Extension du modèle puissance–temps limite pour estimer la production d’énergie aérobie et anaérobie lors de l’exercice intense

Aim

Examine how the modelling of the relation between power and time to exhaustion can provide an estimation of the production of aerobic and anaerobic energy during intense exercise.

Current knowledge

The hyperbolic model made it possible to define the critical power corresponding to the maximal rate of energy renewed by aerobic metabolism. A new model distinguishing the critical power from the maximal aerobic power has been built to estimate more precisely the anaerobic contribution. Data from middle distance runners and subjects tested on cycle ergometer showed a relative contribution of anaerobic metabolism arising from critical power and increasing until around 10 % of total power when aerobic energy production reaches its maximum.

Prospects

Considering the slow component of oxygen uptake would provide a more precise analysis of energy production and transformation during exercise at high intensity.     

Effets de l'entraı̂nement sur les potentiels aérobie et anaérobie de jeunes nageurs. Exercice réalisé avec les bras

Aims – Investigate the influence of exercise training on the aerobic and anaerobic capacities of young swimmers.Methods – Ten male swimmers aged 15.2 ± 3.8 years participated: five sprint specialists and five middle-distance specialists. Each subject performed, an arm ergocycle, two laboratory tests, a maximal incremental exercise test and a force–velocity test, once in February (T1) and then again in June (T2).Results – For all subjects combined (n=10), the results showed a significant increase in maximal anaerobic power (p < 0.01) between T1 and T2. Aerobic capacity did not change significantly between the two tests in either group.Conclusion – This study demonstrates the interest of evaluating aerobic and anaerobic capacity in young swimmers during arm exercise. The change in results over the 5-month period between the two tests indicates the importance of scheduling exercise tests during the course of athletic training programs.     

Paramètres physiologiques à l'exercice sous-maximal aérobie : interaction entre sexe et entraı&#x0302;nement

Objective – Examine possible gender differences in cardiocirculatory responses during submaximal exercise, after an endurance training program.Methods and results – Oxygen uptake and heart rate were determined at differently submaximal work loads (35; 52.5; 70 Watts) before and after a 13 week endurance training program. The present longitudinal study shows a decrease in heart rate at submaximal work loadin prepubertal children after an aerobic training program and that such a decrease is similar in boys and girls.     

Estimation de la contribution énergétique d'origine aérobie et anaérobie et de sa répartition au cours d'un 800 m couru sur le mode compétition

Aim – Determine the part of each energetic system at different times of 800m competition. Oxygen uptake and speed were recorded continuously.Materials and methods – Five athletes performed on an outdoor track a test to determine the maximal oxygen uptake and the maximal aerobic speed and a supramaximal exercise of 800m.Results – The overall energetic expenditure as well as the oxygen deficit assessed at 31.9% were almost identical at those obtained during an 800m race running on a treadmill. Only the repartition of the oxygen deficit notably differed during the race. This suggered that the kinetic of the speed had a determining incidence on the anaerobic contribution as well as aerobic contribution when there were changes in running velocity.     

Un test de terrain simple pour la détermination du seuil anaérobie

Aim – Validate a simple and indirect methodology which supplies a reliable estimate of the run velocity correspondent to the anaerobic threshold.Materials and methods – Twelve subjects took part to this study and each subject was asked to perform a maximum test on 1000, 1500, 2000 and 3000 m. For each athlete was calculate the straight line which joins the values of run tests on 1000 and 1500 and the values on the run tests on 2000 and 3000 m, moreover, the linear regression line interpolating the run values of the 4 tests was calculated. The value of the equation coefficient b of the 2 straight lines and of the regression line was considered the value correspondent to the velocity of the anaerobic threshold. Then each athlete was asked to perform 20 min of continuous run at the 3 various run velocities previously calculated. During the tests previously mentioned the production of haematic lactate was analysed.Results – The 2000 and 3000 m distances are the most suitable to determine the velocity of the anaerobic threshold.     

Évolution de la puissance maximale anaérobie au cours de la croissance chez le footballeur

Purpose – The aim of the study was to assess the improvement in Maximal Anaerobic Power (PMAna) from two tests in soccer players during growth.Methods – The experiment was carried out in 328 players, 11–18 years old, during their stay at the Clairefontaine National Soccer Center. PMAna was measured from the last 10 meters of the a 40 m-sprint test (ST) and a jump test (JT). The skeletal age (AO) is used as reference, and not the chronological one.Results – The results of the two tests are highly correlated (r= 0.8–0.9), PMAna values being always higher in the ST than in the JT.The most significant increase in PMAna occurs between 13 and 14 years AO (+47% for the ST, +27% for the JT), remains still significant up to 16 AO (respectively +38% and +24% between 14 and 16 AO), but the maximum value is reached at 17 AO. Between 12 and 16 AO, the PMAna value is multiplied by 2.29 for the ST and 1.81 for the JT.Conclusions – Sprint and jump tests seem well adapted to estimate PMAna in soccer players. The measure of the skeletal age during growth is needed for a better interpretation of the results. In addition, results obtained during growth allow a reliable estimation of PMAna in adulthood.     

Répercussion de l’asthme induit par l’exercice sur la performance aérobie de l’enfant

Introduction. – Exercise-induced asthma is a clinical syndrome leading to a transient narrowing of the airways after the end of the exercise.Synthesis of results. – In order to observe its effect on aerobic performance 60 prepubescent children including 36 asthmatics have achieved a maximal increased exercise and a 8min constant exercise. The maximal expiratory flow-volume significantly decreased after the 2nd exercise in the exercise-induced asthma children. This means that airways were narrowing with exercise intensity. These narrowing did not seem to have any effect on the aerobic parameters measured in our study.Conclusion. – We conclude that controlled asthma does not limit the aerobic performance in prepubescent children.     

Reproductibilité test–retest des mesures stabilométriques après reconstruction du ligament croisé antérieur du genou chez le sujet sportif

Objective

To define the 3 day interval test-retest reproducibility of stabilometric measurements in two- and one legged stance in sport subjects recently operated from a knee anterior cruciate ligament reconstruction.

Méthode

Ten subjects aged between 16 to 33 years (23 year ± 5); carried out at 15 days after the knee surgery two sessions to measure steadiness in two legged stance with opened and closed eyes; in one legged stance with opened eyes, in healthy and operated leg, with full knee extension and with 20 degrees knee flexion. The reproducibility was determined using the intraclass correlation coefficient and the standard error of measurement was calculated.

Results

In two legged stance and in one legged stance, knee in 20 degrees flexion, the 95% sway area and the average antero-posterior excursion of the centre of pressure are reproducible (ICC > 0,75).The stabilometric parameters are not reproducible in one legged stance, knee in extension.

Conclusion

The reproducibility of stabilometric parameters is good, in two and in one legged stance knee flexed at 20 degrees, to evaluate the postural progress after anterior cruciate ligament reconstruction.     

读者&#183;作者&#183;编者

尊敬的编辑老师:您们好!我一直是贵刊的忠实读者,太喜欢《人民军医》杂志了,我深感该刊内容丰富,资料详实,编辑校对严谨认真,不愧是医学界的核心期刊。作为一名基层军队医务工作者,我也曾在贵刊发表过几篇论文。而对于我的每一篇拙文,您们都能够逐字推敲、反复修改,无论刊用与否均给予认真笔答,并且指出哪方面不足,应该向哪方面努力。您们这种“为他人做嫁衣”的服务态度和敬业精神真是太令我感动了,这将永远激励我在基层医疗岗位上尽职尽责地工作、默默无闻地奉献。您们不愧是期刊编辑学方面的专家,通过认真考虑您们对稿件的修改意见,使我撰写论文的思路越来越清晰,同时,通过不断的修改,也使我的业务水平有了较大提高。借此机会,请允许我向您们表示崇高的敬意和衷心的感谢!相信“天道酬勤”、“厚德载物”,贵刊一定会越办越好!新疆拜城69223部队卫生队单文俊2007年10月23日读者&#183;作者&#183;编者     

读者&#183;作者&#183;编者

来稿中关于统计分析方法的叙述,要写出具体名称,如成组设计资料的t检验、两因素析因设计资料的方差分析、多个均数之间两两比较的q检验。统计量的具体值,如t值、χ^2值、F值等,应尽可能给出具体的P值;当涉及总体参数,如总体均数、总体率等时,在给出显著性检验结果的同时,还应给出95％可信区间。     

<Superscript>68</Superscript>Ga-labeled cyclic RGD dimers with Gly<Subscript>3</Subscript> and PEG<Subscript>4</Subscript> linkers: promising agents for tumor integrin α<Subscript>v</Subscript>β<Subscript>3</Subscript> PET imaging

Purpose  Radiolabeled cyclic RGD (Arg-Gly-Asp) peptides have great potential for the early tumor detection and noninvasive monitoring of tumor metastasis and therapeutic response. ¹⁸F-labeled RGD analogs ([¹⁸F]-AH111585 and [¹⁸F]Galacto-RGD) have been investigated in clinical trials for positron emission tomography (PET) imaging of integrin expression in cancer patients. To develop new RGD radiotracers with higher tumor accumulation, improved in vivo kinetics, easy availability and low cost, we developed two new RGD peptides and labeled them with generator-eluted ⁶⁸Ga (t_1/2 = 68 min) for PET imaging of integrin α_vβ₃ expression in tumor xenograft models. Materials and methods  The two new cyclic RGD dimers, E[PEG₄-c(RGDfK)]₂ (P₄-RGD2, PEG₄ = 15-amino-4,7,10,13-tetraoxapentadecanoic acid) and E[Gly₃-c(RGDfK)]₂ (G₃-RGD2, G₃ = Gly-Gly-Gly) were designed, synthesized and conjugated with 1,4,7-triazacyclononanetriacetic acid (NOTA) for ⁶⁸Ga labeling. The microPET imaging and biodistribution of the ⁶⁸Ga labeled RGD tracers were investigated in integrin α_vβ₃-positive tumor xenografts. Results  The new RGD dimers with the Gly₃ and PEG₄ linkers showed higher integrin α_vβ₃ binding affinity than no-linker RGD dimer (RGD2). NOTA-G₃-RGD2 and NOTA-P₄-RGD2 could be labeled with ⁶⁸Ga within 30 min with higher purity (>98%) and specific activity (8.88–11.84 MBq/nmol). Both ⁶⁸Ga-NOTA-P₄-RGD2 and ⁶⁸Ga-NOTA-G₃-RGD2 exhibited significantly higher tumor uptake and tumor-to-normal tissue ratios than ⁶⁸Ga-NOTA-RGD2. Conclusion  Because of their high affinity, high specificity and excellent pharmacokinetic properties, further investigation of the two novel RGD dimers for clinical PET imaging of integrin α_vβ₃ expression in cancer patients is warranted. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Prévalence des troubles du comportement alimentaire chez le sportif

AimThe aim of the study was to determine the prevalence and relationships between disordered eating and psychological characteristics in 127 male and female elite athletes competing in 5 different sports and 31 non-competitive students matched for BMI and used as controls. All these parameters were assessed by a health/medical, dieting and menstrual history questionnaire, the Eating Attitudes Test (EAT-26), the Multidimensional perfectionism scale, the Body esteem scale, and the Self-Esteem scale.Results and discussion19% of female athletes had scores above the cut-off point on the Eating Attitudes Test questionnaire. 30.7% of female cyclists (30.7%), 25% of judoists and 22.3% of gymnasts (22.3%) would be "at risk" of EDs (EAT-26 > 20) and 0% in the male and female sedentary groups, basket- ball group and male athlete groups. The total frequency of menstrual dysfunction among females athletes was 33.1%. Females with eating disorders presented higher menstrual disturbances (71.4%) than the non-EDs (27.7%).ConclusionThe prevalence of disordered eating was higher in athletes than in sedentary groups, higher in female than in male athletes and more common among those competing in leanness-dependent and weight-dependent sports than in other sports. The prevalence of clinical eating disorders would increase when Self-oriented Perfectionism would be high and Body Satisfaction low.     

青春期男性的"三要""三不要"

要正确对待“面子”问题在进入青春期以后,男孩子的胡须开始生长,大多数人脸上还会长出许多“青春痘”,这本来是正常的生理现象,可有些男孩子最初对这种变化却不能接受,并往往因此而做出一些不正确的举动来:粉刺长出来了就去挤,胡须长出来了就去拔。岂不知,这样做是非常危险的。粉刺熟了自然会结痂脱落,如果在其结痂脱落前用手去挤,手上的细菌就有可能感染粉刺部位,造成发炎、红肿、甚至流脓,有的还会留下很难看的疤痕。男孩子的胡须是宜刮不宜拔的。这是因为人的面部(尤其是被称作“危险三角区”的口唇部位)是很容易被病菌感染的地方,即使…     

<Superscript>68</Superscript>Ga-labeled multimeric RGD peptides for microPET imaging of integrin α<Subscript>v</Subscript>β<Subscript>3</Subscript> expression

PURPOSE: We and others have reported that (18)F- and (64)Cu-labeled arginine-glycine-aspartate (RGD) peptides allow positron emission tomography (PET) quantification of integrin alpha(v)beta(3) expression in vivo. However, clinical translation of these radiotracers is partially hindered by the necessity of cyclotron facility to produce the PET isotopes. Generator-based PET isotope (68)Ga, with a half-life of 68 min and 89% positron emission, deserves special attention because of its independence of an onsite cyclotron. The goal of this study was to investigate the feasibility of (68)Ga-labeled RGD peptides for tumor imaging. METHODS: Three cyclic RGD peptides, c(RGDyK) (RGD1), E[c(RGDyK)](2) (RGD2), and E{E[c(RGDyK)](2)}(2) (RGD4), were conjugated with macrocyclic chelator 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and labeled with (68)Ga. Integrin affinity and specificity of the peptide conjugates were assessed by cell-based receptor binding assay, and the tumor targeting efficacy of (68)Ga-labeled RGD peptides was evaluated in a subcutaneous U87MG glioblastoma xenograft model. RESULTS: U87MG cell-based receptor binding assay using (125)I-echistatin as radioligand showed that integrin affinity followed the order of NOTA-RGD4 > NOTA-RGD2 > NOTA-RGD1. All three NOTA conjugates allowed nearly quantitative (68)Ga-labeling within 10 min (12-17 MBq/nmol). Quantitative microPET imaging studies showed that (68)Ga-NOTA-RGD4 had the highest tumor uptake but also prominent activity accumulation in the kidneys. (68)Ga-NOTA-RGD2 had higher tumor uptake (e.g., 2.8 +/- 0.1%ID/g at 1 h postinjection) and similar pharmacokinetics (4.4 +/- 0.4 tumor/muscle ratio, 2.0 +/- 0.1 tumor/liver ratio, and 1.1 +/- 0.1 tumor/kidney ratio) compared with (68)Ga-NOTA-RGD1. CONCLUSIONS: The dimeric RGD peptide tracer (68)Ga-NOTA-RGD2 with good tumor uptake and favorable pharmacokinetics warrants further investigation for potential clinical translation to image integrin alpha(v)beta(3).