[Show abstract][Hide abstract] ABSTRACT: Taurine is released by contracting muscles, but its actual role remains unspecified. In this study, we investigated whether the exercise-stimulated release of taurine from muscle into the plasma regulates the modification of osmolality induced by intramuscular osmolyte production. Six subjects performed 90 min of cycling exercise (at 70% maximum power output) on two occasions, with (HC) or without (DC) fluid intake. Taurine content was determined in plasma, blood cells and urine before and after the endurance events, together with plasma osmolality. Plasma osmolality increased by 4% in the DC experiment ( P<0.01), but remained stable in the HC condition. The exercise also induced changes in the mean (SD) plasma taurine content to a greater degree in HC [+63 (26)%] than in DC [+33 (18)%; P<0.05], supporting the hypothesis that taurine is released into the plasma via an osmoregulatory process. However, the higher plasma taurine content in HC was not related to changes in renal taurine. In addition, the increase of taurine in plasma was not related to its release from blood cells since their taurine concentration increased by 70% both in HC [429 (77) to 680 (82) microM; P=0.003] and in DC [451 (57) to 731 (34) microM; P<0.001]. The lack of correlation between plasma volume modification and the mass ratio of taurine would exclude a major role for taurine exchange in plasma volume regulation. Sodium ( R=0.967, P<0.001), chloride ( R=0.917, P<0.001) and osmolality ( R=0.924, P<0.001) seem to be the main regulators of plasma volume changes during exercise. In conclusion, changes in the plasma taurine content during endurance exercise is related to an osmoregulatory process, but this alone does not control plasma volume changes.
[Show abstract][Hide abstract] ABSTRACT: The Parliament of the French Community has edited a decree concerning the promotion of health by sport, the fight against doping in the French Community. This decree declares that federations are responsible for the public health in sport practice. This establishes a link between sport and health. The sport physician must add to his medical practice an ethical dimension. The decree proposes a profound reflection about the good practice in sport medicine.
[Show abstract][Hide abstract] ABSTRACT: Changes in urinary and plasma taurine and amino acids have been evaluated in trained runners competing in the Rotterdam Marathon, 1998, both immediately after completing the event and 24h after recovery. There were significant changes in the urinary amino acids excretion, the majority showing a significant decrease both immediately at the completion of the Marathon and after 24h recovery. In contrast urinary taurine excretion increased immediately post Marathon, although not significantly as the range of results was wide. Such changes in urinary taurine correlated with percentage changes in plasma creatine kinase both immediately post race, (r = 0.972, P < 0.001), and 24h later (r = 0.872, P < 0.001), possibly indicating that the source of the taurine was muscle. Significant correlations between the individual values for urinary and plasma amino acids in all of the athletes were calculated for taurine (r = 0.528), glycine (r = 0.853), threonine (r = 0.749), alanine (r = 0.747), serine (r = 0.620), glutamine (0.614), arginine (r = 0.507), histidine (r = 0.470) and valine (r = 0.486). Changes in the mean plasma concentrations of amino acids were comparable to our previously published data (Ward et al., 1999) the majority showing significant decreases immediately and 24h post Marathon, such an adaptation being due primarily to their utilisation for gluconeogenesis. However, in contrast, the mean taurine concentrations were significantly elevated both post race, P < 0.01 and after 24h, P < 0.05. The physiological response by the muscle to exhaustive exercise, particularly with regard to changes in plasma and urinary taurine concentrations remain to be elucidated, but is probably related to muscle function impairment. The increase in taurine urinary excretion could be used as an indicator of muscle damage occurring during exhaustive exercise. Whether taurine supplementation would minimise such changes is an interesting scientific question and merits investigation.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to analyse lower leg skin blood flow (laser Doppler flowmetry) in five individuals with high-level paraplegia (T5-T9), six participants with low-level paraplegia (T10-T12) and six able-bodied controls during 3-minute light and heavy arm-cranking exercises (approximately 15% and 80% peak power output, respectively). Throughout light exercise, cutaneous vasoconstriction was shown for the control group (-20%), but not the low-level (+62%) or the high-level paraplegic group (+33%). During heavy exercise, vasoconstriction was initially found for controls followed by an increase in skin blood flow during the last 2 minutes, whereas the participants with paraplegia demonstrated skin blood flow increases. Skin blood flow responses were not related to lesion level. Metabolic parameters were not different among the three groups, but heart rates for participants with paraplegia were higher during heavy exercise than in controls. These results suggest impaired sympathetic vasoconstriction in individuals with paraplegia during exercise.
Journal of Rehabilitation Medicine 02/2001; 33(1):16-20. DOI:10.1080/165019701300006489 · 1.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study investigated whether a 60-minute arm-cranking exercise at 50% of the individual maximal power output would increase lower limb skin blood flow (laser Doppler flowmetry) in individuals with high-level (T5-T9; n = 6) and low-level paraplegia (T10-T12; n = 6), compared to 6 able-bodied controls. Significant (P < 0.05) group by time interactions (two-way repeated measures ANOVA) were found for leg cutaneous vascular conductance, leg skin temperature and esophageal temperature. Cutaneous vascular conductance increased to a peak of approximately 180% of pre-exercise rest in both paraplegic groups and to -436% in the control group, with differences after 15, 30, 45 and 60 minutes of exercise. Leg skin temperature increased by approximately 0.3 C in individuals with paraplegia and decreased by approximately 2.0 C in able-bodied. Esophageal temperature increases at the end of exercise were higher in individuals with paraplegia (approximately 0.9 C) than in able-bodied subjects (approximately 0.5 C). Heart rate was higher in the paraplegic groups than in able-bodied, whilst stroke volume and cardiac output were not different (impedance cardiography). The data suggest that lesion level had no influence on the results. These findings indicate that there is no excessive shunting of blood to the skin of the lower limbs of individuals with paraplegia during sustained exercise.
International Journal of Sports Medicine 02/2001; 22(2):97-102. DOI:10.1055/s-2001-11344 · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: difference, P<0.05). The paraplegics developed a higher esophageal and leg skin temperature, which was attributed to the lack of active vasodilation and evaporative cooling over the legs. The results indicate that individuals with paraplegia suffer from impaired cutaneous vasoconstriction at the onset of arm exercise, and possess only a limited vasodilatory capability in the paralyzed regions. During intense exercise, thermoregulation depends critically on active cutaneous vasodilation and skin cooling.
[Show abstract][Hide abstract] ABSTRACT: The veno-arteriolar reflex (VAR) in spinal-cord-injured subjects (SCI) has been attributed little interest, although it might
contribute substantially to their blood redistribution. This peripheral reflex response, which is based on an axon reflex,
consists of a reduction in limb blood flow following an increase in venal transmural pressure. The purpose of the present
investigation was to assess the peripheral and central cardiovascular adaptations of paraplegics with high (HP) and low (LP)
spinal lesions to subsequent, passive posture changes involving leg dependency and upright sitting, and to compare them to
able-bodied (AB) subjects. Lower-limb cutaneous vascular conductance (CVC) was evaluated from skin blood flow measurements
(laser Doppler flowmetry) taken from the dorsal foot, and from ankle blood pressure. Cardiac stroke volume, heart rate and
myocardial performance were assessed using impedance cardiography and brachial blood pressure. During leg dependency, a significant
vasoconstriction was noted in all three groups. The initial decrease in CVC was higher in HP (−76.82%) than in AB (−45.82%),
the values for LP (−67.08%) lying in between these two (significant group × time interaction: F = 2.832; P = 0.042). There were no differences for parameters of central hemodynamics. No between-group differences were noted in any
parameter tested during upright sitting. CVC remained at a similar low level as compared to leg dependency, stroke volume
decreased, heart rate and blood pressure increased, and myocardial performance remained constant. The present results suggest
that paraplegics have a peripheral VAR in their paralyzed lower limbs, and that this contributes to their cardiovascular stability.
[Show abstract][Hide abstract] ABSTRACT: The sulphonated amino acid taurine increased significantly in the plasma of trained athletes after three endurance exercises of different duration and intensity, a 90 min run on a treadmill at 75% of an individual's VO2 peak, a Marathon, 42.2 km and a 100 km run, by 19%, 77% and 36%, respectively. Such results indicated that the speed at which the exercise is performed, referred to as the intensity, rather than the duration of the exercise, correlated with the elevated taurine levels possibly indicating its release from muscle fibres. The plasma amino acid pool decreased significantly in relationship with the duration of the exercise, caused by their utilisation for glucogenesis. The possible sources of the increased plasma taurine are discussed.
[Show abstract][Hide abstract] ABSTRACT: A new ensemble-averaging (EA) approach was developed with the goal of investigating central hemodynamics by transthoracic impedance cardiography during maximal arm cranking. This EA procedure of the first time derivative of impedance changes (dZ/dt) over several cardiac cycles differs from previously reported techniques with respect to cycle selection strategy, according to fixed criteria, and processing methods.
First, the primary elements of the Kubicek stroke volume (SV) formula, as determined by EA, were compared with the values determined by the standard hand-processing (HP) method over a large range of cardiac outputs.
Results showed a very high reliability for ventricular ejection time (r = 0.996), (dZ/dt)min (r = 0.995), SV (r = 0.977), and heart rate (r = 0.999). Second, the EA procedure was applied to six subjects performing a continuous, multistage arm cranking test to volitional fatigue. The present technique allowed for an effective filtering of movement and breathing artifacts of the original signal. Thus, interpretation of the dZ/dt wave form was convenient, even at maximal arm cranking power outputs up to 120 W. Stroke volume ranged from 63.83 to 127.18 mL.beat-1, showing no significant variations with oxygen consumption. Cardiac output increased linearly with oxygen uptake, reaching a mean maximal value of 16 L.min-1.
The present procedure opens a new field of application to impedance cardiography, permitting to measure cardiac output during maximal arm cranking exercise.
Medicine & Science in Sports & Exercise 09/1998; 30(8):1321-7. DOI:10.1097/00005768-199808000-00022 · 4.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to develop an original friction loaded ergometer allowing measurement of the resisting torque (Mb) and the angular velocity (omega) by means of a force transducer and an optical pick-up during all-out arm cranking exercises. Taking into account the kinetic energy variations of the flywheel, the peak power developed at the crank (P(c)peak) and the peak angular velocity (omegapeak) were determined in 6 male and 6 female able-bodied subjects during 6-8 bouts of 3 s duration, performed at maximal velocity, with Mb varying from 0.07 to 0.87 Nm x kg(-1). In each subject, the Mb increase was related to a decrease of omegapeak. This relationship was expressed through a negative linear regression (0.92 < R2 < 0.99) for omegapeak between 13 and 28 rad x s(-1) for the males and 10 and 24 rad x s(-1) for the females. The relationship between P(c)peak and Mb did not fit well for all subjects (0.01 < R2 < 0.93) with a parabolic equation, indicating that for upper limb testing, the maximal power should be defined as the highest power measured during several bouts performed with appropriate resisting torque. The present study also demonstrated the importance of taking into account the inertia of the moving flywheel during the acceleration phase of an all-out arm crank exercise, when determining the peak power output.
International Journal of Sports Medicine 11/1997; 18(8):600-6. DOI:10.1055/s-2007-972688 · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The hypothesis of magnesium deficiency in isoproterenol (ISO) induced myocardial injury has been investigated by 31P nuclear magnetic resonance spectroscopy. High energy phosphate concentrations, pHi, and intracellular free magnesium concentration ([Mg2+]i) were measured in isolated rabbit hearts perfused at constant flow and subjected to 10(-6)M isoproterenol during 30 min. Recent calibrations were used for [Mg2+]i measurements, and uncertainties on [Mg2+]i estimated values were calculated. During isoproterenol infusion, pHi, [PCr], and [ATP] decreased, while [P(i)] increased. When it was stopped, [PCr] completely repleted, whereas only a partial restoration was observed for pHi and [P(i)]. A rise of end-diastolic pressure and perfusion pressure expressed a contracture, concomitant with a lack of [ATP] recovery, which remained at 59 +/- 13% of the rest value. These results establish that 10(-6) M isoproterenol caused severe myocardial injury. [Mg2+]i increased from 0.70 mM at rest to 0.88 mM at the end of the isoproterenol period. Considering the estimated uncertainties on the [Mg2+]i values, this increase was not significant. After isoproterenol infusion, [Mg2+]i progressively decreased to reach 0.72 mM at 45 min recovery. It is concluded that isoproterenol myocardial toxicity may not be related to [Mg2+]i deficiency.
Canadian Journal of Physiology and Pharmacology 09/1997; 75(8):1015-21. · 1.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The hypothesis of magnesium deficiency in isoproterenol (ISO) induced myocardial injury has been investigated by P-31 nuclear magnetic resonance spectroscopy. High energy phosphate concentrations, pH(i), and intracellular free magnesium concentration ([Mg2+](i)) were measured in isolated rabbit hearts perfused at constant flow and subjected to 10(-6) M isoproterenol during 30 min. Recent calibrations were used for [Mg2+](i) measurements, and uncertainties on [Mg2+](i) estimated values were calculated. During isoproterenol infusion, pH(i), [PCr], and [ATP] decreased, while [P-i] increased. When it was stopped, [PCr] completely repleted, whereas only a partial restoration was observed for pH(i) and [P-i]. A rise of end-diastolic pressure and perfusion pressure expressed a contracture, concomitant with a lack of [ATP] recovery, which remained at 59 +/- 13% of the rest value. These results establish that 10(-6) M isoproterenol caused severe myocardial injury. [Mg2+](i) increased from 0.70 mM at rest to 0.88 mM at the end of the isoproterenol period. Considering the estimated uncertainties on the [Mg2+](i) values, this increase was not significant. After isoproterenol infusion, [Mg2+](i) progressively decreased to reach 0.72 mM at 45 min recovery. It is concluded that isoproterenol myocardial toxicity may not be related to [Mg2+](i) deficiency.
Canadian Journal of Physiology and Pharmacology 08/1997; 75(8):1015-1021. DOI:10.1139/cjpp-75-8-1015 · 1.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The creatine kinase reaction has been studied by 31P NMR in exercising human calf muscle. Quantitative analysis of high energy phosphates and saturation transfer study of the creatine kinase flux in the direction of ATP synthesis (Vfor) were performed at rest and during exercise. As expected, exercise induced a [PCr] decrease (from 28.5 +/- 0.9 to 21.9 +/- 1.5 mM, P < 0.01) matched by a Pi increase (from 4.5 +/- 0.2 to 8.9 +/- 1.8 mM, P = 0.06). pHi and [ATP] remained unchanged. Vfor did not change from rest (12.4 +/- 0.9 mM s(-1)) to moderate exercise and decreased at the highest exercise level (8.4 +/- 1.4 mM s(-1), P = 0.006). This observation differs from the prediction of the creatine kinase rate equation, showing an increase in the flux with exercise intensity. Computations suggest that this discrepancy arises from metabolite compartmentalization and/or from the reaction kinetics of a dead end complex stabilized by planar anions.
Magnetic Resonance in Medicine 05/1997; 37(5):744-53. DOI:10.1002/mrm.1910370518 · 3.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study presents a mathematical model by which power output (PO) delivered to the rear wheel during handrim wheelchair propulsion on a roller ergometer can be determined for individual wheelchair-user combinations. PO is calculated from the torque applied to the wheel and its angular velocity. The torque applied is a function of one total internal torque of the wheelchair-ergometer system, the rotational moment of inertia of the rear wheel, the one of the roller and its angular acceleration. The total internal torque reflects all internal friction forces and is determined with a deceleration test. To assess the reliability of this approach, 11 able-bodied subjects underwent progressively increasing exercise tests on two different occasions. PO values ranged from 12 to 63 W and were highly reliable (r2 > 0.95). Peak physiological responses were never different from test 1 and 2 (repeated measures ANOVA; p: N.S.) and correlations were 0.90, 0.72, 0.88, 0.82, 0.70 and 0.85 for PO, oxygen uptake (VO2), heart rate, minute ventilation, carbon dioxide production and blood lactate concentration, respectively. After an initial increase, gross mechanical efficiency dropped at higher velocities, with values ranging from 4.64 to 11.26%. In conclusion, the roller ergometer, the mathematical model to determine PO and the protocol used seem to be adequate to exercise test people in a handrim wheelchair. It is feasible to apply the theoretical procedure to other roller ergometers which would allow for comparisons of exercise intensities and protocols between different devices used in exercise physiology and rehabilitation.
International Journal of Sports Medicine 11/1996; 17(8):564-71. DOI:10.1055/s-2007-972896 · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tracers have been used extensively to study lactate metabolism in humans during rest and exercise. Nevertheless, quantification of in vivo lactate kinetics as measured by lactate tracers remains controversial and new data are necessary to clarify the issue. The present study has developed a simple kinetic model which does not require labelled molecules and which yields proportional and quantitative information on lactate metabolism in humans during postexercise recovery performed at different levels of intensity. Five subjects took part in six experiments each of which began with the same strenuous exercise (StrEx; 1 min, 385 W, 110 rpm). The StrEx of each session was followed by a different intensity of recovery: passive recovery (PR) and active recoveries (AR) with power outputs of 60, 90, 120, 150 and 180 W, respectively. Blood lactate concentration was measured prior to and immediately after StrEX and regularly during the 1st h of recovery. Oxygen uptake (\(\dot VO_2 \)) was measured every 30 s during the whole session. The results showed that the disappearance rate constant (ke) increases abruptly from PR [0.080 (SEM 0.004) min−1] to moderate AR [60W: 0.189 (SEM 0.039) min−1] and decreases slowly during more intense AR [180 W: 0.125 (SEM 0.027) min−1]. The lactate apparent clearance (Cl·F−1) was calculated from the area under the lactate concentration-time curve. The Cls·F−1 increased 1.81 (SEM 0.17) fold from PR to moderate AR (60 W) and only 1.31 (SEM 0.14) from PR to the most intense AR (180 W). Using the model, the apparent lactate production (F″K0) was also calculated. The F″K0 increased regularly following a slightly curvilinear function of\(\dot VO_2 \) and was 2.61 (SEM 0.53) fold greater during the most intense AR (180 W) than during PR. Because of the lack of data concerning the size of apparent lactate distribution volume (V
d), the apparent turnover rate (Rbl) has been presented here related toV
d. The Rbl·V
increased also following a slightly curvilinear function of\(\dot VO_2 \). The Rbl·V
was 85.90 (SEM 14.42) μmol·min−1·l−1 during PR and reached 314.09 (SEM 153.95) μmol·min−1·l−1 during the most intense AR (180 W). In conclusion the model presented here does not require labelled molecules and firstly makes it possible to follow the proportional change of apparent lactate clearance and apparent lactate production during active postexercise recovery in comparison with passive recovery conditions and secondly to estimate the blood lactate turnover.
European Journal of Applied Physiology and Occupational Physiology 02/1995; 72(1-2):58-66. DOI:10.1007/BF00964115
[Show abstract][Hide abstract] ABSTRACT: We have developed implements that permit the federal authorities to give advice concerning young swimmers and their future in sports. Based on a review, a test battery has been established. First, some kinanthropometric variables were measured: full-height, weight, foot length, length of the upper member and the articular amplitude. Specific variables were also estimated. The aim of these measurements was to evaluate the individual qualities of a subject in the swimming pool. In this respect, the capacity to maintain a hydrodynamic position, floatability and stroke efficiency were evaluated. Statistical analysis has established the reference norms, to verify the opportunity of every test and to assure the descriptive character of all the measured variables. The results yielded for each subject, a profile that situates the subject versus a group of statistically known swimmers. Principal component analysis (PCA) has also been used to evaluate the situation of a a subject versus his own group considering all the variables. After testing the technical qualities, the selected individuals were submitted, twice a year to a functional exercise laboratory test. Based on measured data, we have stablished the physiological profile of young french swimmers (Francaux et al, 1987). The VO2 max measured using a cycloergometer test must be considered as the evaluation of physiological capacity that only the well trained subjects can allow during swimming exercise. This investigation is thus, very important as it evaluates the intrinsic physiological value of a swimmer without his stroke efficiency. Nevertheless, to provide the trainers with easily interpretable information, it was essential to quit the laboratory. Therefore, the study of the physiological adaptation of the swimmers was therefore carried out in the swimming pool. According to the protocols proposed by Mader et al (1978) and completed by Olbrecht et al (1985), we have used a lactate test under real swimming conditions. The results of this test gave the trainers clear information about the reactions of the swimmer versus the ended training cycle and about the training intensities for future training sessions.