The role of sense of effort on self-selected cycling power output

PURPOSE: We explored the effects of the sense of effort and accompanying perceptions of peripheral discomfort on self-selected cycle power output under two different inspired O2 fractions. METHODS: On separate days, eight trained males cycled for 5 min at a constant subjective effort (sense of effort of '3' on a modified Borg CR10 scale), immediately followed by five 4-s progressive submaximal (sense of effort of "4, 5, 6, 7, and 8"; 40 s between bouts) and two 4-s maximal (sense of effort of "10"; 3 min between bouts) bouts under normoxia (NM: fraction of inspired O2 [FiO2] 0.21) and hypoxia (HY: [FiO2] 0.13). Physiological (Heart Rate, arterial oxygen saturation (SpO2) and quadriceps Root Mean Square (RMS) electromyographical activity) and perceptual responses (overall peripheral discomfort, difficulty breathing and limb discomfort) were recorded. RESULTS: Power output and normalized quadriceps RMS activity were not different between conditions during any exercise bout (p > 0.05) and remained unchanged across time during the constant-effort cycling. SpO2 was lower, while heart rate and ratings of perceived difficulty breathing were higher under HY, compared to NM, at all time points (p < 0.05). During the constant-effort cycling, heart rate, overall perceived discomfort, difficulty breathing and limb discomfort increased with time (all p < 0.05). All variables (except SpO2) increased along with sense of effort during the brief progressive cycling bouts (all p < 0.05). During the two maximal cycling bouts, ratings of overall peripheral discomfort displayed an interaction between time and condition with ratings higher in the second bout under HY vs. NM conditions. CONCLUSION: During self-selected, constant-effort and brief progressive, sub-maximal, and maximal cycling bouts, mechanical work is regulated in parallel to the sense of effort, independently from peripheral sensations of discomfort

Preceding Race Efforts Affect Pacing and Short-Track Speed Skating Performance

Purpose: To examine whether preceding high-intensity race efforts in a competitive weekend affected pacing behaviour and performance in elite short-track speed skaters. Methods: Finishing and intermediate lap times were gathered from 500, 1000 and 1500 m Short Track Speed Skating World Cups during the seasons 2011-2016. The effect of preceding races on pacing behaviour and performance was explored using two studies. Study I: the effect of competing in extra races due to the Repechage (Rep) system, leading to an increased number of high-intensity race efforts prior to the subsequent main tournament race, was explored (500m: N=32, 1000m: N=34; 1500m: N=47). Study II: the performance of skaters over the tournament days was evaluated (500m: N=129, 1000m: N=54; 1500m: N=114). For both analytic approaches, a two-way repeated measures ANOVA was used to assess differences in pacing and performance within the skater over the races. Results: An additional number of preceding high-intensity race efforts due to the Rep system reduced the qualification percentage in the first main tournament race for the next stage of competition in all events (500m: Direct qualification=57.3%, Rep=25.0%; 1000m: Direct=44.2%, Rep=28.3%; 1500m: Direct=27.1%, Rep=18.2%), and led to a decreased pace in the initial two laps of the 500m event. In contrast, Tournament day (Saturday vs Sunday) only affected the pacing behaviour of female skaters during the 1500m event. Conclusion: High-intensity race efforts earlier on the day affected pacing and performance of elite skaters, while the effect of high-intensity race efforts from the previous day seem to be only marginal

Mechanisms of CFTR Functional Variants That Impair Regulated Bicarbonate Permeation and Increase Risk for Pancreatitis but Not for Cystic Fibrosis

CFTR is a dynamically regulated anion channel. Intracellular WNK1-SPAK activation causes CFTR to change permeability and conductance characteristics from a chloride-preferring to bicarbonate-preferring channel through unknown mechanisms. Two severe CFTR mutations (CFTRsev) cause complete loss of CFTR function and result in cystic fibrosis (CF), a severe genetic disorder affecting sweat glands, nasal sinuses, lungs, pancreas, liver, intestines, and male reproductive system. We hypothesize that those CFTR mutations that disrupt the WNK1-SPAK activation mechanisms cause a selective, bicarbonate defect in channel function (CFTRBD) affecting organs that utilize CFTR for bicarbonate secretion (e.g. the pancreas, nasal sinus, vas deferens) but do not cause typical CF. To understand the structural and functional requirements of the CFTR bicarbonate-preferring channel, we (a) screened 984 well-phenotyped pancreatitis cases for candidate CFTRBD mutations from among 81 previously described CFTR variants; (b) conducted electrophysiology studies on clones of variants found in pancreatitis but not CF; (c) computationally constructed a new, complete structural model of CFTR for molecular dynamics simulation of wild-type and mutant variants; and (d) tested the newly defined CFTRBD variants for disease in non-pancreas organs utilizing CFTR for bicarbonate secretion. Nine variants (CFTR R74Q, R75Q, R117H, R170H, L967S, L997F, D1152H, S1235R, and D1270N) not associated with typical CF were associated with pancreatitis (OR 1.5, p = 0.002). Clones expressed in HEK 293T cells had normal chloride but not bicarbonate permeability and conductance with WNK1-SPAK activation. Molecular dynamics simulations suggest physical restriction of the CFTR channel and altered dynamic channel regulation. Comparing pancreatitis patients and controls, CFTRBD increased risk for rhinosinusitis (OR 2.3, p<0.005) and male infertility (OR 395, p≪0.0001). WNK1-SPAK pathway-activated increases in CFTR bicarbonate permeability are altered by CFTRBD variants through multiple mechanisms. CFTRBD variants are associated with clinically significant disorders of the pancreas, sinuses, and male reproductive system. © 2014 Whitcomb et al

Physiological and Psychological Effects of Deception on Pacing Strategy and Performance: A Review

The aim of an optimal pacing strategy during exercise is to enhance performance whilst ensuring physiological limits are not surpassed, which has been shown to result in a metabolic reserve at the end of the exercise. There has been debate surrounding the theoretical models that have been proposed to explain how pace is regulated, with more recent research investigating a central control of exercise regulation. Deception has recently emerged as a common, practical approach to manipulate key variables during exercise. There are a number of ways in which deception interventions have been designed, each intending to gain particular insights into pacing behaviour and performance. Deception methodologies can be conceptualised according to a number of dimensions such as deception timing (prior to or during exercise), presentation frequency (blind, discontinuous or continuous) and type of deception (performance, biofeedback or environmental feedback). However, research evidence on the effects of deception has been perplexing and the use of complex designs and varied methodologies makes it difficult to draw any definitive conclusions about how pacing strategy and performance are affected by deception. This review examines existing research in the area of deception and pacing strategies, and provides a critical appraisal of the different methodological approaches used to date. It is hoped that this analysis will inform the direction and methodology of future investigations in this area by addressing the mechanisms through which deception impacts upon performance and by elucidating the potential application of deception techniques in training and competitive settings

Drive in sports: How mental fatigue affects endurance performance

Performance in endurance sports relies on athletes' drive, which is the sum of all factors pushing athletes to exert effort during exercise. Mental fatigue can influence endurance performance by decreasing athletes' drive to exercise. From a psychological point of view, mental fatigue has two separate components: it can affect drive by increasing the perceived effort necessary for a given task ("I cannot do this, I am too exhausted"), or by decreasing the perceived value of the reward that can be obtained ("I do not want to do this, it is not worth it"). Neurophysiological theories confirm this dual nature of mental fatigue. It is suggested that mental fatigue can activate the inhibition centers of the brain, increasing perceived effort for a given task, hence decreasing drive and willingness to act. On the other hand, it may also deactivate facilitative brain centers (normally responsible for motivated behavior and increased drive toward a reward), also resulting in decreased drive. In this Perspective we will adopt a multidimensional approach, describing how mental fatigue interacts with drive and performance in endurance exercise. We aim to show how mental fatigue affects endurance performance via two main mechanisms: perceived effort and reward. We will study the interaction between mental fatigue and other factors impacting on drive, such as perceived exertion and motivation, and examine how these factors combined result in athletes' exercise behavior (such as pacing) and performance. This will provide researchers, coaches, and athletes with useful tools in order to understand, influence and enhance athletes' drive in exercise, which is of high relevance in elite endurance sports, where mental fatigue, motivation, and stakes all are of the highest level

Abatement of styrene waste gas emission by biofilter and biotrickling filter: comparison of packing materials and inoculation procedures

The removal of styrene was studied using 2 biofilters packed with peat and coconut fibre (BF1-P and BF2-C, respectively) and 1 biotrickling filter (BTF) packed with plastic rings. Two inoculation procedures were applied: an enriched culture with strain Pseudomonas putida CECT 324 for biofilters and activated sludge from a municipal wastewater treatment plant for the BTF. Inlet loads (ILs) between 10 and 45 g m-3 h-1 and empty bed residence times (EBRTs) from 30 to 120 s were applied. At inlet concentrations ranging between 200 and 400 mg Nm-3, removal efficiencies between 70 and 95% were obtained in the 3 bioreactors. Maximum elimination capacities (ECs) of 81 and 39 g m-3 h-1 were obtained for the first quarter of the BF1-P and BF2-C, respectively (IL of 173 g m-3 h-1 and EBRT of 60 s in BF1-P; IL of 89 g m-3 h-1 and EBRT of 90 s in BF2-C). A maximum EC of 52 g m-3 h-1 was obtained for the first third of the BTF (IL of 116 g m-3 h-1, EBRT of 45 s). Problems regarding high pressure drop appeared in the peat biofilter, whereas drying episodes occurred in the coconut fibre biofilter. DGGE revealed that the pure culture used for biofilter inoculation was not detected by day 105. Although 2 different inoculation procedures were applied, similar styrene removal at the end of the experiments was observed. The use as inoculum of activated sludge from municipal wastewater treatment plant appears a more feasible option

Targeted emission reductions from global super-polluting power plant units

There are more than 30,000 biomass- and fossil-fuel-burning power plants now operating worldwide, reflecting a tremendously diverse infrastructure, which ranges in capacity from less than a megawatt to more than a gigawatt. In 2010, 68.7% of electricity generated globally came from these power plants, compared with 64.2% in 1990. Although the electricity generated by this infrastructure is vital to economic activity worldwide, it also produces more CO2 and air pollutant emissions than infrastructure from any other industrial sector. Here, we assess fuel- and region-specific opportunities for reducing undesirable air pollutant emissions using a newly developed emission dataset at the level of individual generating units. For example, we find that retiring or installing emission control technologies on units representing 0.8% of the global coal-fired power plant capacity could reduce levels of PM2.5 emissions by 7.7–14.2%. In India and China, retiring coal-fired plants representing 1.8% and 0.8% of total capacity can reduce total PM2.5 emissions from coal-fired plants by 13.2% and 16.0%, respectively. Our results therefore suggest that policies targeting a relatively small number of ‘super-polluting’ units could substantially reduce pollutant emissions and thus the related impacts on both human health and global climate

The diagnosis of male infertility:an analysis of the evidence to support the developments of global WHO guidance. Challenges and future research opportunities

Background: Herein, we describe the consensus guideline methodology, summarize the evidence-based recommendations we provided to the World Health Organization (WHO) for their consideration in the development of global guidance and present a narrative review of the diagnosis of male infertility as related to the eight prioritized (problem or population (P), intervention (I), comparison (C) and outcome(s) (O) (PICO)) questions. Additionally, we discuss the challenges and research gaps identified during the synthesis of this evidence.Objective and Rationale: The aim of this paper is to present an evidence-based approach for the diagnosis of male infertility as related to the eight prioritized PICO questions.Search Methods: Collating the evidence to support providing recommendations involved a collaborative process as developed by WHO, namely: identification of priority questions and critical outcomes; retrieval of up-to-date evidence and existing guidelines; assessment and synthesis of the evidence; and the formulation of draft recommendations to be used for reaching consensus with a wide range of global stakeholders. For each draft recommendation the quality of the supporting evidence was then graded and assessed for consideration during a WHO consensus.Outcomes: Evidence was synthesized and recommendations were drafted to address the diagnosis of male infertility specifically encompassing the following: What is the prevalence of male infertility and what proportion of infertility is attributable to the male? Is it necessary for all infertile men to undergo a thorough evaluation? What is the clinical (ART/non ART) value of traditional semen parameters? What key male lifestyle factors impact on fertility (focusing on obesity, heat and tobacco smoking)? Do supplementary oral antioxidants or herbal therapies significantly influence fertility outcomes for infertile men? What are the evidence-based criteria for genetic screening of infertile men? How does a history of neoplasia and related treatments in the male impact on (his and his partner’s) reproductive health and fertility options? And lastly, what is the impact of varicocele on male fertility and does correction of varicocele improve semen parameters and/or fertility?Wider Implications: This evidence synthesis analysis has been conducted in a manner to be considered for global applicability for the diagnosis of male infertility

Regulation of Pacing Strategy during Athletic Competition

Background: Athletic competition has been a source of interest to the scientific community for many years, as a surrogate of the limits of human ambulatory ability. One of the remarkable things about athletic competition is the observation that some athletes suddenly reduce their pace in the mid-portion of the race and drop back from their competitors. Alternatively, other athletes will perform great accelerations in mid-race (surges) or during the closing stages of the race (the endspurt). This observation fits well with recent evidence that muscular power output is regulated in an anticipatory way, designed to prevent unreasonably large homeostatic disturbances. Principal Findings: Here we demonstrate that a simple index, the product of the momentary Rating of Perceived Exertion (RPE) and the fraction of race distance remaining, the Hazard Score, defines the likelihood that athletes will change their velocity during simulated competitions; and may effectively represent the language used to allow anticipatory regulation of muscle power output. Conclusions: These data support the concept that the muscular power output during high intensity exercise performance is actively regulated in an anticipatory manner that accounts for both the momentary sensations the athlete is experiencing as well as the relative amount of a competition to be completed

Use of cultivation-dependent and -independent techniques to assess contamination of central venous catheters: a pilot study

<p>Abstract</p> <p>Background</p> <p>Catheters are the most common cause of nosocomial infections and are associated with increased risk of mortality, length of hospital stay and cost. Prevention of infections and fast and correct diagnosis is highly important.</p> <p>Methods</p> <p>In this study traditional semiquantitative culture-dependent methods for diagnosis of bacteria involved in central venous catheter-related infections as described by Maki were compared with the following culture-independent molecular biological methods: Clone libraries, denaturant gradient gel electrophoresis, phylogeny and fluorescence in situ hybridization.</p> <p>Results</p> <p>In accordance with previous studies, the cultivation of central venous catheters from 18 patients revealed that <it>S. epidermidis </it>and other coagulase-negative staphylococci were most abundant and that a few other microorganisms such as <it>P. aeruginosa </it>and <it>K. pneumoniae </it>occasionally were found on the catheters. The molecular analysis using clone libraries and sequencing, denaturant gradient gel electrophoresis and sequencing provided several important results. The species found by cultivation were confirmed by molecular methods. However, many other bacteria belonging to the phyla <it>Proteobacteria, Firmicutes, Actinobacteria </it>and <it>Bacteroidetes </it>were also found, stressing that only a minor portion of the species present were found by cultivation. Some of these bacteria are known to be pathogens, some have not before been described in relation to human health, and some were not closely related to known pathogens and may represent new pathogenic species. Furthermore, there was a clear difference between the bacterial species found in biofilm on the external (exluminal) and internal (luminal) side of the central venous catheter, which can not be detected by Maki's method. Polymicrobial biofilms were observed on most of the catheters and were much more common than the cultivation-dependent methods indicated.</p> <p>Conclusion</p> <p>The results show that diagnosis based on molecular methods improves the detection of microorganisms involved in central catheter-related infections. The importance of these microorganisms needs to be investigated further, also in relation to contamination risk from improper catheter handling, as only in vivo contaminants are of interest. This information can be used for development of fast and more reliable diagnostic tools, which can be used in combination with traditional methods.</p