Venous tonus enhancement after a short cycle of intermittent pneumatic compression.

Objectives: To test if intermittent pneumatic compression (IPC) used with a short cycle could reproduce and confirm the 30 min vasoconstriction effect observed after a long cycle of pressure.

Methods: Eighteen subjects took part in the study, 12 with venous insufficiency (VI) and six without VI (NonVI). Duplex scanner was used to evaluate the diameter of six sites of veins on each of both lower limbs before and after the treatment.

Role of taurine in osmoregulation during endurance exercise.

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.

Central and peripheral haemodynamics in individuals with paraplegia during light and heavy exercise.

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.

[Ethical reflections regarding the decree promoting health through sports].

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.

Changes in plasma and urinary taurine and amino acids in runners immediately and 24h after a marathon.

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.

Cutaneous vascular response and thermoregulation in individuals with paraplegia during sustained arm-cranking exercise.

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 vasomotor adjustments during arm-cranking in individuals with paraplegia.

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.

Blood distribution adaptations in paraplegics during posture changes: peripheral and central reflex responses.

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.

Changes in plasma taurine levels after different endurance events.

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.

Impedance cardiography applied to maximal arm cranking exercise: a matter of sampling and processing strategy.

Purpose: 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.

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.

Measurement of the power output during the acceleration phase of all-out arm cranking exercise.

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.

Free magnesium concentration in isolated rabbit hearts subjected to high dose isoproterenol infusion: a 31P NMR study.

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.

31P NMR saturation transfer study of the creatine kinase reaction in human skeletal muscle at rest and during exercise.

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.

A new procedure to determine external power output during handrim wheelchair propulsion on a roller ergometer: a reliability study.

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.

A study of lactate metabolism without tracer during passive and active postexercise recovery in humans.

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.

Variations in lactate apparent clearance during rest and exercise in normal man.

The purpose of this study is to present a simple kinetic model for the study of the lactate metabolism. This model based on pharmacokinetic theory, does not require labelled molecules and yields a finer approach to lactate metabolism than does a simple observation of blood lactate concentration. The variations in parameter values have been studied in six male subjects after intensive exercise (385 W, 110 rpm and 1 min) (IE) followed by three different recovery periods: passive recovery (RE), moderate exercise (ME) and heavy exercise (HE).

The maximum lactate clearance: a new concept to approach the endurance level of an athlete.

The purpose of this study is to present a mathematical model based on physiological observations which describes the evolution of the blood lactate concentration ([LA-]) versus the oxygen uptake (VO2) during a continuous graded exercise test. This model is based on several assumptions: 1) [LA-] reflects the balance between the rates of appearance and disappearance of the lactate in the blood compartment; 2) VO2 measured at the end of each step, is a linear function of the power output and thus of the time; 3) the appearance rate of lactate into the blood is an exponential function of VO2; 4) the rate of disappearance is a saturable process which can be modelized by Michaelis-Menten kinetics; 5) the volume of distribution of lactate in the blood compartment is a constant during exercise. The parameters used in this model correspond to the integration of several biochemical and physiological phenomenons.

Simple kinetic model for the study of lactate metabolic adaptation to exercise in sportsmen routine evaluation.

The interindividual specific lactate metabolic adaptation to exercise has been studied. A simple kinetic model was used which did not require labelled molecules. An one open compartment model with a first-order release rate constant described the release of lactate from the muscle.

The prevention by creatinol O-phosphate of myocardial lesions evoked by isoprenaline.

Isoprenaline 30 mg/kg has been injected subcutaneously in rats pretreated or not with Creatinol O-phosphate (200 mg/kg intraperitoneously). Isoprenaline-induced cardionecrosis and the associated alterations of the ionic composition of the heart were reduced when Creatinol O-phosphate was injected 4 hr before isoprenaline.

Ionic changes evoked by isoprenaline in rat hearts in vivo and in vitro and their reduction by creatinol O-phosphate.

The action of large doses of catecholamines on the Ca and Mg content of rat heart has been examined both in vivo and in vitro. It was observed that the ionic changes evoked in vitro by isoprenaline 10(-5) mol/l were similar to those evoked in vivo by isoprenaline 30 mg/kg and that both were reduced by N-methyl-N-(beta-hydroxy-ethyl)guanidine O-phosphate (creatinol O-phosphate) in a dose-dependent manner. ED50 was equal to 3 x 10(-7) mol/l.