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We assessed the time course of running mechanical alterations during an 800-m. On a 200-m indoor track, 18 physical education students performed an 800-m self-paced run. Once per lap, ground reaction forces were measured by a 5-m-long force platform system, and used to determine running kinetics/kinematics and spring-mass characteristics. Compared with 100 m (19.4±1.8 km.h-1) running velocity progressively decreased at 300, 500 m but levelled-off at 700 m marks (-5.7±4.6, -10.4±8.3, and -9.1±13.5%, respectively; P 0.05) and leg compression (+2.8±3.9%; P>0.05) remained unchanged, whereas centre of mass vertical displacement (+24.0±7.0%; P 0.05). During an 800 m by physical education students, highest running velocity was achieved early during the run, with a progressive decrease in the second half of the trial. While vertical ground force characteristics remained unchanged, non-specialist runners produced lower peak braking and push-off forces, in turn leading to shorter stride length. Spring-mass model characteristics changed toward lower vertical stiffness values, whereas leg stiffness did not change.

Background Restoring the axis of rotation is often considered crucial to achieving good functional outcomes of total elbow arthroplasty. The objective of this work was to evaluate whether variations in implant positioning correlated with clinical outcomes. Hypothesis Clinical outcomes are dictated by the quality of implant positioning. Material and methods A retrospective review was conducted of data from 25 patients (26 elbows). Function was assessed using a pain score, the Disabilities of the Arm, Shoulder, and Hand (DASH) Score, and the Mayo Elbow Performance Score (MEPS). The patients also underwent a clinical evaluation for measurements of motion range and flexion/extension strength. Position of the humeral and ulnar implants was assessed by computed tomography with reconstruction using OsiriX software. Indices reflecting anterior offset, lateral offset, valgus, height, and rotation were computed by subtracting the ulnar value of each of these variables from the corresponding humeral value. These indices provided a quantitative assessment of whether position errors for the two components had additive effects or, on the contrary, counterbalanced each other. Elbows with prosthetic loosening or extensive epiphyseal destruction were excluded. Results Of the 26 elbows, 5 were excluded. In the remaining 21 elbows, the discrepancy between the humeral and ulnar lateral offsets was significantly associated with pain intensity ( P ≤ 0.05) and the MEPS ( P ≤ 0.05). Anterior position of the ulna relative to the humerus was associated with decreased extension strength ( P ≤ 0.05) and worse results for all functional parameters ( P ≤ 0.05). Discussion In the absence of loosening, positioning errors seem to adversely affect functional outcomes, probably by placing inappropriate stress on the soft tissues. Level of evidence III.

Exercise efficiency is an important determinant of exercise capacity. However, little is known about the physiological factors that can modulate muscle efficiency during exercise. We examined whether improved O2availability would 1) impair mitochondrial efficiency and shift the energy production toward aerobic ATP synthesis and 2) reduce the ATP cost of dynamic contraction owing to an improved neuromuscular efficiency, such that 3) whole body O2cost would remain unchanged. We used31P-magnetic resonance spectroscopy, surface electromyography, and pulmonary O2consumption (V̇o2p) measurements in eight active subjects during 6 min of dynamic knee-extension exercise under different fractions of inspired O2(FiO2, 0.21 in normoxia and 1.0 in hyperoxia). V̇o2p(755 ± 111 ml/min in normoxia and 799 ± 188 ml/min in hyperoxia, P > 0.05) and O2cost ( P > 0.05) were not significantly different between normoxia and hyperoxia. In contrast, the total ATP synthesis rate and the ATP cost of dynamic contraction were significantly lower in hyperoxia than normoxia ( P < 0.05). As a result, the ratio of the rate of oxidative ATP synthesis from the quadriceps to V̇o2pwas lower in hyperoxia than normoxia but did not reach statistical significance (16 ± 3 mM/ml in normoxia and 12 ± 5 mM/ml in hyperoxia, P = 0.07). Together, these findings reveal dynamic and independent regulations of mitochondrial and contractile efficiency as a consequence of O2availability in young active individuals. Furthermore, muscle efficiency appears to be already optimized in normoxia and is unlikely to contribute to the well-established improvement in exercise capacity induced by hyperoxia.

a b s t r a c t Functional near-infrared spectroscopy (fNIRS) is suitable for investigating cerebral oxygenation changes during motor and/or mental tasks. In the present study, we investigated how an additional mental load during a motor task at two submaximal loadings affects the fNIRS-measured brain activation over the right prefrontal cortex (PFC). Fifteen healthy males performed isometric grasping contractions at 15% and 30% of the maximal voluntary contraction (MVC) with or without an additional mental (i.e., arithmetic) task. Mental performance, force variability, fNIRS and subjective perception responses were measured in each condition. The performance of the mental task decreased significantly while the force variability increased significantly at 30% MVC as compared to 15% MVC, suggesting that performance of dual-task required more attentional resources. PFC activity increased significantly as the effort increased from 15% to 30% MVC (p < .001). Although a larger change in the deoxyhemoglobin was observed in dual-task conditions (p = .051), PFC activity did not change significantly as compared to the motor tasks alone. In summary, participants were unable to invest more attention and effort in performing the more difficult levels in order to maintain adequate mental performance.

Resume Objectif Evaluer les effets d’une preparation physique proprioceptive sur l’equilibre statique et dynamique du veliplanchiste. Materiels et methodes Le protocole experimental etait compose de 11 sujets de haut niveau qui ont ete partages en deux groupes (GP = 6 et GT = 5), un groupe proprioception (GP) effectuant une preparation physique proprioceptive sur surface instable et un groupe temoin (GT) conservant une preparation physique « classique ». La periode d’experimentation a dure six semaines et l’equilibre a ete evalue de deux facons en pre- et post-entrainement : equilibre statique a l’aide d’une plateforme de force et equilibre dynamique a l’aide d’un accelerometre. Resultats A l’issue du protocole, seul GP a ameliore significativement son equilibre statique en appui unipodal et son equilibre dynamique. Il en ressort qu’un entrainement proprioceptif decontextualise ameliore significativement la perception de l’equilibre en planche a voile olympique. Ces resultats suggerent la prise en compte de l’importance de developper les habiletes perceptives dans une pratique telle que la voile.

INTRODUCTION: Endurance training elicits tremendous adaptations of the mitochondrial energetic capacity. Yet, the effects of training or physical fitness on mitochondrial efficiency during exercise are still unclear. Accordingly, the purpose of the present study was to examine in vivo the differences in mitochondrial efficiency and ATP cost of contraction during exercise in two groups of adults differing in their aerobic capacity. METHOD: We simultaneously assessed the ATP synthesis and O2 fluxes with P-magnetic resonance spectroscopy and pulmonary gas exchange measurements in seven endurance-trained (ET, V˙O2max: 67 ± 8 mL·min⁻¹·kg⁻¹) and seven recreationally active (RA, V˙O2max: 43 ± 7 mL·min⁻¹·kg⁻¹) subjects during 6 min of dynamic moderate-intensity knee extension. RESULTS: The ATP cost of dynamic contraction was not significantly different between ET and RA (P > 0.05). Similarly, end-exercise O2 consumption was not significantly different between groups (ET: 848 ± 155 mL·min⁻¹ and RA: 760 ± 131 mL·min⁻¹, P > 0.05). During the recovery period, the PCr offset time constant was significantly faster in ET compared with RA (ET: 32 ± 8 s and RA: 43 ± 10 s, P < 0.05), thus indicating an increased mitochondrial capacity for ATP synthesis in the quadriceps of ET. In contrast, the estimated mitochondrial efficiency during exercise was not significantly different (P/O, ET: 2.0 ± 1.0 and RA: 1.8 ± 0.4, P > 0.05). Consequently, the higher mitochondrial capacity for ATP synthesis in ET likely originated from an elevated mitochondrial volume density, mitochondria-specific respiratory capacity, and/or slower postexercise inactivation of oxidative phosphorylation by the parallel activation mechanism. CONCLUSION: Together, these findings reveal that 1) mitochondrial and contractile efficiencies are unaltered by several years of endurance training in young adults, and 2) the training-induced improvement in mitochondrial energetic capacity appears to be independent from changes in mitochondrial coupling.y.

El rendimiento en el servicio puede deteriorarse cuando, debido a la fatiga, la fuerza muscular de los jugadores disminuye afectando a la contribución de los miembros inferiores en la realización de los golpes. El presente estudio examina este efecto e investiga la incidencia del juego de tenis prolongado sobre la velocidad del golpe y las fuerzas verticales máximas durante los primeros servicios (planos y cortados) y los segundos servicios (liftados). Se comentan los resultados y se proporcionan sugerencias para que los jugadores que entrenan puedan manejar los efectos de la fatiga.

To better understand the mechanisms underlying the pulmonary O(2) uptake (V(O(2P))) slow component during high-intensity exercise, we used (31)P magnetic resonance spectroscopy, gas exchange, surface electromyography and near-infrared spectroscopy measurements to examine the potential relationship between the slow components of V(O(2P)) and phosphocreatine (PCr), muscle recruitment and tissue oxygenation in endurance-trained athletes and sedentary subjects. Specifically, six endurance-trained and seven sedentary subjects performed a dynamic high-intensity exercise protocol during 6 min at an exercise intensity corresponding to 35-40% of knee-extensor maximal voluntary contraction. The slow component of V(O(2P))(117 ± 60 ml min(-1), i.e. 20 ± 10% of the total response) was associated with a paradoxical PCr resynthesis in endurance-trained athletes (-0.90 ± 1.27 mm, i.e. -12 ± 16% of the total response). Meanwhile, oxygenated haemoglobin increased throughout the second part of exercise and was significantly higher at the end of exercise compared with the value at 120 s (P < 0.05), whereas the integrated EMG was not significantly changed throughout exercise. In sedentary subjects, a slow component was simultaneously observed for V(O(2P)) and [PCr] time-dependent changes (208 ± 14 ml min(-1), i.e. 38 ± 18% of the total V(O(2P))response, and 1.82 ± 1.39 mm, i.e. 16 ± 13% of the total [PCr] response), but the corresponding absolute or relative amplitudes were not correlated. The integrated EMG was significantly increased throughout exercise in sedentary subjects. Taken together, our results challenge the hypothesis of a mechanistic link between [PCr] and V(O(2P)) slow components and demonstrate that, as a result of a tighter metabolic control and increased O(2) availability, the [PCr] slow component can be minimized in endurance-trained athletes while the V(O(2P)) slow component occurs.

Determining and accurately restoring the flexion-extension axis of the elbow is essential for functional recovery after total elbow arthroplasty (TEA). We evaluated the effect of morphological features of the elbow on variations of alignment of the components at TEA. Morphological and positioning variables were compared by systematic CT scans of 22 elbows in 21 patients after TEA. There were five men and 16 women, and the mean age was 63 years (38 to 80). The mean follow-up was 22 months (11 to 44). The anterior offset and version of the humeral components were significantly affected by the anterior angulation of the humerus (p = 0.052 and p = 0.004, respectively). The anterior offset and version of the ulnar components were strongly significantly affected by the anterior angulation of the ulna (p < 0.001 and p < 0.001). The closer the anterior angulation of the ulna was to the joint, the lower the ulnar anterior offset (p = 0.030) and version of the ulnar component (p = 0.010). The distance from the joint to the varus angulation also affected the lateral offset of the ulnar component (p = 0.046). Anatomical variations at the distal humerus and proximal ulna affect the alignment of the components at TEA. This is explained by abutment of the stems of the components and is particularly severe when there are substantial deformities or the deformities are close to the joint. Cite this article: Bone Joint J 2015;97-B:1539–45.

This study investigated fatigue-induced changes in spring-mass model characteristics during repeated running sprints. Sixteen active subjects performed 12 × 40 m sprints interspersed with 30 s of passive recovery. Vertical and anterior-posterior ground reaction forces were measured at 5-10 m and 30-35 m and used to determine spring-mass model characteristics. Contact (P 0.001), flight (P 0.05) and swing times (P 0.001) together with braking, push-off and total stride durations (P 0.001) lengthened across repetitions. Stride frequency (P 0.001) and push-off forces (P 0.05) decreased with fatigue, whereas stride length (P = 0.06), braking (P = 0.08) and peak vertical forces (P = 0.17) changes approached significance. Center of mass vertical displacement (P 0.001) but not leg compression (P 0.05) increased with time. As a result, vertical stiffness decreased (P 0.001) from the first to the last repetition, whereas leg stiffness changes across sprint trials were not significant (P 0.05). Changes in vertical stiffness were correlated (r 0.7; P 0.001) with changes in stride frequency. When compared to 5-10 m, most of ground reaction force-related parameters were higher (P 0.05) at 30-35 m, whereas contact time, stride frequency, vertical and leg stiffness were lower (P 0.05). Vertical stiffness deteriorates when 40 m run-based sprints are repeated, which alters impact parameters. Maintaining faster stride frequencies through retaining higher vertical stiffness is a prerequisite to improve performance during repeated sprinting.

The relationship between bone mass and muscle mass may be due to the site-specific effects of loading on bone in adults and to lifestyle, nutritional, and hormonal factors. Another hypothesis is that the maintenance with aging of both appendicular muscle and bone mass may be determined by factors independent of all these previous factors, including genetic factors. In 160 healthy men aged 20 to 72years, we recorded femoral neck bone mineral density (FN BMD), relative appendicular skeletal muscle mass [RASM; appendicular skeletal muscle mass (kg)/height (cm)], age, body mass, maximum grip and knee extension strength, lifetime physical activities, calcium intake, tobacco smoking, and serum parathyroid hormone (PTH), estradiol (E2), free testosterone, dehydroepiandrosterone sulphate (DHEAS), insulin-like growth factor (IGF-I), sex hormone-binding globulin (SHBG), calcium, 25(OH) vitamin D, albumin, and creatinine clearance. The correlation between FN BMD and RASM (that includes upper and lower limb muscle mass) was of slightly greater magnitude than that between FN BMD and the relative upper limb muscle mass and between FN BMD and the relative leg muscle mass (r=0.39; p< or =0.001 versus r=0.36; p< or =0.001 and r=0.34; p< or =0.001, respectively). The stepwise multiple linear regression model showed that FN BMD was significantly associated with RASM (15% of FN BMD variance, p

The purpose of the present study was to assess the reliability of metabolic parameters measured using 31P magnetic resonance spectroscopy (31P MRS) during two standardized rest-exercise-recovery protocols. Twelve healthy subjects performed the standardized protocols at two different intensities; i.e., a moderate intensity (MOD) repeated over a two-month period and heavy intensity (HEAVY) repeated over a year's time. Test-retest reliability was analyzed using coefficient of variation (CV), limits of agreement (LOA), and intraclass correlation coefficients (ICC). During exercise and recovery periods, most of the metabolic parameters exhibited a good reliability. The CVs of individual concentration of phosphocreatine ([PCr]), concentration of adenosine diphosphate ([ADP]), and pH values recorded at end of the HEAVY exercise were lower than 15%. The CV calculated for the rate of PCr resynthesis and the maximal oxidative capacity were less than 13% during the HEAVY protocol. Inferred parameters such as oxidative and total adenosine triphosphate (ATP) production rates exhibited a good reliability (ICC ≈ 0.7; CV < 15% during the HEAVY protocol). Our results demonstrated that measurement error using 31P-MRS during a standardized exercise was low and that biological variability accounted for the vast majority of the measurement variability. In addition, the corresponding metabolic measurements can reliably be used for longitudinal studies performed even over a long period of time. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc.

The effects of a priming exercise bout on both muscle energy production and the pattern of muscle fibre recruitment during a subsequent exercise bout are poorly understood. The purpose of the present study was to determine whether a prior exercise bout which is known to increase O(2) supply and to induce a residual acidosis could alter energy cost and muscle fibre recruitment during a subsequent heavy-intensity knee-extension exercise. Fifteen healthy subjects performed two 6 min bouts of heavy exercise separated by a 6 min resting period. Rates of oxidative and anaerobic ATP production, determined with (31)P-magnetic resonance spectroscopy, and breath-by-breath measurements of pulmonary oxygen uptake were obtained simultaneously. Changes in muscle oxygenation and muscle fibre recruitment occurring within the quadriceps were measured using near-infrared spectroscopy and surface electromyography. The priming heavy-intensity exercise increased motor unit recruitment (P < 0.05) in the early part of the subsequent exercise bout but did not alter muscle energy cost. We also observed a reduced deoxygenation time delay, whereas the deoxygenation amplitude was increased (P < 0.01). These changes were associated with an increased oxidative ATP cost after approximately 50 s (P < 0.05) and a slight reduction in the overall anaerobic rate of ATP production (0.11 +/- 0.04 mM min(-1) W(-1) for bout 1 and 0.06 +/- 0.11 mM min(-1) W(-1) for bout 2; P < 0.05). We showed that a priming bout of heavy exercise led to an increased recruitment of motor units in the early part of the second bout of heavy exercise. Considering the increased oxidative cost and the unaltered energy cost, one could suggest that our results illustrate a reduced metabolic strain per fibre.

International audience; We previously showed that transfer of adult myoblasts (MB) into cardiotoxin-damaged muscle improved the properties of reinnervated tibialis anterior muscle of rabbits. However, this cell therapy protocol cannot be applied to humans because of the hazardous effects of the myotoxin. To circumvent this approach, we used the recently developed high-density injection technique to autotransplant cultured cells 1 mm from each other into the tibialis anterior muscle without previous cardiotoxin-induced damage. Two months after transection and immediate suture of the common peroneal nerve, we transferred by this technique two types of precursor cells, MB or cells isolated from the adipose tissue stromal vascular fraction. In contrast to our previous results, muscles studied at 4 months showed no benefits in terms of function or morphology, whatever the transferred cells. These results, together with the results of earlier studies, emphasize the importance of delivery methods and the muscle environment in supporting cell integration into host tissues.

L'introduction recente des nouveaux systemes d'ancrages intra-osseux appeles mini-vis, permettant une mise en charge immediate, a revolutionne l'approche clinique et biomecanique de l'ancrage en orthodontie. L'insertion trans-gingivale par un tournevis manuel se fait aisement et le plus frequemment sans avant-trou. L'objectif de cette etude experimentale est de demontrer que la realisation d'un avant-trou limite les contraintes intra-osseuses lors du vissage, ceci ayant des consequences a court terme sur la stabilite primaire des mini-vis et a long terme sur leur maintien. Materiels et methodes : deux mini-vis auto-forantes et auto-taraudantes Aarhus Medicon de diametres 1,6 et 1,3 mm sont vissees avec un tournevis manuel, sans puis avec un avant-trou, dans une lamelle d'os cortical fixee sur un capteur mesurant les forces et le couple. Resultats : la realisation d'un avant-trou dans l'os cortical diminue significativement la force verticale maximale (FVM) au debut du vissage (p : le vissage sans avant-trou conduit au delabrement de la couche osseuse superficielle par l'apparition de microfractures limitant les possibilites de blocage des mini-vis.

Sports characterized by little or moderate weight bearing or impact have a low osteogenic effect. However, the action of such sports on bone turnover remains unclear. The objective of this study was to determine the effect on bone remodelling of physical activities that induce moderate external loading on the skeleton. Thirty-eight male athletes aged 18-39 years (cyclists, n = 11; swimmers, n = 13; triathletes, n = 14) and 10 age-matched sedentary controls aged 22-35 years participated in the study. The study combined measurement of bone mineral density by dual-energy X-ray absorptiometry and bone turnover assessment from specific biochemical markers: serum bone-specific alkaline phosphatase, osteocalcin, urinary type I collagen C-telopeptide and calcium. Compared with the controls and swimmers, adjusted bone mineral density was higher (P < 0.05) in triathletes at the total proximal femur and lower limbs. No differences in bone mineral density were found between cyclists, swimmers and controls. Compared with controls, osteocalcin was higher (P < 0.05) in triathletes and swimmers and urinary type I collagen C-telopeptide was higher in swimmers only. Serum bone-specific alkaline phosphatase was lower (P < 0.05) in cyclists than in all other groups. In conclusion, an osteogenic effect was found only in triathletes, mainly at bone sites under high mechanical stress. Bone turnover differed in athletes compared with controls, suggesting that bone turnover may be sport-practice dependent. Despite some encouraging observations, it was not possible to show that changes in the bone remodelling process were sport-discipline dependent.

International audience; The regenerating skeletal muscle environment is capable of inducing uncommitted progenitors to terminally differentiate. The aim of this work was to determine whether adipose tissue-derived stromal cells were able to participate in muscle regeneration and to characterize the effect on muscle mass and functional capacities after transplantation of these cells. Adipose tissue stromal cells labeled with Adv cyto LacZ from 3-day-old primary cultures (SVF1) were autotransplanted into damaged tibialis anterior muscles. Fifteen days later, beta-glactosidase staining of regenerated fibers was detected, showing participation of these cells in muscle regeneration. Two months after SVF1 cell transfer, muscles were heavier, showed a significantly larger fiber section area, and developed a significantly higher maximal force compared with damaged control muscles. These results are similar to those previously obtained after satellite cell transplantation. However, SVF1 transfer also generated a small amount of adipose tissue localized along the needle course. To minimize these adipose contaminants, we transferred cells from 7-day-old secondary cultures of the SVF1, containing only a small proportion of already engaged preadipocytes (SVF2). Under these conditions, no adipose tissue was observed in regenerated muscle but there was also no effect on muscle performances compared with damaged control muscles. This result provides further evidence for the existence of progenitor cells in the stromal fraction of freshly isolated adipose tissue cells, which, under our conditions, keep some of their pluripotent properties in primary cultures.

Skeletal muscle demonstrates a force deficit after repair of injured peripheral nerves. We tested the hypothesis that transplantation of satellite cells into reinnervated rabbit tibialis anterior (TA) muscles improves their properties. Adult rabbits underwent transection and immediate suture of the common peroneal nerve. In order to provide an environment favorable for cell transplantation, TA were then made to degenerate by cardiotoxin injection, either immediately or after a 2-month delay, which is sufficient for muscle reinnervation. In both cases, the injured TA were transplanted with cultured satellite cells 5 days after induction of muscle degeneration. When cells were transferred immediately after nerve repair, drastic morphological and functional muscle alterations were observed. However, when the muscles were allowed to become reinnervated before cell transplantation, muscles were heavier and developed a significantly higher maximal force compared to denervated-reinnervated muscles. Thus, application of the cell therapy protocol improved properties of denervated muscles only when they were allowed to become innervated. These results, which represent the application of cell therapy to improve force recovery of reinnervated muscles, will be of significant interest in certain clinical contexts, particularly after immediate or delayed muscle reinnervation.

The aim of this study was to examine the forces and torque developed during root canal preparation with the balanced force technique using a recently described force-analyser device. A tooth was placed in a holder within the Endograph and forces and torques exerted were recorded. These parameters, which can be studied during preparation (on-line) or stored and examinated subsequently (off-line) generated endograms, which showed the forces generated with time. In addition, the endograms of preparations performed by students and endodontists, as well as deliberately induced failures in preparation technique (broken instruments), were compared. The values for the forces and torques depended on the size of the instruments and were related to the phase of the preparation. For the endodontists, the vertical and horizontal forces varied, respectively, from 0.08 +/- 0.01 kg for a size 15 to 0.65 +/- 0.10 kg for a size 45, and from 0.01 +/- 0.005 kg for a size 15 to 0.4 +/- 0.1 kg for a size 40. The torque varied from 0.08 +/- 1 kg mm-1 for a size 15 to 1.6 +/- 0.4 kg mm-1 for a size 45. With the endograms used as a reference, the relation between the developed vertical forces and the torque became more similar between the groups of endodontists and students. The Endograph provides a new approach to the analysis of preparation technique because it depicts the relationships between the different parameters of the preparation.

The ability of an obturation technique to fill the root canal system tridimensionally depends partially on the timing and intensity of force applications. The aim of this study was to use the Endographe to analyze the forces and wedging effects developed in the root canal using a new obturation technique: System B. This system uses a heat plugger that simultaneously heats and pushes gutta-percha. The plugger was used to soften and move the gutta-percha apically during the down-pack stage. Two different methods, however, were used to withdraw the plugger from the compacted gutta-percha. One used the burst heat method, and the other was cold withdrawal. Five endodontists performed 50 obturations of prepared extracted teeth and 50 obturations of the "wedging effect" holder of the Endographe. The practitioner-obturation assignment was randomized. For each obturation the biggest plugger possible in relationship to the shape of the canal was chosen. For the obturation of the special holder the same tip was chosen. Endogrammes showed the force application and wedging effect sequences. The mean values for the vertical and horizontal forces and the wedging effect were, respectively, 16 +/- 2 N, 5 +/- 1 N, and 9 +/- 1 N. These results suggest that System B is one of the best techniques in terms of the developed vertical forces (low values) and the resulting wedging effect (high values) in relationship to the plasticity of the gutta-percha. The Endogrammes provide a new approach to the analysis of obturation techniques and a means to demonstrate correct and optimal manipulation of the new System B plugger.

The forces and torque applied during the balanced-force motion technique of root canal preparation were measured with the Endographe. Five endodontists prepared 100 extracted teeth, all straight and with similar root anatomy. The assignment of "tooth practitioner" was randomized. Gates-Glidden burs were used to prepare the coronal part and ensure apical patency for the other instruments. The balanced-force technique with conventional instruments was then used for the body of the canal. For the apical part either the watch-winding pull with conventional instruments or the reversed balanced-force technique with manual GT files was used. The Endogrammes were similar among endodontists for the coronal phase and showed low vertical forces in contrast with the lateral forces. For the body the Endogrammes were highly specific and described perfectly the different steps of instrument work. For the apical part the Endogrammes of the conventional instruments showed a lack of vertical forces. The Endogrammes of the manual GT files showed that torque was applied inversely to that of the conventional instruments. Force application was similar. In conclusion these objective data indicate the correct way of working with the different techniques incorporated into the balanced-force motion technique.

Perennou DA, Leblond C, Amblard B, Mi- callef JP, Herisson C, Pelissier JY. Transcutaneous electric nerve stimulation reduces neglect-related postural instability after stroke. Arch Phys Med Rehabil 2001;82:440-8. Objective: To test the existence of a neglect-related com- ponent of postural imbalance in some stroke patients to deter- mine whether neglect patients (1) show worse postural control compared with nonneglect patients and healthy subjects and (2) have latent postural capacities that could be unmasked by an appropriate somatosensory manipulation. Design: Intervention study with and without transcutaneous electric nerve stimulation (TENS). Setting: Rehabilitation center research laboratory. Participants: Twenty-two stroke patients (mean age, 58.3 2.5yr; average days since stroke, 83.2d) and 14 age-matched healthy subjects. Stroke patients were subdivided into 3 groups: 6 with spatial neglect and 16 without (8 with left lesion, 8 with right lesion). Interventions: All participants were subjected to a dynamic balance task, performed while sitting for 8 seconds on a later- ally rocking platform. Seated on this mobile support, they were asked to maintain actively an erect posture, sitting as still as possible. In patients, TENS was applied on the contralesional side of the neck during the postural task. An effective stimu- lation (intensity corresponding to the threshold of perception, TENS) was compared with a placebo stimulation (.01 threshold of perception, TENS). Main Outcome Measures: Postural performance in each trial was monitored by using 2 criteria: the number of aborted trials caused by loss of balance, and the angular dispersion of the support oscillations in roll. The latter criterion, which increased with body instability, was defined as 2 standard deviations of the angular distribution. Results: Patients showing neglect displayed pronounced postural instability compared with other patients and controls. Although dramatic postural instability in the neglect patients was spectacularly and systematically reduced with TENS, no effect was observed in patients without neglect.

Aim The aim of this study was to locate the areas of direct instrument contact with dentine in the root canal system during rotary preparation and to analyse the relationship between these areas and the vertical forces and torque developed during the preparation. Methodology Canal preparations were performed by endodontists either with the step-back (SB) or the crown-down (CD) technique. In order to locate the areas of contact, the instruments were coated with two layers of gold by electro-deposition. They were photographed before and after use, and a coding system, based on mm from the instrument tip, was devised to designate areas of gold removal or instrument wear due to friction. To standarise the conditions of instrument manipulation, the teeth were fixed in the Endographe holder, and this device was used to measure vertical forces and torque. Results The results showed that the first series of instruments used for the CD technique (taper 0.06) left 2 ± 1 mm of the tip with the gold intact, indicating that these instruments and this step of the CD technique are the safest part of the preparation. For all other instruments (taper 0.04 series), the areas of gold removal involved the 3 mm around the tip and this finding was independent of the order of instrument use and preparation technique (SB or CD). The differences between the two techniques were significant in terms of the mean area of decolouration and the mean force and torque values. For the SB and CD techniques, the contact areas were, respectively, 10 ± 3 and 7 ± 2 mm. The forces and torque values were correspondingly higher for SB vs. CD: the mean values were, respectively, 19 and 21 N for vertical forces and 16 105 and 13 105 Nm for torque. Conclusions The recorded torque values and the location on the instruments of the areas of contact with dentine during this development of torque ie at or near the tip, indicate that great caution should be used with the rotary technique, particularly with the taper 0.04 instruments, regardless of preparation technique.

The aim of this study was to define the "wedging effect" created by the intracanal forces developed during obturations and to measure it using a force analyzer device. In endodontics, the wedging effect is the result of, for example, a plugger pushing gutta-percha into a canal: the plugger functions much as the rod of a hydraulic jack and the vertical force applied by this rod induces in the cylinder (i.e. the canal) a hydrostatic pressure that is relatively equal in all directions. It is these forces resulting from the hydrostatic pressure that have been labeled the wedging effect. The original device, the Endographe, had a monobloc cupule for measuring the external vertical and horizontal forces developed by a practitioner, but it was unable to measure the intracanal forces. With a new cupule composed of two independent parts joined under pressure, the wedging effect was recorded and analyzed. Two obturation methods, warm vertical compaction and lateral condensation, were performed by endodontists. The forces were depicted by Endogrammes as a function of time. For all of the forces developed during the two techniques, the mean values showed a nonsignificant difference between the different practitioners. The use of graphs provides a new approach to the analysis of intracanal forces as they develop our time and permits the comparison of different obturation techniques.

BACKGROUND In addition to the respiratory limitation in patients with chronic obstructive pulmonary disease (COPD), skeletal muscle abnormalities may occur and contribute to the exercise intolerance. This study assessed the ability of the skeletal muscle of patients with COPD to adapt to individualized exercise training at the gas exchange threshold (GET) METHODS: Fourteen patients (8 in a training group and 6 controls) performed the following exercise tests before and after a 3-week training period: an incremental exercise test, maximal voluntary contraction of the quadriceps, and three endurance tests consisting of dynamic contractions of the quadriceps until exhaustion. These endurance tests, characterized by three different power outputs, were used to determine muscle limit times and critical power. RESULTS The results showed that training increased exercise tolerance (+11% for symptom limited peak oxygen consumption (VO2 sl], P < 0.05), maximum voluntary contraction (+8%, P < 0.05), limit times (from +45% to +161%, P < 0.05) and critical power (+39%, P < 0.05). CONCLUSIONS These findings indicate greater muscle strength and endurance after training in COPD patients and suggest better muscular recruitment and improved oxidative capacity in the exercising muscles. The sharp differences in the magnitude of VO2 sl and limit times suggest that the kinetics of peripheral and central changes in response to training are different. In conclusion, peripheral muscle performance can be increased rapidly in response to an individualized training program at the GET in COPD patients.

The aim of this work was to measure and analyze the forces applied by endodontists during an obturation. This was achieved by devising a system of force transducers linked to acquisition software. The software allowed us to study the obturation forces in real time or to store them. In this initial study, the forces developed by endodontists and students during a warm vertical compaction were analyzed. The vertical and frontware backware horizontal direction forces were first stored. Graphs of the compaction forces were then generated, permitting the analysis of the obturation method. Indeed, two cases of obturation failure were analyzed from these graphs. The mean values for the vertical forces applied by the endodontists and students were, respectively, 2.5 +/- 0.4 kg and 1.9 +/- 0.9 kg; the mean values for the lateral forces were, respectively, 0.85 +/- 0.2 kg and 1.4 +/- 0.6 kg. This device permits the analysis of compaction forces and may thus be highly useful in obtaining improvements in obturation techniques.

Summary The effects of rice (compared to bread and aspartame) on submaximal exercise performance were investigated. A first study included ten healthy subjects who performed three sessions in random order. After a 150 minute low intensity cycling session in fasting conditions to slightly reduce blood glucose, they were fed either aspartame (40 mg) given in water, rice (65 g raw rice, ie, 50 g carbohydrate) or bread (100 g, ie, 50 g carbohydrate). Subjects then exercised at 85% of their theoretical maximal heart rate (ie, 75% VO 2max ) until exhaustion. A second study included six healthy volunteers who performed three sessions in random order with either aspartame, rice or bread under the same protocol without a previous fatiguing exercise session. The chemical composition of bread compared to rice revealed mainly significant ( P P P P P P

Resume Un bilan endocrinien approfondi, incluant une epreuve d'effort submaximale de 15 minutes, a ete realise a l'automne (debut de saison d'entrainement) chez 30 gymnastes de classe sportive (18 filles et 12 garcons, âge : 9–15 ans), afin d'etudier leurs caracteristiques metaboliques et hormonales et de proposer un suivi biologique adapte a cette population. Un suivi longitudinal a ete possible chez 21 d'entre eux, explores une seconde fois au printemps, apres 6 mois d'entrainement gymnique. La taille et le poids etaient comparables entre les gymnastes et un groupe de 11 temoins apparies, et la croissance se poursuivait de facon normale pendant l'entrainement. Les gymnastes de sexe masculin avaient une moindre adiposite que les temoins ( p ). Le pourcentage de masse grasse augmentait significativement chez les filles pendant l'entrainement ( p ). Les gymnastes se distinguaient par une plus grande force de prehension ( p ). Les variations de leur capacite aerobie (W 170 ) pendant le suivi etaient negativement correlees a celles du score de surentrainement ( r = − 0,604, p ). Sur le plan hormonal, il existait une augmentation significative des concentrations d'estradiol ( p ) et de testosterone ( p ) entre les deux visites chez les gymnastes en cours de puberte. Les concentrations plasmatiques basales de GH etaient plus faibles chez les gymnastes que chez les temoins en debut de saison ( p ), mais augmentait significativement au printemps ( p ). La reponse de la GH a l'exercice tendait a etre plus elevee chez les gymnastes mais n'etait pas influencee par la periode d'entrainement. L'IGF-I et l'IGFBP-1 etaient identiques dans les deux groupes. L'IGFBP-3 etait abaissee de 25 % chez les gymnastes en debut de saison ( p ). L'IGF-I s'abaissait de 24 % au printemps ( p ). Chez les gymnastes en cours de puberte, l'IGFBP-1 ( p ) et l'IGFBP-3 ( p ) s'abaissaient egalement pendant la saison gymnique. L'IGFBP-3 chez les gymnastes etait correle a la force de prehension sur l'ensemble des deux visites ( r = 0,550, p ). L'axe corticotrope presentait plusieurs particularites : la reponse de l'ACTH a l'exercice etait significativement plus faible chez les gymnastes ( p s 0,01 ). Il en etait de meme pour le cortisol plasmatique ( p ). Au contraire, les valeurs basales de β-endorphine etaient trois fois plus elevee ( p s 0,01 ) chez les sportifs et restaient significativement superieures pendant l'exercice. Ceci conduisait a une alteration tres importante du rapport molaire entre ACTH et β-endorphine, tres abaisse chez les gymnastes au repos comme a l'exercice. Les valeurs de creatine kinase et de myosine plasmatiques etaient significativement plus elevees chez les gymnastes ( p p s 0,05 respectivement). La troponine I squelettique, mesuree uniquement chez les gymnastes avait augmente de 240 % pendant le suivi ( p ). Les taux de ferritine et de zinc serique etaient plus faibles chez les sujets sportifs. Cette etude montre que l'entrainement gymnique pratique par des adolescents a un niveau national est bien tolere en ce qui concerne les parametres physiques de croissance et de maturation sexuelle. En revanche, il existe chez ces jeunes sportifs des modifications tres nettes des fonctions somatotropes et opio-adrenocorticotrope et d'autres marqueurs peu habituels qui pourraient avoir un interet en medecine sportive.

Resume Onze cyclistes de niveau regional presentent apres 3 mois d'entrainement intense (17 heures par semaine) une augmentation de 14 % de leur capacite de travail aerobie et de 12 % de leur force isometrique de prehension, sans amelioration de leur sensibilite a l'insuline ni de leur efficience glucidique. Ces derniers parametres etaient en effet optimaux au prealable. Ainsi, une intensification de l'entrainement de sujets deja bien entraines ameliore encore l'aptitude physique sans amplifier davantage l'utilisation musculaire de glucose.

International audience; BACKGROUND: To investigate the impact of a short-term multimodal rehabilitation program for patients with low back pain (LBP) on trunk muscle reflex responses and feedforward activation induced by postural perturbations. METHODS: Case series (uncontrolled longitudinal study). Thirty chronic patients with LBP (21 women and 19 men, mean age 42.6 +/- 8.6 years, mean weight 73 +/- 14 kg, mean height 174 +/- 10 cm) were included. The intervention consisted in a 5-day program including therapeutic education sessions (360 min), supervised abdominal and back muscle strength exercises (240 min), general aerobic training (150 min), stretching (150 min), postural education (150 min) and aqua therapy (150 min). Feedforward activation level and reflex amplitude determined by surface electromyographic activity triggered by postural perturbations were recorded from abdominal and paraspinal muscles in unexpected and expected conditions. Subjects were tested before, just after and again one month after the rehabilitation program. RESULTS: No main intervention effect was found on feedforward activation levels and reflex amplitudes underlining the absence of changes in the way patients with LBP reacted across perturbation conditions. However, we observed a shift in the behavioral strategy between conditions, in fact feedforward activation (similar in both conditions before the program) decreased in the unexpected condition after the program, whereas reflex amplitudes became similar in both conditions. CONCLUSIONS: The results suggest that a short-term rehabilitation program modifies trunk behavioral strategies during postural perturbations. These results can be useful to clinicians for explaining to patients how to adapt to daily life activities before and after rehabilitation.

The purpose was to propose an alternative data analysis for functional near-infrared spectroscopy (fNIRS)-derived hemodynamics as a function of cortical activation changes. We evaluated hemodynamic responses from the prefrontal cortex region while 38 participants performed a cognitive task. The task consisted of an arithmetic calculation with three levels of complexity (i.e., easy, medium and difficult). These task-dependent hemodynamic responses were analyzed by the slope method (i.e. using a linear regression through the cognitive task) and were compared with the corresponding responses obtained with a traditional approach of the amplitude method. Subjective scales of task loading (assessed by DP15 and NASA-TLX) and behavioral outcomes (performance and reaction time) were also recorded in response to the task complexity. Results revealed that the proposed slope method allowed a better discrimination in terms of cortical activation among all levels of mental workload. There was no significant increase in cortical activation between the medium and difficult levels ( p = .30; d = 0.09) with the amplitude method while the slope coefficient was sensitive to the different levels ( p d = 0.32). These preliminary results from a large sample size demonstrated that the slope method appears suitable for discriminating the changes in cortical activation with respect to the mental workload. Relevance to industry In this work, we proposed an optimum way of quantifying the mental workload of participants in terms of fNIRS-derived cerebral hemodynamic responses.

Striated muscle atrophy and degeneration, which increase with the delay of denervation, represent two of the main causes for poor recovery following delayed nerve repair. The present study, using a rat model, tests the hypothesis that an adjunction of small, free, nonvascularised muscle grafts of contralateral healthy triceps into a chronically denervated triceps improves muscle regeneration and recovery following sciatic nerve repair delayed for 3 months. Our experiments seem to show a relative increase in mechanical properties in animals in which free muscle graft into the triceps was performed 3 weeks following nerve repair. The improvement of the regenerative process of muscles which have suffered a long period of denervation should be considered as an additional therapeutic procedure in the case of late nerve repair. Atrophie et degenerescence du muscle strie squelettique, dont l'importance croit avec la duree de denervation, representent deux des facteurs limitants principaux en cas de reparation nerveuse tardive. Cette etude analyse les effets d'une autogreffe musculaire nonvascularisee provenant du triceps sain controlateral, implantee au niveau d'un muscle triceps reinnerve tardivement par suture du nerf tibial 3 mois apres sa section. D'apres notre experimentation, l'adjonction d'une autogreffe musculaire nonvascularisee au triceps reinnerve tardivement semble en ameliorer les proprietes fonctionnelles, si cette autogreffe est effectuee 3 semaines apres la reparation du nerf tibial. L'amelioration du processus de regeneration d'un muscle ayant subi une longue periode de denervation semble representer un appoint dans la prise en charge des lesions nerveuses vues tardivement. © 1997 Wiley-Liss, Inc. MICROSURGERY 17:545–550 1996

Resume L'axe hormone de croissance - somatomedines est un des systemes anabolisants essentiels de l'organisme et s'est avere en relation avec le niveau d' activite physique et de performance aerobie. Nous avons etudie les relations entre la somatomedine C/IGFI serique, ses proteines porteuses IGFBPI et IGFBP3 et la force musculaire chez 37 gymnastes adolescents soumis depuis 1 a 5 ans a 18–20 heures d'entrainement intensif hebdomadaire ( 13 garcons, 24 filles, âge 10–15 ans, taille 1,55 ± 0,01 m, poids 45,1 ± 1,4 kg). Le bilan nutritionnel montre que ces gymnastes consommaient environ 2 670 ± 380 kCal journalieres, se reparfissant de la sorte: 16% (+2) de protides, 39% (+3) de lipides et 45 % (+1) de glucides. Somatomedine C/IGFI et IGFBP3 restent dans l'enveloppe des valeurs normales, tandis que les valeurs d'IGFBPI semblent se retrouver au dessous de cette enveloppe. Au cours de la puberte l'IGFBPI decroIt ( p r = 0.489 p r =0,3451 p r =−0,431 p r = 0,698 p r = −0,595 p r =−0,553 p r = −0,765 p

Resume Objectifs determiner les parametres temporospatiaux et le profil dynamique de pression plantaire lors de la marche chez des patients hemiplegiques marchant a vitesse normale; etudier la valeur de cette technique pour evaluer la marche de l'hemiplegique. Materiel et methodes 23 hemiplegiques (17 hommes, six femmes, de 23 a 74 ans) ont ete inclus dans l'etude. L'hemiplegie etait d'origine vasculaire, survenue dans un delai inferieur a 2 ans; pour etre inclus le sujet devait etre capable de marcher plus de 50 m sur terrain plat et ne presenter aucune autre deficience susceptible d'influer sur sa qualite de marche. En fonction des scores a l'index de Barthel, les sujets ont ete classes en deux groupes, le groupe A (score de 95 a 100) et le groupe B (score de 75 a 95). Durant le test, on demandait a tous les sujets de marcher a allure normale le long d'un couloir de 30 m de long et de 1,6 m de large, le sujet portant les semelles barosensibles incluses dans la chaussure; le temps d'analyse etait de 25 secondes. Les resultats etaient compares avec ceux d'un groupe controle de 20 sujets sains. Trois essais ont ete realises pour chaque sujet. Resultats parametres temporaux: vitesse de marche, longueur de pas, cadence, sont des parametres significativement diminues par rapport au groupe controle (p Discussion l'exploration baropodometrique de la marche de l'hemiplegique parait une technique sensible, efficace et de mise en ˦uvre facile pour evaluer la marche de l'hemiplegique. Le deficit moteur et la spasticite conduisent l'hemiplegique a adapter sa strategie de marche et surtout le comportement moteur de son membre sain dans le but d'augmenter la stabilite et l'efficacite de sa marche au prix d'une perte de la symetrie du pas.

Resume Introduction. – Le rugby est une discipline demandant a la fois des qualites de force mais aussi une aptitude aerobie elevee afin de pouvoir reproduire des efforts intenses sur 2 × 40 min. Synthese des faits. – Quatorze rugbymen ont realise un test de course progressif maximal puis, 2 sequences de 40 min, respectivement a 60 et 80 % de FC max , entrecoupees de poussees sur un joug equipe de capteurs de force. Lors de l’exercice a 80 % FC max , la force moyenne de poussee (1466 ± 244 N) etait plus faible ( p max (1523 ± 266 N). Conclusion. – Les qualites de force specifique sont directement affectees par l’intensite de course d’ou l’interet d’optimiser le potentiel aerobie notamment pour les joueurs de la premiere ligne directement concernes par le combat.

The aim of this study was to examine the magnitude and the origin of neuromuscular fatigue induced by half-squat static whole-body vibration (WBV) exercise, and to compare it to a non-WBV condition. Nine healthy volunteers completed two fatiguing protocols (WBV and non-WBV, randomly presented) consisting of five 1-min bouts of static half-squat exercise with a load corresponding to 50 % of their individual body mass. Neuromuscular fatigue of knee and ankle muscles was investigated before and immediately after each fatiguing protocol. The main outcomes were maximal voluntary contraction (MVC) torque, voluntary activation, and doublet peak torque. Knee extensor MVC torque decreased significantly (P

Since most stresses are known to modify blood rheology, we studied .hemorheologlcal parameters during labor and delivery, which are highly stressful physiological events. In 80 pregnant women we measured blood viscosity, plasma viscosity and red blood cell (RBe) aggregation during labor (b~fore and atter 4 cm diratation), during delivery, and during ~elivery of the placenta. Blood viscosity at both native and corrected ,",ematocrlt increases (p < 0.001) with a peak during delivery followed by a rapid normalization during delivery of the placenta (p < 0.01). Hematocrit and plasma viscosity do not change during labor and delivery, but decrease during delivery of the placenta. RBe aggregation (physrologically increased during late pregnancy) acutely returns to normal during delivery (p

Serum zinc was measured in 20 adolescent gymnasts (9 boys, 11 girls, age 12-15 yr) explored for detecting possible adverse effects of intense training on pubertal maturation and growth. They had low serum zinc (0.599 +/- 0.026 mg/L) when compared to matched control sedentary children (n = 118 mean 0.81 +/- 0.014 p0.001). Girls had lower zinc than boys (0.557 +/- 0.023 vs 0.651 +/- 0.044 p0.001). Zinc was correlated to isometric adductor strength (r = 0.468 p0.05). Children with serum zinc0.6 mg/L had lower insulin-like growth factor binding protein 3 than others (2.326 +/- 0.264 vs 2.699 +/- 0.12 p0.01). Thus, zinc is lowered in trained adolescent gymnasts and even lower in females. This reduction could play some role in abnormalities of puberty, growth, or muscular performance.

To better understand the mechanisms underlying the pulmonary O(2) uptake (V(O(2P))) slow component during high-intensity exercise, we used (31)P magnetic resonance spectroscopy, gas exchange, surface electromyography and near-infrared spectroscopy measurements to examine the potential relationship between the slow components of V(O(2P)) and phosphocreatine (PCr), muscle recruitment and tissue oxygenation in endurance-trained athletes and sedentary subjects. Specifically, six endurance-trained and seven sedentary subjects performed a dynamic high-intensity exercise protocol during 6 min at an exercise intensity corresponding to 35-40% of knee-extensor maximal voluntary contraction. The slow component of V(O(2P))(117 ± 60 ml min(-1), i.e. 20 ± 10% of the total response) was associated with a paradoxical PCr resynthesis in endurance-trained athletes (-0.90 ± 1.27 mm, i.e. -12 ± 16% of the total response). Meanwhile, oxygenated haemoglobin increased throughout the second part of exercise and was significantly higher at the end of exercise compared with the value at 120 s (P0.05), whereas the integrated EMG was not significantly changed throughout exercise. In sedentary subjects, a slow component was simultaneously observed for V(O(2P)) and [PCr] time-dependent changes (208 ± 14 ml min(-1), i.e. 38 ± 18% of the total V(O(2P))response, and 1.82 ± 1.39 mm, i.e. 16 ± 13% of the total [PCr] response), but the corresponding absolute or relative amplitudes were not correlated. The integrated EMG was significantly increased throughout exercise in sedentary subjects. Taken together, our results challenge the hypothesis of a mechanistic link between [PCr] and V(O(2P)) slow components and demonstrate that, as a result of a tighter metabolic control and increased O(2) availability, the [PCr] slow component can be minimized in endurance-trained athletes while the V(O(2P)) slow component occurs.

Bringard, Aurelien Layec, Gwenael Micallef, Jean-Paul Bendahan, David Perrey, Stephane Research Support, Non-U.S. Gov't Validation Studies Netherlands Respiratory physiology & neurobiology Respir Physiol Neurobiol. 2012 Jun 15;182(1):37-46. doi: 10.1016/j.resp.2012.02.005. Epub 2012 Feb 17.; Although simultaneous measurements of pulmonary oxygen uptake (VO2) and Phosphorus-31 magnetic resonance spectroscopy ((31)P MRS) is attractive to investigate muscular metabolism during exercise, the superconducting magnet requires the design of specific gas exchange analyser (GEA). Thus, this study aimed to assess the validity of a commercial GEA system (ZAN600) compatible with (31)P MRS measurements. Using nonmagnetic pneumotachograph and prolonged sampling line (from 2m, control condition, to 6.5m) did not alter the proper synchronisation between flow and gas concentration signals. Also, end-expiratory fraction of O2 (FETO2) and CO(2) (FETCO2), and finally the values of steady-state ventilation (V(E)), carbon dioxide production (VCO2) and VO2 kinetics during moderate knee-extension exercise were not significantly different between 2m and 6.5m conditions and between 6.5m condition inside and outside the magnet. These results showed that a prolonged sampling line used inside the superconducting magnet did not affect the accuracy of VO2 measurements of a commercial GEA system; the latter appears suitable for simultaneous measurements of VO2 and (31)P MRS.

We investigated whether the spontaneous transition between walking and running during moving with increasing speed corresponds to the speed at which walking becomes less economical than running. Seven active male subjects [mean age, 23.7 (SEM 0.7) years, mean maximal oxygen uptake ( $$\dot V{\text{O}}_{2\max } $$ ), 57.5 (SEM 3.3) ml·kg −1·min −1, mean ventilatory threshold (VTh), 37.5 (SEM 3) ml·kg −1 ·min −1] participated in this study. Each subject performed four exercise tests separated by 1-week intervals: test 1, $$\dot V{\text{O}}_{2\max } $$ and VTh were determined; test 2, the speed at which the transition between walking and running spontaneously occurs (ST) during increasing speed (increases of 0.5 km·h −1 every 4 min from 5 km·h −1) was determined; test 3, the subjects were constrained to walk for 4 min at ST, at ST ± 0.5 km·h −1 and at ST ± 1 km·h −1; and test 4, the subjects were constrained to run for 4 min at ST, at ST±0.5 km·-h −1 and at ST±1 km·h −1. During exercise, oxygen uptake ( $$\dot V{\text{O}}_2 $$ ), heart rate (HR), ventilation ( $$\dot V_{\text{E}} $$ ), ventilatory equivalents for oxygen and carbon dioxide (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmOvayaaca% WaaSbaaSqaaiaabweaaeqaaOGaai4laiqadAfagaGaamaaBaaaleaa% caqGYaaabeaakiaacYcacaqGGaGaaeiiaiqadAfagaGaamaaBaaale% aacaqGfbaabeaakiaac+caceWGwbGbaiaacaqGdbGaae4tamaaBaaa% leaacaaIYaaabeaaaaa!4240!\[\dot V_{\text{E}} /\dot V_{\text{2}} ,{\text{ }}\dot V_{\text{E}} /\dot V{\text{CO}}_2 \]), respiratory exchange ratio (R), stride length (SL), and stride frequency (SF) were measured. The results showed that: ST occurred at 2.16 (SEM 0.04) m·s −1; $$\dot V{\text{O}}_2 $$ , HR and speed at ST were significantly lower than the values measured at VTh (P< 0.001, P< 0.001 and P< 0.05, respectively); $$\dot V{\text{O}}_2 $$ changed significantly with speed (P< 0.001) but was greater during running than walking below ST (ST minus 1 km·h −1, P< 0.001; ST minus 0.5 km·h −1, P< 0.05) with the converse above ST (ST.plus 1 km·h −1, P

Resume Nous avons etudie les oscillations posturales de 184 garcons âges de 11 a 17 ans en fonction des cinq stades de maturation pubertaires de la classification de Tanner (1962) . Le but de ce travail est d'evaluer l'influence de la maturation dans la maitrise de l'equilibre chez l'adolescent. Les mouvements regulateurs posturaux ont ete recueillis, dans les plans frontal (X) et sagittal (Y), pendant 10 secondes en appui bipodal avec les yeux ouverts (indice yo) puis avec les yeux fermes (indice yf). Nous avons utilise une plate-forme de forces couplee a une table X/Y pour enregistrer et visualiser les deplacements de la projection du centre de gravite du corps, sur un plan horizontal. Une analyse de variance completee par un Newman-Keuls a montre une baisse significative des deplacements maximaux droite-gauche ( P P = 0,02) lors de l'experimentation yeux ouverts en fonction de la croissance. Il s'en suit une diminution sensible ( P = 0,01) de la surface d'equilibration (S yo ). Les deplacements droite-gauche sont significativement ( P yf , y yf ) ainsi que de la surface d'equilibration (S yf ). L'indice de Romberg (1 = 100(S yf /S yo ) ne montra pas de variation significative en fonction des stades pubertaires. Le rapport R yf (X yf /Y yf ) yeux fermes est inferieur au rapport R yo yeux ouverts ( P

Increases in blood viscosity during various kinds of strenuous exercise have been repeatedly described. In this study we investigated the rheologic effects of long duration low intensity exercise. Twelve volunteers (21-39 yr, 6 men and 6 women), after overnight fasting, performed a 60 min exercise on cycloergometer at 55% of the theoretical maximal heart rate. After an early increase at the 10th minute (p < 0.001), blood lactate dicreases (p < 0.02) and returns to normal. During exercise there is an increase in plasma viscosity (p < 0.001) and hematocrit (p < 0.05) at the 10th minute. Red cell rigidity index "Tk" increases at the 20 th minute (p