Biomedical subjects

Yves Papelier

Publications and source records attributed to Yves Papelier.

5 recordsLinked to original sources

PubMed2006

An algorithm for robust and efficient location of T-wave ends in electrocardiograms.

The purpose of this paper is to propose a new algorithm for T-wave end location in electrocardiograms, mainly through the computation of an indicator related to the area covered by the T-wave curve. Based on simple assumptions, essentially on the concavity of the T-wave form, it is formally proved that the maximum of the computed indicator inside each cardiac cycle coincides with the T-wave end. Moreover, the algorithm is robust to acquisition noise, to wave form morphological variations and to baseline wander. It is also computationally very simple: the main computation can be implemented as a simple finite impulse response filter. When evaluated with the PhysioNet QT database in terms of the mean and the standard deviation of the T-wave end location errors, the proposed algorithm outperforms the other algorithms evaluated with the same database, according to the most recent available publications up to our knowledge.

Algorithms↗

PubMed2004

Heart rate variability during exercise performed below and above ventilatory threshold.

PURPOSE: To examine whether differences in heart rate variability (HRV) can distinguish sub- from supra-ventilatory-threshold exercise and whether the exercise duration at supra-threshold intensity alters cardiorespiratory synchronization. METHODS: Beat-to-beat RR interval, VO2, VCO2, VE, and blood lactate concentration of 11 healthy well-trained young subjects were collected during two exercise tests: 1) a moderate-intensity test: 15 min performed below the power at ventilatory threshold (pVT); and 2) a heavy-intensity test: above pVT until exhaustion. Fast Fourier transform, smoothed pseudo Wigner-Ville distribution, and complex demodulation were applied to RR time series. RESULTS: 1) Moderate exercise shows a prevalence of low-frequency (LF) spectral energy compared with the high-frequency (HF) one (LF = 80 +/- 10% vs HF = 20 +/- 10%, P < 0.001), whereas the reverse is observed during heavy exercise (LF = 11 +/- 8% vs HF = 89 +/- 8%, P < 0.001). 2) During heavy exercise, the HF amplitude and the tidal volume (Vt) remained constant, whereas the breathing frequency (BF) increased (BF: 0.70 +/- 0.18 vs 0.93 +/- 0.31, P < 0.01) and mean RR decreased (342 +/- 15 vs 317 +/- 16, P < 0.01). Despite the RR series and the breathing signal remaining synchronized, HR/BF ratio decreased and stabilized at 3 RR for one breathing cycle, whatever the initial ratio. CONCLUSION: 1) HRV allows us to differentiate sub- from supra-ventilatory-threshold exercise and 2) exercise duration at supra-threshold intensity does not alter the cardiorespiratory synchronization.

Adolescent↗

PubMed2004

Spectral analysis of heart rate variability during exercise in trained subjects.

PURPOSE: To investigate the effects of strenuous exercise on heart rate variability (HRV). METHODS: We evaluated the effects of exercise intensity and duration on HRV indices in 14 healthy trained subjects. Each subject exercised for 3, 6, and 9 min at 60 and 70% of the power achieved at maximal oxygen consumption (PVO2(max)) and for 3 and 6 min (or 3 min twice) at 80% of PVO2(max). The electrocardiogram RR intervals were recorded then processed by fast(FFT) and short-time (STFT) Fourier transform for determination of low-frequency (LF, 0.045-0.15 Hz) and high-frequency (HF, 0.15-1.0 Hz) components. RESULTS: The LF and HF components expressed as absolute power (ms2) decreased significantly at the onset of exercise (P < 0.05). However, with increasing exercise intensity, the HF component expressed as normalized units (n.u.) (reflecting parasympathetic modulation) increased significantly, whereas the LF component (n.u.) and LF/HF ratio (both reflecting sympathetic modulation) decreased significantly (P < 0.05). STFT showed that increasing exercise intensity was associated with a shift in HF peak frequency related to an increase in respiratory rate and a marked decrease in LF power (ms2). Moreover, HFn.u. rose (r = 0.918, P < 0.01) and LFms2 fell as minute ventilation increased (r = 0.906, P < 0.01). CONCLUSIONS: Parasympathetic respiratory control and nonautonomic mechanisms may influence the HF-peak shift during strenuous exercise. HRV and the usual indexes of sympathetic activity do not accurately reflect changes in autonomic modulation during exhaustive exercise.

Adult↗

PubMed2003

Heart rate variability during cycloergometric exercise or judo wrestling eliciting the same heart rate level.

This study compared heart rate variability (HRV) in ten male judokas between two types of exercise eliciting the same near-maximal average heart rate (HR): judo wrestling vs. cycloergometric bout. Beat-to-beat RR intervals were recorded during (1) a 4-min judo randori (wrestling); (2) a 4-min cycloergometric exercise eliciting maximal oxygen consumption (VO(2MAX)). Time series were analyzed both by short term Fourier transform (STFT) and Poincaré plot (PP). The main results are as follows. First, despite the fact that the same maximal HR was reached during the two exercises, the spectral energy computed from the judo recordings was significantly higher than that recorded from the cycloergometric exercise. Second, according to the PP index of rapid HRV (SD1), the high-frequency spectral energy (HF) was significantly higher during judo than cycloergometric exercise as well. Third, judo spectra show chaotic harmonics in place of the precise HF peak observed during cycloergometric exercise. Fourth, the respective parts of normalized LFn and HFn are not different between the two exercise modes, suggesting that autonomic control during severe exercise cannot depend on the type of exercise. In conclusion, this study shows that it is possible, according to the observed kind of variability from RR time series, to differentiate between two types of effort: steady-state dynamic exercise or conversely exercise made of both isometric and irregular dynamic efforts (wrestling, collective sports, and others).

Adult↗

PubMed2002

Effect of fatigue on spontaneous velocity variations in human middle-distance running: use of short-term Fourier transformation.

Best performances in middle-distance running are characterized by coefficients of variation of the velocity ranging from 1% to 5%. This seems to suggest that running at constant velocity is a strain inducing an increase in physiological variables such as oxygen uptake. This study tested three questions. (l) Does velocity variability during a middle-distance all-out run increase with fatigue? (2) Does velocity variability alter the slow phase of the oxygen kinetic because of small spontaneous recoveries, compared with the same distance run at constant velocity? (3) Is a maintained average velocity over a given distance enhanced by a variable-pace rather than by a constant-pace? Ten long-distance runners performed two series of all-out runs over the distance (previously determined) which they could cover maintaining a velocity equal to 90% of that eliciting maximal oxygen consumption. In the first series ( free-pace) the subjects were asked to run as fast as possible, without any predetermined velocity profile. In the second series, the same distance was covered at a constant velocity (equal to the average in the previous free-pace run), set by a cyclist preceding the runner. Short-term Fourier transform was used to analyse velocity oscillations. Our results show that: (1) for all subjects, the mean energy spectrum did not change throughout the free-pace runs, suggesting that velocity variability did not increase with fatigue (2-way ANOVA, P=0.557); (2) the kinetic of oxygen uptake and its asymptote were not changed during the free-pace runs compared to the constant-velocity run; (3) performance was not significantly improved by free-pace average velocity [mean (SD) 4.22 (0.47) compared to 4.25 (0.52) m x s(-1) for constant and free-pace respectively, t=-0.58, P=0.57]. These results indicate that during middle-distance running, fatigue does not increase variations in velocity, and free-pace changes neither performance nor the oxygen kinetic.

Adult↗