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Critical power and fatigue

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https://www.readbyqxmd.com/read/28720183/g-loc-warning-algorithms-based-on-emg-features-of-the-gastrocnemius-muscle
#1
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
https://www.readbyqxmd.com/read/28700603/the-language-of-glove-wireless-gesture-decoder-with-low-power-and-stretchable-hybrid-electronics
#2
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
https://www.readbyqxmd.com/read/28640386/photoresponsive-smart-coloration-electrochromic-supercapacitor
#3
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...
June 22, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28608135/can-proportional-ventilation-modes-facilitate-exercise-in-critically-ill-patients-a-physiological-cross-over-study-pressure-support-versus-proportional-ventilation-during-lower-limb-exercise-in-ventilated-critically-ill-patients
#4
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
https://www.readbyqxmd.com/read/28596738/intensity-and-duration-based-options-to-regulate-endurance-training
#5
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
https://www.readbyqxmd.com/read/28332113/the-critical-power-concept-applications-to-sports-performance-with-a-focus-on-intermittent-high-intensity-exercise
#6
REVIEW
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
https://www.readbyqxmd.com/read/28265030/wind-resource-assessment-in-heterogeneous-terrain
#7
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
https://www.readbyqxmd.com/read/28160103/stents-biomechanics-biomaterials-and-insights-from-computational-modeling
#8
REVIEW
Georgia S Karanasiou, Michail I Papafaklis, Claire Conway, Lampros K Michalis, Rami Tzafriri, Elazer R Edelman, Dimitrios I Fotiadis
Coronary stents have revolutionized the treatment of coronary artery disease. Improvement in clinical outcomes requires detailed evaluation of the performance of stent biomechanics and the effectiveness as well as safety of biomaterials aiming at optimization of endovascular devices. Stents need to harmonize the hemodynamic environment and promote beneficial vessel healing processes with decreased thrombogenicity. Stent design variables and expansion properties are critical for vessel scaffolding. Drug-elution from stents, can help inhibit in-stent restenosis, but adds further complexity as drug release kinetics and coating formulations can dominate tissue responses...
February 3, 2017: Annals of Biomedical Engineering
https://www.readbyqxmd.com/read/28008101/muscle-metabolic-and-neuromuscular-determinants-of-fatigue-during-cycling-in-different-exercise-intensity-domains
#9
Matthew I Black, Andrew M Jones, Jamie R Blackwell, Stephen J Bailey, Lee J Wylie, Sinead T J McDonagh, Christopher Thompson, James Kelly, Paul Sumners, Katya N Mileva, Joanna L Bowtell, Anni Vanhatalo
Lactate or gas exchange threshold (GET) and critical power (CP) are closely associated with human exercise performance. We tested the hypothesis that the limit of tolerance (Tlim) during cycle exercise performed within the exercise intensity domains demarcated by GET and CP is linked to discrete muscle metabolic and neuromuscular responses. Eleven men performed a ramp incremental exercise test, 4-5 severe-intensity (SEV; >CP) constant-work-rate (CWR) tests until Tlim, a heavy-intensity (HVY; <CP but >GET) CWR test until Tlim, and a moderate-intensity (MOD; <GET) CWR test until Tlim Muscle biopsies revealed that a similar (P > 0...
March 1, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/27991483/differing-six-minute-pacing-strategies-effect-anaerobic-contribution-oxygen-uptake-muscle-deoxygenation-and-cycle-performance
#10
John Murray, Michael McCrudden, Juan M Murias, Volker Nolte, Glen R Belfry
BACKGROUND: This study compared an all-out start (AO) to a constant power start strategy (CON) during a 6 min cycle performance on utilization of W ́ (energy above critical power (CP)), muscle deoxygenation (HHb), oxygen uptake (VO2) and performance in recreationally active individuals. The AO strategy was similar to that employed by rowers. METHODS: Eight healthy males (age = 24 ± 3 y) completed a ramp test to fatigue (VO2peak = 4.42 ± 0.54 L∙min-1; peak power = 385 ± 35 W) and a 3-min all-out test to determine CP and the CON work rate...
December 16, 2016: Journal of Sports Medicine and Physical Fitness
https://www.readbyqxmd.com/read/27806677/power-duration-relationship-physiology-fatigue-and-the-limits-of-human-performance
#11
Mark Burnley, Andrew M Jones
The duration that exercise can be maintained decreases as the power requirements increase. In this review, we describe the power-duration (PD) relationship across the full range of attainable power outputs in humans. We show that a remarkably small range of power outputs is sustainable (power outputs below the critical power, CP). We also show that the origin of neuromuscular fatigue differs considerably depending on the exercise intensity domain in which exercise is performed. In the moderate domain (below the lactate threshold, LT), fatigue develops slowly and is predominantly of central origin (residing in the central nervous system)...
November 3, 2016: European Journal of Sport Science
https://www.readbyqxmd.com/read/27802700/response-measurement-by-laser-doppler-vibrometry-in-vibration-qualification-tests-with-non-gaussian-random-excitation
#12
M Troncossi, R Di Sante, A Rivola
In the field of vibration qualification testing, random excitations are typically imposed on the tested system in terms of a power spectral density (PSD) profile. This is the one of the most popular ways to control the shaker or slip table for durability tests. However, these excitations (and the corresponding system responses) exhibit a Gaussian probability distribution, whereas not all real-life excitations are Gaussian, causing the response to be also non-Gaussian. In order to introduce non-Gaussian peaks, a further parameter, i...
October 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27788474/compression-fatigue-behavior-and-failure-mechanism-of-porous-titanium-for-biomedical-applications
#13
Fuping Li, Jinshan Li, Tingting Huang, Hongchao Kou, Lian Zhou
Porous titanium and its alloys are believed to be one of the most attractive biomaterials for orthopedic implant applications. In the present work, porous pure titanium with 50-70% porosity and different pore size was fabricated by diffusion bonding. Compression fatigue behavior was systematically studied along the out-of-plane direction. It resulted that porous pure titanium has anisotropic pore structure and the microstructure is fine-grained equiaxed α phase with a few twins in some α grains. Porosity and pore size have some effect on the S-N curve but this effect is negligible when the fatigue strength is normalized by the yield stress...
January 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/27571960/development-of-superlattice-crn-nbn-coatings-for-joint-replacements-deposited-by-high-power-impulse-magnetron-sputtering
#14
Papken Ehiasarian Hovsepian, Arutiun Papken Ehiasarian, Yashodhan Purandare, Arunprabhu Arunachalam Sugumaran, Tim Marriott, Imran Khan
The demand for reliable coating on medical implants is ever growing. In this research, enhanced performance of medical implants was achieved by a CrN/NbN coating, utilising nanoscale multilayer/superlattice structure. The advantages of the novel high power impulse magnetron sputtering technology, namely, its unique highly ionised plasma, were exploited to deposit dense and strongly adherent coatings on CoCr implants. Transmission electron microscopy analysis revealed coating superlattice structure with bi-layer thickness of 3...
September 2016: Journal of Materials Science. Materials in Medicine
https://www.readbyqxmd.com/read/27478563/comparison-of-proximally-versus-distally-placed-spatially-distributed-sequential-stimulation-electrodes-in-a-dynamic-knee-extension-task
#15
Marco Laubacher, Efe A Aksöz, Stuart Binder-Macleod, Kenneth J Hunt
Spatially distributed sequential stimulation (SDSS) has demonstrated substantial power output and fatigue benefits compared to single electrode stimulation (SES) in the application of functional electrical stimulation (FES). This asymmetric electrode setup brings new possibilities but also new questions since precise placement of the electrodes is one critical factor for good muscle activation. The aim of this study was to compare the power output, fatigue and activation properties of proximally versus distally placed SDSS electrodes in an isokinetic knee extension task simulating knee movement during recumbent cycling...
June 13, 2016: European Journal of Translational Myology
https://www.readbyqxmd.com/read/27396243/mechanically-robust-39-ghz-cut-off-frequency-graphene-field-effect-transistors-on-flexible-substrates
#16
Wei Wei, Emiliano Pallecchi, Samiul Haque, Stefano Borini, Vanessa Avramovic, Alba Centeno, Zurutuza Amaia, Henri Happy
Graphene has been regarded as a promising candidate channel material for flexible devices operating at radio-frequency (RF). In this work we fabricated and fully characterized double bottom-gate graphene field effect transistors on flexible polymer substrates for high frequency applications. We report a record high as-measured current gain cut-off frequency (ft) of 39 GHz. The corresponding maximum oscillation frequency (fmax) is 13.5 GHz. These state of the art high frequency performances are stable against bending, with a typical variation of around 10%, for a bending radius of up to 12 mm...
August 7, 2016: Nanoscale
https://www.readbyqxmd.com/read/27128663/disease-induced-skeletal-muscle-atrophy-and-fatigue
#17
Scott K Powers, Gordon S Lynch, Kate T Murphy, Michael B Reid, Inge Zijdewind
Numerous health problems, including acute critical illness, cancer, diseases associated with chronic inflammation, and neurological disorders, often result in skeletal muscle weakness and fatigue. Disease-related muscle atrophy and fatigue is an important clinical problem because acquired skeletal muscle weakness can increase the duration of hospitalization, result in exercise limitation, and contribute to a poor quality of life. Importantly, skeletal muscle atrophy is also associated with increased morbidity and mortality of patients...
November 2016: Medicine and Science in Sports and Exercise
https://www.readbyqxmd.com/read/27121994/an-eeg-based-fatigue-detection-and-mitigation-system
#18
Kuan-Chih Huang, Teng-Yi Huang, Chun-Hsiang Chuang, Jung-Tai King, Yu-Kai Wang, Chin-Teng Lin, Tzyy-Ping Jung
Research has indicated that fatigue is a critical factor in cognitive lapses because it negatively affects an individual's internal state, which is then manifested physiologically. This study explores neurophysiological changes, measured by electroencephalogram (EEG), due to fatigue. This study further demonstrates the feasibility of an online closed-loop EEG-based fatigue detection and mitigation system that detects physiological change and can thereby prevent fatigue-related cognitive lapses. More importantly, this work compares the efficacy of fatigue detection and mitigation between the EEG-based and a nonEEG-based random method...
June 2016: International Journal of Neural Systems
https://www.readbyqxmd.com/read/27031742/critical-power-an-important-fatigue-threshold-in-exercise-physiology
#19
David C Poole, Mark Burnley, Anni Vanhatalo, Harry B Rossiter, Andrew M Jones
: The hyperbolic form of the power-duration relationship is rigorous and highly conserved across species, forms of exercise, and individual muscles/muscle groups. For modalities such as cycling, the relationship resolves to two parameters, the asymptote for power (critical power [CP]) and the so-called W' (work doable above CP), which together predict the tolerable duration of exercise above CP. Crucially, the CP concept integrates sentinel physiological profiles-respiratory, metabolic, and contractile-within a coherent framework that has great scientific and practical utility...
November 2016: Medicine and Science in Sports and Exercise
https://www.readbyqxmd.com/read/26868642/critical-load-a-novel-approach-to-determining-a-sustainable-intensity-during-resistance-exercise
#20
Vivian M Arakelian, Renata G Mendes, Renata Trimer, Flavia C Rossi Caruso, Nuno M de Sousa, Vanessa C Borges, Camila do Valle Gomes Gatto, Vilmar Baldissera, Ross Arena, Audrey Borghi-Silva
BACKGROUND: A hyperbolic function as well as a linear relationship between power output and time to exhaustion (Tlim) has been consistently observed during dynamic non-resistive exercises. However, little is known about its concept to resistance exercises (RE), which could be defined as critical load (CL). This study aimed to verify the existence of CL during dynamic RE and to verify the number of workbouts necessary to determine the optimal modeling to achieve it. METHODS: Fifteen healthy men (23±2...
May 2017: Journal of Sports Medicine and Physical Fitness
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