[Show abstract][Hide abstract] ABSTRACT: To elucidate the mechanisms of orthostatic intolerance (OI) after endurance exercise which are incompletely understood.
We investigated beat-to-beat haemodynamic and autonomic parameters in 51 male athletes during supine rest and after active standing the day before and 2 h after a marathon run. None of the subjects before the marathon [non-orthostatic intolerance (Non-OI)], but 14 after the marathon [orthostatic intolerance (OI)] exhibited with pre-syncope. There were no differences between OI and Non-OI before the marathon. After the marathon, only Non-OI was able to increase sympathetic modulation to resistance vessels from already increased basal levels in response to standing; OI could not. OI instead exhibited a decrease in total peripheral resistance and a paradoxical increase in parasympathetic sinus node modulation. We observed a significant correlation between serum potassium before the race and the maximally achieved sympathetic drive after the marathon (r = 0.55, P = 0.001).
Post-exercise OI is associated with a 'high basal sympathetic modulation of vasomotor tone in combination with a diminished orthostatic sympathetic response' to resistance vessels. This situation may mimic the OI in some clinical conditions, which are also known to be associated with increased 'basal' sympathetic tone. The role of serum potassium deserves further study.
Preview · Article · Jul 2008 · European Heart Journal
[Show abstract][Hide abstract] ABSTRACT: To test the hypothesis that enhanced postexercise vasodilatation is related to sympathetic drive to resistance vessels and to fast marathon performance.
Prospective field study before and after running a marathon.
51 healthy amateur runners who volunteered to participate. The fastest competitor finished fourth, the slowest 1290 th out of 1324 participants.
Competition time, beat-to-beat blood pressure by the vascular unloading technique, oscillometric blood pressure, beat-to-beat stroke volume by impedance cardiography, total peripheral resistance changes calculated from blood pressure and stroke volume changes, sympathetic modulation of vasomotor tone and parasympathetic modulation of sinus node function by spectral analysis of blood pressure and heart rate variability, baroreceptor reflex sensitivity by the sequence method.
Slow performers, in contrast to fast performers, exhibited a higher 0.1 Hz band of diastolic blood pressure variability before the competition (0.1 Hz BPV) (40.0 (SD 2.39) vs 54.9 (2.47), p<0.001), diminished vasodilatation (-11.3 (4.78) vs -29.4 (3.23), p<0.01) and a decrease in stroke index (-14.9 (3.55) vs +0.9 (3.37), p<0.001) in response to the race. Single and multiple regression analyses further corroborated the findings.
Fast performance in the marathon is associated with low sympathetic modulation of vasomotor tone, maintained stroke index postcompetition and enhanced exercise-induced vasodilatation. We postulate that maintaining a low level of sympathetic modulation to resistance vessels during the course of training may indicate its appropriateness, thus enabling fast performance by optimal postexercise vasodilatation and by prevention of postcompetition cardiac dysfunction. This will have to be tested in future longitudinal studies.
No preview · Article · Feb 2008 · British Journal of Sports Medicine
[Show abstract][Hide abstract] ABSTRACT: We hypothesized that the extreme endurance exercise of an Ironman competition would lead to long-standing hemodynamic and autonomic changes. We investigated also the possibility of predicting competition performance from baseline hemodynamic and autonomic parameters. We have investigated 27 male athletes before competition, 1 h after, and then for the following week after the competition. The Task Force monitor was used to measure beat-to-beat hemodynamic and autonomic parameters during supine rest and active standing. Heart rate (P < 0.001) was increased, and stroke index (P = 0.011), systolic blood pressure (P = 0.004), diastolic blood pressure (P < 0.001), total peripheral resistance index (P < 0.001), and baroreceptor reflex sensitivity (P < 0.001) were decreased after the competition. The 0.05- to 0.17-Hz band of heart rate and blood pressure variability was increased (P < 0.001 and P < 0.001, respectively), the 0.17- to 0.40-Hz band of heart rate interval variability was decreased after the competition (P < 0.001). All parameters returned to baseline values 3 days after the competition. After the competition, the autonomic response to orthostasis was significantly impaired. The 0.05- to 0.17-Hz band of diastolic blood pressure variability before competition and weekly net exercise training, but not the other hemodynamic and autonomic parameters, were related to competition time in multivariate regression analysis (multiple r = 0.70, P < 0.001). The marked hemodynamic and autonomic changes after an ultraendurance race, which are compatible with myocardial depression in the face of sympathetic activation and reduction of afterload, return to baseline after only 1-3 days. Because the 0.05- to 0.17-Hz band of diastolic blood pressure variability contributes to the prediction of competition time, the analysis of blood pressure variability in the frequency domain deserves further study for the prediction of endurance capacity.
No preview · Article · Dec 2005 · Journal of Applied Physiology
[Show abstract][Hide abstract] ABSTRACT: Methods for stroke volume (SV) and ejection fraction (EF) measurements require the presence of qualified physicians and are not suited for continuous monitoring.
To develop an automated non-invasive method for the measurement and continuous monitoring of SV and EF.
We have designed a method for the measurement of EF and SV using multiple-site-impedance (z0) measurements, applying multiple frequencies of 5, 40 and 200 kHz whereby various segments of the human body, including volume changes within these segments, could be defined electrically. The obtained variables were used to train neuronal nets and related by multiple regression analyses to cardiac output (CO) as measured by a partial rebreathing Fick method (CO(r-fick)) or EF as measured by echocardiography (EF(echo)), respectively. A total of 129 subjects (48 with normal heart function and 81 with CHF, NYHA I-IV) were investigated.
The multiply derived values of z0 and of change of impedance (dz/dt) were shown, by multiple regression analysis, to be significantly related to CO(r-fick) and to EF(echo), (total r=0.77, n=35, p<0.001, and r=0.81, n=47, p<0.001, respectively.). By training a neuronal net with the electrical data of 67 (out of 94) subjects, EF(echo) could be predicted in the remaining 27 subjects which were unknown to the neuronal net with a combined r=0.71 (p<0.001,n=27). In contrast, conventional impedance cardiography (ICG) was unable to predict either CO(r-fick) or EF(echo).
The new method, which we call multi-site-frequency electromechanocardiography (msf-ELMC) appears promising for the automated electrical measurement of the mechanical heart action in patients with normal and reduced cardiac function.
Preview · Article · Nov 2005 · European Journal of Heart Failure