1,721,040 research outputs found
T-wave and heart rate variability changes to assess training in world-class athletes
No full textPurpose: A decrease of electrocardiographic T-wave voltage with increasing training loads has been reported in elite endurance athletes and ascribed to training-related adaptation in sympathetic activity to the ventricles. A switch from vagal to sympathetic predominance in sino-atrial node regulation on going from low to peak training load has been reported in world-class rowers. In this study on world-class endurance athletes, we tested the hypothesis that training-induced variations in T-wave amplitude at higher training loads are paralleled by changes in HR spectral profile. Methods: We studied eight male rowers of the Italian national team in the season culminating with the Rowing World Championship. Athletes were evaluated at 50 and 100% of training load, similar to 20 d before the World Championship, and during the World Championship, when the intensity was markedly reduced. We assessed T-wave maximum amplitude in chest lead V6 and cardiac autonomic regulation by power spectral analysis of R-R interval variability. Results: The increase in training load from 50 to 100% was accompanied by a significant decrease in high frequency and a significant increase in low-frequency R-R variability (in normalized units) with a concomitant significant decrease in T-wave amplitude (muV). Reduction in training load during the World Championship resulted in a return of spectral profile to the level observed at 50% training load and in a partial recovery of T-wave amplitude. HR did not change significantly. Conclusions: In high-performance world-class athletes, training load simultaneously affects both ventricular repolarization and HR variability patterns possibly through variations in cardiac sympathetic modulation to the ventricles and the sino-atrial node. Information on concomitant changes in ventricular repolarization and autonomic cardiac regulation might be employed to tailor training protocols of elite athletes
Time-independent indices of circadian blood pressure and heart rate regulation from ambulatory blood pressure monitoring
No full textObjectives We hypothesized that addressing the 24-h relationship between RR interval and systolic arterial pressure (SAP) during ambulatory blood pressure monitoring could detect alterations in circadian arterial pressure and heart rate profile and could also be linked to the ambulatory arterial stiffness index. Methods We analyzed retrospectively 676 ambulatory blood pressure monitoring 24-h recordings. Individuals were median split into low (n = 338) and high (n = 338) SAP groups (mean 24 h of 120 +/- 7, 140 +/- 10 mmHg, respectively). We estimated for each individual ambulatory blood pressure monitoring, the slope (ms/mmHg) of the regression of RR interval on SAP over 24-h (defined as theta index). Results Theta index was significantly (P < 0.001) steeper in individuals with lower pressure than those with higher pressure, whereas day-night difference in SAP did not differ significantly. Theta index was also less negative in nondipper than in dipper individuals and displayed a significant interaction (P < 0.001) with hypertension. The theta index correlated significantly with age and ambulatory arterial stiffness index. Moreover, approximately 14-month reproducibility, as assessed by intraclass correlation coefficient, for theta index was similar to SAP (0.703 and 0.757, respectively). Conclusion These results indicate that theta can detect differences in circadian arterial pressure profile that could assess the efficiency of arterial pressure ( and heart rate) regulatory mechanisms over the whole day in individuals with different arterial pressure levels. Theta can be easily obtained under ambulatory conditions without any assumption on underlying mathematical models or operator-dependent attribution of arterial pressure and heart rate values to daytime or night-time subperiods. Cross-sectional and prospective studies relating theta to target organ damage and cardiovascular outcomes will inform us about its clinical relevance. J Hypertens 27:1178-1185 (C) 2009 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins
Noninvasive evaluation of incremental elastic modulus in humans: state of the heart and perspectives
No full textreview article, abstract not availabl
Assessment of arterial cardiopulmonary baroreflex gains from simultaneous recordings of spontaneous cardiovascular and respiratory variability
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Spontaneous baroreflex sensitivity estimates during graded bicycle exercise: a comparative study
No full textMultivariate decomposition of arterial blood pressure variability for the assessment of arterial control of circulation
No full textAnalysis of Baroreflex and Cardio-Pulmonary Interference by Lexycographic Cluster Analysis and Entropy
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