Biomedical subjects

Stéphane Perrey

Publications and source records attributed to Stéphane Perrey.

6 recordsLinked to original sources

PubMed2004

Decrease in heart rate variability with overtraining: assessment by the Poincaré plot analysis.

Numerous symptoms have been associated with the overtraining syndrome (OT), including changes in autonomic function. Heart rate variability (HRV) provides non-invasive data about the autonomic regulation of heart rate in real-life conditions. The aims of the study were to: (i) characterize the HRV profile of seven athletes (OA) diagnosed as suffering of OT, compared with eight healthy sedentary (C) and eight trained (T) subjects during supine rest and 60 degrees upright, and (ii) compare the traditional time- and frequency-domain analysis assessment of HRV with the non-linear Poincaré plot analysis. In the latter each R-R interval is plotted as a function of the previous one, and the standard deviations of the instantaneous (SD1) and long-term R-R interval variability are calculated. Total power was higher in T than in C and OA both in supine (1158 +/- 1137, 6092 +/- 3554 and 2970 +/- 2947 ms2 for C, T and OA, respectively) and in upright (640 +/- 499, 1814 +/- 806 and 1092 +/- 712 ms2 for C, T and OA, respectively; P<0.05) positions. In supine position, indicators of parasympathetic activity to the sinus node were higher in T compared with C and OA (high-frequency power: 419.1 +/- 381.2, 1105.3 +/- 781.4 and 463.7 +/- 715.8 ms2 for C, T and OA, respectively; P<0.05; SD1: 29.5 +/- 18.5, 75.2 +/- 17.2 and 37.6 +/- 27.5 for C, T and OA, respectively; P<0.05). OA had a marked predominance of sympathetic activity regardless of the position (LF/HF were 0.47 +/- 0.35, 0.47 +/- 0.50 and 3.96 +/- 5.71 in supine position for C, T and OA, respectively, and 2.09 +/- 2.17, 7.22 +/- 6.82 and 12.04 +/- 10.36 in upright position for C, T and OA, respectively). The changes in HRV indexes induced by the upright posture were greater in T than in OA. The shape of the Poincaré plots allowed the distinction between the three groups, with wide and narrow shapes in T and OA, respectively, compared with C. As Poincaré plot parameters are easy to compute and associated with the 'width' of the scatter gram, they corroborate the traditional time- and frequency-domain analysis. We suggest that they could be used to indicate fatigue and/or prevent OT.

Adolescent↗

PubMed2004

Influence of repeated isometric contractions on muscle deoxygenation and pulmonary oxygen uptake kinetics in humans.

The purpose of the present study was to compare simultaneously vastus lateralis (VL) deoxygenation and pulmonary O(2) uptake (O(2)) kinetics during fatiguing knee extension exercise with minimal cardiac load. Eight healthy subjects realized an intermittent bilateral knee-extension exercise (3-s contraction/3-s relaxation) at 40% of maximum voluntary contraction for 10 min. VL deoxygenation was recorded by near infrared spectroscopy at 2 Hz (NIRO-300, Hamamatsu Photonics, Japan) and O(2) was determined breath-by-breath (K4b(2), Cosmed, Italy). After a time delay of 16 +/- 5 s, deoxygenation kinetics at the onset of exercise followed an exponential time course at a significant faster rate than O(2) (time constant of 5.4 +/- 4.0 s vs. 31.6 +/- 10.4 s, P<0.01) reflecting a mismatch between local O(2) consumption and perfusion. Thereafter, a rise in O(2) of 223 +/- 123 ml min(-1) (consistent with the mathematical model, 259 +/- 126 ml min(-1)) was observed between minutes 2 and 10. During the same exercise time, changes in tissue oxygenation index decreased significantly and were individually correlated with the corresponding increased O(2) (P<0.05), suggesting that the majority of the slow rise of O(2) arose from the exercising limbs. Averaged heart rate increased from 67 +/- 11 to 116 +/- 20 beats min(-1) during exercise. Knee extension exercise may be relevant to estimate the cardiopulmonary and deoxygenation of working skeletal muscle responses for assessment of exercise limiting factors in clinical settings or in the exercise physiology.

Adult↗

PubMed2003

Faster oxygen uptake kinetics at the onset of submaximal cycling exercise following 4 weeks recombinant human erythropoietin (r-HuEPO) treatment.

We tested the hypothesis that prolonged administration of moderate doses of recombinant human erythropoietin (r-HuEPO) accelerates the initial rate of rise in pulmonary O2 uptake (VO2) in response to submaximal exercise and increases the maximal rate of O2 uptake (VO(2,max)). Sixteen endurance-trained athletes were divided into two groups: r-HuEPO- (n=9) or placebo-treated (n=7). r-HuEPO or placebo (saline) injections were given s.c. 3 times a week for 4 weeks. Exercise testing, before and after the 4 weeks, comprised incremental maximal tests and several transitions from rest to 10-min cycling exercise at 65% VO(2,max). VO2 was measured breath-by-breath during all tests. In the r-HuEPO group, resting haemoglobin concentration (+9.6%) and haematocrit (+8.3%), as well as VO(2,max) (+7.0%) and power output (+7.2%) increased significantly (P<0.05) after the 4 weeks, whereas no change was observed in the control group. The time constant of the primary VO2 response was significantly faster (+18%) after the 4 weeks r-HuEPO treatment than before (mean+/-SD; 29.3+/-4.5 vs. 35.7+/-7.4 s, respectively, P<0.05) but was unaffected in the placebo group (34.5+/-7.3 vs. 33.4+/-7.9 s). Collectively, our findings suggest that r-HuEPO contributes both to an acceleration of the dynamic response of VO2 to submaximal exercise and to an increase in maximal exercise capacity.

Adult↗

PubMed2003

Quantitative Poincaré plot analysis of heart rate variability: effect of endurance training.

The aim of the study was to evaluate the effectiveness of the Poincaré plot analysis of heart rate variability (HRV) in observing endurance training-induced changes. Four 10-min manoeuvres were performed (supine lying, standing, steady state exercising and subsequent recovery) by eight control subjects before and after a short-term endurance training and by eight subjects trained for at least 3 years. HRV was assessed by traditional time- and frequency-domain indexes, in parallel with the Poincaré plot analysis. In the latter each R-R interval is plotted as a function of the previous one, and the standard deviations of the instantaneous and long-term R-R interval variability are calculated. In our subjects, the Poincaré scatter grams became gradually narrower from supine to exercising, with progressive parasympathetic withdrawal. Short- and long-term endurance training led to higher aerobic power ( p<0.05) and ventilatory threshold shifted towards higher power output ( p<0.05). All HRV evaluation methods showed that HRV values were higher after training both during supine lying and standing ( p<0.05). The Poincaré scatter grams were wider in the trained state. Standard deviations of the Poincaré plot were significantly correlated with the main parameters of the time- and frequency-domain analyses, especially concerning the parasympathetic indicators. These results suggested that Poincaré plot parameters as well as the "width" of the scatter gram could be considered as surrogates of time- and frequency-domain analysis to assess training-induced changes in HRV.

Adult↗

PubMed2003

Cardiovascular and oxygen uptake kinetics during sequential heavy cycling exercises.

The purpose of the present study was to assess the relationship between the rapidity of increased oxygen uptake (VO2) and increased cardiac output (CO) during heavy exercise. Six subjects performed repeated bouts on a cycle ergometer above the ventilatory threshold (approximately 80% of peak VO2) separated by 10-min recovery cycling at 35% peak VO2. VO2 was determined breath-by-breath and CO was determined continuously by impedance cardiography. CO and VO2 values were significantly higher during the 2-min period preceding the second bout. The overall responses for VO2 and CO were significantly related and were faster during the second bout. Prior heavy exercise resulted in a significant increase in the amplitude of the fast component of VO2, with no change in the time constant and a decrease in the slow component. Under these circumstances, the amplitude of the fast component was more sensitive to prior heavy exercise than was the associated time constant.

Adult↗

PubMed2003

Dynamic responses of O2 uptake at the onset and end of exercise in trained subjects.

Inconsistencies about dynamic asymmetry between the on- and off-transient responses in .VO2 are found in the literature. Therefore the purpose of this study was to examine .VO2on- and off-transients during moderate- and heavy-intensity cycling exercise in trained subjects. Ten men underwent an initial incremental test for the estimation of ventilatory threshold (VT) and, on different days, two bouts of square-wave exercise at moderate ( VT) intensities. .VO2 kinetics in exercise and recovery were better described by a single exponential model ( VT). For moderate exercise, we found a symmetry of .VO2 kinetics between the on- and off-transients (i.e., fundamental component), consistent with a system manifesting linear control dynamics. For heavy exercise, a slow component superimposed on the fundamental phase was expressed in both the exercise and recovery, with similar parameter estimates. But the on-transient values of the time constant were appreciably faster than the associated off-transient, and independent of the work rate imposed ( VT). Our results do not support a dynamically linear system model of .VO2 during cycling exercise in the heavy-intensity domain.

Adult↗