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Critical power and fatigue

Reem Jarrad, Sawsan Hammad, Tagreed Shawashi, Naser Mahmoud
Aim: This study aimed to detect if there were differences in compassion fatigue (CF) among nurses based on substance use and demographic variables of gender, marital status, type of health institution and income. Background: Compassion fatigue is considered an outcome of poorly handled stressful situations in which nurses may respond with self-harming behaviours like substance use. Evidence in this area is critically lacking. Methods: This study used a descriptive design to survey differences in CF of 282 nurses...
2018: Annals of General Psychiatry
Ida E Clark, Anni Vanhatalo, Stephen J Bailey, Lee J Wylie, Brett S Kirby, Brad W Wilkins, Andrew M Jones
INTRODUCTION: Changes in the parameters of the power-time relationship (critical power (CP) and W') during endurance exercise would have important implications for performance. We tested the hypotheses that CP and W', estimated using the end-test power (EP) and the work done above EP (WEP), respectively, during a the 3-min all-out test (3MT), can be reliably determined, and would be lower, after completing 2-h of heavy-intensity exercise. METHODS: In study 1, six cyclists completed a 3MT immediately following 2-h of heavy-intensity exercise on two occasions to establish the reliability of EP and WEP...
March 8, 2018: Medicine and Science in Sports and Exercise
Leandro Camati Felippe, Guilherme Assuncao Ferreira, Sara Kely Learsi, Daniel Boari, Rômulo Bertuzzi, Adriano Eduardo Lima-Silva
The link between total work performed above critical power (CP) and peripheral muscle fatigue during self-paced exercise is unknown. We investigated the influence of caffeine on the total work done above CP during a 4-km cycling time trial (TT), and the subsequent consequence on the development of central and peripheral fatigue. Nine cyclists performed three constant-load exercise trials to determine CP and two 4-km TT ~75 min after oral caffeine (5 mg·kg-1 ) or cellulose (placebo) ingestion. Neuromuscular functions were assessed before and 50 min after supplementation, and 1 min after TT...
February 22, 2018: Journal of Applied Physiology
Haley C Bergstrom, M Travis Byrd, Brian J Wallace, Jody L Clasey
This study examined the acute effects of a multi-ingredient pre-workout supplement on: 1) total, lower, and upper body volume of resistance exercise; and 2) the subsequent lower body strength (isokinetic leg extension and flexion), lower (vertical jump [VJ] height), upper body power (bench-throw velocity [BTv]), and cycle ergometry performance (critical power [CP] and anaerobic work capacity [AWC]). Twelve men completed baseline strength and power measures prior to two experimental visits, supplement (SUP) and placebo (PL)...
February 1, 2018: Journal of Strength and Conditioning Research
Gill Sang Han, Seongha Lee, Matthew Duff, Fen Qin, Jung-Kun Lee
We report highly bendable and efficient perovskite solar cells (PSCs) that use thermally oxidized layer of Ti metal plate as an electron transport layer (ETL). The power conversion efficiency (PCE) of flexible PSCs reaches 14.9 % with short-circuit current density (Jsc) of 17.9 mA/cm2, open circuit voltage (Voc) of 1.09, and fill factor (ff) of 0.74. Moreover, the Ti metal based PSCs exhibit a superior fatigue resistance over ITO/PEC substrate. Flexible PSCs maintain 100 % of their initial PCE even after PSCs are bent 1000 times at the bending radius of 4 mm...
January 16, 2018: ACS Applied Materials & Interfaces
J Matt McCrary, Bronwen J Ackermann, Mark Halaki
OBJECTIVES: Electromyographic (EMG) fatigue threshold (EMGFT ) is utilised as a correlate of critical power, torque, and force thresholds that establishes a theoretical exercise intensity-the power, torque, or force at which the rate of change of EMG amplitude (ΔEM¯G) is zero-below which neuromuscular fatigue is negligible and unpredictable. Recent studies demonstrating neuromuscular fatigue below critical thresholds raise questions about the construct validity of EMGFT . The purpose of this analysis is to evaluate the construct validity of EMGFT by aggregating ΔEM¯G and time to task failure (Tlim ) data...
November 11, 2017: Journal of Science and Medicine in Sport
Hawbeer Salam, Samuele M Marcora, James G Hopker
PURPOSE: Time to exhaustion (TTE) tests used in the determination of critical power (CP) and curvature constant (W') of the power-duration relationship are strongly influenced by the perception of effort (PE). This study aimed to investigate whether manipulation of the PE alters the CP and W'. METHODS: Eleven trained cyclists completed a series of TTE tests to establish CP and W' under two conditions, following a mentally fatiguing (MF), or a control (CON) task...
January 2018: European Journal of Applied Physiology
Paul Ansdell, Kevin Thomas, Glyn Howatson, Markus Amann, Stuart Goodall
PURPOSE: To investigate the effects of feedback, in the form of a virtual avatar paced at 100 and 102% of baseline performance, on neuromuscular fatigue following a 4 km cycling time trial (TT). We hypothesised that improved cycling performance would occur due to participants exceeding a previously established critical threshold, and experiencing greater neuromuscular fatigue. METHODS: Following familiarisation, ten well-trained cyclists performed a baseline 4 km TT without feedback (BASE), followed by two, 4 km TT where they raced against an avatar (set at 100% [accurate - ACC] and 102% [deception - DEC] of baseline power output), in a randomised and counterbalanced order...
November 7, 2017: Medicine and Science in Sports and Exercise
Philippa Miller, Andrew Soundy
AIM: The clinical aim was to provide up-to-date evidence-based recommendations for the treatment of MS-related fatigue (MSRF). The scientific aim was to prioritise topics for future randomised clinical trials with sufficient power. METHODS: A systematic search of review based research that considered MSRF in adults (18years and over) was undertaken in May 2016. Data from reviews was extracted, critically appraised and synthesised using four specific techniques. RESULTS: A total of 24 reviews were identified (17 non-pharmacological, 5 pharmacological, 2 combining both), which contained 339 studies on interventions deigned to improve MSRF...
October 15, 2017: Journal of the Neurological Sciences
Priyantha Herath, Martin Carmichael, Angela Murphy, Leonardo Bonilha, Roger Newman-Norlund, Chris Rorden, Mark Davis
Strenuous exercise leads to a progressive reduction in the performance of voluntary physical exercise. This is due to a process described as fatigue and is defined as the failure to maintain the required or expected power output. While some of this is muscular in origin, there are data suggestive of how fatigue is modulated by cortical signals, leading to a concept of central fatigue. The previously reported fatigue-induced changes in cortical activity may have been due to blood oxygen-dependent (BOLD) signal drift and/or neural habituation alone...
2017: Frontiers in Neurology
Amitava Halder, Kalev Kuklane, Chuansi Gao, Michael Miller, Mattias Delin, Johan Norén, Karl Fridolf
Stair ascending performance is critical during evacuation from buildings and underground infrastructures. Healthy subjects performed self-paced ascent in three settings: 13 floor building, 31 floor building, 33 m stationary subway escalator. To investigate leg muscle and cardiorespiratory capacities and how they constrain performance, oxygen uptake (VO2), heart rate (HR) and ascending speed were measured in all three; electromyography (EMG) in the first two. The VO2 and HR ranged from 89 to 96% of the maximum capacity reported in the literature...
January 2018: Applied Ergonomics
Angelos P Kassianos, Myria Ioannou, Marianna Koutsantoni, Haris Charalambous
PURPOSE: Specialized palliative care (SPC) is currently underutilized or provided late in cancer care. The aim of this systematic review and meta-analysis is to critically evaluate the impact of SPC on patients' health-related quality of life (HRQoL). METHODS: Five databases were searched through June 2016. Randomized controlled trials (RCTs) and prospective studies using a pre- and post- assessment of HRQoL were included. The PRISMA reporting statement was followed...
January 2018: Supportive Care in Cancer: Official Journal of the Multinational Association of Supportive Care in Cancer
Tushti Bhardwaj, Jonathan Koffman
OBJECTIVES: Fatigue is common among children living with cancer, particularly in advance stages. Little is known about the effectiveness of non-pharmacological approaches to manage this complex and distressing symptom among children. Thus, the present paper aim to critically examine the effectiveness and setting for non-pharmacological interventions to manage fatigue among children with cancer. METHODS: Six electronic databases were screened first in February 2013 and at second instance in March 2015...
July 31, 2017: BMJ Supportive & Palliative Care
Sungho Kim, Taehwan Cho, Yongkyun Lee, Hyojin Koo, Booyong Choi, Dongsoo Kim
BACKGROUND: G-induced loss of consciousness (G-LOC) is mainly caused by failure to sustain an oxygenated blood supply to the pilot's brain because of the sudden acceleration in the direction of the +Gz axis, and is considered a critical safety issue. The purpose of this study was to develop G-LOC warning algorithms based on monitoring electromyograms (EMG) of the gastrocnemius muscle on the calf. METHODS: EMG data was retrieved from a total of 67 pilots and pilot trainees of the Korean Air Force during high-G training on a human centrifugal simulator...
August 1, 2017: Aerospace Medicine and Human Performance
Timothy F O'Connor, Matthew E Fach, Rachel Miller, Samuel E Root, Patrick P Mercier, Darren J Lipomi
This communication describes a glove capable of wirelessly translating the American Sign Language (ASL) alphabet into text displayable on a computer or smartphone. The key components of the device are strain sensors comprising a piezoresistive composite of carbon particles embedded in a fluoroelastomer. These sensors are integrated with a wearable electronic module consisting of digitizers, a microcontroller, and a Bluetooth radio. Finite-element analysis predicts a peak strain on the sensors of 5% when the knuckles are fully bent...
2017: PloS One
Tae Gwang Yun, Donghyuk Kim, Yong Ho Kim, Minkyu Park, Seungmin Hyun, Seung Min Han
Electrochromic devices have been widely adopted in energy saving applications by taking advantage of the electrode coloration, but it is critical to develop a new electrochromic device that can undergo smart coloration and can have a wide spectrum in transmittance in response to input light intensity while also functioning as a rechargeable energy storage system. In this study, a photoresponsive electrochromic supercapacitor based on cellulose-nanofiber/Ag-nanowire/reduced-graphene-oxide/WO3 -composite electrode that is capable of undergoing "smart" reversible coloration while simultaneously functioning as a reliable energy-storage device is developed...
August 2017: Advanced Materials
Evangelia Akoumianaki, Nicolas Dousse, Aissam Lyazidi, Jean-Claude Lefebvre, Severine Graf, Ricardo Luiz Cordioli, Nathalie Rey, Jean-Christophe Marie Richard, Laurent Brochard
BACKGROUND: Early exercise of critically ill patients may have beneficial effects on muscle strength, mass and systemic inflammation. During pressure support ventilation (PSV), a mismatch between demand and assist could increase work of breathing and limit exercise. A better exercise tolerance is possible with a proportional mode of ventilation (Proportional Assist Ventilation, PAV+ and Neurally Adjusted Ventilatory Assist, NAVA). We examined whether, in critically ill patients, PSV and proportional ventilation have different effects on respiratory muscles unloading and work efficiency during exercise...
December 2017: Annals of Intensive Care
Peter Hofmann, Gerhard Tschakert
The regulation of endurance training is usually based on the prescription of exercise intensity. Exercise duration, another important variable of training load, is rarely prescribed by individual measures and mostly set from experience. As the specific exercise duration for any intensity plays a substantial role regarding the different kind of cellular stressors, degree, and kind of fatigue as well as training effects, concepts integrating the prescription of both intensity and duration within one model are needed...
2017: Frontiers in Physiology
Andrew M Jones, Anni Vanhatalo
The curvilinear relationship between power output and the time for which it can be sustained is a fundamental and well-known feature of high-intensity exercise performance. This relationship 'levels off' at a 'critical power' (CP) that separates power outputs that can be sustained with stable values of, for example, muscle phosphocreatine, blood lactate, and pulmonary oxygen uptake ([Formula: see text]), from power outputs where these variables change continuously with time until their respective minimum and maximum values are reached and exercise intolerance occurs...
March 2017: Sports Medicine
C Vanderwel, M Placidi, B Ganapathisubramani
High-resolution particle image velocimetry data obtained in rough-wall boundary layer experiments are re-analysed to examine the influence of surface roughness heterogeneities on wind resource. Two different types of heterogeneities are examined: (i) surfaces with repeating roughness units of the order of the boundary layer thickness (Placidi & Ganapathisubramani. 2015 J. Fluid Mech.782, 541-566. (doi:10.1017/jfm.2015.552)) and (ii) surfaces with streamwise-aligned elevated strips that mimic adjacent hills and valleys (Vanderwel & Ganapathisubramani...
April 13, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
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