Fingertip force and electromyography of finger flexor muscles during a prolonged intermittent exercise in elite climbers and sedentary individuals   总被引：1，自引：1，他引：0  

Vigouroux L  Quaine F 《Journal of sports sciences》2006,24(2):181-186

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   

Routes and Realms: The Power of Place in the Early Islamic World; Mapping Frontiers across Medieval Islam: Geography,Translation, and the ʿAbbāsid Empire     

Nicola Clarke 《Al-Masaq: Islam & the Medieval Mediterranean》2016,28(2):206-209

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Understanding key performance indicators for breast support: An analysis of breast support effects on biomechanical,physiological and subjective measures during running     

Debbie Risius  Alexandra Milligan  Jason Berns  Nicola Brown 《Journal of sports sciences》2017,35(9):842-851

To assess the effectiveness of breast support previous studies monitored breast kinematics and kinetics, subjective feedback, muscle activity (EMG), ground reaction forces (GRFs) and physiological measures in isolation. Comparing these variables within one study will establish the key performance variables that distinguish between breast supports during activities such as running. This study investigates the effects of changes in breast support on biomechanical, physiological and subjective measures during running. Ten females (34D) ran for 10 min in high and low breast supports, and for 2 min bare breasted (2.8 m·s^?1). Breast and body kinematics, EMG, expired air and heart rate were recorded. GRFs were recorded during 10 m overground runs (2.8 m·s^?1) and subjective feedback obtained after each condition. Of the 62 variables measured, 22 kinematic and subjective variables were influenced by changes in breast support. Willingness to exercise, time lag and superio-inferior breast velocity were most affected. GRFs, EMG and physiological variables were unaffected by breast support changes during running. Breast displacement reduction, although previously advocated, was not the most sensitive variable to breast support changes during running. Instead breast support products should be assessed using a battery of performance indicators, including the key kinematic and subjective variables identified here.  相似文献   

Thermoneutral immersion exercise accelerates heart rate recovery: A potential novel training modality     

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 (P_ext) 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 P_ext 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 P_ext 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   

Compensatory changes in physical activity and sedentary time in children and adolescents with cystic fibrosis     

Kelly A. Mackintosh  Nicola D. Ridgers  Melitta A. McNarry 《Journal of sports sciences》2019,37(13):1506-1511

Physical activity (PA) is a key element in Cystic Fibrosis (CF) treatment strategies, yet little is known as to whether activity compensation occurs. This study examined whether PA and/or sedentary time on one day were temporally associated with time spent in these intensities the following day in youth with CF. Time spent sedentary and in different PA intensities were objectively-measured for seven consecutive days in 50 youth (22 boys; 12.0 ± 2.7 years); 25 with mild-to-moderate CF and 25 age- and sex-matched controls. Multilevel analyses (day and child) were conducted using generalised linear latent and mixed models. On any given day, every additional 10 minutes spent in sedentary time or moderate-to-vigorous physical activity (MVPA) were associated with 1.9 (95%CI: ?3.6 to ?1.2) and 12.4 (95%CI: ?22.1 to ?2.9) minutes less sedentary time the following day, respectively. These temporal associations were also observed when split by group (3.1 vs. 1.9 minutes for healthy and CF, respectively). These findings indicate that youth do not compensate their PA, irrespective of disease status, between days, but may compensate their sedentary time between days. Experimental studies are warranted to fully elucidate whether compensatory responses to PA and sedentary time occur, which is fundamental for informing PA promotion strategies.  相似文献   

Keeping things different: coexistence within European markets for cleantech and biofuels     

Liliana Doganova  Brice Laurent 《Journal of Cultural Economy》2016,9(2):141-156

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   

Do cognitive training strategies improve motor and positive psychological skills development in soccer players? Insights from a systematic review     

Maamer Slimani  Nicola Luigi Bragazzi  David Tod  Alexandre Dellal  Olivier Hue  Foued Cheour 《Journal of sports sciences》2016,34(24):2338-2349

ABSTRACT

Soccer players are required to have well-developed physical, technical and cognitive abilities. The present systematic review, adhering to Preferred Reporting Items for Systematic reviews and Meta-Analysis guidelines, examined the effects of cognitive training strategies on motor and positive psychological skills development in soccer performance and identified the potential moderators of the “cognitive training–soccer performance” relationship. Thirteen databases were systematically searched using keywords related to psychological or cognitive training in soccer players. The review is based on 18 studies, employing 584 soccer players aged 7–39 years. Cognitive strategies, particularly imagery, appear to improve sports performance in soccer players. Regarding imagery, the combination of two different types of cognitive imagery training (i.e., cognitive general and cognitive specific) has a positive influence on soccer performance during training, whereas motivational imagery (i.e., motivational general-arousal, motivational general-mastery and motivational specific) enhance competition performance. Younger soccer players employ cognitive general and cognitive specific imagery techniques to a greater extent than older soccer players. Combined cognitive training strategies were more beneficial than a single cognitive strategy relative to motor skills enhancement in elite (particularly midfielders) and amateur (i.e., when practising complex and specific soccer skills in precompetitive period) soccer players. In conclusion, it appears that there are differences in cognitive/psychological training interventions, and their efficacy, according to whether they are directed towards training or competition, and the age, standard and playing position of the players.  相似文献   

Genomic consequences of population decline in critically endangered pangolins and their demographic histories     

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   

Local and teleconnected temperature effects of afforestation and vegetation greening in China     

Yue Li  Shilong Piao  Anping Chen  Philippe Ciais  Laurent Z X Li 《国家科学评论(英文版)》2020,7(5):897

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   

Exploring Sign Use in Two Settings     

Nicola Grove  Sine McDougall 《British Journal of Special Education》1991,18(4):149-156

Nicola Grove, speech/language therapist, and Sine McDougall, psychologist, from the Division of Psychiatry of Disability, Department of Mental Health Sciences, St. George's Hospital Medical School, London, explore use of Makaton signs in teacher-directed and free play settings by children with severe learning difficulties.  相似文献