variability, and Baroreflex Sensitivity in Overtrained Athletes

Objective:To assess the effects of abruptly intensified physical training on cardiovascular control. Design:Retrospective longitudinal study. Setting:Research laboratory. Participants:Ten healthy athletes (5 men and 5 women) from track and field as well as triathlon. Interventions:A 2-week training camp, including daily stepwise increasing cycling tests, running of 40 minutes, and additional cycling of 60 minutes. Main Outcome Measurements:Time and frequency domain parameters of resting heart rate and blood pressure variability (HRV and BPV) and baroreflex sensitivity (BRS), before, during, and after the training camp. Results:We found significantly reduced HRV during the training camp (mean beat-to-beat interval: 1042 [937 to 1194] ms vs. 933 [832 to 1103] ms vs. 1055 [947 to 1183] ms, P < 0.01; root-mean-square of beat-to-beat interval differences: 68 [52 to 95] ms vs. 52 [38 to 71] ms vs. 61 [48 to 78] ms, P < 0.05). Further, BRS was significantly reduced: 25.2 (20.4 to 40.4) ms/mmHg vs. 17.0 (12.9 to 25.7) ms/mmHg vs. 25.7 (18.8 to 29.1) ms/mmHg, P < 0.05. These effects disappeared at a large degree after 3 to 4 days of recovery. Conclusion:Abruptly intensified physical training results in an altered autonomic cardiovascular activity towards parasympathetic inhibition and sympathetic activation that can be monitored by means of HRV and BRS analyses and might provide useful markers to avoid the overtraining syndrome.

ESTIMATING THE COMPLEXITY OF HEART RATE FLUCTUATIONS — AN APPROACH BASED ON COMPRESSION ENTROPY

Heart rate exhibits spontaneous fluctuations that are mainly modulated by control loops within the autonomic nervous system. Assessing the dynamics of heart rate fluctuations can provide valuable information about regulatory processes and patho-physiological behavior. In this paper heart rate fluctuations and its entropy are assessed using an algorithmic information theoretic concept applying a data compressor. First, the beat-to-beat fluctuations of heart rate are binary coded for decreases and increases, respectively. Subsequently, those symbol sequences are compressed using the LZ77 algorithm. The ratio of the length of the compressed sequences to the original length is used as an estimate of entropy. We investigated the compressibility of heart rate fluctuations in athletes before, during, and after a training camp. Heart rate time series were obtained from ECGs recorded over 30 minutes under supine resting conditions. We found a significant entropy reduction during the training camp, reflecting the effects of physical fatigue. In conclusion, the compression entropy seems to be a suitable approach to assess the complexity of heart rate fluctuations.

Exercise-induced changes of left ventricular diastolic function in postmenopausal amateur marathon runners: assessment by echocardiography and cardiac biomarkers

Purpose Diastolic dysfunction is common among elderly women. Recently, concerns regarding marathon-induced myocardial damage were raised among young male runners. The goal of our study was to assess the impact of marathon running on systolic and diastolic ventricular function before and immediately after completing a marathon among postmenopausal well-trained amateur women. Methods A total of 89 female runners of the Berlin Marathon were included (35 postmenopausal and 54 premenopausal female controls) and examined before, immediately, and 2 weeks after the race by echocardiography (including tissue Doppler- and 2D strain speckle tracking) and underwent blood tests. Results After the marathon, there was a significant increase in E/E′ (postmenopausal 8.5 ± 2.3 vs. 10.9 ± 3.2 post race; control: 8.1 ± 1.8 vs. 9.9 ± 2.9 post race, p < 0.001) and a decrease in E/A in both groups (postmenopausal 1.3 ± 0.36 vs. 0.9 ± 0.21 post race; control 1.7 ± 0.6 vs. 1.1 ± 0.3; p < 0.001). In contrast, regardless of the hormonal status the atrial contraction increased significantly. Left and right ventricular systolic contractility, as assessed by speckle tracking and pulsed-wave tissue Doppler velocities, showed a significant increase in both groups. Of all runners, 55 (61.8%) experienced increases in troponin T and/or N-terminal-B-type natriuretic peptide after the race. All echocardiographic and laboratory parameters returned to normal within 2 weeks. Conclusions 2D strain analysis of the left and right ventricles showed an acute improvement of the systolic function after marathon running in pre- and postmenopausal well-trained women. There were no long lasting detrimental effects on the diastolic function.

Scaling graphs of heart rate time series in athletes demonstrating the VLF, LF and HF regions

Scaling analysis of heart rate time series has emerged as a useful tool for the assessment of autonomic cardiac control. We investigate the heart rate time series of ten athletes (five males and five females), by applying detrended fluctuation analysis (DFA). High resolution ECGs are recorded under standardized resting conditions over 30 min and subsequently heart rate time series are extracted and artifacts filtered. We find three distinct regions of scale invariance, which correspond to the well-known VLF, LF and HF bands in the power spectra of heart rate variability. The scaling exponents alpha are alpha(HF): 1.15 [0.96-1.22], alpha(LF): 0.68 [0.57-0.84], alpha(VLF): 0.83[0.82-0.99], p < 10(-5)). In conclusion, DFA scaling exponents of heart rate time series should be fitted to the VLF, LF and HF ranges, respectively.

Changes in heart rate variability of athletes during a training camp

Abstract Heart rate variability (HRV) reflects regulatory processes of the cardiovascular system and reveals fractal characteristics. In this paper we investigated standard HRV parameters and scaling characteristics in ten athletes before, during, and after a 2-week training camp to assess the effects of short-term overtraining on cardiovascular control. High-resolution ECGs were recorded over 30 min under resting conditions 1 week before the training camp, after 1 week of training in the camp, and after 3–4 days of recovery. Standard HRV analysis was performed according to Task Force recommendations. Scaling characteristics were assessed, applying detrended fluctuation analysis (DFA). Standard HRV analysis showed significant changes in meanNN and rmssd during the training camp. DFA revealed three distinct regions of scale-invariance and significant alterations during the training camp. In conclusion, HRV might be used to monitor the training state in athletes.

Marathon running increases circulating endothelial- and thrombocyte-derived microparticles

Background Acute vascular effects of high intensity physical activity are incompletely characterized. Circulating microparticles are cellular markers for vascular activation and damage. Methods Microparticles were analysed in 99 marathon runners (49 ± 6 years, 22% female) of the prospective Berlin Beat of Running study. Blood samples were taken within three days before, immediately after and within two days after the marathon run. Endothelial-derived microparticles were labelled with CD144, CD31 and CD62E, platelet-derived microparticles with CD62P and CD42b, leukocyte-derived microparticles with CD45 and monocyte-derived microparticles with CD14. Results Marathon running induced leukocytosis (5.9 ± 0.1 to 14.8 ± 0.3 109/l, p < 0.0001) and increased platelet counts (239 ± 4.6 to 281 ± 5.9 109/l, p < 0.0001) immediately after the marathon. Blood monocytes increased and lymphocytes decreased after the run (p < 0.0001). Endothelial-derived microparticles were acutely increased (p = 0.008) due to a 23% increase of apoptotic endothelial-derived microparticles (p = 0.007) and returned to baseline within two days after the marathon. Thrombocyte-derived microparticles acutely increased by 38% accompanied by an increase in activated and apoptotic thrombocyte-derived microparticles (p ≤ 0.0001) each. Both monocyte- and leukocyte-derived microparticles were decreased immediately after marathon run (p < 0.0001) and remained below baseline until day 2. Troponin T increased from 12 to 32 ng/l (p < 0.0001) immediately after the run and returned to baseline after two days. Conclusion Circulating apoptotic endothelial- and thrombocyte-derived microparticles increased after marathon running consistent with an acute pro-thrombotic and pro-inflammatory state. Exercise-induced vascular damage reflected by microparticles could indicate potential mechanisms of post-exertional cardiovascular complications. Further studies are warranted to investigate microparticles as markers to identify individuals prone to such complications.

Frequency of exercise-induced ST-T-segment deviations and cardiac arrhythmias in recreational endurance athletes during a marathon race: results of the prospective observational Berlin Beat of Running study

Objectives While regular physical exercise has many health benefits, strenuous physical exercise may have a negative impact on cardiac function. The ‘Berlin Beat of Running’ study focused on feasibility and diagnostic value of continuous ECG monitoring in recreational endurance athletes during a marathon race. We hypothesised that cardiac arrhythmias and especially atrial fibrillation are frequently found in a cohort of recreational endurance athletes. The main secondary hypothesis was that pathological laboratory findings in these athletes are (in part) associated with cardiac arrhythmias. Design Prospective observational cohort study including healthy volunteers. Setting and participants One hundred and nine experienced marathon runners wore a portable ECG recorder during a marathon race in Berlin, Germany. Athletes underwent blood tests 2–3 days prior, directly after and 1–2 days after the race. Results Overall, 108 athletes (median 48 years (IQR 45–53), 24% women) completed the marathon in 249±43 min. Blinded ECG analysis revealed abnormal findings during the marathon in 18 (16.8%) athletes. Ten (9.3%) athletes had at least one episode of non-sustained ventricular tachycardia, one of whom had atrial fibrillation; eight (7.5%) individuals showed transient ST-T-segment deviations. Abnormal ECG findings were associated with advanced age (OR 1.11 per year, 95% CI 1.01 to 1.23), while sex and cardiovascular risk profile had no impact. Directly after the race, high-sensitive troponin T was elevated in 18 (16.7%) athletes and associated with ST-T-segment deviation (OR 9.9, 95% CI 1.9 to 51.5), while age, sex and cardiovascular risk profile had no impact. Conclusions ECG monitoring during a marathon is feasible. Abnormal ECG findings were present in every sixth athlete. Exercise-induced transient ST-T-segment deviations were associated with elevated high-sensitive troponin T (hsTnT) values. Trial registration ClinicalTrials.gov NCT01428778; Results.