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1.
The aim of this study was to characterize forearm muscle fatigue identified by the decrease in electromyogram median frequency and/or fingertip force during intermittent exercise. Nine elite climbers (international competitive level, USA 5.14a on sight) and ten non-climbers were instructed to maintain a fingertip force of 80% of their maximal voluntary contraction force on a dynamometer mimicking a rock climbing grip during a 5 s effort/5 s rest cycle for 36 repetitions (i.e. 6 min of exercise). Elite climbers lasted twice as long as non-climbers (climbers: 3 min; non-climbers: 1 min 30 s) before the force could no longer be maintained (i.e. the failure point). After this moment, fingertip force decreased and stabilized until the end of the exercise around 50% maximum voluntary contraction force in non-climbers and 63% in elite climbers. Electromyogram median frequency showed a greater decrease in non-climbers than in elite climbers before the failure point. No change in median frequency was observed after the failure point in elite climbers or in non-climbers. These results confirm that elite climbers are better adapted than non-climbers for performing the intermittent fingertip effort before the failure point. After this point, the better fingertip force of elite climbers suggests different forearm muscle properties, while the electromyography results do not provide any indication about the fatigue process. 相似文献
2.
Mauricio Garzon Olivier Dupuy Laurent Bosquet Anil Nigam Alain Steve Comtois Martin Juneau 《European Journal of Sport Science》2017,17(3):310-316
This study compared heart rate recovery (HRR) after incremental maximal exercise performed at the same external power output (Pext) on dry land ergocycle (DE) vs. immersible ergocycle (IE). Fifteen young healthy participants (30?±?7 years, 13 men and 2 women) performed incremental maximal exercise tests on DE and on IE. The initial Pext on DE was 25?W and was increased by 25?W/min at a pedalling cadence between 60 and 80?rpm, while during IE immersion at chest level in thermoneutral water (30°C), the initial Pext deployment was at a cadence of 40?rpm which was increased by 10?rpm until 70?rpm and thereafter by 5?rpm until exhaustion. Gas exchange and heart rate (HR) were measured continuously during exercise and recovery for 5?min. Maximal HR (DE: 176?±?15 vs. IE 169?±?12?bpm) reached by the subjects in the two conditions did not differ (P?>?.05). Parasympathetic reactivation parameters (ΔHR from 10 to 300?s) were compared during the DE and IE HR recovery recordings. During the IE recovery, parasympathetic reactivation in the early phase was more predominant (HRR at Δ10–Δ60?s, P?<?.05), but similar in the late phase (HRR at Δ120–Δ300?s, P?>?.05) when compared to the DE condition. In conclusion, incremental maximal IE exercise at chest level immersion in thermoneutral water accelerates the early phase parasympathetic reactivation compared to DE in healthy young participants. 相似文献
3.
Environmental policy increasingly resorts to market-based instruments in order to meet sustainability objectives. The ‘carbon market’ instituted by the European Emissions Trading directive from 2003 is a canonical example, which has been described, and critiqued, as a delegation of policy objectives to market exchanges. In this paper, we examine the complex ways in which the operationalization of policy objectives and the organization of markets are intertwined, focusing on two other examples of European environmental regulation. The first one is the Integrated Pollution Prevention and Control directive from 1996, which defined the ‘best available techniques’ to curb emissions in air, water and soil. The second one is the Renewable Energy Directive from 2009, which introduced criteria for the definition of the sustainability of biofuels. Through the analysis of the design and implementation of these two directives, we identify a central concern for the coexistence of various objects, and various initiatives undertaken by European institutions, member states and private actors. We use the notion of coexistence to describe a European political and economic ordering that is inherently hybrid, and cannot be reduced to a mere delegation of policy objectives to the market, or a legal constraint imposed on all European actors. It grounds its political legitimacy and economic rationality on the distribution of roles and responsibilities across public and private actors, and on the ability to ‘keep things different’ according to local variabilities. 相似文献
4.
Jing-Yang Hu Zi-Qian Hao Laurent Frantz Shi-Fang Wu Wu Chen Yun-Fang Jiang Hong Wu Wei-Min Kuang Haipeng Li Ya-Ping Zhang Li Yu 《国家科学评论(英文版)》2020,7(4):798
Pangolins are among the most critically endangered animals due to heavy poaching and worldwide trafficking. However, their demographic histories and the genomic consequences of their recent population declines remain unknown. We generated high-quality de novo reference genomes for critically endangered Malayan (Manis javanica, MJ) and Chinese (M. pentadactyla, MP) pangolins and re-sequencing population genomic data from 74 MJs and 23 MPs. We recovered the population identities of illegally traded pangolins and previously unrecognized genetic populations that should be protected as evolutionarily distinct conservation units. Demographic reconstruction suggested environmental changes have resulted in a population size fluctuation of pangolins. Additionally, recent population size declines due to human activities have resulted in an increase in inbreeding and genetic load. Deleterious mutations were enriched in genes related to cancer/diseases and cholesterol homeostasis, which may have increased their susceptibility to diseases and decreased their survival potential to adapt to environmental changes and high-cholesterol diets. This comprehensive study provides not only high-quality pangolin reference genomes, but also valuable information concerning the driving factors of long-term population size fluctuations and the genomic impact of recent population size declines due to human activities, which is essential for pangolin conservation management and global action planning. 相似文献
5.
Afforestation in China provides carbon sequestration and prevents soil erosion, but its remote impacts on climate in other regions via the coupling of forest energy fluxes with atmospheric circulation are largely unknown. Here, we prescribe inventory-based forest cover change and satellite-observed leaf area index from 1982 to 2011 in a coupled land-atmosphere model to simulate their biophysical climate effects. Both local and global surface air temperatures show a seasonal contrast in response to past vegetation cover expansion over China: a phenomenon we primarily attribute to a variation of seasonality of vegetation greening. A large cooling in spring results in concurrent decreases in geopotential height over China and zonal wind over Mongolia, causing a dipole structure in the upper troposphere over the Arctic. This accounts for ∼58% of simulated spring warming over the Russian Arctic and ∼61% of simulated spring cooling over the Canadian Artic. Our results imply that spring vegetation dynamics in China may affect climate in northern high latitudes. 相似文献
6.
Jeremy B. Coquart Daniel Mercier Montassar Tabben Laurent Bosquet 《Journal of sports sciences》2015,33(11):1124-1131
The aim was to test the influence of sex and specialty (3000, 5000 and 10000 m) on the validity of middle-distance running performance predictions obtained from the Mercier et al.’s nomogram. Consequently, we examined all official French track running rankings for the 3000-, 5000- and 10000-m events (men and women) from 2006 to 2012. A scoring table was used to determine the runners’ specialties. Only runners who performed in the three distance events within the same year were included (75 women and 400 men). The Mercier et al.’s nomogram was used to predict one running performance from the other two. The results showed no significant difference between actual and predicted running performances (P = 0.77). Female runners had significantly lower performances than male runners (P < 0.001). Specialty did not influence performances (P = 0.11). Very high correlations were found between actual and predicted performances (0.91 < r < 0.99), with the exception of women (r = 0.85) in 5000 m. Moreover, low limits of agreement were obtained for male and female runners, whatever the specialty. These results support the validity of the nomogram to predict running performance in the 3000-, 5000- and 10000-m events for male and female runners, whatever the specialty. The predicted running performances may be used in training programmes (e.g., to prescribe tempo runs) and competitions (e.g., to establish split times). 相似文献
7.
Philipe De Souto Barreto Laurent Demougeot Bruno Vellas Yves Rolland 《Journal of sports sciences》2015,33(2):116-124
Information on the amount of exercise practised by nursing home (NH) residents is scarce. This study aimed at describing NH residents’ participation in exercise classes, as well as to examine whether the presence of a professional exercise instructor in the facilities is associated with residents’ exercise habits. The cross-sectional data of 5402 residents (median age = 88 years; mostly women (75.2%)) from 163 NHs in France were analysed. Adjusted logistic and linear regressions were performed to examine whether the presence of a professional exercise instructor in the NH was associated with exercise habits: exercise participation, frequency, duration, and levels. From the 5402 participants, 1914 were participating in exercise classes provided in the NH. Most of them had an exercise frequency of 1x/week or less. Median duration of exercise sessions was 45 min. Exercise levels were rated as: highly active (n = 487), intermediately active (n = 1096), and poorly active (n = 331). The presence of a professional exercise instructor working in the facility was significantly associated with exercise participation and with higher exercise frequencies and levels, and session duration. In conclusion, the presence of professional exercise instructors is associated with better exercise habits in NH residents. Improved exercise habits may potentially be translated into better health in this population. 相似文献
8.
Tony Monnet Mathias Samson Anthony Bernard Laurent David Patrick Lacouture 《Sports Engineering》2014,17(3):171-181
Current trends in swimming biomechanics are focused on accurate measurements. Nowadays, reliable calibration methods have been proposed to reach an accuracy of about 1 mm on rigid structure. But the question remains about the final accuracy for three-dimensional hand kinematics measurement during the underwater phase of front crawl swimming. Furthermore, most research is based on manual tracking with two or more cameras. In this paper we propose a protocol to acquire three-dimensional hand kinematics when swimming in a specific pool with a motion analysis system behind windows. Results highlight the benefits of using such a system in terms of accuracy and feasibility: the time allowed for post-processing is ten times lower and the quantified improved accuracy is better than with manual tracking. 相似文献
9.
FRANCAUX Marc MALISOUX Laurent THEISEN Daniel 《首都体育学院学报》2007,19(6):1-9
随着特殊的训练计划被教练员们采用以促进运动员的肌肉适应能力,肌肉训练也成为渐进式康复的重要组成部分,它能阻止与丧失运动能力、老化、疾病或微重力相关的萎缩效应。为了优化不同类型的干扰措施,需要更好地理解运动训练产生的反应,以及识别决定肌肉功能的各种机制。虽然整体肌肉活动在某种程度上是通过适应运动神经元爆发、运动单元补充模式或者肌肉量来进行的,本研究着重探讨肌肉纤维类型的表达以及训练后收缩肌的功能性适应能力。单一无皮纤维被证明是常用的实验模型,用于研究与肌浆球蛋白重链对碘氧基苯甲醚相关的试管内收缩特性。人体纤维主要的功能和生化特性在过去二十年中已经被详细研究了,但近来,无皮纤维模式正被用于研究不同类型的诱发训练后单纤维的功能适应性。本文的目的是概述收缩肌对于特定运动训练计划的反应,以及帮助形成适用于运动科学和康复的训练计划。 相似文献
10.
Rupprecht P Golé L Rieu JP Vézy C Ferrigno R Mertani HC Rivière C 《Biomicrofluidics》2012,6(1):14107-1410712
We have developed a method for studying cellular adhesion by using a custom-designed microfluidic device with parallel non-connected tapered channels. The design enables investigation of cellular responses to a large range of shear stress (ratio of 25) with a single input flow-rate. For each shear stress, a large number of cells are analyzed (500–1500 cells), providing statistically relevant data within a single experiment. Besides adhesion strength measurements, the microsystem presented in this paper enables in-depth analysis of cell detachment kinetics by real-time videomicroscopy. It offers the possibility to analyze adhesion-associated processes, such as migration or cell shape change, within the same experiment. To show the versatility of our device, we examined quantitatively cell adhesion by analyzing kinetics, adhesive strength and migration behaviour or cell shape modifications of the unicellular model cell organism Dictyostelium discoideum at 21 °C and of the human breast cancer cell line MDA-MB-231 at 37 °C. For both cell types, we found that the threshold stresses, which are necessary to detach the cells, follow lognormal distributions, and that the detachment process follows first order kinetics. In addition, for particular conditions’ cells are found to exhibit similar adhesion threshold stresses, but very different detachment kinetics, revealing the importance of dynamics analysis to fully describe cell adhesion. With its rapid implementation and potential for parallel sample processing, such microsystem offers a highly controllable platform for exploring cell adhesion characteristics in a large set of environmental conditions and cell types, and could have wide applications across cell biology, tissue engineering, and cell screening. 相似文献