891 resultados para maximal voluntary contraction
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This paper uses data on the world's copper mining industry to measure the impact on efficiency of the adoption of the ISO 14001 environmental standard. Anecdotal and case study literature suggests that firms are motivated to adopt this standard so as to achieve greater efficiency through changes in operating procedures and processes. Using plant level panel data from 1992-2007 on most of the world's industrial copper mines, the study uses stochastic frontier methods to investigate the effects of ISO adoption. The variety of models used in this study find that adoption either tends to improve efficiency or has no impact on efficiency, but no evidence is found that ISO adoption decreases efficiency.
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PURPOSE: This study investigated maximal cardiometabolic response while running in a lower body positive pressure treadmill (antigravity treadmill (AG)), which reduces body weight (BW) and impact. The AG is used in rehabilitation of injuries but could have potential for high-speed running, if workload is maximally elevated. METHODS: Fourteen trained (nine male) runners (age 27 ± 5 yr; 10-km personal best, 38.1 ± 1.1 min) completed a treadmill incremental test (CON) to measure aerobic capacity and heart rate (V˙O2max and HRmax). They completed four identical tests (48 h apart, randomized order) on the AG at BW of 100%, 95%, 90%, and 85% (AG100 to AG85). Stride length and rate were measured at peak velocities (Vpeak). RESULTS: V˙O2max (mL·kg·min) was similar across all conditions (men: CON = 66.6 (3.0), AG100 = 65.6 (3.8), AG95 = 65.0 (5.4), AG90 = 65.6 (4.5), and AG85 = 65.0 (4.8); women: CON = 63.0 (4.6), AG100 = 61.4 (4.3), AG95 = 60.7 (4.8), AG90 = 61.4 (3.3), and AG85 = 62.8 (3.9)). Similar results were found for HRmax, except for AG85 in men and AG100 and AG90 in women, which were lower than CON. Vpeak (km·h) in men was 19.7 (0.9) in CON, which was lower than every other condition: AG100 = 21.0 (1.9) (P < 0.05), AG95 = 21.4 (1.8) (P < 0.01), AG90 = 22.3 (2.1) (P < 0.01), and AG85 = 22.6 (1.6) (P < 0.001). In women, Vpeak (km·h) was similar between CON (17.8 (1.1) ) and AG100 (19.3 (1.0)) but higher at AG95 = 19.5 (0.4) (P < 0.05), AG90 = 19.5 (0.8) (P < 0.05), and AG85 = 21.2 (0.9) (P < 0.01). CONCLUSIONS: The AG can be used at maximal exercise intensities at BW of 85% to 95%, reaching faster running speeds than normally feasible. The AG could be used for overspeed running programs at the highest metabolic response levels.
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"Vegeu el resum a l'inici del document del fitxer adjunt."
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In this paper, we investigate the agency costs of government ownership and their impact on corporate governance and firm value. China is used as a laboratory because of the prevalent state shareholdings in exchange-listed firms. In this context, we specifically consider the trade-offs involved in the voluntary formation of an audit committee when the controlling shareholder is the state. The decision to improve corporate governance (in this case, introduce an audit committee) is shown to be value relevant and a function of existing agency relationships and non-trivial implementation costs. Our findings are robust to the level of pyramid groups, the ownership-control wedge, and financial leverage. The research adds to the debate regarding the effect of government shareholdings on corporate culture and performance - a topic that hastaken on renewed importance in recent times.
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"Vegeu el resum a l'inici del document del fitxer adjunt."
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"Vegeu el resum a l'inici del document del fitxer adjunt."
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The division problem consists of allocating a given amount of an homogeneous and perfectly divisible good among a group of agents with single-peaked preferences on the set of their potential shares. A rule proposes a vector of shares for each division problem. The literature has implicitly assumed that agents will find acceptable any share they are assigned to. In this paper we consider the division problem when agents' participation is voluntary. Each agent has an idiosyncratic interval of acceptable shares where his preferences are single-peaked. A rule has to propose to each agent either to not participate or an acceptable share because otherwise he would opt out and this would require to reassign some of the remaining agents' shares. We study a subclass of efficient and consistent rules and characterize extensions of the uniform rule that deal explicitly with agents' voluntary participation.
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In chronic severe infection with Schistosoma mansoni, portal hypertension and related vascular alterations usually develop as a consequence of granulomatous response to eggs. In order to investigate a putative direct effect of worms on the reactivity of their host portal vein, mice infected only with male worms were used in the present study. An higher reactivity to 5-hydroxytryptamine (5-HT) characterized by an increase in the maximal contraction and sensitivity was observed in portal vein from infected mice compared to healthy mice. Blockade of NO-synthase with l-NAME induced a small increase in 5-HT potency in portal vein from non-infected mice without changing the amplitude of the contractions, whereas it did not alter the reactivity of veins from infected mice. The present results show that unisexual infection of mice with male S. mansoni increased the reactivity of the portal vein to 5-HT which seems to be partially related to an alteration in the nitric oxide release by endothelium.
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Introduction. Respiratory difficulties in athletes are common, especially in adolescents, even in the absence of exercise-induced bronchoconstriction. Immaturity of the respiratory muscles coupling at high respiratory rates could be a potential mechanism. Whether respiratory muscle training (RMT) can positively influence it is yet unknown. Goal. We investigate the effects of RMT on ventilation and performance parameters in adolescent athletes and hypothesize that RMT will enhance respiratory capacity. Methods. 12 healthy subjects (8 male, 4 female, 17±0.5 years) from a sports/study high school class, competitively involved in various sports (minimum of 10 hours per week) underwent respiratory function testing, maximal minute ventilation (MMV) measurements and a maximal treadmill incremental test with VO2max and ventilatory thresholds (VT1 and VT2) determination. They then underwent one month of RMT (4 times/week) using a eucapnic hyperventilation device, with an incremental training program. The same tests were repeated after RMT. Results. Subjects completed 14.8 sessions of RMT, with an increase in total ventilation per session of 211±29% during training. Borg scale evaluation of the RMT session was unchanged or reduced in all subjects, despite an increase in total respiratory work. No changes (p>0.05) were observed pre/post RMT in VO2max (53.4±7.5 vs 51.6±7.7 ml/kg/min), VT2 (14.4±1.4 vs 14.0±1.1 km/h) or Speed max at end of test (16.1±1.7 vs 15.8±1.7 km/h). MVV increased by 9.2% (176.7±36.9 vs 192.9±32.6 l/min, p<0.001) and FVC by 3.3% (6.70±0.75 vs 4.85±0.76 litres, p<0.05). Subjective evaluation of respiratory sensations during exercise and daily living were also improved. Conclusions. RMT improves MMV and FVC in adolescent athletes, along with important subjective respiratory benefits, although no changes are seen in treadmill maximal performance tests and VO2max measurements. RMT can be easily performed in adolescent without side effects, with a potential for improvement in training capacity and overall well-being.
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The present study was aimed at examining the role of nitric oxide (NO) in the hypoxic contraction of isolated small pulmonary arteries (SPA) in the rat. Animals were treated with either saline (sham experiments) or Escherichia coli lipolysaccharide [LPS, to obtain expression of the inducible NO synthase (iNOS) in the lung] and killed 4 h later. SPA (300- to 600-micrometer outer diameter) were mounted as rings in organ chambers for the recording of isometric tension, precontracted with PGF2alpha, and exposed to either severe (bath PO2 8 +/- 3 mmHg) or milder (21 +/- 3 mmHg) hypoxia. In SPA from sham-treated rats, contractions elicited by severe hypoxia were completely suppressed by either endothelium removal or preincubation with an NOS inhibitor [NG-nitro-L-arginine methyl ester (L-NAME), 10(-3) M]. In SPA from LPS-treated rats, contractions elicited by severe hypoxia occurred irrespective of the presence or absence of endothelium and were largely suppressed by L-NAME. The milder hypoxia elicited no increase in vascular tone. These results indicate an essential role of NO in the hypoxic contractions of precontracted rat SPA. The endothelium independence of HPV in arteries from LPS-treated animals appears related to the extraendothelial expression of iNOS. The severe degree of hypoxia required to elicit any contraction is consistent with a mechanism of reduced NO production caused by a limited availability of O2 as a substrate for NOS.
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Review of DHSSPS Training Support Funding Programme For Social Care Voluntary Organisations
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INTRODUCTION: Spectral frequencies of the surface electromyogram (sEMG) increase with contraction force, but debate still exists on whether this increase is affected by various methodological and anatomical factors. This study aimed to investigate the influence of inter-electrode distance (IED) and contraction modality (step-wise vs. ramp) on the changes in spectral frequencies with increasing contraction strength for the vastus lateralis (VL) and vastus medialis (VM) muscles. METHODS: Twenty healthy male volunteers were assessed for isometric sEMG activity of the VM and VL, with the knee at 90° flexion. Subjects performed isometric ramp contractions in knee extension (6-s duration) with the force gradually increasing from 0 to 80 % MVC. Also, subjects performed 4-s step-wise isometric contractions at 10, 20, 30, 40, 50, 60, 70, and 80 % MVC. Interference sEMG signals were recorded simultaneously at different IEDs: 10, 20, 30, and 50 mm. The mean (F mean) and median (F median) frequencies and root mean square (RMS) of sEMG signals were calculated. RESULTS: For all IEDs, contraction modalities, and muscles tested, spectral frequencies increased significantly with increasing level of force up to 50-60 % MVC force. Spectral indexes increased systematically as IED was decreased. The sensitivity of spectral frequencies to changes in contraction force was independent of IED. The behaviour of spectral indexes with increasing contraction force was similar for step-wise and ramp contractions. CONCLUSIONS: In the VL and VM muscles, it is highly unlikely that a particular inter-electrode distance or contraction modality could have prevented the observation of the full extent of the increase in spectral frequencies with increasing force level.
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Mission statement: åÊ To save lives of those at risk of developing cancer and enhance the quality of life of those living with cancer in Northern Ireland. åÊ Services include: - Women’s early detection service åÊ – mammography, cervical screening and breast awareness (including a mobile clinic) åÊ - Awareness campaigns on breast, cervical, prostate and testicular cancer åÊ - Counselling and complementary therapy for cancer patients and their families åÊ - Health promotion in schools, workplaces and communities åÊ - Funding for cancer research and the Regional Cancer Genetics Servic åÊ