Biomedical subjects

Laurent Mourot

Publications and source records attributed to Laurent Mourot.

7 recordsLinked to original sources

PubMed2006

Side-effects of L-dopa on venous tone in Parkinson's disease: a leg-weighing assessment.

In the present study, the effects of L-dopa treatment on cardiovascular variables and peripheral venous tone were assessed in 13 patients with Parkinson's disease (PD) with Hoehn and Yahr stages 1-4. Patients were investigated once with their regular treatment and once after 12 h of interruption of L-dopa treatment. L-Dopa intake significantly reduced systolic and diastolic blood pressure, heart rate and plasma noradrenaline and adrenaline in both the supine and upright (60 degrees ) positions. A significant reduction in stroke volume and cardiac output was also seen with L-dopa. The vascular status of the legs was assessed through thigh compression during leg weighing, a new technique developed in our laboratory. Healthy subjects were used to demonstrate that this technique provided reproducible results, consistent with those provided by strain gauge plethysmography of the calf. When using this technique in patients with PD, L-dopa caused a significant lowering of vascular tone in the lower limbs as shown, in particular, by an increase in venous distensibility. Combined with the results of the orthostatic tilting, these findings support that the treatment-linked lowering of plasma noradrenaline in patients with PD was concomitant with a significant reduction in blood pressure, heart rate and vascular tone in the lower limbs. These pharmacological side-effects contributed to reduce venous return and arterial blood pressure which, together with a lowered heart rate, worsened the haemodynamic status.

Adult↗

PubMed2005

Effect of endurance training on different mechanical efficiency indices during submaximal cycling in subjects unaccustomed to cycling.

The purpose of this study was to evaluate different efficiency indices, i.e., gross (GE: no baseline correction), net (NE: resting metabolism as baseline correction), and work (WE: unloaded exercise as baseline correction), to reveal the effect of endurance training on mechanical efficiency. Nine healthy sedentary women undertook an incremental test and submaximal cycling exercise, at an intensity corresponding to 50% of the pretraining peak oxygen uptake, before and after 6 weeks of endurance training (18 sessions of 45 min). The training effects on efficiency indices were tested by comparisons based on GE, NE, and WE as well as by the differences between the percentage changes of all indices (%GE, %NE, %WE). Endurance training resulted in significantly higher GE (+11.1%; p < 0.001) and NE (+9.1%; p < 0.01). Only minor significant improvement (+2.4%; p < 0.05) was observed with the WE index because the value used for baseline subtraction was significantly reduced by the training sessions, due perhaps to improvement in pedaling skill. As a consequence, %WE was significantly lower than %GE (p < 0.01) and %NE (p < 0.05), while %GE and %NE were not significantly different. We conclude that mechanical efficiency of cycling increases with training in women previously unfamiliar with cycling, and that the WE index is less sensitive to this training effect than GE and NE indices.

Adult↗

PubMed2004

Short- and long-term effects of a single bout of exercise on heart rate variability: comparison between constant and interval training exercises.

Heart rate variability (HRV) was assessed during the short- (within 1 h) and long- (within 48 h) term recovery following a single bout of either constant (CST) or interval training (SWEET) exercise performed at the same total physical work [9.4 (0.3) kJ kg(-1)]. R-R intervals, systolic (SAP) and diastolic (DAP) arterial pressures were recorded in supine and upright positions before and 1, 24 and 48 h after the termination of the exercises in ten male subjects [mean (SEM), age 24.6 (0.6) years, height 177.2 (1.1) cm and body mass 68.5 (0.9) kg]. The parameters were also recorded in the supine position during the first 20 min following the end of the exercise. Spectral analysis parameters of HRV [total (TP), low- (LF), and high- (HF) frequency power, and LF/TP, HF/TP and LF/HF ratios] were determined over 5 min during each phase. Except for higher HF values in both supine and upright positions during the first hour following CST compared with SWEET, cardiovascular and HRV analysis responses were of the same magnitude after their termination. R-R intervals, TP, and HF/TP were significantly decreased while LF/TP and LF/HF were significantly increased during the early recovery, when compared with control values. This could be a response to the significant decrease in SAP and DAP at this time. Twenty-four and 48 h after the end of the exercise, HRV parameters were at the same levels as before exercises in the supine posture, but a persistent tachycardia continued to be observed in the upright posture, together with reduced TP values, showing that cardiovascular functions were still disturbed. The short-term HRV recovery seemed dependent on the type of exercise, contrary to the long-term recovery.

Adult↗

PubMed2004

Supra-maximal cycling efficiency assessed in humans by using a new protocol.

This study proposed a non-invasive method to determine the gross (GE, no baseline correction), net (NE, resting metabolism as the baseline correction) and work (WE, unloaded cycling as the baseline correction) efficiencies during cycling at an intensity higher than the maximal aerobic power (MAP). Twelve male subjects performed two exercises consisting of 4 min at 50% MAP followed either by 8 min at 63% MAP or by 8 sequences of 60 s divided into 10 s at 130% MAP and 50 s at 50% MAP (i.e., 63% MAP on average). Oxygen uptake was continuously measured to calculate GE, NE and WE at 50%, 63% and 130% MAP, and the data presented as the means and standard deviations. The GE values were 18.2%, 19.1%, 22.7%, the NE values were 22.4%, 22.8%, 24.3% and the WE values were 34.2%, 31.4% and 27.2% at 50%, 63% and 130% MAP, respectively. The GE and NE increased (P < 0.001) whereas the WE decreased (P < 0.001) with each increment in power output. The GE was lower than the NE (P < 0.001) at 50% and 63% MAP and than the WE (P < 0.001) at all intensities. The NE was lower (P < 0.001) than the WE at 50% and 63% MAP. These results showed that (1) efficiency index values obtained during supra-maximal exercise were consistent with previous proposals and (2) the efficiency-power output relationships were not limited to sub-maximal intensity levels but were confirmed at higher power output.

Adult↗

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↗

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↗