Correlations between serum and salivary hormonal concentrations in response to resistance exercise     

Eduardo Cadore  Francisco Lhullier  Michel Brentano  Eduardo Silva  Melissa Ambrosini  Rafael Spinelli 《Journal of sports sciences》2013,31(10):1067-1072

Abstract

The aim of present study was to examine the relationships between serum and salivary values of free testosterone, dehydroepiandrosterone, and cortisol before and after a session of resistance exercise. Twenty-eight healthy men (mean age 40 years, s = 4) participated in the present study. Serum and salivary samples were collected at rest and after a multiple-sets resistance exercise protocol, of approximately 25 minutes duration. Concentrations of free testosterone, dehydroepiandrosterone, and cortisol were measured using radioimmunoassay kits. No significant correlation was observed between serum free testosterone and salivary testosterone (r = 0.22 to 0.26, P > 0.05). Serum cortisol was significantly correlated with salivary cortisol before (r = 0.52, P = 0.005) and after (r = 0.62, P = 0.001) the exercise protocol. Serum and salivary concentrations of dehydroepiandrosterone were significantly correlated before (r = 0.68, P < 0.001) and after (r = 0.7, P < 0.001) exercise. The results of the present study suggest that even under exercise conditions, the salivary values of cortisol and dehydroepiandrosterone can reflect the behaviour of these hormones in blood. However, further studies are necessary to verify if salivary testosterone reflects the behaviour of serum free testosterone during resistance exercise.  相似文献   

A comparison of lactate indices during ramp exercise using modelling techniques and conventional methods     

Vincent Thomas  Frédéric Costes  Michel Chatagnon  Jean-Pierre Pouilly 《Journal of sports sciences》2013,31(13):1387-1395

Abstract

The aim of this study was to compare the lactate indices provided by single- and double-breakpoint models with lactate thresholds obtained with conventional methods. Arterial samples for the determination of lactate concentrations were drawn from eight participants at rest and every minute during a ramp test (15 W · min^?1) on a cycle ergometer. Lactate thresholds were determined from a blood lactate concentration equal to 4 mM (LT₄), from an increase of 1 mM above the resting level (Δ1 mM), and from indirect methods using ventilatory parameters. Other indices were computed from the modelling of the lactate curve using an exponential function (LSI), a polynomial function (Dmax), a semi-log model (SLog), a parabola plus delay model (Mod P), and a two-breakpoint model (Mod M). Mod P and Mod M showed poor agreement with the other methods. LT₄, Dmax, LSI, and respiratory exchange ratio equal to 1 were correlated with each other (0.81 ≤ R ≤ 0.92) and their mean differences ranged from 2.8 to 15 W, with limits of agreement within the range ± 24.6 to ± 42.4 W. These results question the interest in breakpoints models to detect lactate thresholds, knowing that LT₄, LSI, Dmax, and respiratory exchange ratio equal to 1 provide indices that occur at similar power outputs.  相似文献   

Is there an influence of relative age on participation in non-physical sports activities? The example of shooting sports     

Nicolas Delorme  Michel Raspaud 《Journal of sports sciences》2013,31(10):1035-1042

Abstract

The aims of this study were to test for the presence of a relative age effect among male (n = 119,715) and female (n = 12,823) members of the shooting sports federation, and to determine whether any such effect has an impact on dropout from the sport. For the boys and girls, the results show a uniform distribution of dropout. A relative age effect was not found for the girls, showing that in female shooting sports there is no such effect. For the males, a significant statistical relative age effect was not detected in the 18–20 and 13–14 year categories. However, a relative age effect was found among adults and the 11–12 and under 11 year categories. A significant “inverse” relative age effect was found for the 15–17 year group. Further qualitative research is needed to clarify which factors contribute to this asymmetric distribution of birth dates in French male shooting sports.  相似文献   

Changes in swimming technique during time to exhaustion at freely chosen and controlled stroke rates     

Morgan Alberty  François Potdevin  Jeanne Dekerle  Patrick Pelayo  Philippe Gorce  Michel Sidney 《Journal of sports sciences》2013,31(11):1191-1200

Abstract

The aim of this study was to assess technical changes during constrained swimming in time-to-exhaustion tests. Ten swimmers of national standard performed a maximal 400-m front crawl and two sets of exhaustion tests at 95%, 100%, and 110% of mean 400-m speed. In the first set (free), swimmers had to maintain their speeds until exhaustion and mean stroke rate was recorded for each test. In the second set (controlled), the same speed and individual corresponding stroke rate were imposed. The durations of the exhaustion tests, relative durations of the stroke phases, and arm coordination were analysed. For each speed in the “controlled” set, the exhaustion tests were shorter. Moreover, variables were consistent, suggesting a stabilization of stroke technique. Under the free condition, stroke rate increased to compensate for the decrease in stroke length. At the same time, swimmers reduced the relative duration of their non-propulsive phases in favour of the propulsive phases. Thus, swimmers changed their arm coordination, which came close to an opposition mode. These two constraints enable swimmers both to maintain their stroking characteristics and develop compensatory mechanisms to maintain speed. Moreover, stroke rate can be seen as a useful tool for controlling arm technique during paced exercise.  相似文献   

The effects of task constraints on the organization of interception movements     

Valerie Fayt  Reinoud J. Bootsma  Ronald G. Marteniuk  Christine L. Mackenzie  Michel Laurent 《Journal of sports sciences》2013,31(6):581-586

In the light of the intensity coupling effects reported in the literature, subjects' capacities for independently controlling the absolute velocity of their movement at the point of interception was evaluated by asking them to learn to propel orthogonally approaching balls, varying in their speed of approach, into target boxes placed at various distances from the interception point. As required for successful accomplishment of the task, movement velocity was found to be adapted to the distance to be covered, with the near target giving rise to lower velocities and the far target giving rise to higher velocities even when the conditions were presented in random order. Nevertheless, even though target distance accounted for a substantial proportion of the total variance, a small but significant effect of ball approach speed on movement velocity was found, suggesting that intensity coupling is a persistent but modulable phenomenon in interception tasks.  相似文献   

Evaluation of Food Protection and Defense Outreach Education Programs     

John M. Shutske  Jennifer Pierquet  Laura Michel  Ruth Rasmussen  Debra Olson 《Journal of Food Science Education》2008,7(4):69-77

ABSTRACT: This analysis documents the outcomes and impacts from a series of food protection and defense educational programs conducted over a 3‐y period for private and public sector food system professionals. Several measures were used to determine the professions of participants; their improvements in skills and abilities that resulted from workshops; the audiences' most valued program content; practice changes resulting from educational program participation; abilities to recognize and change food system vulnerabilities; and changes in knowledge levels. Findings indicate that the knowledge level and interest within the target audience progressed over the 3‐y period from basic awareness level through more complex and higher order skills and competencies such as being able to walk through a food production, processing, distribution, or retail facility and identify specific vulnerabilities and make specific risk control recommendations. Pre‐ and posttest scores from the 3rd y of educational activities indicate that baseline awareness levels of core content on food protection and defense is now high among those most likely to attend these types of events, and that participants need to be challenged with additional higher‐level education to promote specific skills. This program series proved successful in building important relationships among food industry and regulatory partners. Analysis of the food security investigation (FSI) series will be useful in the development and delivery of new education and outreach efforts. It is hoped that the analysis and discussion will provide the motivation to further develop a set of competencies that can be used to ground educational efforts that focus on securing and defending our food system.  相似文献   

Genetic evidence for bidirectional effects of early lexical and grammatical development     

Dionne G  Dale PS  Boivin M  Plomin R 《Child development》2003,74(2):394-412

This article addresses the autonomy hypothesis of vocabulary and grammar and bootstrapping mechanisms in early language development. Two birth cohorts of 1,505 and 1,049 same-sex twin pairs from the UK were assessed at 2 and 3 years on grammar and vocabulary, using adapted versions of the MacArthur Communicative Development Inventory. Vocabulary and grammar correlate strongly at both 2 and 3 years in both cohorts. Multivariate genetic modeling reveals a consistently high genetic correlation between vocabulary and grammar at 2 and 3 years. This finding suggests the same genetic influences operate for both vocabulary and grammar, a finding incompatible with traditional autonomy hypothesis, at least in early acquisition. Crosslagged longitudinal genetic models indicate both lexical and syntactical bootstrapping operate from 2 to 3 years.  相似文献   

Complex Education Systems: from steering change to governance     

Alain Michel 《European Journal of Education》2016,51(4):513-521

The theories and approaches of steering/monitoring a process of change within education systems have evolved over the last 20 years or so as a result of many factors such as globalisation and decentralisation, a faster pace of change, increasing expectations and demands from various stakeholders (parents, employers, teacher unions, etc.) and the growing influence of OECD and of the EU in the field of education because of some more or less explicit standards and policy recommendations. All these evolutions contributed to increase the complexity of the education systems and of the instruments and procedures required to establish some coherence between the initiatives of a large number of more autonomous stakeholders. Our main objective here is to describe how the previous notions and concepts used in analysing the conditions for steering education systems have been gradually integrated within a larger paradigm: the ‘governance of multi‐level complex education systems’.  相似文献   

Arithmetic and cryptography     

Michel Waldschmidt 《Resonance》2008,13(5):440-455

Among the unexpected features of recent developments in technology are the connections between classical arithmetic on the one hand, and new methods for reaching a better security of data transmission on the other. We will illustrate this aspect of the subject by showing how modern cryptography is related to our knowledge of some properties of natural numbers. As an example, we explain how prime numbers play a key role in the process which enables you to withdraw safely your money from your bank account using ATM (Automated Teller Machines) with your secret PIN (Personal Identification Number) code.  相似文献   

Linkages Between Children's and Their Friends' Social and Physical Aggression: Evidence for a Gene–Environment Interaction?     

Mara Brendgen  Michel Boivin  Frank Vitaro  William M. Bukowski  Ginette Dionne  Richard E. Tremblay  Daniel Pérusse 《Child development》2008,79(1):13-29

Based on a sample of 406 seven-year-old twins, this study examined whether exposure to friends' social or physical aggression, respectively, moderates the effect of heritability on children's own social and physical aggression. Univariate analyses showed that children's own social and physical aggression were significantly explained by genetic factors, whereas friends' social and physical aggression represented "true" environmental factors that were unrelated to children's genetic dispositions. Multivariate analyses further suggested a possible gene–environment interaction in the link between friends' and children's physical aggression but not in the link between friends' and children's social aggression. Instead, friends' social aggression was directly related to children's social aggression, in addition to genetic effects on this behavior. Theoretical and practical implications of these results are discussed.  相似文献