Respiratory muscle training in healthy humans: Resolving the controversy

Specific respiratory muscle training offers the promise of improved exercise tolerance and athletic performance for a wide range of users. However, the literature addressing respiratory muscle training in healthy people remains controversial. Studies into the effect of respiratory muscle training upon whole body exercise performance have used at least one of the following modes of training: voluntary isocapnic hyperpnea, flow resistive loading, and pressure threshold loading. Each of these training modes has the potential to improve specific aspects of respiratory muscle function. Some studies have demonstrated significant improvements in either time to exhaustion or time trial performance, whilst others have demonstrated no effect. We present an overview of the literature that rationalizes its contradictory findings. Retrospective analysis of the literature suggests that methodological factors have played a crucial role in the outcome of respiratory muscle training studies. We conclude that in most well controlled and rigorously designed studies, utilizing appropriate outcome measures, respiratory muscle training has a positive influence upon exercise performance. The mechanisms by which respiratory muscle training improves exercise performance are unclear. Putative mechanisms include a delay of respiratory muscle fatigue, a redistribution of blood flow from respiratory to locomotor muscles, and a decrease in the perceptions of respiratory and limb discomfort

Inspiratory muscle training reduces blood lactate concentration during volitional hyperpnoea

Although reduced blood lactate concentrations ([lac−]B) have been observed during whole-body exercise following inspiratory muscle training (IMT), it remains unknown whether the inspiratory muscles are the source of at least part of this reduction. To investigate this, we tested the hypothesis that IMT would attenuate the increase in [lac−]B caused by mimicking, at rest, the breathing pattern observed during high-intensity exercise. Twenty-two physically active males were matched for 85% maximal exercise minute ventilation (V˙Emax) and divided equally into an IMT or a control group. Prior to and following a 6 week intervention, participants performed 10 min of volitional hyperpnoea at the breathing pattern commensurate with 85% V˙Emax

Heterogeneous consumption in OLG model with horizontal innovations

The paper develops a general equilibrium endogenous growth model involving heterogeneous consumption by an age-structured population with uncertain but limited life span and balanced life-time budget without bequests. The heterogeneity is introduced via weights which the individuals attribute in their utility function to consumption of different goods depending on the vintage of the good. The goods are produced by monopolistically competitive firms and the variety of available goods/technologies is determined endogenously through R&D investments. A competitive bank sector provides financial resources for investments, secured by agents’ savings and future firms profits. The general equilibrium is characterized by a system of functional equations and is analytically or numerically determined for several particular weight functions. It is shown that the investments by agents alone may be insufficient to sustain growth, while additional investments provided by the bank sector may lead to growth. The resulting imbalance between agents’ assets and the total value of firms can grow unboundedly in the case of homogeneous consumption. The results exhibit the qualitative difference between the dynamics of the model with heterogeneous versus homogeneous consumption. In particular heterogeneous con- sumption (when old goods are discounted) reduces the additional investments by the financial sector so that the values of firms become balanced by the assets of agents in the long run.info:eu-repo/semantics/publishedVersio

The intensive and the extensive margins : not only an international issue

Empirical evidence shows that quantity (intensive margin) and variety availability (extensive margin) have effects of different magnitude on populations’ welfare. Indeed, the pattern of a market dynamics may cause changes in welfare inequality. Low income consumers benefit more from quantity than high income consumers, who are more interested in enjoying variety. These facts have been usu- ally addressed as consequences of trade liberalization by international trade theory. However, market dynamics are also present within the borders of every country. It is important to understand what forces, unrelated with international trade, affect these dynamics. This paper explores the transmission of different real shocks into mar- ket dynamics in a new-Keynesian closed economy. Results show that the source of the shock is crucial to determine the magnitude and direction of the effects on each margin.info:eu-repo/semantics/publishedVersio

Robust tests for time-invariant individual heterogeneity versus dynamic state dependence

We derive tests for persistent effects in a general linear dynamic panel data context. Two sources of persistent behavior are considered: time-invariant unobserved factors (captured by an individual random effect) and dynamic persistence or “state dependence” (captured by autoregressive behavior). We will use a maximum likelihood framework to derive a family of tests that help researchers learn whether persistence is due to individual heterogeneity, dynamic effect, or both. The proposed tests have power only in the direction they are designed to perform, that is, they are locally robust to the presence of alternative sources of persistence, and consequently, are able to identify which source of persistence is active. A Monte Carlo experiment is implemented to explore the finite sample performance of the proposed procedures. The tests are applied to a panel data series of real GDP growth for the period 1960–2005

Early assembly of the most massive galaxies

The current consensus is that galaxies begin as small density fluctuations in the early Universe and grow by in situ star formation and hierarchical merging. Stars begin to form relatively quickly in sub-galactic sized building blocks called haloes which are subsequently assembled into galaxies. However, exactly when this assembly takes place is a matter of some debate. Here we report that the stellar masses of brightest cluster galaxies, which are the most luminous objects emitting stellar light, some 9 billion years ago are not significantly different from their stellar masses today. Brightest cluster galaxies are almost fully assembled 4-5 Gyrs after the Big Bang, having grown to more than 90% of their final stellar mass by this time. Our data conflict with the most recent galaxy formation models based on the largest simulations of dark matter halo development. These models predict protracted formation of brightest cluster galaxies over a Hubble time, with only 22% of the stellar mass assembled at the epoch probed by our sample. Our findings suggest a new picture in which brightest cluster galaxies experience an early period of rapid growth rather than prolonged hierarchical assembly.Comment: Published in Nature 2nd April 2009. This astro ph version includes main text and supplementary material combine

The XMM Cluster Survey: An independent demonstration of the fidelity of the eFEDS galaxy cluster data products and implications for future studies

We present the first comparison between properties of clusters of galaxies detected by the eROSITA Final Equatorial-Depth Survey (eFEDS) and the XMM Cluster Survey (XCS). We have compared, in an ensemble fashion, properties from the eFEDS X-ray cluster catalogue with those from the Ultimate XMM eXtragaLactic (XXL) survey project (XXL-100-GC). We find the redshift and temperature (TX) distributions to be similar, with a larger proportion of clusters above 4 keV in the XXL-100-GC sample; fractional temperature uncertainties are significantly larger in eFEDS compared to XXL. We find 62 eFEDS cluster candidates with XMM data (eFEDS-XMM sample); 10 do not have good enough XMM data to confirm or deny, 11 are classed as sample contaminants, and 4 have their X-ray flux contaminated by another source. The majority of eFEDS-XMM sources have longer XMM exposures than eFEDS, and most eFEDS positions are within 100 kpc of XCS positions. Our eFEDS-XCS sample of 37 clusters is used to calculate minimum sample contamination fractions of ∼18 and ∼9 per cent in the eFEDS X-ray and optically confirmed samples, respectively, in general agreement with eFEDS findings. We directly compare 29 X-ray luminosities (LX) measured by eFEDS and XCS, finding excellent agreement. Eight clusters have a TX measured by XCS and eFEDS, and we find that XMM temperatures are 25 ± 9 per cent larger than their eROSITA counterparts. Finally, we construct LX-TX scaling relations based on eFEDS and XCS measurements, which are in tension; the tension is decreased when we measure a third scaling relation with calibrated XCS temperatures

The XMM Cluster Survey: New evidence for the 3.5-keV feature in clusters is inconsistent with a dark matter origin

There have been several reports of a detection of an unexplained excess of X-ray emission at $\simeq$3.5 keV in astrophysical systems. One interpretation of this excess is the decay of sterile neutrino dark matter. The most influential study to date analysed 73 clusters observed by the XMM-Newton satellite. We explore evidence for a â 3.5-keV excess in the XMM-PN spectra of 117 redMaPPer galaxy clusters (0.1 < z < 0.6). In our analysis of individual spectra, we identify three systems with an excess of flux at $\simeq$3.5 keV. In one case (XCS J0003.3+0204), this excess may result from a discrete emission line. None of these systems are the most dark matter dominated in our sample. We group the remaining 114 clusters into four temperature (TX) bins to search for an increase in â 3.5-keV flux excess with TX-a reliable tracer of halo mass. However, we do not find evidence of a significant excess in flux at â 3.5 keV in any TX bins. To maximize sensitivity to a potentially weak dark matter decay feature at â 3.5 keV, we jointly fit 114 clusters. Again, no significant excess is found at â 3.5 keV. We estimate the upper limit of an undetected emission line at â 3.5 keV to be 2.41 × 10-6 photons cm-2 s-1, corresponding to a mixing angle of sin 2(2θ) = 4.4 × 10-11, lower than previous estimates from cluster studies. We conclude that a flux excess at â 3.5 keV is not a ubiquitous feature in clusters and therefore unlikely to originate from sterile neutrino dark matter decay. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society

Development of the Adolescent Preoccupation with Screens Scale

Abstract Background Although public health concerns have been raised regarding the detrimental health effects of increasing rates of electronic screen use among adolescents, such effects have been small. Instruments currently available tend to be lengthy, have a clinical research focus, and assess young people’s screen use on specific screen-based activities (e.g., TV, computer, or internet). None appear to address screen use across a broad range of screens, including mobile devices and screen-based activities. The objective was to develop a new and short self-report scale for investigating adolescents’ screen use across all screens and screen-based activities in non-clinical settings. Methods The Adolescent Preoccupation with Screens Scale (APSS) was developed over a three stage process. First, a review of the current literature and existing instruments was undertaken and suitable items identified. Second, the draft APSS was piloted with adolescents and item affectivity and discrimination indices were calculated. Third, a cross sectional school based online survey of 1967 Australian adolescents in grades 5 (10 years old), 7 (13 years) and 9 (15 years) from 25 randomly selected schools was conducted. Results Factor Analysis on a sub-sample of the data (n = 782) and Confirmatory Factor Analysis on the remaining sub-sample (n = 1185), supported a two-factor model. The first factor reflects adolescents’ mood management with screen use, and the second reflects a behavioural preoccupation. The measure demonstrated strong invariance across sex and across Grades 5, 7, and 9. Both factors displayed good internal consistency (α = .91 and .87, respectively). Sex and grade differences on both scales were investigated and boys in Grade 5 reported higher levels of both mood management and behavioural preoccupation with screens. There were no sex differences on mood management in Grades 7 and 9, but girls reported higher behavioural preoccupation in both these later grades. Conclusion The APSS provides researchers with a new, brief and robust measure of potentially problematic screen use across a wide array of screens, including mobile devices, so readily accessed during adolescence

Ventilatory muscle strength, diaphragm thickness and pulmonary function in world-class powerlifters.

Resistance training activates the ventilatory muscles providing a stimulus similar to ventilatory muscle training. We examined the effects of elite powerlifting training upon ventilatory muscle strength, pulmonary function and diaphragm thickness in world-class powerlifters (POWER) and a control group (CON) with no history of endurance or resistance training, matched for age, height and body mass