Fatigue and Recovery Profiles of Unilateral Resistance Exercise in a Resistance Trained Population

Recent data shows that fatiguing unilateral isometric contractions affect the performance of the non-exercising, contralateral muscles (i.e., cross-over effect). However, there is limited data on the time-course of the contralateral response, whether the effects occur during resistance exercise, and the influence of resistance training experience. PURPOSE: To examine force and electromyographic (EMG) activity during and after a fatiguing unilateral resistance exercise protocol for the ipsilateral and contralateral elbow flexors in a resistance trained population. METHODS: Eight participants (7 right hand dominant; mean age=22yrs; 7 males; resistance trained with ≥ 2days/week upper body) visited the laboratory on two days separated by ≥ 48 hrs. On the first visit, maximal dynamic strength was determined for the ipsilateral arm and control procedures for maximal isometric strength of the contralateral arm was performed. On the second visit, participants completed 4 sets of unilateral dynamic bicep curls to failure with 50% 1RM with 2 min rest intervals between sets. Maximal voluntary contractions (MVC) and EMG activity of the elbow flexors were recorded immediately before exercise and after each set for both arms, except for set 1 and 3 where only the ipsilateral arm performed MVC’s. The responses during acute recovery were recorded at 2.5 min, 5 mins, and 10 mins post exercise. Separate repeated measures ANOVA tests were performed on the MVC and EMG responses for each arm. Alpha was set at 0.05. RESULTS: The results of the analysis show that for the ipsilateral arm, baseline MVC values declined to set 1 (p\u3c0.01; ~26%), with no significant differences in force loss thereafter for set 2 (~29%), set 3 (~28%), set 4 (~30%), recovery 1 (~28%), recovery 2 (~27%), or recovery 3 (~24%). There was no significant change in maximal EMG activity for the ipsilateral biceps brachii (p=0.189; ηp2 =0.177). For the contralateral biceps brachii, there was no significant difference across time in maximal EMG activity between the fatigue visit versus the control visit (p=0.732; ηp2=0.018). However, collapsed across visit, there was a significant decrease in maximal EMG amplitude (p\u3c0.01; ηp2=0.614) that appears to be explained by the fatigue visit (p=0.319; d=0.379). For the contralateral arm, there was no significant change in MVC across time for either visit (p=0.166; ηp2=0.211). CONCLUSION: These results show that following acute resistance exercise performed to failure, there is no change in maximal force of the contralateral elbow flexors. This finding brings into question whether the cross-over effect of fatigue occurs during resistance exercise or in resistance trained populations. The fatigability profile of the ipsilateral arm demonstrates there was no compounding effect on force loss with additional sets to failure. The lack of force recovery following acute resistance exercise emphasizes the importance of task dependency. The applications of these data suggests that relative fatigability may not be a useful metric to monitor training session outcomes

Author Correction: Clustering and climate associations of Kawasaki Disease in San Diego County suggest environmental triggers.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper

‘Working With Kids At Risk and Making a Difference, On The Street’

If you are an educator, a teacher, a student or a community leader you need NOT to miss this presentation. Learn how a group of Georgia Southern students are changing the lives of children at risk in their town, Statesboro, Georgia

Development of an international scale of socio-economic position based on household assets.

The importance of studying associations between socio-economic position and health has often been highlighted. Previous studies have linked the prevalence and severity of lung disease with national wealth and with socio-economic position within some countries but there has been no systematic evaluation of the association between lung function and poverty at the individual level on a global scale. The BOLD study has collected data on lung function for individuals in a wide range of countries, however a barrier to relating this to personal socio-economic position is the need for a suitable measure to compare individuals within and between countries. In this paper we test a method for assessing socio-economic position based on the scalability of a set of durable assets (Mokken scaling), and compare its usefulness across countries of varying gross national income per capita.Ten out of 15 candidate asset questions included in the questionnaire were found to form a Mokken type scale closely associated with GNI per capita (Spearmans rank rs = 0.91, p = 0.002). The same set of assets conformed to a scale in 7 out of the 8 countries, the remaining country being Saudi Arabia where most respondents owned most of the assets. There was good consistency in the rank ordering of ownership of the assets in the different countries (Cronbachs alpha = 0.96). Scores on the Mokken scale were highly correlated with scores developed using principal component analysis (rs = 0.977).Mokken scaling is a potentially valuable tool for uncovering links between disease and socio-economic position within and between countries. It provides an alternative to currently used methods such as principal component analysis for combining personal asset data to give an indication of individuals relative wealth. Relative strengths of the Mokken scale method were considered to be ease of interpretation, adaptability for comparison with other datasets, and reliability of imputation for even quite large proportions of missing values

Venturi air-jet vacuum ejectors for high-volume atmospheric sampling on aircraft platforms

Documentation of the installation and use of venturi air-jet vacuum ejectors for high-volume atmospheric sampling on aircraft platforms is presented. Information on the types of venturis that are useful for meeting the pumping requirements of atmospheric-sampling experiments is also presented. A description of the configuration and installation of the venturi system vacuum line is included with details on the modifications that were made to adapt a venturi to the NASA Electra aircraft at GSFC, Wallops Flight Facility. Flight test results are given for several venturis with emphasis on applications to the Differential Absorption Carbon Monoxide Measurement (DACOM) system at LaRC. This is a source document for atmospheric scientists interested in using the venturi systems installed on the NASA Electra or adapting the technology to other aircraft

Science for a wilder Anthropocene: synthesis and future directions for trophic rewilding research

Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and resulting trophic downgrading, it often focuses on restoring functional megafaunas. Trophic rewilding is increasingly being implemented for conservation, but remains controversial. Here, we provide a synthesis of its current scientific basis, highlighting trophic cascades as the key conceptual framework, discussing the main lessons learned from ongoing rewilding projects, systematically reviewing the current literature, and highlighting unintentional rewilding and spontaneous wildlife comebacks as underused sources of information. Together, these lines of evidence show that trophic cascades may be restored via species reintroductions and ecological replacements. It is clear, however, that megafauna effects may be affected by poorly understood trophic complexity effects and interactions with landscape settings, human activities, and other factors. Unfortunately, empirical research on trophic rewilding is still rare, fragmented, and geographically biased, with the literature dominated by essays and opinion pieces. We highlight the need for applied programs to include hypothesis testing and science-based monitoring, and outline priorities for future research, notably assessing the role of trophic complexity, interplay with landscape settings, land use, and climate change, as well as developing the global scope for rewilding and tools to optimize benefits and reduce human–wildlife conflicts. Finally, we recommend developing a decision framework for species selection, building on functional and phylogenetic information and with attention to the potential contribution from synthetic biology

Association between chronic airflow obstruction and socio-economic position in Morocco: BOLD results.

Objective. Chronic Obstructive Lung Disease (COPD) is the third most common cause of death in the world. Other factors than smoking could be involved in the development of COPD such as socio-economic status. The aim of this study was to investigate the association between chronic airflow obstruction and socio-economic status in Morocco. Design. In the BOLD (Burden of Obstructive Lung Disease) study carried out in Fez Morocco, questionnaires and spirometry tests were performed. Socio-economic status was evaluated using a wealth score (0-10) based on household assets. The forced expiratory volume in 1s (FEV1)/ forced vital capacity (FVC) ratio was used to measure airflow obstruction. Results. In total, 760 subjects were included in the analysis. The mean age was 55.3 years (SD=10.2); the wealth score was on average 7.54 (SD=1.63). After controlling for other factors and potential confounders, the FEV1/ FVC increased by 0.4% (95% CI: 0.01, 0.78; p<0.04) per unit increase in wealth score. Aging, tobacco-smoking, underweight, history of tuberculosis and asthma were also independently associated with a higher risk of airflow obstruction. Conclusion. Our findings suggest that airflow obstruction is associated with poverty in Morocco. Further investigations are needed to better understand the mechanisms of this association

The Hemocompatibility of a Nitric Oxide Generating Polymer that Catalyzes S-nitrosothiol Decomposition in an Extracorporeal Circulation Model

Nitric oxide (NO) generating (NOGen) materials have been shown previously to create localized increases in NO concentration by the catalytic decomposition of blood S-nitrosothiols (RSNO) via copper (Cu)-containing polymer coatings and may improve extracorporeal circulation (ECC) hemocompatibility. In this work, a NOGen polymeric coating composed of a Cuo-nanoparticle (80 nm)-containing hydrophilic polyurethane (SP-60D-60) combined with the intravenous infusion of an RSNO, S- nitroso-N-acetylpenicillamine (SNAP), is evaluated in a 4 h rabbit thrombogenicity model and the anti-thrombotic mechanism is investigated. Polymer films containing 10 wt.% Cuo-nanoparticles coated on the inner walls of ECC circuits are employed concomitantly with systemic SNAP administration (0.1182 μmol/kg/min) to yield significantly reduced ECC thrombus formation compared to polymer control + systemic SNAP or 10 wt.% Cu NOGen + systemic saline after 4 h blood exposure (0.4 ± 0.2 NOGen/SNAP vs 4.9 ± 0.5 control/SNAP or 3.2 ± 0.2 pixels/cm2 NOGen/saline). Platelet count (3.9 ± 0.7 NOGen/SNAP vs 1.8 ± 0.1 control/SNAP or 3.0 ± 0.2 × 108/ml NOGen/saline) and plasma fibrinogen levels were preserved after 4 h blood exposure with the NOGen/SNAP combination vs either the control/SNAP or the NOGen/saline groups. Platelet function as measured by aggregometry (51 ± 9 NOGen/SNAP vs 49 ± 3% NOGen/saline) significantly decreased in both the NOGen/SNAP and NOGen/saline groups while platelet P-selectin mean fluorescence intensity (MFI) as measured by flow cytometry was not decreased after 4 h on ECC to ex vivo collagen stimulation (26 ± 2 NOGen/SNAP vs 29 ± 1 MFI baseline). Western blotting showed that fibrinogen activation as assessed by Aγ dimer expression was reduced after 4 h on ECC with NOGen/SNAP (68 ± 7 vs 83 ± 3% control/SNAP). These results suggest that the NOGen polymer coating combined with SNAP infusion preserves platelets in blood exposure to ECCs by attenuating activated fibrinogen and preventing platelet aggregation. These NO-mediated platelet changes were shown to improve thromboresistance of the NOGen polymer-coated ECCs when adequate levels of RSNOs are present