Evaluating Fatigue in Operational Settings: The NASA Ames Fatigue Countermeasures Program

NASA Technical Reports Server (NTRS)

Rosekind, Mark R.; Gregory, Kevin; Miller, Donna; Webbon, Lissa; Oyung, Ray

1996-01-01

In response to a 1980 Congressional request, NASA Ames initiated a program to examine fatigue in flight operations. The Program objectives are to examine fatigue, sleep loss, and circadian disruption in flight operations, determine the effects of these factors on flight crew performance, and the development of fatigue countermeasures. The NASA Ames Fatigue Countermeasures Program conducts controlled laboratory experiments, full-mission flight simulations, and field studies. A range of subjective, behavioral, performance, physiological, and environmental measures are used depending on study objectives. The Program has developed substantial expertise in gathering data during actual flight operations and in other work settings. This has required the development of ambulatory and other measures that can be carried throughout the world and used at 41,000 feet in aircraft cockpits. The NASA Ames Fatigue Countermeasures Program has examined fatigue in shorthaul, longhaul, overnight cargo, and helicopter operations. A recent study of planned cockpit rest periods demonstrated the effectiveness of a brief inflight nap to improve pilot performance and alertness. This study involved inflight reaction time/vigilance performance testing and EEG/EOG measures of physiological alertness. The NASA Ames Fatigue Countermeasures Program has applied scientific findings to the development of education and training materials on fatigue countermeasures, input to federal regulatory activities on pilot flight, duty, and rest requirements, and support of National Transportation Safety Board accident investigations. Current activities are examining fatigue in nonaugmented longhaul flights, regional/commuter flight operations, corporate/business aviation, and psychophysiological variables related to performance.

Fatigue during high-intensity intermittent exercise: application to bodybuilding.

PubMed

Lambert, Charles P; Flynn, Michael G

2002-01-01

Resistance exercise is an activity performed by individuals interested in competition, those who wish to improve muscle mass and strength for other sports, and for individuals interested in improving their strength and physical appearance. In this review we present information suggesting that phosphocreatine depletion, intramuscular acidosis and carbohydrate depletion are all potential causes of the fatigue during resistance exercise. In addition, recommendations are provided for nutritional interventions, which might delay muscle fatigue during this type of activity.

Parkinson's disease-related fatigue: A case definition and recommendations for clinical research.

PubMed

Kluger, Benzi M; Herlofson, Karen; Chou, Kelvin L; Lou, Jau-Shin; Goetz, Christopher G; Lang, Anthony E; Weintraub, Daniel; Friedman, Joseph

2016-05-01

Fatigue is one of the most common and disabling symptoms in Parkinson's disease (PD). Since fatigue was first described as a common feature of PD 20 years ago, little progress has been made in understanding its causes or treatment. Importantly, PD patients attending the 2013 World Parkinson Congress voted fatigue as the leading symptom in need of further research. In response, the Parkinson Disease Foundation and ProjectSpark assembled an international team of experts to create recommendations for clinical research to advance this field. The working group identified several areas in which shared standards would improve research quality and foster progress including terminology, diagnostic criteria, and measurement. Terminology needs to (1) clearly distinguish fatigue from related phenomena (eg, sleepiness, apathy, depression); (2) differentiate subjective fatigue complaints from objective performance fatigability; and (3) specify domains affected by fatigue and causal factors. We propose diagnostic criteria for PD-related fatigue to guide participant selection for clinical trials and add rigor to mechanistic studies. Recommendations are made for measurement of subjective fatigue complaints, performance fatigability, and neurophysiologic changes. We also suggest areas in which future research is needed to address methodological issues and validate or optimize current practices. Many limitations in current PD-related fatigue research may be addressed by improving methodological standards, many of which are already being successfully applied in clinical fatigue research in other medical conditions (eg, cancer, multiple sclerosis). © 2016 International Parkinson and Movement Disorder Society. © 2016 International Parkinson and Movement Disorder Society.

Effect of burdock extract on physical performance and physiological fatigue in mice

PubMed Central

CHEN, Wen-Chyuan; HSU, Yi-Ju; LEE, Mon-Chien; LI, Hua Shuai; HO, Chun-Sheng; HUANG, Chi-Chang; CHEN, Fu-An

2017-01-01

Burdock (BD) is a common vegetable with many pharmacological properties. However, few studies have examined the effect of BD on exercise performance and physical fatigue. We aimed to evaluate the potential beneficial effects of BD on fatigue and ergogenic functions following physical challenge in mice. Methods: Male ICR mice were divided into four groups to receive either vehicle, or BD at 348.5, 697 or 1,742.5 mg/kg/day, by daily oral gavage for 4 weeks. Exercise performance and fatigue were evaluated from forelimb grip strength, exhaustive swimming time, and post-exercise levels of physical fatigue-related biomarkers serum lactate, ammonia, glucose, and creatine kinase (CK). Results: BD supplementation elevated endurance and grip strength in a dose-dependent manner. It also significantly decreased lactate, ammonia, and CK levels after physical challenge. In addition, BD supplementation had few subchronic toxic effects. Conclusions: Supplementation with BD has a wide spectrum of bioactive effects, including health promotion, performance improvement, and fatigue reduction. PMID:28890521

The effect of residual stresses induced by prestraining on fatigue life of notched specimens

NASA Astrophysics Data System (ADS)

Sadeler, R.; Ozel, A.; Kaymaz, I.; Totik, Y.

2005-06-01

The effect of tensile prestraining-induced residual stress on the fatigue life of notched steel parts was investigated. The study was performed on AISI 4140 steel. Rotating bending fatigue tests were carried out on semicircular notched specimens with different notch radii in the as-quenched and tempered conditions. Metallography of the specimens was performed by means of light optical microscopy. The finite-element method was used to evaluate the residual stress distribution near the notch region. Fatigue tests revealed fatigue life improvement for notched specimens, which changes depending on the notch radii and applied stress. Scanning electron microscopy was used to examine the fracture surfaces of the specimens.

Development of a plasma sprayed ceramic gas path seal for high pressure turbine applications

NASA Technical Reports Server (NTRS)

Shiembob, L. T.

1977-01-01

The plasma sprayed graded layered yittria stabilized zirconia (ZrO2)/metal(CoCrAlY) seal system for gas turbine blade tip applications up to 1589 K (2400 F) seal temperatures was studied. Abradability, erosion, and thermal fatigue characteristics of the graded layered system were evaluated by rig tests. Satisfactory abradability and erosion resistance was demonstrated. Encouraging thermal fatigue tolerance was shown. Initial properties for the plasma sprayed materials in the graded, layered seal system was obtained, and thermal stress analyses were performed. Sprayed residual stresses were determined. Thermal stability of the sprayed layer materials was evaluated at estimated maximum operating temperatures in each layer. Anisotropic behavior in the layer thickness direction was demonstrated by all layers. Residual stresses and thermal stability effects were not included in the analyses. Analytical results correlated reasonably well with results of the thermal fatigue tests. Analytical application of the seal system to a typical gas turbine engine application predicted performance similar to rig specimen thermal fatigue performance. A model for predicting crack propagation in the sprayed ZrO2/CoCrAlY seal system was proposed, and recommendations for improving thermal fatigue resistance were made. Seal system layer thicknesses were analytically optimized to minimize thermal stresses in the abradability specimen during thermal fatigue testing. Rig tests on the optimized seal configuration demonstrated some improvement in thermal fatigue characteristics.

Incubating Isolated Mouse EDL Muscles with Creatine Improves Force Production and Twitch Kinetics in Fatigue Due to Reduction in Ionic Strength

PubMed Central

Head, Stewart I.; Greenaway, Bronwen; Chan, Stephen

2011-01-01

Background Creatine supplementation can improve performance during high intensity exercise in humans and improve muscle strength in certain myopathies. In this present study, we investigated the direct effects of acute creatine incubation on isolated mouse fast-twitch EDL muscles, and examined how these effects change with fatigue. Methods and Results The extensor digitorum longus muscle from mice aged 12–14 weeks was isolated and stimulated with field electrodes to measure force characteristics in 3 different states: (i) before fatigue; (ii) immediately after a fatigue protocol; and (iii) after recovery. These served as the control measurements for the muscle. The muscle was then incubated in a creatine solution and washed. The measurement of force characteristics in the 3 different states was then repeated. In un-fatigued muscle, creatine incubation increased the maximal tetanic force. In fatigued muscle, creatine treatment increased the force produced at all frequencies of stimulation. Incubation also increased the rate of twitch relaxation and twitch contraction in fatigued muscle. During repetitive fatiguing stimulation, creatine-treated muscles took 55.1±9.5% longer than control muscles to lose half of their original force. Measurement of weight changes showed that creatine incubation increased EDL muscle mass by 7%. Conclusion Acute creatine application improves force production in isolated fast-twitch EDL muscle, and these improvements are particularly apparent when the muscle is fatigued. One likely mechanism for this improvement is an increase in Ca2+ sensitivity of contractile proteins as a result of ionic strength decreases following creatine incubation. PMID:21850234

Improvement in Fatigue Performance of Aluminium Alloy Welded Joints by Laser Shock Peening in a Dynamic Strain Aging Temperature Regime.

PubMed

Su, Chun; Zhou, Jianzhong; Meng, Xiankai; Huang, Shu

2016-09-26

As a new treatment process after welding, the process parameters of laser shock peening (LSP) in dynamic strain aging (DSA) temperature regimes can be precisely controlled, and the process is a non-contact one. The effects of LSP at elevated temperatures on the distribution of the surface residual stress of AA6061-T6 welded joints were investigated by using X-ray diffraction technology with the sin² ϕ method and Abaqus software. The fatigue life of the welded joints was estimated by performing tensile fatigue tests. The microstructural evolution in surface and fatigue fractures of the welded joints was presented by means of surface integrity and fracture surface testing. In the DSA temperature regime of AA6061-T6 welded joints, the residual compressive stress was distributed more stably than that of LSP at room temperature. The thermal corrosion resistance and fatigue properties of the welded joints were also improved. The experimental results and numerical analysis were in mutual agreement.

Improvement in Fatigue Performance of Aluminium Alloy Welded Joints by Laser Shock Peening in a Dynamic Strain Aging Temperature Regime

PubMed Central

Su, Chun; Zhou, Jianzhong; Meng, Xiankai; Huang, Shu

2016-01-01

As a new treatment process after welding, the process parameters of laser shock peening (LSP) in dynamic strain aging (DSA) temperature regimes can be precisely controlled, and the process is a non-contact one. The effects of LSP at elevated temperatures on the distribution of the surface residual stress of AA6061-T6 welded joints were investigated by using X-ray diffraction technology with the sin2ϕ method and Abaqus software. The fatigue life of the welded joints was estimated by performing tensile fatigue tests. The microstructural evolution in surface and fatigue fractures of the welded joints was presented by means of surface integrity and fracture surface testing. In the DSA temperature regime of AA6061-T6 welded joints, the residual compressive stress was distributed more stably than that of LSP at room temperature. The thermal corrosion resistance and fatigue properties of the welded joints were also improved. The experimental results and numerical analysis were in mutual agreement. PMID:28773920

Experimental Investigation and Finite Element Analysis on Fatigue Behavior of Aluminum Alloy 7050 Single-Lap Joints

NASA Astrophysics Data System (ADS)

Zhou, Bing; Cui, Hao; Liu, Haibo; Li, Yang; Liu, Gaofeng; Li, Shujun; Zhang, Shangzhou

2018-03-01

The fatigue behavior of single-lap four-riveted aluminum alloy 7050 joints was investigated by using high-frequency fatigue test and scanning electron microscope (SEM). Stress distributions obtained by finite element (FE) analysis help explain the fatigue performance. The fatigue test results showed that the fatigue lives of the joints depend on cold expansion and applied cyclic loads. FE analysis and fractography indicated that the improved fatigue lives can be attributed to the reduction in maximum stress and evolution of fatigue damage at the critical location. The beneficial effects of strengthening techniques result in tearing ridges or lamellar structure on fracture surface, decrease in fatigue striations spacing, delay of fatigue crack initiation, crack deflection in fatigue crack propagation and plasticity-induced crack closure.

Integrating Oil Debris and Vibration Gear Damage Detection Technologies Using Fuzzy Logic

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Afjeh, Abdollah A.

2002-01-01

A diagnostic tool for detecting damage to spur gears was developed. Two different measurement technologies, wear debris analysis and vibration, were integrated into a health monitoring system for detecting surface fatigue pitting damage on gears. This integrated system showed improved detection and decision-making capabilities as compared to using individual measurement technologies. This diagnostic tool was developed and evaluated experimentally by collecting vibration and oil debris data from fatigue tests performed in the NASA Glenn Spur Gear Fatigue Test Rig. Experimental data were collected during experiments performed in this test rig with and without pitting. Results show combining the two measurement technologies improves the detection of pitting damage on spur gears.

Spiral Bevel Gear Damage Detection Using Decision Fusion Analysis

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Handschuh, Robert F.; Afjeh, Abdollah A.

2002-01-01

A diagnostic tool for detecting damage to spiral bevel gears was developed. Two different monitoring technologies, oil debris analysis and vibration, were integrated using data fusion into a health monitoring system for detecting surface fatigue pitting damage on gears. This integrated system showed improved detection and decision-making capabilities as compared to using individual monitoring technologies. This diagnostic tool was evaluated by collecting vibration and oil debris data from fatigue tests performed in the NASA Glenn Spiral Bevel Gear Fatigue Rigs. Data was collected during experiments performed in this test rig when pitting damage occurred. Results show that combining the vibration and oil debris measurement technologies improves the detection of pitting damage on spiral bevel gears.

Effects of exercise on fatigue, sleep, and performance: a randomized trial.

PubMed

Coleman, Elizabeth Ann; Goodwin, Julia A; Kennedy, Robert; Coon, Sharon K; Richards, Kathy; Enderlin, Carol; Stewart, Carol B; McNatt, Paula; Lockhart, Kim; Anaissie, Elias J

2012-09-01

To compare usual care with a home-based individualized exercise program (HBIEP) in patients receiving intensive treatment for multiple myeloma (MM)and epoetin alfa therapy. Randomized trial with repeated measures of two groups (one experimental and one control) and an approximate 15-week experimental period. Outpatient setting of the Myeloma Institute for Research and Therapy at the Rockfellow Cancer Center at the University of Arkansas for Medical Sciences. 187 patients with newly diagnosed MM enrolled in a separate study evaluating effectiveness of the Total Therapy regimen, with or without thalidomide. Measurements included the Profile of Mood States fatigue scale, Functional Assessment of Cancer Therapy-Fatigue, ActiGraph® recordings, 6-Minute Walk Test, and hemoglobin levels at baseline and before and after stem cell collection. Descriptive statistics were used to compare demographics and treatment effects, and repeated measures analysis of variance was used to determine effects of HBIEP. Fatigue, nighttime sleep, performance (aerobic capacity) as dependent or outcome measures, and HBIEP combining strength building and aerobic exercise as the independent variable. Both groups were equivalent for age, gender, race, receipt of thalidomide, hemoglobin levels, and type of treatment regimen for MM. No statistically significant differences existed among the experimental and control groups for fatigue, sleep, or performance (aerobic capacity). Statistically significant differences (p < 0.05) were found in each of the study outcomes for all patients as treatment progressed and patients experienced more fatigue and poorer nighttime sleep and performance (aerobic capacity). The effect of exercise seemed to be minimal on decreasing fatigue, improving sleep, and improving performance (aerobic capacity). Exercise is safe and has physiologic benefits for patients undergoing MM treatment; exercise combined with epoetin alfa helped alleviate anemia.

Indentation hardness: A simple test that correlates with the dissipated-energy predictor for fatigue-life in bovine pericardium membranes for bioprosthetic heart valves.

PubMed

Tobaruela, Almudena; Rojo, Francisco Javier; García Paez, José María; Bourges, Jean Yves; Herrero, Eduardo Jorge; Millán, Isabel; Alvarez, Lourdes; Cordon, Ángeles; Guinea, Gustavo V

2016-08-01

The aim of this study was to evaluate the variation of hardness with fatigue in calf pericardium, a biomaterial commonly used in bioprosthetic heart valves, and its relationship with the energy dissipated during the first fatigue cycle that has been shown to be a predictor of fatigue-life (García Páez et al., 2006, 2007; Rojo et al., 2010). Fatigue tests were performed in vitro on 24 pericardium specimens cut in a root-to-apex direction. The specimens were subjected to a maximum stress of 1MPa in blocks of 10, 25, 50, 100, 250, 500, 1000 and 1500 cycles. By means of a modified Shore A hardness test procedure, the hardness of the specimen was measured before and after fatigue tests. Results showed a significant correlation of such hardness with fatigue performance and with the energy dissipated in the first cycle of fatigue, a predictor of pericardium durability. The study showed indentation hardness as a simple and reliable indicator of mechanical performance, one which could be easily implemented in improving tissue selection. Copyright © 2016 Elsevier Ltd. All rights reserved.

Cognitive and Other Strategies to Mitigate the Effects of Fatigue. Lessons from Staff Physicians Working in Intensive Care Units.

PubMed

Henrich, Natalie; Ayas, Najib T; Stelfox, Henry T; Peets, Adam D

2016-09-01

Fatigue is common among physicians and adversely affects their performance. To identify strategies that attending physicians use when fatigued to maintain clinical performance in the intensive care unit (ICU). We conducted a qualitative study using focus groups and structured interviews of attending ICU physicians working in academic centers in Canada. In three focus group meetings, we engaged a total of 11 physicians to identify strategies used to prevent and cope with fatigue. In the focus groups, 21 cognitive strategies were identified and classified into 9 categories (minimizing number of tasks, using techniques to improve retention of details, using a structured approach to patient care, asking for help, improving opportunities for focusing, planning ahead, double-checking, adjusting expectations, and modulating alertness). In addition, various lifestyle strategies were mentioned as important in preventing fatigue (e.g., protecting sleep before call, adequate exercise, and limiting alcohol). Telephone interviews were then conducted (n = 15 physicians) with another group of intensivists. Structured questions were asked about the strategies identified in the focus groups that were most useful during ICU activities. In the interviews, the most useful and frequently used strategies were prioritizing tasks that need to be done immediately and postponing tasks that can wait, working systematically, using a structured approach, and avoiding distractions. ICU physicians reported using a variety of deliberate cognitive and lifestyle strategies to prevent and cope with fatigue. Given the low cost and intuitive nature of the majority of these strategies, further investigations should be done to better characterize their effectiveness in improving performance.

Effect of Curcumin Supplementation on Physiological Fatigue and Physical Performance in Mice

PubMed Central

Huang, Wen-Ching; Chiu, Wan-Chun; Chuang, Hsiao-Li; Tang, Deh-Wei; Lee, Zon-Min; Wei, Li; Chen, Fu-An; Huang, Chi-Chang

2015-01-01

Curcumin (CCM) is a well-known phytocompound and food component found in the spice turmeric and has multifunctional bioactivities. However, few studies have examined its effects on exercise performance and physical fatigue. We aimed to evaluate the potential beneficial effects of CCM supplementation on fatigue and ergogenic function following physical challenge in mice. Male ICR mice were divided into four groups to receive vehicle or CCM (180 μg/mL) by oral gavage at 0, 12.3, 24.6, or 61.5 mL/kg/day for four weeks. Exercise performance and anti-fatigue function were evaluated after physical challenge by forelimb grip strength, exhaustive swimming time, and levels of physical fatigue-associated biomarkers serum lactate, ammonia, blood urea nitrogen (BUN), and glucose and tissue damage markers such as aspartate transaminase (AST), alanine transaminase (ALT), and creatine kinase (CK). CCM supplementation dose-dependently increased grip strength and endurance performance and significantly decreased lactate, ammonia, BUN, AST, ALT, and CK levels after physical challenge. Muscular glycogen content, an important energy source for exercise, was significantly increased. CCM supplementation had few subchronic toxic effects. CCM supplementation may have a wide spectrum of bioactivities for promoting health, improving exercise performance and preventing fatigue. PMID:25647661

Physical exercise-induced fatigue: the role of serotonergic and dopaminergic systems

PubMed Central

Cordeiro, L.M.S.; Rabelo, P.C.R.; Moraes, M.M.; Teixeira-Coelho, F.; Coimbra, C.C.; Wanner, S.P.; Soares, D.D.

2017-01-01

Brain serotonin and dopamine are neurotransmitters related to fatigue, a feeling that leads to reduced intensity or interruption of physical exercises, thereby regulating performance. The present review aims to present advances on the understanding of fatigue, which has recently been proposed as a defense mechanism instead of a “physiological failure” in the context of prolonged (aerobic) exercises. We also present recent advances on the association between serotonin, dopamine and fatigue. Experiments with rodents, which allow direct manipulation of brain serotonin and dopamine during exercise, clearly indicate that increased serotoninergic activity reduces performance, while increased dopaminergic activity is associated with increased performance. Nevertheless, experiments with humans, particularly those involving nutritional supplementation or pharmacological manipulations, have yielded conflicting results on the relationship between serotonin, dopamine and fatigue. The only clear and reproducible effect observed in humans is increased performance in hot environments after treatment with inhibitors of dopamine reuptake. Because the serotonergic and dopaminergic systems interact with each other, the serotonin-to-dopamine ratio seems to be more relevant for determining fatigue than analyzing or manipulating only one of the two transmitters. Finally, physical training protocols induce neuroplasticity, thus modulating the action of these neurotransmitters in order to improve physical performance. PMID:29069229

Cerebral mechanisms underlying the effects of music during a fatiguing isometric ankle-dorsiflexion task.

PubMed

Bigliassi, Marcelo; Karageorghis, Costas I; Nowicky, Alexander V; Orgs, Guido; Wright, Michael J

2016-10-01

The brain mechanisms by which music-related interventions ameliorate fatigue-related symptoms during the execution of fatiguing motor tasks are hitherto under-researched. The objective of the present study was to investigate the effects of music on brain electrical activity and psychophysiological measures during the execution of an isometric fatiguing ankle-dorsiflexion task performed until the point of volitional exhaustion. Nineteen healthy participants performed two fatigue tests at 40% of maximal voluntary contraction while listening to music or in silence. Electrical activity in the brain was assessed by use of a 64-channel EEG. The results indicated that music downregulated theta waves in the frontal, central, and parietal regions of the brain during exercise. Music also induced a partial attentional switching from associative thoughts to task-unrelated factors (dissociative thoughts) during exercise, which led to improvements in task performance. Moreover, participants experienced a more positive affective state while performing the isometric task under the influence of music. © 2016 Society for Psychophysiological Research.

Plasma immersion ion implantation on 15-5PH stainless steel: influence on fatigue strength and wear resistance

NASA Astrophysics Data System (ADS)

Bonora, R.; Cioffi, M. O. H.; Voorwald, H. J. C.

2017-05-01

Surface improvement in steels is of great interest for applications in industry. The aim of this investigation is to study the effect of nitrogen ion implantation on the axial fatigue strength and wear resistance of 15-5 PH stainless steel. It is well know that electroplated coatings, which are used to improve abrasive wear and corrosion properties, affects negatively the fatigue strength. It is also important to consider requirements to reduce the use of coated materials with electroplated chromium and cadmium, that produce waste, which is harmful to health and environment. The HVOF (High velocity oxygen fuel) process provides hardness, wear strength and higher fatigue resistance in comparison to electroplated chromium. Plasma immersion ion implantation has been used to enhance the hardness, wear, fatigue and corrosion properties of metals and alloys. In the present research the fatigue life increased twice for 15-5 PH three hours PIII treated in comparison to base material. From the abrasive wear tests a lower pin mass reduction was observed, associated to the superficial treatments. The improvement of fatigue and mechanical performance is attributed to a combination of nitrides phase structure and compressive residual stresses during the PIII treatment.

Temporal profile of prolonged, night-time driving performance: breaks from driving temporarily reduce time-on-task fatigue but not sleepiness.

PubMed

Phipps-Nelson, Jo; Redman, Jennifer R; Rajaratnam, Shantha M W

2011-09-01

Breaks are often used by drivers to counteract sleepiness and time-on-task fatigue during prolonged driving. We examined the temporal profile of changes in driving performance, electroencephalogram (EEG) activity and subjective measures of sleepiness and fatigue during prolonged nocturnal driving in a car simulator. In addition, the study examined the impact of regular breaks from driving on performance, sleepiness and fatigue. Healthy volunteers (n=12, 23-45 years) maintained a regular sleep-wake pattern for 14 days and were then in a laboratory from 21:00 to 08:30 hours. The driving simulator scene was designed to simulate monotonous night-time rural driving. Participants drove 4 × 2-h test sessions, with a break from driving of 1 h between each session. During the break participants performed tests assessing sleepiness and fatigue, and psychomotor performance (~30 mins), and then were permitted to sit quietly. They were monitored for wakefulness, and not permitted to nap or ingest caffeine. EEG was recorded during the driving task, and subjective assessments of sleepiness and fatigue were obtained at the start and completion of each session. We found that driving performance deteriorated (2.5-fold), EEG delta, theta and alpha activity increased, and subjective sleepiness and fatigue ratings increased across the testing period. Driving performance and fatigue ratings improved following the scheduled breaks from driving, while the breaks did not affect EEG activity and subjective sleepiness. Time-on-task effects increased through the testing period, indicating that these effects are exacerbated by increasing sleepiness. Breaks from driving without sleep temporarily ameliorate time-on-task fatigue, but provide little benefit to the sleepy driver. © 2010 European Sleep Research Society.

Neuropsychological Training of Attention Improves MS-Related Fatigue: Results of a Randomized, Placebo-Controlled, Double-Blind Pilot Study.

PubMed

Flachenecker, Peter; Meissner, Heike; Frey, Rebecca; Guldin, Wolfgang

2017-01-01

Attentional deficits may be pathophysiologically relevant in MS-associated fatigue. Thirty MS patients with fatigue and attentional deficits in neuropsychological testing participated in this randomized, placebo-controlled, double-blind trial. The intervention group (IG; n = 14) was treated with 10 h of computerized, specific neuropsychological training performing simple reaction time tasks, whereas the control group (CG; n = 16) also runs through computerized, but unspecific neuropsychological training using tasks without time components. The subjective feeling of fatigue was assessed with the Würzburg Fatigue Inventory for Multiple Sclerosis (WEIMuS) questionnaire, and testing of alertness was used as an objective measure at baseline and after the 2-week study period. Reaction times of alertness were significantly decreased in IG but not CG after 2 weeks. The subjective feeling of fatigue was ameliorated in both groups but more pronounced in IG. Effect sizes were below 0.7 for alertness and WEIMuS scores in CG but large and clinically meaningful in IG for both measures. Our pilot study suggests that neuropsychological training of attention may improve both measures of fatigue. The parallel improvement of attentional deficits and subjective fatigue after specific neuropsychological training support previous findings that fatigue may be at least partially caused by impaired intensity of attention. © 2017 S. Karger AG, Basel.

The hybrid assistive limb (HAL) for Care Support successfully reduced lumbar load in repetitive lifting movements.

PubMed

Miura, Kousei; Kadone, Hideki; Koda, Masao; Abe, Tetsuya; Kumagai, Hiroshi; Nagashima, Katsuya; Mataki, Kentaro; Fujii, Kengo; Noguchi, Hiroshi; Funayama, Toru; Kawamoto, Hiroaki; Sankai, Yoshiyuki; Yamazaki, Masashi

2018-05-03

Work-related low back pain is a serious socioeconomic problem. This study examined whether HAL for Care Support, which is a newly developed wearable robot, would decrease lumbar fatigue and improve lifting performance during repetitive lifting movements. Eighteen healthy volunteers (11 men, 7 women) performed repetitive stoop lifting movements of a cardboard box weighing 12 kg as many times as possible. The first lifting trial was executed without HAL for Care Support, and the second was with it. We evaluated the VAS of lumbar fatigue as the lumbar load and the number of lifts and the lifting time as lifting performance. Without HAL for Care Support, the mean VAS of lumbar fatigue, the number of lifts and lifting time were 68 mm, 60 and 230 s; with HAL for Care Support, they were 51 mm, 87 and 332 s, respectively. Both lifting performance measures were significantly improved by using HAL for Care Support (Fig. 2). A power analysis showed that there was sufficient statistical power for the VAS of lumbar fatigue (0.99), the number of lifts (0.92), and lifting time (0.93). All participants performed their repetitive lifting trials safely. There were no adverse events caused by using HAL for Care Support. In conclusion, the HAL for Care Support can decrease lumbar load and improve the lifting performance during repetitive stoop lifting movements in healthy adults. Copyright © 2018. Published by Elsevier Ltd.

A pilot study evaluating the safety and efficacy of modafinal for cancer-related fatigue.

PubMed

Blackhall, Leslie; Petroni, Gina; Shu, Jianfen; Baum, Lora; Farace, Elena

2009-05-01

Fatigue is a common symptom that lowers the quality of life of patients with cancer, affecting between 60% and 90% of patients. Relatively few options are available for the treatment of this debilitating condition. Modafinal, a psychostimulant developed for the treatment of narcolepsy, has been used to treat fatigue in other diseases such as multiple sclerosis, but little data support its use in cancer patients. The primary objective of this open-label pilot study was to evaluate the safety, and efficacy of modafinil in improving cancer-related fatigue (CRF) as measured by the Brief Fatigue Inventory (BFI). The effect of this agent on depression, quality of life, functional status, and cognitive function was also assessed. Modafinal was self-administered at a dose of 100 mg/d during weeks 1-2, and 200 mg during weeks 3-4. Assessments were performed at baseline, 2, and 4 weeks. BFI score was improved in 46% of patients at 2 weeks and 75% at 4 weeks (p = 0.025). Hospital Anxiety and Depression Scale scores declined at 2 and 4 weeks (p < 0.001). Most scales for neurocognitive function were unchanged. Score for all Functional Assessment of Cancer Therapy-Brain (FACT-BR) subscales (measuring quality of life), except social/family well-being, were improved (p < 0.05) at 2 and 4 weeks. Significant changes in Eastern Cooperative Oncology Group (ECOG) performance status were noted, with 40% of patients improving at least one level. Modafinil was well-tolerated with only one patient discontinuing treatment due to drug-related toxicity. In this pilot study modafinil was well-tolerated and effective for fatigue in patients with cancer. Improvements were also seen in mood, quality of life, and functional status.

The relationship between cell phone use and management of driver fatigue: It's complicated.

PubMed

Saxby, Dyani Juanita; Matthews, Gerald; Neubauer, Catherine

2017-06-01

Voice communication may enhance performance during monotonous, potentially fatiguing driving conditions (Atchley & Chan, 2011); however, it is unclear whether safety benefits of conversation are outweighed by costs. The present study tested whether personalized conversations intended to simulate hands-free cell phone conversation may counter objective and subjective fatigue effects elicited by vehicle automation. A passive fatigue state (Desmond & Hancock, 2001), characterized by disengagement from the task, was induced using full vehicle automation prior to drivers resuming full control over the driving simulator. A conversation was initiated shortly after reversion to manual control. During the conversation an emergency event occurred. The fatigue manipulation produced greater task disengagement and slower response to the emergency event, relative to a control condition. Conversation did not mitigate passive fatigue effects; rather, it added worry about matters unrelated to the driving task. Conversation moderately improved vehicle control, as measured by SDLP, but it failed to counter fatigue-induced slowing of braking in response to an emergency event. Finally, conversation appeared to have a hidden danger in that it reduced drivers' insights into performance impairments when in a state of passive fatigue. Automation induced passive fatigue, indicated by loss of task engagement; yet, simulated cell phone conversation did not counter the subjective automation-induced fatigue. Conversation also failed to counter objective loss of performance (slower braking speed) resulting from automation. Cell phone conversation in passive fatigue states may impair drivers' awareness of their performance deficits. Practical applications: Results suggest that conversation, even using a hands-free device, may not be a safe way to reduce fatigue and increase alertness during transitions from automated to manual vehicle control. Copyright © 2017 Elsevier Ltd and National Safety Council. All rights reserved.

Electroacupuncture for fatigue, sleep, and psychological distress in breast cancer patients with aromatase inhibitor-related arthralgia: a randomized trial.

PubMed

Mao, Jun J; Farrar, John T; Bruner, Deborah; Zee, Jarcy; Bowman, Marjorie; Seluzicki, Christina; DeMichele, Angela; Xie, Sharon X

2014-12-01

Although fatigue, sleep disturbance, depression, and anxiety are associated with pain in breast cancer patients, it is unknown whether acupuncture can decrease these comorbid symptoms in cancer patients with pain. The objective of this study was to evaluate the effect of electroacupuncture (EA) on fatigue, sleep, and psychological distress in breast cancer survivors who experience joint pain related to aromatase inhibitors (AIs). The authors performed a randomized controlled trial of an 8-week course of EA compared with a waitlist control (WLC) group and a sham acupuncture (SA) group in postmenopausal women with breast cancer who self-reported joint pain attributable to AIs. Fatigue, sleep disturbance, anxiety, and depression were measured using the Brief Fatigue Inventory (BFI), the Pittsburgh Sleep Quality Index (PSQI), and the Hospital Anxiety and Depression Scale (HADS). The effects of EA and SA versus WLC on these outcomes were evaluated using mixed-effects models. Of the 67 randomly assigned patients, baseline pain interference was associated with fatigue (Pearson correlation coefficient [r]=0.75; P < .001), sleep disturbance (r=0.38; P=.0026), and depression (r=0.58; P < .001). Compared with the WLC condition, EA produced significant improvements in fatigue (P=.0095), anxiety (P=.044), and depression (P=.015) and a nonsignificant improvement in sleep disturbance (P=.058) during the 12-week intervention and follow-up period. In contrast, SA did not produce significant reductions in fatigue or anxiety symptoms but did produce a significant improvement in depression compared with the WLC condition (P=.0088). Compared with usual care, EA produced significant improvements in fatigue, anxiety, and depression; whereas SA improved only depression in women experiencing AI-related arthralgia. © 2014 American Cancer Society.

Objectively measured muscle fatigue in Crohn's disease: correlation with self-reported fatigue and associated factors for clinical application.

PubMed

van Langenberg, D R; Della Gatta, P; Warmington, S A; Kidgell, D J; Gibson, P R; Russell, A P

2014-02-01

The association of fatigue with decreased physical performance and underlying mechanisms are poorly understood in Crohn's disease (CD). We aimed to measure and compare self-reported fatigue with skeletal muscle fatigue in CD subjects and healthy controls, and to identify associated factors that may be amenable to change. Demographic and clinical data were collected and fatigue assessed using the Fatigue Impact Scale (FIS) in 27 consecutive CD patients and 22 matched healthy controls. Circulating cytokines and growth factors were measured. The rate of quadriceps muscle fatigue was assessed using an isokinetic dynamometer as the decrement of force with 30 contractions performed over a 5-minute period. Compared with healthy controls, CD patients reported greater levels of fatigue (mean global FIS score 45.3 vs 10.5, physical dimension score 12.3 vs 2.7 respectively; each p<0.01) and muscle fatigue (-5.2 vs -1.3 Nm min(-1); p<0.05). The two indices were correlated (r = -0.52 in CD; p<0.01). Patients with CD had lower mean serum IGF-1 levels (16.1 vs 25.4 pmol/L, p<0.01) and higher oxidative stress (TBARS assay 4.3 vs 3.9 μM, p<0.05). On multivariate analysis, low serum vitamin D, IGF-1 and magnesium, and higher IL-6 levels were associated with increased muscle fatigue (all p ≤ 0.05). Subjects with CD had more muscle fatigue than matched healthy controls and this correlated well with self-reported fatigue. Of circulating factors that were independently associated with increased muscle fatigue, vitamin D, magnesium and IGF-1 could be targeted in future studies to reduce fatigue and improve physical performance. © 2013.

Effect of interlaminar normal stresses on the uniaxial zero-to-tension fatigue behavior of graphite/epoxy tubes

NASA Technical Reports Server (NTRS)

Krempl, Erhard; An, Deukman

1991-01-01

Fatigue tests conducted with and without internal pressure have been found to possess approximately the same fatigue life as (+/-45)s graphite/epoxy tubes for zero-to-tension axial load-controlled conditions on an axial torsion servohydraulic apparatus. These tests therefore cannot be considered as confirmations of the suspected detrimental effect of interlaminar tensile stresses on the fatigue performance of thin-walled tubes. The addition of 90-deg plies on both the inside and the outside is found to significantly improve the tubes' static and fatigue strengths.

The effect of porosity and gamma-gamma' eutectic content on the low cycle fatigue behavior of hydrogen-charged PWA-1480

NASA Technical Reports Server (NTRS)

Gayda, John; Dreshfield, Robert L.; Gabb, Timothy P.

1991-01-01

Single crystal superalloys such as PWA 1480 are considered for turbopump blades in the main engines of the space shuttle. As fatigue resistance in a hydrogen environment is a key issue in this application, a study of the effect of porosity and gamma-gamma' eutectic content on the fatigue life of a hydrogen-charged PWA 1480 was performed. Porosity and eutectic were linked to fatigue initiation, and therefore reduction of either of both may be one means to improve fatigue life of PWA 1480 when hydrogen is present.

Modafinil effects on cognitive function in HIV+ patients treated for fatigue: a placebo controlled study.

PubMed

McElhiney, Martin; Rabkin, Judith; Van Gorp, Wilfred; Rabkin, Richard

2010-06-01

Both mild cognitive impairment and fatigue are common among people with HIV/AIDS. This study examined the efficacy of modafinil for HIV+ patients who sought treatment for fatigue in a placebo-controlled double-blind 4-week trial. A battery of standard neuropsychological tests was administered at study entry and Week 4, and change in performance was compared for 59 patients receiving modafinil versus 44 patients receiving placebo. A significant effect on fatigue was observed. In addition, cognitive performance, as measured by a global change score, improved more in the modafinil than in the placebo group although the effect was not specific to any cognitive domain.

Enhanced fatigue performance of porous coated Ti6Al4V biomedical alloy

NASA Astrophysics Data System (ADS)

Apachitei, I.; Leoni, A.; Riemslag, A. C.; Fratila-Apachitei, L. E.; Duszczyk, J.

2011-05-01

Biofunctional coatings are necessary to improve integration of titanium implants in the host tissue but they may be detrimental for the implant fatigue properties. This study presents an attempt towards enhancement of the in vitro fatigue strength of plasma electrolytic oxidation coated Ti6Al4V alloy by applying shot peening process prior to coating. The electrolytic oxidation was performed in calcium acetate and calcium glycerophosphate electrolytes that allowed formation of porous oxide coatings with high surface free energy and apatite like ability. A deformed surface layer coupled with induced residual compressive stresses seem to affect oxide growth rate and fatigue behavior of the titanium alloy.

Investigation on the performance of a viscoelastic dielectric elastomer membrane generator.

PubMed

Zhou, Jianyou; Jiang, Liying; Khayat, Roger E

2015-04-21

Dielectric elastomer generators (DEGs), as a recent transduction technology, harvest electrical energy by scavenging mechanical energy from diverse sources. Their performance is affected by various material properties and failure modes of the dielectric elastomers. This work presents a theoretical analysis on the performance of a dielectric elastomer membrane generator under equi-biaxial loading conditions. By comparing our simulation results with the experimental observations existing in the literature, this work considers the fatigue life of DE-based devices under cyclic loading for the first time. From the simulation results, it is concluded that the efficiency of the DEG can be improved by raising the deforming rate and the prescribed maximum stretch ratio, and applying an appropriate bias voltage. However, the fatigue life expectancy compromises the efficiency improvement of the DEG. With the consideration of the fatigue life, applying an appropriate bias voltage appears to be a more desirable way to improve the DEG performance. The general framework developed in this work is expected to provide an increased understanding on the energy harvesting mechanisms of the DEGs and benefit their optimal design.

Fatigue on the flight deck: the consequences of sleep loss and the benefits of napping.

PubMed

Hartzler, Beth M

2014-01-01

The detrimental effects of fatigue in aviation are well established, as evidenced by both the number of fatigue-related mishaps and numerous studies which have found that most pilots experience a deterioration in cognitive performance as well as increased stress during the course of a flight. Further, due to the nature of the average pilot's work schedule, with frequent changes in duty schedule, early morning starts, and extended duty periods, fatigue may be impossible to avoid. Thus, it is critical that fatigue countermeasures be available which can help to combat the often overwhelming effects of sleep loss or sleep disruption. While stimulants such as caffeine are typically effective at maintaining alertness and performance, such countermeasures do nothing to address the actual source of fatigue - insufficient sleep. Consequently, strategic naps are considered an efficacious means of maintaining performance while also reducing the individual's sleep debt. These types of naps have been advocated for pilots in particular, as opportunities to sleep either in the designated rest facilities or on the flight deck may be beneficial in reducing both the performance and alertness impairments associated with fatigue, as well as the subjective feelings of sleepiness. Evidence suggests that strategic naps can reduce subjective feelings of fatigue and improve performance and alertness. Despite some contraindications to implementing strategic naps while on duty, such as sleep inertia experienced upon awakening, both researchers and pilots agree that the benefits associated with these naps far outweigh the potential risks. This article is a literature review detailing both the health and safety concerns of fatigue among commercial pilots as well as benefits and risks associated with strategic napping to alleviate this fatigue. Published by Elsevier Ltd.

Exercise-Induced Fatigue and Caffeine Supplementation Affect Psychomotor Performance but Not Covert Visuo-Spatial Attention

PubMed Central

Connell, Charlotte J. W.; Thompson, Benjamin; Kuhn, Gustav; Gant, Nicholas

2016-01-01

Fatigue resulting from strenuous exercise can impair cognition and oculomotor control. These impairments can be prevented by administering psychostimulants such as caffeine. This study used two experiments to explore the influence of caffeine administered at rest and during fatiguing physical exercise on spatial attention—a cognitive function that is crucial for task-based visually guided behavior. In independent placebo-controlled studies, cohorts of 12 healthy participants consumed caffeine and rested or completed 180 min of stationary cycling. Covert attentional orienting was measured in both experiments using a spatial cueing paradigm. We observed no alterations in attentional facilitation toward spatial cues suggesting that covert attentional orienting is not influenced by exercise fatigue or caffeine supplementation. Response times were increased (impaired) after exercise and this deterioration was prevented by caffeine supplementation. In the resting experiment, response times across all conditions and cues were decreased (improved) with caffeine. Covert spatial attention was not influenced by caffeine. Together, the results of these experiments suggest that covert attentional orienting is robust to the effects of fatiguing exercise and not influenced by caffeine. However, exercise fatigue impairs response times, which can be prevented by caffeine, suggesting that pre-motor planning and execution of the motor responses required for performance of the cueing task are sensitive to central nervous system fatigue. Caffeine improves response time in both fatigued and fresh conditions, most likely through action on networks controlling motor function. PMID:27768747

Exercise-Induced Fatigue and Caffeine Supplementation Affect Psychomotor Performance but Not Covert Visuo-Spatial Attention.

PubMed

Connell, Charlotte J W; Thompson, Benjamin; Kuhn, Gustav; Gant, Nicholas

2016-01-01

Fatigue resulting from strenuous exercise can impair cognition and oculomotor control. These impairments can be prevented by administering psychostimulants such as caffeine. This study used two experiments to explore the influence of caffeine administered at rest and during fatiguing physical exercise on spatial attention-a cognitive function that is crucial for task-based visually guided behavior. In independent placebo-controlled studies, cohorts of 12 healthy participants consumed caffeine and rested or completed 180 min of stationary cycling. Covert attentional orienting was measured in both experiments using a spatial cueing paradigm. We observed no alterations in attentional facilitation toward spatial cues suggesting that covert attentional orienting is not influenced by exercise fatigue or caffeine supplementation. Response times were increased (impaired) after exercise and this deterioration was prevented by caffeine supplementation. In the resting experiment, response times across all conditions and cues were decreased (improved) with caffeine. Covert spatial attention was not influenced by caffeine. Together, the results of these experiments suggest that covert attentional orienting is robust to the effects of fatiguing exercise and not influenced by caffeine. However, exercise fatigue impairs response times, which can be prevented by caffeine, suggesting that pre-motor planning and execution of the motor responses required for performance of the cueing task are sensitive to central nervous system fatigue. Caffeine improves response time in both fatigued and fresh conditions, most likely through action on networks controlling motor function.

Preliminary study of an exercise programme for reducing fatigue and improving sleep among long-term haemodialysis patients.

PubMed

Maniam, Radha; Subramanian, Pathmawathi; Singh, Surindar Kaur Surat; Lim, Soo Kun; Chinna, Karuthan; Rosli, Roshaslina

2014-09-01

Fatigue and quality of sleep are the main factors that contribute to a poor quality of life among patients on long-term haemodialysis. Studies have also emphasised the importance of exercise for improving the wellbeing of dialysis patients. This study aimed to determine the effectiveness of a predialysis low-to-moderate-intensity exercise programme for reducing fatigue and improving sleep disorders among long-term haemodialysis patients. In this quasi-experimental study, an exercise programme was conducted three times a week for 12 weeks before long-term haemodialysis patients underwent dialysis at two centres. The patients were categorised into either the exercise group (n = 28) or control group (n = 27). The latter was asked to maintain their current lifestyles. Assessments of fatigue and sleep disorder levels were performed for both groups using self-reported questionnaires at baseline and after intervention. The patients' perception of the exercise programme was also determined using self-reported questionnaires. Paired sample t-test indicated improvements in fatigue level in the exercise group (mean fatigue score: post-treatment 40.5 ± 7.9 vs. pre-treatment 30.0 ± 10.9). Improvements in sleep disorders were also observed in the exercise group (mean score: post-treatment 7.6 ± 3.3 vs. pre-treatment 10.1 ± 3.8). However, sleep quality deteriorated in the control group (mean score: post-treatment 10.7 ± 2.9 vs. pre-treatment 9.3 ± 2.9). Simple low-to-moderate-intensity exercise is effective for improving fatigue, sleep disorders and the overall quality of life among haemodialysis patients.

Effectiveness of aerobic gymnastic exercise on stress, fatigue, and sleep quality during postpartum: A pilot randomized controlled trial.

PubMed

Yang, Chiu-Ling; Chen, Chung-Hey

2018-01-01

Gymnastics is a preferable safe exercise for postnatal women performing regularly. The aim of this pilot randomized controlled trial was to determine whether the aerobic gymnastic exercise improves stress, fatigue, sleep quality and depression in postpartum women. Single-blinded, randomized controlled trial held from December 2014 until September 2015. Postnatal clinic of a medical center in southern Taiwan. 140 eligible postnatal women were systematically assigned, with a random start to experimental (n=70) or a control (n=70) group. Engage in aerobic gymnastic exercise at least three times (15min per section) a week for three months using compact disc in the home. Perceived Stress Scale, Postpartum Fatigue Scale, Postpartum Sleep Quality Scale, and Edinburgh Postnatal Depression Scale. In a two-way ANOVA with repeated measures, the aerobic gymnastic exercise group showed significant decrease in fatigue after practicing exercise 4 weeks and the positive effects extended to the 12-week posttests. Paired t-tests revealed that aerobic gymnastic exercise participants had improved significantly in perceived stress and fatigue after 4 weeks gymnastic exercise; these positive effects extended to the 12-week posttests. In addition, the changes in physical symptoms-related sleep inefficiency after 12 weeks gymnastic exercise were significantly decreased in the experimental group compared with the control group. The findings can be used to encourage postnatal women to perform moderate-intensity gymnastic exercise in their daily life to reduce their stress, fatigue and improve sleep quality. Copyright © 2017 Elsevier Ltd. All rights reserved.

Present Situation of the Anti-Fatigue Processing of High-Strength Steel Internal Thread Based on Cold Extrusion Technology: A Review

NASA Astrophysics Data System (ADS)

Miao, Hong; Jiang, Cheng; Liu, Sixing; Zhang, Shanwen; Zhang, Yanjun

2017-03-01

The adoption of cold-extrusion forming for internal thread net forming becomes an important component of anti-fatigue processing with the development of internal thread processing towards high performance, low cost and low energy consumption. It has vast application foreground in the field of aviation, spaceflight, high speed train and etc. The internal thread processing and anti-fatigue manufacture technology are summarized. In terms of the perspective of processing quality and fatigue serving life, the advantages and disadvantages of the processing methods from are compared. The internal thread cold-extrusion processing technology is investigated for the purpose of improving the anti-fatigue serving life of internal thread. The superiorities of the plastic deformation law and surface integrity of the metal layer in the course of cold extrusion for improving its stability and economy are summed up. The proposed research forecasts the development tendency of the internal thread anti-fatigue manufacturing technology.

Comparison of the cohesive and delamination fatigue properties of atomic-layer-deposited alumina and titania ultrathin protective coatings deposited at 200 °C

PubMed Central

Sadeghi-Tohidi, Farzad; Samet, David; Graham, Samuel; Pierron, Olivier N

2014-01-01

The fatigue properties of ultrathin protective coatings on silicon thin films were investigated. The cohesive and delamination fatigue properties of 22 nm-thick atomic-layered-deposited (ALD) titania were characterized and compared to that of 25 nm-thick alumina. Both coatings were deposited at 200 °C. The fatigue rates are comparable at 30 °C, 50% relative humidity (RH) while they are one order of magnitude larger for alumina compared to titania at 80 °C, 90% RH. The improved fatigue performance is believed to be related to the improved stability of the ALD titania coating with water compared to ALD alumina, which may in part be related to the fact that ALD titania is crystalline, while ALD alumina is amorphous. Static fatigue crack nucleation and propagation was not observed. The underlying fatigue mechanism is different from previously documented mechanisms, such as stress corrosion cracking, and appears to result from the presence of compressive stresses and a rough coating–substrate interface. PMID:27877645

Improved cognitive functioning in obese adolescents after a 30-week inpatient weight loss program.

PubMed

Vantieghem, Stijn; Bautmans, Ivan; Guchtenaere, Ann De; Tanghe, Ann; Provyn, Steven

2018-06-15

Studies linked obesity with a large number of medical conditions including decreased cognitive functioning. The relation between BMI and cognition was proven in adults, but in adolescents the results are conflicting. Further, limited data are available on the impact of weight loss on cognition. This study analyzed the impact of a 30-week lasting weight loss program on cognition and determined the impact of changes in body composition and self-perceived fatigue on changes in cognition. Sixty-two obese adolescents were evaluated at baseline and after 30 weeks. Stroop test (ST; selective attention), Continuous Performance Test (CPT; sustained attention) and Ray Auditory verbal learning test (RAVLT; short-term memory) were assessed. Additionally, body composition parameters and fatigue (MFI-20) were evaluated. Improved reaction times were found for ST and CPT after the intervention, but were independent for reductions in BMI, fat mass, fat%, and fatigue. Short memory also improved with decreased fatigue as an influencing parameter. Accuracy of ST and CPT showed no significant changes. A 30-week lasting inpatient weight loss program improved selective attention, sustained attention, and short-term memory. Changes in body composition did not explain the improvements in cognitive functioning. Decreased fatigue resulted in improved aspects of cognition.

Detection of fatigue cracks by nondestructive testing methods

NASA Technical Reports Server (NTRS)

Anderson, R. T.; Delacy, T. J.; Stewart, R. C.

1973-01-01

The effectiveness was assessed of various NDT methods to detect small tight cracks by randomly introducing fatigue cracks into aluminum sheets. The study included optimizing NDT methods calibrating NDT equipment with fatigue cracked standards, and evaluating a number of cracked specimens by the optimized NDT methods. The evaluations were conducted by highly trained personnel, provided with detailed procedures, in order to minimize the effects of human variability. These personnel performed the NDT on the test specimens without knowledge of the flaw locations and reported on the flaws detected. The performance of these tests was measured by comparing the flaws detected against the flaws present. The principal NDT methods utilized were radiographic, ultrasonic, penetrant, and eddy current. Holographic interferometry, acoustic emission monitoring, and replication methods were also applied on a reduced number of specimens. Generally, the best performance was shown by eddy current, ultrasonic, penetrant and holographic tests. Etching provided no measurable improvement, while proof loading improved flaw detectability. Data are shown that quantify the performances of the NDT methods applied.

Probabilistic Flexural Fatigue in Plain and Fiber-Reinforced Concrete

PubMed Central

Ríos, José D.

2017-01-01

The objective of this work is two-fold. First, we attempt to fit the experimental data on the flexural fatigue of plain and fiber-reinforced concrete with a probabilistic model (Saucedo, Yu, Medeiros, Zhang and Ruiz, Int. J. Fatigue, 2013, 48, 308–318). This model was validated for compressive fatigue at various loading frequencies, but not for flexural fatigue. Since the model is probabilistic, it is not necessarily related to the specific mechanism of fatigue damage, but rather generically explains the fatigue distribution in concrete (plain or reinforced with fibers) for damage under compression, tension or flexion. In this work, more than 100 series of flexural fatigue tests in the literature are fit with excellent results. Since the distribution of monotonic tests was not available in the majority of cases, a two-step procedure is established to estimate the model parameters based solely on fatigue tests. The coefficient of regression was more than 0.90 except for particular cases where not all tests were strictly performed under the same loading conditions, which confirms the applicability of the model to flexural fatigue data analysis. Moreover, the model parameters are closely related to fatigue performance, which demonstrates the predictive capacity of the model. For instance, the scale parameter is related to flexural strength, which improves with the addition of fibers. Similarly, fiber increases the scattering of fatigue life, which is reflected by the decreasing shape parameter. PMID:28773123

Probabilistic Flexural Fatigue in Plain and Fiber-Reinforced Concrete.

PubMed

Ríos, José D; Cifuentes, Héctor; Yu, Rena C; Ruiz, Gonzalo

2017-07-07

The objective of this work is two-fold. First, we attempt to fit the experimental data on the flexural fatigue of plain and fiber-reinforced concrete with a probabilistic model (Saucedo, Yu, Medeiros, Zhang and Ruiz, Int. J. Fatigue, 2013, 48, 308-318). This model was validated for compressive fatigue at various loading frequencies, but not for flexural fatigue. Since the model is probabilistic, it is not necessarily related to the specific mechanism of fatigue damage, but rather generically explains the fatigue distribution in concrete (plain or reinforced with fibers) for damage under compression, tension or flexion. In this work, more than 100 series of flexural fatigue tests in the literature are fit with excellent results. Since the distribution of monotonic tests was not available in the majority of cases, a two-step procedure is established to estimate the model parameters based solely on fatigue tests. The coefficient of regression was more than 0.90 except for particular cases where not all tests were strictly performed under the same loading conditions, which confirms the applicability of the model to flexural fatigue data analysis. Moreover, the model parameters are closely related to fatigue performance, which demonstrates the predictive capacity of the model. For instance, the scale parameter is related to flexural strength, which improves with the addition of fibers. Similarly, fiber increases the scattering of fatigue life, which is reflected by the decreasing shape parameter.

Capsaicin Supplementation Reduces Physical Fatigue and Improves Exercise Performance in Mice

PubMed Central

Hsu, Yi-Ju; Huang, Wen-Ching; Chiu, Chien-Chao; Liu, Yan-Lin; Chiu, Wan-Chun; Chiu, Chun-Hui; Chiu, Yen-Shuo; Huang, Chi-Chang

2016-01-01

Chili pepper is used as a food, seasoning and has been revered for its medicinal and health claims. It is very popular and is the most common spice worldwide. Capsaicin (CAP) is a major pungent and bioactive phytochemical in chili peppers. CAP has been shown to improve mitochondrial biogenesis and adenosine triphosphate (ATP) production. However, there is limited evidence around the effects of CAP on physical fatigue and exercise performance. The purpose of this study was to evaluate the potential beneficial effects of CAP on anti-fatigue and ergogenic functions following physiological challenge. Female Institute of Cancer Research (ICR) mice from four groups (n = 8 per group) were orally administered CAP for 4 weeks at 0, 205, 410, and 1025 mg/kg/day, which were respectively designated the vehicle, CAP-1X, CAP-2X, and CAP-5X groups. The anti-fatigue activity and exercise performance was evaluated using forelimb grip strength, exhaustive swimming time, and levels of serum lactate, ammonia, glucose, BUN (blood urea nitrogen) and creatine kinase (CK) after a 15-min swimming exercise. The grip strength and exhaustive swimming time of the CAP-5X group were significantly higher than other groups. CAP supplementation dose-dependently reduced serum lactate, ammonia, BUN and CK levels, and increased glucose concentration after the 15-min swimming test. In addition, CAP also increased hepatic glycogen content, an important energy source for exercise. The possible mechanism was relevant to energy homeostasis and the physiological modulations by CAP supplementation. Therefore, our results suggest that CAP supplementation may have a wide spectrum of bioactivities for promoting health, performance improvement and fatigue amelioration. PMID:27775591

Capsaicin Supplementation Reduces Physical Fatigue and Improves Exercise Performance in Mice.

PubMed

Hsu, Yi-Ju; Huang, Wen-Ching; Chiu, Chien-Chao; Liu, Yan-Lin; Chiu, Wan-Chun; Chiu, Chun-Hui; Chiu, Yen-Shuo; Huang, Chi-Chang

2016-10-20

Chili pepper is used as a food, seasoning and has been revered for its medicinal and health claims. It is very popular and is the most common spice worldwide. Capsaicin (CAP) is a major pungent and bioactive phytochemical in chili peppers. CAP has been shown to improve mitochondrial biogenesis and adenosine triphosphate (ATP) production. However, there is limited evidence around the effects of CAP on physical fatigue and exercise performance. The purpose of this study was to evaluate the potential beneficial effects of CAP on anti-fatigue and ergogenic functions following physiological challenge. Female Institute of Cancer Research (ICR) mice from four groups ( n = 8 per group) were orally administered CAP for 4 weeks at 0, 205, 410, and 1025 mg/kg/day, which were respectively designated the vehicle, CAP-1X, CAP-2X, and CAP-5X groups. The anti-fatigue activity and exercise performance was evaluated using forelimb grip strength, exhaustive swimming time, and levels of serum lactate, ammonia, glucose, BUN (blood urea nitrogen) and creatine kinase (CK) after a 15-min swimming exercise. The grip strength and exhaustive swimming time of the CAP-5X group were significantly higher than other groups. CAP supplementation dose-dependently reduced serum lactate, ammonia, BUN and CK levels, and increased glucose concentration after the 15-min swimming test. In addition, CAP also increased hepatic glycogen content, an important energy source for exercise. The possible mechanism was relevant to energy homeostasis and the physiological modulations by CAP supplementation. Therefore, our results suggest that CAP supplementation may have a wide spectrum of bioactivities for promoting health, performance improvement and fatigue amelioration.

Chemical Durability Improvement and Static Fatigue of Glasses.

DTIC Science & Technology

1982-08-01

Afl-Alla 837 RENSSELAER POLYIECmfJ!C INST TRtOY NY DEPT OF MATERIAL--ETC F/6 ii/ CHEMICAL DURABILITY IMPROVEMENT AND STATIC FATIGUE OF GLASSESW AUC2...82 M TOMOZAWA NOGGIN 7A-C-0315 UNC LASS IF IED N ENEEEEEE FINAL TECHNICAL REPORT For the period April 1, 1978 "u March 31, 198200 CHEMICAL DURABILITY...REPORT A PERIOD COVERED Chemical Durability Improvement and Static Final Technical Report Fatiue o GlasesApril 1, 1978"’,March 31, 1982 S. PERFORMING ORG

Fatigue Behavior under Multiaxial Stress States Including Notch Effects and Variable Amplitude Loading

NASA Astrophysics Data System (ADS)

Gates, Nicholas R.

The central objective of the research performed in this study was to be able to better understand and predict fatigue crack initiation and growth from stress concentrations subjected to complex service loading histories. As such, major areas of focus were related to the understanding and modeling of material deformation behavior, fatigue damage quantification, notch effects, cycle counting, damage accumulation, and crack growth behavior under multiaxial nominal loading conditions. To support the analytical work, a wide variety of deformation and fatigue tests were also performed using tubular and plate specimens made from 2024-T3 aluminum alloy, with and without the inclusion of a circular through-thickness hole. However, the analysis procedures implemented were meant to be general in nature, and applicable to a wide variety of materials and component geometries. As a result, experimental data from literature were also used, when appropriate, to supplement the findings of various analyses. Popular approaches currently used for multiaxial fatigue life analysis are based on the idea of computing an equivalent stress/strain quantity through the extension of static yield criteria. This equivalent stress/strain is then considered to be equal, in terms of fatigue damage, to a uniaxial loading of the same magnitude. However, it has often been shown, and was shown again in this study, that although equivalent stress- and strain-based analysis approaches may work well in certain situations, they lack a general robustness and offer little room for improvement. More advanced analysis techniques, on the other hand, provide an opportunity to more accurately account for various aspects of the fatigue failure process under both constant and variable amplitude loading conditions. As a result, such techniques were of primary interest in the investigations performed. By implementing more advanced life prediction methodologies, both the overall accuracy and the correlation of fatigue life predictions were found to improve for all loading conditions considered in this study. The quantification of multiaxial fatigue damage was identified as being a key area of improvement, where the shear-based Fatemi-Socie (FS) critical plane damage parameter was shown to correlate all fully-reversed constant amplitude fatigue data relatively well. Additionally, a proposed modification to the FS parameter was found to result in improved life predictions in the presence of high tensile mean stress and for different ratios of nominal shear to axial stress. For notched specimens, improvements were also gained through the use of more robust notch deformation and stress gradient models. Theory of Critical Distances (TCD) approaches, together with pseudo stress-based plasticity modeling techniques for local stress-strain estimation, resulted in better correlation of multiaxial fatigue data when compared to traditional approaches such as Neuber's rule with fatigue notch factor. Since damage parameters containing both stress and strain terms, such as the FS parameter, are able to reflect changes in fatigue damage due to transient material hardening behavior, this issue was also investigated with respect to its impact on variable amplitude life predictions. In order to ensure that material deformation behavior was properly accounted for, stress-strain predictions based on an Armstrong-Frederick-Chaboche style cyclic plasticity model were first compared to results from deformation tests performed under a variety of complex multiaxial loading conditions. The model was simplified based on the assumption of Masing material behavior, and a new transient hardening formulation was proposed so that all modeling parameters could be determined from a relatively limited amount of experimental data. Overall, model predictions were found to agree fairly well with experimental results for all loading histories considered. Finally, in order to evaluate life prediction procedures under realistic loading conditions, variable amplitude fatigue tests were performed using axial, torsion, and combined axial-torsion loading histories derived from recorded flight test data on the lower wing skin area of a military patrol aircraft (tension-dominated). While negligible improvements in life predictions were obtained through the consideration of transient material deformation behavior for these histories, crack initiation definition was found to have a slightly larger impact on prediction accuracy. As a result, when performing analyses using the modified FS damage parameter, transient stress-strain response, and a 0.2 mm crack initiation definition, nearly all variable amplitude fatigue lives, for un-notched and notched specimens, were predicted within a factor of 3 of experimental results. However, variable amplitude life predictions were still more non-conservative than those observed for constant amplitude loading conditions.

Fatigue: an overview.

PubMed

Rosenthal, Thomas C; Majeroni, Barbara A; Pretorius, Richard; Malik, Khalid

2008-11-15

Fatigue, a common presenting symptom in primary care, negatively impacts work performance, family life, and social relationships. The differential diagnosis of fatigue includes lifestyle issues, physical conditions, mental disorders, and treatment side effects. Fatigue can be classified as secondary to other medical conditions, physiologic, or chronic. The history and physical examination should focus on identifying common secondary causes (e.g., medications, anemia, pregnancy) and life-threatening problems, such as cancer. Results of laboratory studies affect management in only 5 percent of patients, and if initial results are normal, repeat testing is generally not indicated. Treatment of all types of fatigue should include a structured plan for regular physical activity that consists of stretching and aerobic exercise, such as walking. Caffeine and modafinil may be useful for episodic situations requiring alertness. Short naps are proven performance enhancers. Selective serotonin reuptake inhibitors, such as fluoxetine, paroxetine, or sertraline, may improve energy in patients with depression. Patients with chronic fatigue may respond to cognitive behavior therapy. Scheduling regular follow-up visits, rather than sporadic urgent appointments, is recommended for effective long-term management.

Systematic content evaluation and review of measurement properties of questionnaires for measuring self-reported fatigue among older people.

PubMed

Egerton, Thorlene; Riphagen, Ingrid I; Nygård, Arnhild J; Thingstad, Pernille; Helbostad, Jorunn L

2015-09-01

The assessment of fatigue in older people requires simple and user-friendly questionnaires that capture the phenomenon, yet are free from items indistinguishable from other disorders and experiences. This study aimed to evaluate the content, and systematically review and rate the measurement properties of self-report questionnaires for measuring fatigue, in order to identify the most suitable questionnaires for older people. This study firstly involved identification of questionnaires that purport to measure self-reported fatigue, and evaluation of the content using a rating scale developed for the purpose from contemporary understanding of the construct. Secondly, for the questionnaires that had acceptable content, we identified studies reporting measurement properties and rated the methodological quality of those studies according to the COSMIN system. Finally, we extracted and synthesised the results of the studies to give an overall rating for each questionnaire for each measurement property. The protocol was registered with PROSPERO (CRD42013005589). Of the 77 identified questionnaires, twelve were selected for review after content evaluation. Methodological quality varied, and there was a lack of information on measurement error and responsiveness. The PROMIS-Fatigue item bank and short forms perform the best. The FACIT-Fatigue scale, Parkinsons Fatigue Scale, Perform Questionnaire, and Uni-dimensional Fatigue Impact Scale also perform well and can be recommended. Minor modifications to improve performance are suggested. Further evaluation of unresolved measurement properties, particularly with samples including older people, is needed for all the recommended questionnaires.

A randomized, controlled trial of aerobic exercise for treatment-related fatigue in men receiving radical external beam radiotherapy for localized prostate carcinoma.

PubMed

Windsor, Phyllis M; Nicol, Kathleen F; Potter, Joan

2004-08-01

Advice to rest and take things easy if patients become fatigued during radiotherapy may be detrimental. Aerobic walking improves physical functioning and has been an intervention for chemotherapy-related fatigue. A prospective, randomized, controlled trial was performed to determine whether aerobic exercise would reduce the incidence of fatigue and prevent deterioration in physical functioning during radiotherapy for localized prostate carcinoma. Sixty-six men were randomized before they received radical radiotherapy for localized prostate carcinoma, with 33 men randomized to an exercise group and 33 men randomized to a control group. Outcome measures were fatigue and distance walked in a modified shuttle test before and after radiotherapy. There were no significant between group differences noted with regard to fatigue scores at baseline (P = 0.55) or after 4 weeks of radiotherapy (P = 0.18). Men in the control group had significant increases in fatigue scores from baseline to the end of radiotherapy (P = 0.013), with no significant increases observed in the exercise group (P = 0.203). A nonsignificant reduction (2.4%) in shuttle test distance at the end of radiotherapy was observed in the control group; however, in the exercise group, there was a significant increase (13.2%) in distance walked (P = 0.0003). Men who followed advice to rest and take things easy if they became fatigued demonstrated a slight deterioration in physical functioning and a significant increase in fatigue at the end of radiotherapy. Home-based, moderate-intensity walking produced a significant improvement in physical functioning with no significant increase in fatigue. Improved physical functioning may be necessary to combat radiation fatigue.

Effect of Cryorolling and Aging on Fatigue Behavior of Ultrafine-grained Al6061

NASA Astrophysics Data System (ADS)

Yadollahpour, M.; Hosseini-Toudeshky, H.; Karimzadeh, F.

2016-05-01

The effects of cryorolling (rolling at liquid nitrogen temperature) and heat treatment on tensile and high-cycle fatigue properties and fatigue crack growth rate of Al6061 alloy have been investigated in the present work. First, the solid solution-treated bulk Al6061 alloy was subjected to cryorolling with 90% total thickness reduction and subsequent short annealing at 205°C for 5 min and peak aging at 148°C for 39 h to achieve grain refinement and simultaneous improvement of the strength and ductility. Then, hardness measurements, tensile tests, fatigue life, and fatigue crack growth rate tests including fractography analyses using scanning electron microscopy were performed on bulk Al6061 alloy, cryorolled (CR), and cryorolled material followed by peak aging (PA). The PA specimen showed improved yield strength by 24%, ultimate tensile strength by 20%, and ductility by 12% as compared with the bulk Al6061 alloy. It is shown that the fatigue strength of both CR and PA specimens under a high-cycle fatigue regime are larger than that of the bulk Al6061 alloy. Also, fatigue crack growth rates of the CR and PA specimens show significant enhancement in fatigue crack growth resistances as compared with the bulk Al6061 alloy, as a result of grain refinement.

NASA GRC Fatigue Crack Initiation Life Prediction Models

NASA Technical Reports Server (NTRS)

Arya, Vinod K.; Halford, Gary R.

2002-01-01

Metal fatigue has plagued structural components for centuries, and it remains a critical durability issue in today's aerospace hardware. This is true despite vastly improved and advanced materials, increased mechanistic understanding, and development of accurate structural analysis and advanced fatigue life prediction tools. Each advance is quickly taken advantage of to produce safer, more reliable, more cost effective, and better performing products. In other words, as the envelope is expanded, components are then designed to operate just as close to the newly expanded envelope as they were to the initial one. The problem is perennial. The economic importance of addressing structural durability issues early in the design process is emphasized. Tradeoffs with performance, cost, and legislated restrictions are pointed out. Several aspects of structural durability of advanced systems, advanced materials and advanced fatigue life prediction methods are presented. Specific items include the basic elements of durability analysis, conventional designs, barriers to be overcome for advanced systems, high-temperature life prediction for both creep-fatigue and thermomechanical fatigue, mean stress effects, multiaxial stress-strain states, and cumulative fatigue damage accumulation assessment.

A Primer In Advanced Fatigue Life Prediction Methods

NASA Technical Reports Server (NTRS)

Halford, Gary R.

2000-01-01

Metal fatigue has plagued structural components for centuries, and it remains a critical durability issue in today's aerospace hardware. This is true despite vastly improved and advanced materials, increased mechanistic understanding, and development of accurate structural analysis and advanced fatigue life prediction tools. Each advance is quickly taken advantage of to produce safer, more reliable more cost effective, and better performing products. In other words, as the envelop is expanded, components are then designed to operate just as close to the newly expanded envelop as they were to the initial one. The problem is perennial. The economic importance of addressing structural durability issues early in the design process is emphasized. Tradeoffs with performance, cost, and legislated restrictions are pointed out. Several aspects of structural durability of advanced systems, advanced materials and advanced fatigue life prediction methods are presented. Specific items include the basic elements of durability analysis, conventional designs, barriers to be overcome for advanced systems, high-temperature life prediction for both creep-fatigue and thermomechanical fatigue, mean stress effects, multiaxial stress-strain states, and cumulative fatigue damage accumulation assessment.

NASA GRC Fatigue Crack Initiation Life Prediction Models

NASA Astrophysics Data System (ADS)

Arya, Vinod K.; Halford, Gary R.

2002-10-01

Metal fatigue has plagued structural components for centuries, and it remains a critical durability issue in today's aerospace hardware. This is true despite vastly improved and advanced materials, increased mechanistic understanding, and development of accurate structural analysis and advanced fatigue life prediction tools. Each advance is quickly taken advantage of to produce safer, more reliable, more cost effective, and better performing products. In other words, as the envelope is expanded, components are then designed to operate just as close to the newly expanded envelope as they were to the initial one. The problem is perennial. The economic importance of addressing structural durability issues early in the design process is emphasized. Tradeoffs with performance, cost, and legislated restrictions are pointed out. Several aspects of structural durability of advanced systems, advanced materials and advanced fatigue life prediction methods are presented. Specific items include the basic elements of durability analysis, conventional designs, barriers to be overcome for advanced systems, high-temperature life prediction for both creep-fatigue and thermomechanical fatigue, mean stress effects, multiaxial stress-strain states, and cumulative fatigue damage accumulation assessment.

Fatigue design curve of a TiNi/Al shape memory alloy composite for aircraft stringer design

NASA Astrophysics Data System (ADS)

Park, Young-Chul; Jo, Young-Jik; Baek, Seok-Heum; Furuya, Yasubumi

2009-05-01

In this study, a TiNi/Al6061 shape memory alloy (SMA) composite was fabricated by the hot press method, and pressed by a roller for its strength improvement using the shape memory fiber shrinkage phenomenon. These two kinds of specimens were fabricated with 0% and 5% volume ratio and 0%, 10 % and 20% reduction ratio of TiNi alloy fiber, respectively. A fatigue test has been performed to evaluate the fatigue life for the fabricated TiNi/Al SMA composite as an S-N curve. The results from the Goodman diagram is able to illustrate the failure criterion and fatigue limit between tensile and bending fatigue strength in the fatigue characterization of TiNi/Al SMA composites.

The effects of moderate fatigue on dynamic balance control and attentional demands.

PubMed

Simoneau, Martin; Bégin, François; Teasdale, Normand

2006-09-28

During daily activities, the active control of balance often is a task per se (for example, when standing in a moving bus). Other constraints like fatigue can add to the complexity of this balance task. In the present experiment, we examined how moderate fatigue induced by fast walking on a treadmill challenged dynamic balance control. We also examined if the attentional demands for performing the balance task varied with fatigue. Subjects (n = 10) performed simultaneously a dynamic balance control task and a probe reaction time task (RT) (serving as an indicator of attentional demands) before and after three periods of moderate fatigue (fast walking on a treadmill). For the balance control task, the real-time displacement of the centre of pressure (CP) was provided on a monitor placed in front of the subject, at eye level. Subjects were asked to keep their CP within a target (moving box) moving upward and downward on the monitor. The tracking performance was measured (time spent outside the moving box) and the CP behavior analyzed (mean CP speed and mean frequency of the CP velocity). Moderate fatigue led to an immediate decrement of the performance on the balance control task; increase of the percentage of time spent outside the box and increase of the mean CP speed. Across the three fatigue periods, subjects improved their tracking performance and reduced their mean CP speed. This was achieved by increasing their frequency of actions; mean frequency of the CP velocity were higher for the fatigue periods than for the no fatigue periods. Fatigue also induced an increase in the attentional demands suggesting that more cognitive resources had to be allocated to the balance task with than without fatigue. Fatigue induced by fast walking had an initial negative impact on the control of balance. Nonetheless, subjects were able to compensate the effect of the moderate fatigue by increasing the frequency of actions. This adaptation, however, required that a greater proportion of the cognitive resources be allocated to the active control of the balance task.

Caffeine administration at night during extended wakefulness effectively mitigates performance impairment but not subjective assessments of fatigue and sleepiness.

PubMed

Paech, Gemma M; Banks, Siobhan; Pajcin, Maja; Grant, Crystal; Johnson, Kayla; Kamimori, Gary H; Vedova, Chris B Della

2016-06-01

The current study investigated the effects of repeated caffeine administration on performance and subjective reports of sleepiness and fatigue during 50h extended wakefulness. Twenty-four, non-smokers aged 22.5±2.9y (mean±SD) remained awake for two nights (50h) in a controlled laboratory environment. During this period, 200mg of caffeine or placebo gum was administered at 01:00, 03:00, 05:00 and 07:00 on both nights (total of 800mg/night). Neurobehavioral performance and subjective reports were assessed throughout the wake period. Caffeine improved performance compared to placebo, but did not affect overall ratings of subjective sleepiness and fatigue. Performance and sleepiness worsened with increasing time awake for both conditions. However, caffeine slowed performance impairments such that after 50h of wakefulness performance was better following caffeine administration compared to placebo. Caffeine also slowed the increase in subjective sleepiness and performance ratings, but only during the first night of wakefulness. After two nights of sleep deprivation, there was no difference in sleepiness ratings between the two conditions. These results demonstrate that strategic administration of caffeine effectively mitigates performance impairments associated with 50h wakefulness but does not improve overall subjective assessments of sleepiness, fatigue and performance. Results indicate that while performance impairment is alleviated, individuals may continue to report feelings of sleepiness. Individuals who use caffeine as a countermeasure in sustained operations may feel as though caffeine is not effective despite impairments in objective performance being largely mitigated. Copyright © 2016 Elsevier Inc. All rights reserved.

Fatigue, self-efficacy, physical activity, and quality of life in women with breast cancer.

PubMed

Haas, Barbara K

2011-01-01

More than 192 000 US women faced the challenge of living with breast cancer in 2009. Although exercise may help combat treatment-related symptoms, cancer-related fatigue has been identified as a potential barrier to engaging in physical activity. Self-efficacy has been proposed to mediate the impact of cancer-related fatigue on physical activity and subsequently improve quality of life (QOL). The purpose of this study was to determine the linkages among the concepts of an introductory model of fatigue related to cancer, self-efficacy for physical activity, physical activity, and QOL in women being treated for breast cancer. Women currently receiving treatment for breast cancer were asked to complete 5 instruments: demographic profile, Piper Fatigue Scale, Physical Activity Assessment Inventory, Human Activity Profile, and McGill QOL Questionnaire. Structural equation modeling of the data was performed to determine the direct and indirect influences of study variables on QOL. The model was tested based on responses of 73 participants. All paths between variables were significant. The model explained 53% of the variance in QOL scores, 28% of the variance in physical activity, and 31% of the variance in self-efficacy. Although fatigue is most commonly thought of as a physical problem requiring physical intervention, this study provides emerging evidence to suggest there may be potential interventions to improve self-efficacy that may mediate the effect of fatigue on QOL. Interventions to improve self-efficacy may contribute to increased physical activity and improved QOL in this population.

Preliminary study of an exercise programme for reducing fatigue and improving sleep among long-term haemodialysis patients

PubMed Central

Maniam, Radha; Subramanian, Pathmawathi; Singh, Surindar Kaur Surat; Lim, Soo Kun; Chinna, Karuthan; Rosli, Roshaslina

2014-01-01

INTRODUCTION Fatigue and quality of sleep are the main factors that contribute to a poor quality of life among patients on long-term haemodialysis. Studies have also emphasised the importance of exercise for improving the wellbeing of dialysis patients. This study aimed to determine the effectiveness of a predialysis low-to-moderate-intensity exercise programme for reducing fatigue and improving sleep disorders among long-term haemodialysis patients. METHODS In this quasi-experimental study, an exercise programme was conducted three times a week for 12 weeks before long-term haemodialysis patients underwent dialysis at two centres. The patients were categorised into either the exercise group (n = 28) or control group (n = 27). The latter was asked to maintain their current lifestyles. Assessments of fatigue and sleep disorder levels were performed for both groups using self-reported questionnaires at baseline and after intervention. The patients’ perception of the exercise programme was also determined using self-reported questionnaires. RESULTS Paired sample t-test indicated improvements in fatigue level in the exercise group (mean fatigue score: post-treatment 40.5 ± 7.9 vs. pre-treatment 30.0 ± 10.9). Improvements in sleep disorders were also observed in the exercise group (mean score: post-treatment 7.6 ± 3.3 vs. pre-treatment 10.1 ± 3.8). However, sleep quality deteriorated in the control group (mean score: post-treatment 10.7 ± 2.9 vs. pre-treatment 9.3 ± 2.9). CONCLUSION Simple low-to-moderate-intensity exercise is effective for improving fatigue, sleep disorders and the overall quality of life among haemodialysis patients. PMID:25273932

The effect of progressive muscle relaxation on the management of fatigue and quality of sleep in patients with chronic obstructive pulmonary disease: A randomized controlled clinical trial.

PubMed

Seyedi Chegeni, Pooya; Gholami, Mohammad; Azargoon, Alireza; Hossein Pour, Amir Hossein; Birjandi, Mehdi; Norollahi, Hamed

2018-05-01

To assess the effect of progressive muscle relaxation (PMR) on fatigue and sleep quality of patients with chronic obstructive pulmonary disease (COPD) stages 3 and 4. The pretest posttest clinical trial recruited 91 patients COPD grades 3 and 4. Following random assignment of subjects, the treatment group (n = 45) performed PMR for eight weeks and the control group (n = 46) received routine cares. At baseline and after the intervention, fatigue and sleep quality was assessed. Data obtained were analyzed in SPSS. It was determined that PMR decreased patients' fatigue level and improved some sleep quality subscales including subjective sleep quality, sleep latency, sleep duration and habitual sleep efficiency, but no improvement was found in global sleep quality and other sleep subscales. An eight-week home-based PMR program can be effective in reducing fatigue and improving certain subscales of sleep quality in patients with COPD stages 3,4. (IRCT2016080124080N3). Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of oral administration of caffeine and D-ribose on mental fatigue.

PubMed

Ataka, Suzuka; Tanaka, Masaaki; Nozaki, Satoshi; Mizuma, Hiroshi; Mizuno, Kei; Tahara, Tsuyoshi; Sugino, Tomohiro; Shirai, Tomoko; Kajimoto, Yoshitaka; Kuratsune, Hirohiko; Kajimoto, Osami; Watanabe, Yasuyoshi

2008-03-01

We examined the effects of administering two different candidate antifatigue substances, caffeine and D-ribose, on mental fatigue. In a double-blinded, placebo-controlled, three-way crossover design, 17 healthy volunteers were randomized to oral caffeine (200 mg/d), D-ribose (2000 mg/d), or placebo for 8 d. As fatigue-inducing mental tasks, subjects performed a 30-min Uchida-Kraepelin psychodiagnostic test and a 30-min advanced trail-making test on four occasions. During the tasks, the task performance of the caffeine group was better than that of the placebo group. However, after the fatigue-inducing tasks, although subjective perception of fatigue, motivation, or sleepiness was not significantly different, plasma branched-chain amino acid levels in the caffeine group were lower than those of the placebo group. Administration of D-ribose had no effect. Because plasma branched-chain amino acid levels are decreased by mental fatigue, these results suggest that administration of caffeine improved task performance through the enhancement of central nervous system activity without increasing the sensation of fatigue. However, further decreases in branched-chain amino acid levels indicate that caffeine might promote deeper fatigue than placebo. Unfortunately, research subsequent to our study design has shown that D-ribose dosing higher than we used is needed to see a clinical effect and therefore no conclusions can be made from this study as to the efficacy of D-ribose.

Positive inotropism in mammalian skeletal muscle in vitro during and after fatigue.

PubMed

Reading, S A; Murrant, C L; Barclay, J K

2004-04-01

We tested the hypothesis that positive inotropic factors decrease fatigue and improve recovery from fatigue in mammalian skeletal muscle in vitro. To induce fatigue, we stimulated mouse soleus and extensor digitorum longus (EDL) to perform isometric tetanic contractions (50 impulses x s(-1) for 0.5 s) at 6 contractions x min(-1) for 60 min in soleus and 3 contractions x min(-1) for 20 min in EDL. Muscles were submerged in Krebs-Henseleit bicarbonate solution (Krebs) at 27 degrees C gassed with 95% nitrogen - 5% carbon dioxide (anoxia). Before and for 67 min after the fatigue period, muscles contracted at 0.6 contractions x min(-1) in 95% oxygen - 5% carbon dioxide (hyperoxia). We added a permeable cAMP analog (N6, 2'-O-dibutyryladenosine 3':5'-cyclic monophosphate at 10(-3) mol x L(-1) (dcAMP)), caffeine (2 x 10(-3) mol x L(-1), or Krebs as vehicle control at 25 min before, during, or at the end of the fatigue period. In soleus and EDL, both challenges added before fatigue significantly increased developed force but only caffeine increased developed force when added during the fatigue period. At the end of fatigue, the decrease in force in challenged muscles was equal to or greater than in controls so that the force remaining was the same or less than in controls. EDL challenged with dcAMP or caffeine at any time recovered more force than controls. In soleus, caffeine improved recovery except when added before fatigue. With dcAMP added to soleus, recovery was better after challenges at 10 min and the end of the fatigue period. Thus, increased intracellular concentrations of cAMP and (or) Ca2+ did not decrease fatigue in either muscle but improved recovery from fatigue in EDL and, in some conditions, in soleus.

Selective Efficacy of Static and Dynamic Imagery in Different States of Physical Fatigue.

PubMed

Kanthack, Thiago Ferreira Dias; Guillot, Aymeric; Altimari, Leandro Ricardo; Nunez Nagy, Susana; Collet, Christian; Di Rienzo, Franck

2016-01-01

There is compelling evidence that motor imagery contributes to improved motor performance, and recent work showed that dynamic motor imagery (dMI) might provide additional benefits by comparison with traditional MI practice. However, the efficacy of motor imagery in different states of physical fatigue remains largely unknown, especially as imagery accuracy may be hampered by the physical fatigue states elicited by training. We investigated the effect of static motor imagery (sMI) and dMI on free-throw accuracy in 10 high-level basketball athletes, both in a non-fatigued state (Experiment 1) and immediately after an incremental running test completed until exhaustion (20 m shuttle run-test-Experiment 2). We collected perceived exhaustion and heart rate to quantify the subjective experience of fatigue and energy expenditure. We found that dMI brought better shooting performance than sMI, except when athletes were physically exhausted. These findings shed light on the conditions eliciting optimal use of sMI and dMI. In particular, considering that the current physical state affects body representation, performing dMI under fatigue may result in mismatches between actual and predicted body states.

Electrophysiological and behavioral effects of frontal transcranial direct current stimulation on cognitive fatigue in multiple sclerosis.

PubMed

Fiene, Marina; Rufener, Katharina S; Kuehne, Maria; Matzke, Mike; Heinze, Hans-Jochen; Zaehle, Tino

2018-03-01

Fatigue is one of the most common and debilitating symptoms affecting patients with multiple sclerosis (MS). Sustained cognitive effort induces cognitive fatigue, operationalized as subjective exhaustion and fatigue-related objective alertness decrements with time-on-task. During prolonged cognitive testing, MS patients show increased simple reaction times (RT) accompanied by lower amplitudes and prolonged latencies of the P300 event-related potential. Previous studies suggested a major role of structural and functional abnormalities in the frontal cortex including a frontal hypo-activation in fatigue pathogenesis. In the present study we investigated the neuromodulatory effect of transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) on objective measures of fatigue-related decrements in cognitive performance in MS patients. P300 during an auditory oddball task and simple reaction times in an alertness test were recorded at baseline, during and after stimulation. Compared to sham, anodal tDCS caused an increase in P300 amplitude that persisted after the end of stimulation and eliminated the fatigue-related increase in RT over the course of a testing session. Our findings demonstrate that anodal tDCS over the left DLPFC can counteract performance decrements associated with fatigue thereby leading to an improvement in the patient's ability to cope with sustained cognitive demands. This provides causal evidence for the functional relevance of the left DLPFC in fatigue pathophysiology. The results indicate that tDCS-induced modulations of frontal activity can be an effective therapeutic option for the treatment of fatigue-related declines in cognitive performance in MS patients.

Effect of the cooling suit method applied to individuals with multiple sclerosis on fatigue and activities of daily living.

PubMed

Özkan Tuncay, Fatma; Mollaoğlu, Mukadder

2017-12-01

To determine the effects of cooling suit on fatigue and activities of daily living of individuals with multiple sclerosis. Fatigue is one of the most common symptoms in people with multiple sclerosis and adversely affects their activities of daily living. Studies evaluating fatigue associated with multiple sclerosis have reported that most of the fatigue cases are related to the increase in body temperature and that cooling therapy is effective in coping with fatigue. This study used a two sample, control group design. The study sample comprised 75 individuals who met the inclusion criteria. Data were collected with study forms. After the study data were collected, cooling suit treatment was administered to the experimental group. During home visits paid at the fourth and eighth weeks after the intervention, the aforementioned scales were re-administered to the participants in the experimental and control groups. The analyses performed demonstrated that the severity levels of fatigue experienced by the participants in the experimental group wearing cooling suit decreased. The experimental group also exhibited a significant improvement in the participants' levels of independence in activities of daily living. The cooling suit worn by individuals with multiple sclerosis was determined to significantly improve the participants' levels of fatigue and independence in activities of daily living. The cooling suit therapy was found to be an effective intervention for the debilitating fatigue suffered by many multiple sclerosis patients, thus significantly improving their level of independence in activities of daily living. © 2017 John Wiley & Sons Ltd.

Interleukin-1 as a mediator of fatigue in disease: a narrative review.

PubMed

Roerink, Megan E; van der Schaaf, Marieke E; Dinarello, Charles A; Knoop, Hans; van der Meer, Jos W M

2017-01-21

Fatigue is commonly reported in a variety of illnesses, and it has major impact on quality of life. Previously, it was thought that fatigue originates in the skeletal muscles, leading to cessation of activity. However, more recently, it has become clear that the brain is the central regulator of fatigue perception. It has been suggested that pro-inflammatory cytokines, especially interleukin-1 alpha (IL-1α) and interleukin-1 beta (IL-1β), play a prominent role in the development of central fatigue, and several studies have been performed to elucidate the connection between inflammation and these central processes.In this narrative review, mechanisms of action of IL-1 are described, with special attention to its effect on the central nervous system. In addition, we present a summary of studies that (i) investigated the relationship between circulating IL-1α and IL-1β and fatigue severity and/or (ii) evaluated the effect of inhibiting IL-1 on fatigue. We aim to improve the understanding of fatigue in both inflammatory and non-inflammatory illnesses, which could help develop strategies to treat fatigue more effectively.Reviewing the studies that have been performed, it appears that there is a limited value of measuring circulating IL-1. However, inhibiting IL-1 has a positive effect on severe fatigue in most studies that have been conducted.

The NASA Performance Assessment Workstation: cognitive performance during head-down bed rest.

PubMed

Shehab, R L; Schlegel, R E; Schiflett, S G; Eddy, D R

1998-01-01

The NASA Performance Assessment Workstation was used to assess cognitive performance changes in eight males subjected to seventeen days of 6 degrees head-down bed rest. PAWS uses six performance tasks to assess directed and divided attention, spatial, mathematical, and memory skills, and tracking ability. Subjective scales assess overall fatigue and mood state. Subjects completed training trials, practice trials, bed rest trials, and recovery trials. The last eight practice trials and all bed rest trials were performed with subjects lying face-down on a gurney. In general, there was no apparent cumulative effect of bed rest. Following a short period of performance stabilization, a slight but steady trend of performance improvement was observed across all trials. For most tasks, this trend of performance improvement was enhanced during recovery. No statistically significant differences in performance were observed when comparing bed rest with the control period. Additionally, fatigue scores showed little change across all periods.

The NASA performance assessment workstation: Cognitive performance during head-down bed rest

NASA Astrophysics Data System (ADS)

Shehab, Randa L.; Schlegel, Robert E.; Schiflett, Samuel G.; Eddy, Douglas R.

The NASA Performance Assessment Workstation was used to assess cognitive performance changes in eight males subjected to seventeen days of 6 ° head-down bed rest. PAWS uses six performance tasks to assess directed and divided attention, spatial, mathematical, and memory skills, and tracking ability. Subjective scales assess overall fatigue and mood state. Subjects completed training trials, practice trials, bed rest trials, and recovery trials. The last eight practice trials and all bed rest trials were performed with subjects lying face-down on a gurney. In general, there was no apparent cumulative effect of bed rest. Following a short period of performance stabilization, a slight but steady trend of performance improvement was observed across all trials. For most tasks, this trend of performance improvement was enhanced during recovery. No statistically significant differences in performance were observed when comparing bed rest with the control period. Additionally, fatigue scores showed little change across all periods.

Fatigue - but not mTBI history, PTSD, or sleep quality - directly contributes to reduced prospective memory performance in Iraq and Afghanistan era Veterans.

PubMed

Rau, Holly K; Hendrickson, Rebecca; Roggenkamp, Hannah C; Peterson, Sarah; Parmenter, Brett; Cook, David G; Peskind, Elaine; Pagulayan, Kathleen F

2017-10-13

Memory problems that affect daily functioning are a frequent complaint among Veterans reporting a history of repetitive mild traumatic brain injury (mTBI), especially in cohorts with comorbid PTSD. Here, we test the degree to which subjective sleep impairment and daytime fatigue account for the association of PTSD and self-reported mTBI history with prospective memory. 82 Veterans with and without personal history of repeated blast-related mTBI during deployment were administered the Clinician Administered PTSD Scale (CAPS), Memory for Intentions Test (MIST), Patient Health Questionnaire-9 (PHQ-9), Neurobehavioral Symptom Inventory (NSI), and the Pittsburgh Sleep Quality Index (PSQI). Relationships between self-reported mTBI, PTSD, self-reported poor sleep and daytime fatigue, and MIST performance were modeled using partial least squares structural equation modeling (PLS-SEM). Reported daytime fatigue was strongly associated with poorer prospective memory performance. Poor subjective sleep quality was strongly and positively associated with reported daytime fatigue, but had no significant direct effect on prospective memory performance. PTSD diagnosis and self-reported mTBI history were only associated with prospective memory via their impact on subjective sleep quality and daytime fatigue. Results suggest that daytime fatigue may be a mediating factor by which both mTBI and PTSD can interfere with prospective memory. Additional attention should be given to complaints of daytime fatigue, independent of subjective sleep quality, in the clinical care of those with a self-reported history of mTBI, and/or PTSD. Further research into whether interventions that decrease daytime fatigue lead to improvement in prospective memory and subjective cognitive functioning is warranted.

Microstructure and fatigue resistance of high strength dual phase steel welded with gas metal arc welding and plasma arc welding processes

NASA Astrophysics Data System (ADS)

Ahiale, Godwin Kwame; Oh, Yong-Jun; Choi, Won-Doo; Lee, Kwang-Bok; Jung, Jae-Gyu; Nam, Soo Woo

2013-09-01

This study presents the microstructure and high cycle fatigue performance of lap shear joints of dual phase steel (DP590) welded using gas metal arc welding (GMAW) and plasma arc welding (PAW) processes. High cycle fatigue tests were conducted on single and double lap joints under a load ratio of 0.1 and a frequency of 20 Hz. In order to establish a basis for comparison, both weldments were fabricated to have the same weld depth in the plate thickness. The PAW specimens exhibited a higher fatigue life, a gentle S-N slope, and a higher fatigue limit than the GMAW specimens. The improvement in the fatigue life of the PAW specimens was primarily attributed to the geometry effect that exhibited lower and wider beads resulting in a lower stress concentration at the weld toe where cracks initiate and propagate. Furthermore, the microstructural constituents in the heat-affected zone (HAZ) of the PAW specimens contributed to the improvement. The higher volume fraction of acicular ferrite in the HAZ beneath the weld toe enhanced the PAW specimen's resistance to fatigue crack growth. The double lap joints displayed a higher fatigue life than the single lap joints without changing the S-N slope.

The Influence of Robotic Assistance on Reducing Neuromuscular Effort and Fatigue during Extravehicular Activity Glove Use

NASA Technical Reports Server (NTRS)

Madden, Kaci E.; Deshpande, Ashish D.; Peters, Benjamin J.; Rogers, Jonathan M.; Laske, Evan A.; McBryan, Emily R.

2017-01-01

The three-layered, pressurized space suit glove worn by Extravehicular Activity (EVA) crew members during missions commonly causes hand and forearm fatigue. The Spacesuit RoboGlove (SSRG), a Phase VI EVA space suit glove modified with robotic grasp-assist capabilities, has been developed to augment grip strength in order to improve endurance and reduce the risk of injury in astronauts. The overall goals of this study were to i) quantify the neuromuscular modulations that occur in response to wearing a conventional Phase VI space suit glove (SSG) during a fatiguing task, and ii) determine the efficacy of Spacesuit RoboGlove (SSRG) in reversing the adverse neuromuscular modulations and restoring altered muscular activity to barehanded levels. Six subjects performed a fatigue sequence consisting of repetitive dynamic-gripping interspersed with isometric grip-holds under three conditions: barehanded, wearing pressurized SSG, and wearing pressurized SSRG. Surface electromyography (sEMG) from six forearm muscles (flexor digitorum superficialis (FDS), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), extensor digitorum (ED), extensor carpi radialis longus (ECRL), and extensor carpi ulnaris (ECU)) and subjective fatigue ratings were collected during each condition. Trends in amplitude and spectral distributions of the sEMG signals were used to derive metrics quantifying neuromuscular effort and fatigue that were compared across the glove conditions. Results showed that by augmenting finger flexion, the SSRG successfully reduced the neuromuscular effort needed to close the fingers of the space suit glove in more than half of subjects during two types of tasks. However, the SSRG required more neuromuscular effort to extend the fingers compared to a conventional SSG in many subjects. Psychologically, the SSRG aided subjects in feeling less fatigued during short periods of intense work compared to the SSG. The results of this study reveal the promise of the SSRG as a grasp-assist device that can improve astronaut performance and reduce the risk of injury by offsetting neuromuscular effort. Modifications to the experimental protocol are needed, however, to improve the outcome of the neuromuscular fatigue metrics and determine the effectiveness of SSRG in increasing astronaut endurance. Nevertheless, these findings will improve the understanding of astronaut-spacesuit interaction and provide direction toward designing improved spacesuit gloves and robotic-assist devices, like the SSRG.

Single-leg hop testing following fatiguing exercise: reliability and biomechanical analysis.

PubMed

Augustsson, J; Thomeé, R; Lindén, C; Folkesson, M; Tranberg, R; Karlsson, J

2006-04-01

A fatiguing exercise protocol was combined with single-leg hop testing to improve the possibilities of evaluating the effects of training or rehabilitation interventions. In the first test-retest experiment, 11 healthy male subjects performed two trials of single-leg hops under three different test conditions: non-fatigued and following fatiguing exercise, which consisted of unilateral weight machine knee extensions at 80% and 50%, respectively, of 1 repetition maximum (1 RM) strength. Intraclass correlation coefficients ranged from 0.75 to 0.98 for different hop test conditions, indicating that all tests were reliable. For the second experiment, eight healthy male subjects performed the fatiguing exercise protocol to investigate how fatigue influences lower-extremity joint kinematics and kinetics during single-leg hops. Hip, knee and ankle joint angles, moments and powers, as well as ground-reaction forces were recorded with a six-camera, motion-capture system and a force platform. Recovery of hop performance following the fatiguing exercise was also measured. During the take-off for the single-leg hops, hip and knee flexion angles, generated powers for the knee and ankle joints, and ground-reaction forces decreased for the fatigued hop conditions compared with the non-fatigued condition (P<0.05). Compared with landing during the non-fatigued condition, hip moments and ground-reaction forces were lower for the fatigued hop conditions (P<0.05). The negative joint power was two to three times greater for the knee than for the hip and five to 10 times greater for the knee than for the ankle during landing for all test conditions (P<0.05). Most measured variables had recovered three minutes post-exercise. It is concluded that the fatiguing exercise protocol combined with single-leg hop testing was a reliable method for investigating functional performance under fatigued test conditions. Further, subjects utilized an adapted hop strategy, which employed less hip and knee flexion and generated powers for the knee and ankle joints during take-off, and less hip joint moments during landing under fatigued conditions. The large negative power values observed at the knee joint during the landing phase of the single-leg hop, during which the quadriceps muscle activates eccentrically, indicate that not only hop distance but also the ability to perform successful landings should be investigated when assessing dynamic knee function.

Crew fatigue safety performance indicators for fatigue risk management systems.

PubMed

Gander, Philippa H; Mangie, Jim; Van Den Berg, Margo J; Smith, A Alexander T; Mulrine, Hannah M; Signal, T Leigh

2014-02-01

Implementation of Fatigue Risk Management Systems (FRMS) is gaining momentum; however, agreed safety performance indicators (SPIs) are lacking. This paper proposes an initial set of SPIs based on measures of crewmember sleep, performance, and subjective fatigue and sleepiness, together with methods for interpreting them. Data were included from 133 landing crewmembers on 2 long-range and 3 ultra-long-range trips (4-person crews, 3 airlines, 220 flights). Studies had airline, labor, and regulatory support, and underwent independent ethical review. SPIs evaluated preflight and at top of descent (TOD) were: total sleep in the prior 24 h and time awake at duty start and at TOD (actigraphy); subjective sleepiness (Karolinska Sleepiness Scale) and fatigue (Samn-Perelli scale); and psychomotor vigilance task (PVT) performance. Kruskal-Wallis nonparametric ANOVA with post hoc tests was used to identify significant differences between flights for each SPI. Visual and preliminary quantitative comparisons of SPIs between flights were made using box plots and bar graphs. Statistical analyses identified significant differences between flights across a range of SPls. In an FRMS, crew fatigue SPIs are envisaged as a decision aid alongside operational SPIs, which need to reflect the relevant causes of fatigue in different operations. We advocate comparing multiple SPIs between flights rather than defining safe/unsafe thresholds on individual SPIs. More comprehensive data sets are needed to identify the operational and biological factors contributing to the differences between flights reported here. Global sharing of an agreed core set of SPIs would greatly facilitate implementation and improvement of FRMS.

Characterization and Modeling of Asphalt Binder Fatigue

NASA Astrophysics Data System (ADS)

Safaei, Farinaz

Fatigue cracking is a primary distress in asphalt pavements caused by the accumulation of damage under repeated traffic loading. Many factors influence fatigue damage in pavements, including pavement structure, environmental conditions, and asphalt mixture volumetric properties. Asphalt binder is the weakest asphalt concrete constituent and, thus, plays a critical role in determining the fatigue resistance of pavements. Therefore, the ability to characterize and model the inherent fatigue performance of an asphalt binder is a necessary first step to design. A comprehensive understanding and prediction of asphalt binder fatigue performance require a suitable experiment coupled with a model to predict how the binder will perform under various traffic, temperature, and structural conditions encountered in the field. The simplified viscoelastic continuum damage (S-VECD) model has been used successfully by researchers to predict the damage evolution in asphalt mixtures for various traffic and climatic conditions using limited uniaxial test data. Although the literature shows promise for applying VECD modeling to asphalt binder fatigue, the past efforts have several shortcomings. It has been demonstrated that flow and adhesion loss can impede DSR fatigue test results. Thus, definition of test conditions (e.g., temperature) where cyclic DSR tests are appropriate for fatigue characterization of binders is necessary. In addition, the applicability of the model to predict fatigue performance under varying loading and thermal history has not been rigorously evaluated. Furthermore, the effects of material nonlinearity have been largely neglected in past modeling efforts for simplicity. In addition, past efforts have employed the parallel plate DSR geometry for the fatigue characterization of asphalt binders. In the parallel plate geometry, the strain depends on the radial distance from the specimen center. Therefore, the material will fail at different rates as a function of radial location. Past efforts have neglected the radial strain gradient, using the apparent shear stress at the sample edge to infer fatigue damage and derive S-VECD model parameters. Apparent edge stress is calculated using linear mapping to the total torque, which is erroneous in the presence of material or geometric nonlinearities (such as cracking). This study seeks to overcome the aforementioned shortcomings of past efforts to improve the ability to characterize and predict asphalt binder fatigue.

Evaluation of Pressurization Fatigue Life of 1441 Al-li Fuselage Panel

NASA Technical Reports Server (NTRS)

Bird, R. Keith; Dicus, Dennis I.; Fridlyander, Joseph; Davydov, Valentin

1999-01-01

A study was conducted to evaluate the pressurization fatigue life of fuselage panels with skins fabricated from 1441 Al-Li, an attractive new Russian alloy. The study indicated that 1441 Al-Li has several advantages over conventional aluminum fuselage skin alloy with respect to fatigue behavior. Smooth 1441 Al-Li sheet specimens exhibited a fatigue endurance limit similar to that for 1163 Al (Russian version of 2024 Al) sheet. Notched 1441 Al-Li sheet specimens exhibited greater fatigue strength and longer fatigue life than 1163 Al. In addition, Tu-204 fuselage panels fabricated by Tupolev Design Bureau using Al-Li skin and ring frames with riveted 7000-series aluminum stiffeners had longer pressurization fatigue lives than did panels constructed from conventional aluminum alloys. Taking into account the lower density of this alloy, the results suggest that 1441 Al-Li has the potential to improve fuselage performance while decreasing structural weight.

The effect of acupressure on fatigue among female nurses with chronic back pain.

PubMed

Movahedi, Maryam; Ghafari, Somayeh; Nazari, Fateme; Valiani, Mahboubeh

2017-08-01

To investigate the effect of acupressure on fatigue among female nurses with chronic back pain. Chronic back pain is one of the most common problems among nurses and has numerous physical and psychological effects. One of these effects is fatigue that impairs an individual's life. This randomized single-blind clinical trial was conducted on 50 nurses with chronic back pain working at the selected hospitals in Isfahan, Iran. After convenient sampling, the subjects were randomly allocated, through lottery, to the two groups of experimental (n=25) and sham (n=25). In the experimental group, acupressure techniques were performed during 9 sessions, 3 times a week for 14min for each patient. In the sham group, points within 1cm of the main points were only touched. Data were collected using the Fatigue Severity Scale (FSS), before, and immediately, 2weeks, and 4weeks after the intervention. Data analysis was performed using SPSS software. The mean score of fatigue severity before the intervention was not significantly different between the two groups (P=0.990). However, it was significantly lower in the experimental group than the sham group immediately (P<0.001), 2weeks (P=0.005), and 1month after the intervention (P<0.001). Acupressure on specific points of the foot and back improves back pain so, reduces fatigue. Therefore, acupressure can be used as a drug-free and low-cost approach without side effects to improve fatigue in nurses with chronic back pain. Copyright © 2017. Published by Elsevier Inc.

Serotonin and central nervous system fatigue: nutritional considerations.

PubMed

Davis, J M; Alderson, N L; Welsh, R S

2000-08-01

Fatigue from voluntary muscular effort is a complex phenomenon involving the central nervous system (CNS) and muscle. An understanding of the mechanisms within muscle that cause fatigue has led to the development of nutritional strategies to enhance performance. Until recently, little was known about CNS mechanisms of fatigue, even though the inability or unwillingness to generate and maintain central activation of muscle is the most likely explanation of fatigue for most people during normal daily activities. A possible role of nutrition in central fatigue is receiving more attention with the development of theories that provide a clue to its biological mechanisms. The focus is on the neurotransmitter serotonin [5-hydroxytryptamine (5-HT)] because of its role in depression, sensory perception, sleepiness, and mood. Nutritional strategies have been designed to alter the metabolism of brain 5-HT by affecting the availability of its amino acid precursor. Increases in brain 5-HT concentration and overall activity have been associated with increased physical and perhaps mental fatigue during endurance exercise. Carbohydrate (CHO) or branched-chain amino acid (BCAA) feedings may attenuate increases in 5-HT and improve performance. However, it is difficult to distinguish between the effects of CHO on the brain and those on the muscles themselves, and most studies involving BCAA show no performance benefits. It appears that important relations exist between brain 5-HT and central fatigue. Good theoretical rationale and data exist to support a beneficial role of CHO and BCAA on brain 5-HT and central fatigue, but the strength of evidence is presently weak.

Impact of Fatigue in Rheumatic Diseases in the Work Environment: A Qualitative Study.

PubMed

Connolly, Deirdre; Fitzpatrick, Clodagh; O'Toole, Lynn; Doran, Michele; O'Shea, Finbar

2015-10-28

Fatigue is a symptom of arthritis that causes difficulty at work. An improved understanding of this symptom could assist its management in the work environment. The aim of this study was to explore people with rheumatic diseases' experiences of fatigue in work. A qualitative descriptive design was used with semi-structured interviews and a constant comparative method of data analysis. There were 18 participants, the majority of them female with Rheumatoid Arthritis (RA) and working full-time. Three themes were identified: "Impact of fatigue on work performance" with cognition, mood and physical abilities being the main difficulties reported. In the second theme "Disclosure at Work" participants discussed disclosing their disease to employers but reported a lack of understanding of fatigue from colleagues. The final theme "work-based fatigue management strategies" included cognitive strategies and energy management techniques, which were mainly self-taught. In this study, fatigue was reported to impact on many areas of work performance with limited understanding from colleagues and employers. Interventions from health professionals to assist with development of work-related self-management skills are required to assist with symptom management in the work place. Such interventions should include education to employers and colleagues on the nature of fatigue in Rheumatic diseases.

Design solutions for the solar cell interconnect fatigue fracture problem

NASA Technical Reports Server (NTRS)

Mon, G. R.; Ross, R. G., Jr.

1982-01-01

Mechanical fatigue of solar cell interconnects is a major failure mechanism in photovoltaic arrays. A comprehensive approach to the reliability design of interconnects, together with extensive design data for the fatigue properties of copper interconnects, has been published. This paper extends the previous work, developing failure prediction (fatigue) data for additional interconnect material choices, including aluminum and a variety of copper-Invar and copper-steel claddings. An improved global fatigue function is used to model the probability-of-failure statistics of each material as a function of level and number of cycles of applied strain. Life-cycle economic analyses are used to evaluate the relative merits of each material choce. The copper-Invar clad composites demonstrate superior performance over pure copper. Aluminum results are disappointing.

Impact of a fatigue management in work programme on meeting work demands of individuals with rheumatic diseases: A pilot study.

PubMed

McCormack, Róisín C; O'Shea, Finbar; Doran, Michele; Connolly, Deirdre

2018-03-25

Work disability and job loss are serious consequences of rheumatic diseases (RDs), and fatigue is a symptom of RDs commonly reported to have an impact on work performance. A FAtigue ManagEment in Work (FAME-W) programme was developed to facilitate the self-management of fatigue in work. The present pilot study explored if FAME-W could facilitate individuals with RDs to manage fatigue in work and improve their ability to meet work demands. Twenty-seven individuals with a variety of rheumatic diagnoses completed a 4-week, 2-h occupational therapy-led self-management programme. Each week focused on fatigue-related topics, including fatigue and activity management, pain management and joint protection, mental well-being, effective communication with employers and work colleagues, and employment legislation. Individual workplace ergonomic assessments were also offered. Study measures (work function, fatigue, pain, mood and self-efficacy) were completed prior to starting FAME-W, immediately post-intervention and 12 weeks post-intervention. Participants (56% male) had a mean age of 43 years. No significant improvements were observed immediately post-programme. However, at the 12-week follow-up, significant improvements were reported in meeting work demands (scheduling [p = 0.046], output [p = 0.002], physical [p = 0.003], mental [p = 0.016]), fatigue [p = 0.001], pain [p = 0.01], anxiety [p = 0.001], depression [p < 0.001], self-efficacy [p < 0.001] and Arthritis Impact Measurement Scales 2-Short Form (physical: p = 0.005; symptoms: p = 0.010; affect: p = 0.010; social: p = 0.001). Significant improvements were reported in participants' ability to meet various demands of their work 3 months post-FAME-W. These findings suggest that FAME-W has the potential to assist individuals with RDs to meet the demands of their work, although further research is required to test the effectiveness of this intervention. Copyright © 2018 John Wiley & Sons, Ltd.

A Review of Non-Invasive Techniques to Detect and Predict Localised Muscle Fatigue

PubMed Central

Al-Mulla, Mohamed R.; Sepulveda, Francisco; Colley, Martin

2011-01-01

Muscle fatigue is an established area of research and various types of muscle fatigue have been investigated in order to fully understand the condition. This paper gives an overview of the various non-invasive techniques available for use in automated fatigue detection, such as mechanomyography, electromyography, near-infrared spectroscopy and ultrasound for both isometric and non-isometric contractions. Various signal analysis methods are compared by illustrating their applicability in real-time settings. This paper will be of interest to researchers who wish to select the most appropriate methodology for research on muscle fatigue detection or prediction, or for the development of devices that can be used in, e.g., sports scenarios to improve performance or prevent injury. To date, research on localised muscle fatigue focuses mainly on the clinical side. There is very little research carried out on the implementation of detecting/predicting fatigue using an autonomous system, although recent research on automating the process of localised muscle fatigue detection/prediction shows promising results. PMID:22163810

Fatigue Countermeasures: Alertness Management in Flight Operations

NASA Technical Reports Server (NTRS)

Co, E. L.; Rosekind, M. R.; Johnson, J. M.; Weldon, K. J.; Smith, R. M.; Gregory, K. G.; Miller, D. L.; Gander, P. H.; Lebacqz, J. V.; Statler, Irving C. (Technical Monitor)

1994-01-01

Since 1980, the NASA Ames Fatigue Countermeasures Program has studied the effects and impact of fatigue on flight operations . Sleep loss and circadian disruption are two of the primary physiological factors that underlie fatigue in flight operations. The Program has developed an array of fatigue countermeasure recommendations that can be used to combat the effects of fatigue and continues to research potential new countermeasures. For example, one such strategy involved a NASA/FAA study on the effects of planned cockpit rest to improve crewmember alertness and performance. Based partly on the study results, the FAA is currently reviewing a proposed Advisory Circular for controlled rest on the flight deck. Since there is no simple answer to the issue of fatigue in aviation, an Education and Training Module has been developed to provide the industry with pertinent information on sleep, circadian rhythms, how flight operations affect these physiological factors, and recommendations for fatigue countermeasures. The Module will be updated as the Program's continued research efforts uncover new information and develop new countermeasure strategies,

The effects of fatigue on performance in simulated nursing work.

PubMed

Barker, Linsey M; Nussbaum, Maury A

2011-09-01

Fatigue is associated with increased rates of medical errors and healthcare worker injuries, yet existing research in this sector has not considered multiple dimensions of fatigue simultaneously. This study evaluated hypothesised causal relationships between mental and physical fatigue and performance. High and low levels of mental and physical fatigue were induced in 16 participants during simulated nursing work tasks in a laboratory setting. Task-induced changes in fatigue dimensions were quantified using both subjective and objective measures, as were changes in performance on physical and mental tasks. Completing the simulated work tasks increased total fatigue, mental fatigue and physical fatigue in all experimental conditions. Higher physical fatigue adversely affected measures of physical and mental performance, whereas higher mental fatigue had a positive effect on one measure of mental performance. Overall, these results suggest causal effects between manipulated levels of mental and physical fatigue and task-induced changes in mental and physical performance. STATEMENT OF RELEVANCE: Nurse fatigue and performance has implications for patient and provider safety. Results from this study demonstrate the importance of a multidimensional view of fatigue in understanding the causal relationships between fatigue and performance. The findings can guide future work aimed at predicting fatigue-related performance decrements and designing interventions.

Effects of caffeine ingestion on endurance performance in mentally fatigued individuals.

PubMed

Azevedo, Rafael; Silva-Cavalcante, Marcos David; Gualano, Bruno; Lima-Silva, Adriano E; Bertuzzi, Romulo

2016-12-01

To examine the effects of caffeine ingestion on physiological and perceptual responses in mentally fatigued individuals. Eight male physically active subjects completed four cycling constant-workload tests in four experimental conditions at 80 % of maximal power output: control (C), mental fatigue (MF), mental fatigue plus caffeine ingestion (5 mg/kg) (MF-CAF), and mental fatigue plus placebo (MF-PLA). The mental fatigue was induced by a continuous performance task A-X version (AX-CPT). Before and after the AX-CPT, the profile of mood state (POMS) and blood samples for lactate measurement were collected. Oxygen consumption ([Formula: see text]), rating of perceived exertion (RPE), and electromyography (EMG) activity were measured during the cycling test. The time to exhaustion in C, MF, MF-PLA, and MF-CAF were 251 ± 30, 222 ± 23, 248 ± 28, and 285 ± 42 s, respectively. Delta values (corrected by C condition) were higher in MF-CAF than MF (P = 0.031). MF-CAF reported higher Vigor scores when compared with C (P = 0.046) and MF (P = 0.020). RPE at the first minute was significantly higher in MF-PLA than in C (P = 0.050); at the second minute, RPE was higher in MF-PLA than in C (P = 0.049) and MF-CAF (P = 0.048). EMG activity was not different between the conditions. Caffeine ingestion increased approximately 14 % endurance performance after the induction of mental fatigue. This effect was accompanied by a tendency to improvement in mood state (i.e., vigor). Therefore, caffeine ingestion can promote a beneficial effect on endurance performance in mentally fatigued individuals.

Influence of subsolvus thermomechanical processing on the low-cycle fatigue properties of haynes 230 alloy

NASA Astrophysics Data System (ADS)

Vecchio, Kenneth S.; Fitzpatrick, Michael D.; Klarstrom, Dwaine

1995-03-01

Strain-controlled low-cycle fatigue tests have been conducted in air at elevated temperature to determine the influence of subsolvus thermomechanical processing on the low-cycle fatigue (LCF) behavior of HAYNES 230 alloy. A series of tests at various strain ranges was conducted on material experimentally processed at 1121 °C, which is below the M23C6 carbide solvus temperature, and on material fully solution annealed at 1232 °C. A comparative strain-life analysis was performed on the LCF results, and the cyclic hardening/softening characteristics were examined. At 760 °C and 871 °C, the fatigue life of the experimental 230/1121 material was improved relative to the standard 230/1232 material up to a factor of 3. The fatigue life advantage of the experimental material was related primarily to a lower plastic (inelastic) strain amplitude response for a given imposed total strain range. It appears the increase in monotonic flow stress exhibited by the finer grain size experimental material has been translated into an increase in cyclic flow stress at the 760 °C and 871 °C test temperatures. Both materials exhibited entirely transgranular fatigue crack initiation and propagation modes at these temperatures. The LCF performance of the experimental material in tests performed at 982 °C was improved relative to the standard material up to a factor as high as 2. The life advantage of the 230/1121 material occurred despite having a larger plastic strain amplitude than the standard 230/1232 material for a given total strain range. Though not fully understood at present, it is suspected that this behavior is related to the deleterious influence of grain boundaries in the fatigue crack initiations of the standard processed material relative to the experimental material, and ultimately to differences in carbide morphology as a result of thermomechanical processing.

Crew Factors in Flight Operations XIV: Alertness Management in Regional Flight Operations Education Module

NASA Technical Reports Server (NTRS)

Rosekind, Mark R.; Co, Elizabeth L.; Neri, David F.; Oyung, Raymond L.; Mallis, Melissa M.

2002-01-01

Regional operations encompass a broad range of pilots and equipment. This module is intended to help all those involved in regional aviation, including pilots, schedulers, dispatchers, maintenance technicians, policy makers, and others, to understand the physiological factors underlying fatigue, how flight operations affect fatigue, and what can be done to counteract fatigue and maximize alertness and performance in their operations. The overall purpose of this module is to promote aviation safety, performance, and productivity. It is intended to meet three specific objectives: (1) to explain the current state of knowledge about the physiological mechanisms underlying fatigue; (2) to demonstrate how this knowledge can be applied to improving flight crew sleep, performance, and alertness; and (3) to offer strategies for alertness management. Aviation Safety Reporting System (ASRS) and National Transportation Safety Board (NISH) reports are used throughout this module to demonstrate that fatigue is a safety issue in the regional operations community. The appendices at the end of this module include the ASRS reports used for the examples contained in this publication, brief introductions to sleep disorders and relaxation techniques, summaries of relevant NASA publications, and a list of general readings on sleep, sleep disorders, and circadian rhythms.

Crew Factors in Flight Operations XV: Alertness Management in General Aviation Education Module

NASA Technical Reports Server (NTRS)

Rosekind, Mark R.; Co, Elizabeth L.; Neri, David F.; Oyung, Raymond L.; Mallis, Melissa M.; Cannon, Mary M. (Technical Monitor)

2002-01-01

Regional operations encompass a broad range of pilots and equipment. This module is intended to help all those involved in regional aviation, including pilots, schedulers, dispatchers, maintenance technicians, policy makers, and others, to understand the physiological factors underlying fatigue, how flight operations affect fatigue, and what can be done to counteract fatigue and maximize alertness and performance in their operations. The overall purpose of this module is to promote aviation safety, performance, and productivity. It is intended to meet three specific objectives: (1) to explain the current state of knowledge about the physiological mechanisms underlying fatigue; (2) to demonstrate how this knowledge can be applied to improving flight crew sleep, performance, and alertness; and (3) to offer strategies for alertness management. Aviation Safety Reporting System (ASRS) and National Transportation Safety Board (NISH) reports are used throughout this module to demonstrate that fatigue is a safety issue in the regional operations community. The appendices at the end of this module include the ASRS reports used for the examples contained in this publication, brief introductions to sleep disorders and relaxation techniques, summaries of relevant NASA publications, and a list of general readings on sleep, sleep disorders, and circadian rhythms.

Effects of inspiratory muscle training on resistance to fatigue of respiratory muscles during exhaustive exercise.

PubMed

Segizbaeva, M O; Timofeev, N N; Donina, Zh A; Kur'yanovich, E N; Aleksandrova, N P

2015-01-01

The aim of this study was to assess the effect of inspiratory muscle training (IMT) on resistance to fatigue of the diaphragm (D), parasternal (PS), sternocleidomastoid (SCM) and scalene (SC) muscles in healthy humans during exhaustive exercise. Daily inspiratory muscle strength training was performed for 3 weeks in 10 male subjects (at a pressure threshold load of 60% of maximal inspiratory pressure (MIP) for the first week, 70% of MIP for the second week, and 80% of MIP for the third week). Before and after training, subjects performed an incremental cycle test to exhaustion. Maximal inspiratory pressure and EMG-analysis served as indices of inspiratory muscle fatigue assessment. The before-to-after exercise decreases in MIP and centroid frequency (fc) of the EMG (D, PS, SCM, and SC) power spectrum (P<0.05) were observed in all subjects before the IMT intervention. Such changes were absent after the IMT. The study found that in healthy subjects, IMT results in significant increase in MIP (+18%), a delay of inspiratory muscle fatigue during exhaustive exercise, and a significant improvement in maximal work performance. We conclude that the IMT elicits resistance to the development of inspiratory muscles fatigue during high-intensity exercise.

Improved fatigue performance for wood-based structural panels using slot and tab construction

Treesearch

Jinghao Li; John F. Hunt; Shaoqin Gong; Zhiyong Cai

2016-01-01

This paper presents static and fatigue bending behavior for a wood-based structural panel having a slot and tab (S/T) construction technique. Comparisons were made with similarly fabricated panels without the S/T construction technique. Experimental results showed that both types of panels had similar bending properties in the static tests. However, the panels with S/T...

The effects of fatigue on decision making and shooting skill performance in water polo players.

PubMed

Royal, Kylie A; Farrow, Damian; Mujika, Iñigo; Halson, Shona L; Pyne, David; Abernethy, Bruce

2006-08-01

The aim of this study was to assess the effects of fatigue on decision making and goal shooting skill in water polo. Fourteen junior elite male players (age 17.2 +/- 0.5 years; mass 84.2 +/- 7.6 kg; height 1.85 +/- 0.05 m) completed four sets of eight repetitions of an approximately 18 s maximal water polo specific drill. Progressively declining rest ratios for each successive set of the drill were employed to induce increasing fatigue and reflect the demands of match-play. A video-based temporally occluded decision-making task (verbalized response to various tactical situations) or goal shooting skill test (qualitative and quantitative analysis of goal shooting) was performed after each set. Heart rate, rating of perceived exertion (RPE) and blood lactate concentration were recorded. Heart rate (159 +/- 12, 168 +/- 13, 176 +/- 12, 181 +/- 12 Deats min-1; P < 0.001) and RPE (13.1 +/- 2.2, 15.5 +/- 1.7, 17.3 +/- 1.6, 19.1 +/- 1.1; P < 0.001) increased with declining rest ratios. At very high fatigue, decision-making accuracy was 18.0 +/- 21.8% better than at low fatigue (P = 0.008). Shooting accuracy and velocity were unaffected by incremental fatigue; however, skill proficiency (technique) decreased by 43 +/- 24% between the pre-test and high-fatigue conditions (P < 0.001). In conclusion, incremental increases in fatigue differentially influenced decision making (improved) relative to the technical performance (declined), accuracy and speed of the ball (unchanged) of a water polo goal shot.

Evoked EMG-based torque prediction under muscle fatigue in implanted neural stimulation

NASA Astrophysics Data System (ADS)

Hayashibe, Mitsuhiro; Zhang, Qin; Guiraud, David; Fattal, Charles

2011-10-01

In patients with complete spinal cord injury, fatigue occurs rapidly and there is no proprioceptive feedback regarding the current muscle condition. Therefore, it is essential to monitor the muscle state and assess the expected muscle response to improve the current FES system toward adaptive force/torque control in the presence of muscle fatigue. Our team implanted neural and epimysial electrodes in a complete paraplegic patient in 1999. We carried out a case study, in the specific case of implanted stimulation, in order to verify the corresponding torque prediction based on stimulus evoked EMG (eEMG) when muscle fatigue is occurring during electrical stimulation. Indeed, in implanted stimulation, the relationship between stimulation parameters and output torques is more stable than external stimulation in which the electrode location strongly affects the quality of the recruitment. Thus, the assumption that changes in the stimulation-torque relationship would be mainly due to muscle fatigue can be made reasonably. The eEMG was proved to be correlated to the generated torque during the continuous stimulation while the frequency of eEMG also decreased during fatigue. The median frequency showed a similar variation trend to the mean absolute value of eEMG. Torque prediction during fatigue-inducing tests was performed based on eEMG in model cross-validation where the model was identified using recruitment test data. The torque prediction, apart from the potentiation period, showed acceptable tracking performances that would enable us to perform adaptive closed-loop control through implanted neural stimulation in the future.

Effectiveness of Shot Peening in Suppressing Fatigue Cracking at Non-Metallic Inclusions in Udimet(trademark) 720

NASA Technical Reports Server (NTRS)

Barrie, Robert L.; Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; Prescenzi, Anthony; Biles, Tiffany; Bonacuse, Peter J.

2005-01-01

The fatigue lives of modern powder metallurgy disk alloys can be reduced by over an order of magnitude by surface cracking at inherent non-metallic inclusions. The objective of this work was to study the effectiveness of shot peening in suppressing LCF crack initiation and growth at surface nonmetallic inclusions. Inclusions were carefully introduced at elevated levels during powder metallurgy processing of the nickel-base disk superalloy Udimet 720. Multiple strain-controlled fatigue tests were then performed on machined specimens at 427 and 650 C in peened and unpeened conditions. Analyses were performed to compare the low cycle fatigue lives and failure initiation sites as a function of inclusion content, shot peening, and fatigue conditions. A large majority of the failures in as-machined specimens with introduced inclusions occurred at cracks initiating from inclusions intersecting the specimen surface. The inclusions could reduce fatigue life by up to 100X. Large inclusions had the greatest effect on life in tests at low strain ranges and high strain ratios. Shot peening can be used to improve life in these conditions by reducing the most severe effects of inclusions.

An intriguing design concept to enhance the pulsatile fatigue life of self-expanding stents.

PubMed

Hsiao, Hao-Ming; Yin, Ming-Ting

2014-02-01

Intravascular stenting has emerged as the primary treatment for vascular diseases and has received great attention from the medical community since its introduction two decades ago. The endovascular self-expanding stent is used to treat peripheral artery diseases; however, once implanted, these stents suffer from various cyclic motions caused by pulsatile blood pressure and daily activities. Due to this challenging environment, fatigue performance has become a critical issue for stent design. In this paper, a simple yet intriguing concept of stent design aimed at enhancing pulsatile fatigue life is investigated. The concept of this design is to shift the highly concentrated stresses/strains away from the crown and re-distribute them along the stress-free bar arm by tapering its strut width. Finite element models were developed to evaluate the mechanical integrity and pulsatile fatigue resistance of the stent to various loading conditions. Results show that the fatigue safety factor jumped to 2.5-3.0 times that of the standard stent with constant strut width. This is astonishing considering that the stent profile and scaffolding were not compromised. The findings of this paper provide an excellent approach to the optimization of future stent design to greatly improve stent fatigue performance.

Fatigue Analysis Before and After Shaker Exercise: Physiologic Tool for Exercise Design

PubMed Central

White, Kevin T.; Easterling, Caryn; Roberts, Niles; Shaker, Reza

2016-01-01

Recent studies suggest that the Shaker exercise induces fatigue in the upper esophageal sphincter (UES) opening muscles and sternocleidomastoid (SCM), with the SCMs fatiguing earliest. The aim of this study was to measure fatigue induced by the isometric portion of the Shaker exercise by measuring the rate of change in the median frequency (MF rate) of the power spectral density (PSD) function, which is interpreted as proportional to the rate of fatigue, from surface electromyography (EMG) of suprahyoid (SHM), infrahyoid (IHM), and SCM. EMG data compared fatigue-related changes from 20-, 40-, and 60-s isometric hold durations of the Shaker exercise. We found that fatigue-related changes were manifested during the 20-s hold. The findings confirm that the SCM fatigues initially and as fast as or faster than the SHM and IHM. In addition, upon completion of the exercise protocol, the SCM had a decreased MF rate, implying improved fatigue resistance, while the SHM and IHM showed increased MF rates, implying that these muscles increased their fatiguing effort. We conclude that the Shaker exercise initially leads to increased fatigue resistance of the SCM, after which the exercise loads the less fatigue-resistant SHM and IHM, potentiating the therapeutic effect of the Shaker exercise regimen with continued exercise performance. PMID:18369673

A Fatigue Life Prediction Model of Welded Joints under Combined Cyclic Loading

NASA Astrophysics Data System (ADS)

Goes, Keurrie C.; Camarao, Arnaldo F.; Pereira, Marcos Venicius S.; Ferreira Batalha, Gilmar

2011-01-01

A practical and robust methodology is developed to evaluate the fatigue life in seam welded joints when subjected to combined cyclic loading. The fatigue analysis was conducted in virtual environment. The FE stress results from each loading were imported to fatigue code FE-Fatigue and combined to perform the fatigue life prediction using the S x N (stress x life) method. The measurement or modelling of the residual stresses resulting from the welded process is not part of this work. However, the thermal and metallurgical effects, such as distortions and residual stresses, were considered indirectly through fatigue curves corrections in the samples investigated. A tube-plate specimen was submitted to combined cyclic loading (bending and torsion) with constant amplitude. The virtual durability analysis result was calibrated based on these laboratory tests and design codes such as BS7608 and Eurocode 3. The feasibility and application of the proposed numerical-experimental methodology and contributions for the technical development are discussed. Major challenges associated with this modelling and improvement proposals are finally presented.

Factors associated with work-related fatigue and recovery in hospital nurses working 12-hour shifts.

PubMed

Han, Kihye; Trinkoff, Alison M; Geiger-Brown, Jeanne

2014-10-01

Nurse fatigue threatens both nurse and patient safety; fatigue affects nurses' neurocognitive functioning and hinders their work performance. The authors assessed the association of work and non-work factors with acute and chronic fatigue and intershift recovery among hospital nurses working 12-hour shifts. This study used survey data from 80 nurses who provided full-time direct patient care on medical-surgical and critical care units in a large teaching hospital. Psychological job demands (e.g., work load and social support from supervisor or coworker) were significantly associated with acute and chronic fatigue and intershift recovery. Rotating shifts were significantly related to acute fatigue. Findings suggest the need for a comprehensive approach to fatigue management, including organizational support to provide healthful work schedules and favorable nursing work environments, fewer psychological and physical demands, and assistance to improve nurses' sleep quality and quantity. [Workplace Health Saf 2014;62(10):409-414.]. Copyright 2014, SLACK Incorporated.

Shot-Peening Effect on High Cycling Fatigue of Al-Cu Alloy

NASA Astrophysics Data System (ADS)

Fouad, Yasser; Metwally, Mostafa El

2013-12-01

The present work was aimed at evaluating the effects of shot-peening on the high cycle fatigue performance of the age-hardening aircraft alloy Al 2024 at different almen intensities. Shot-peening to full coverage (100 pct) was performed using spherically conditioned cut wire (SCCW 14) with an average shot size of 0.36 mm and at almen intensities of 0.1, 0.2, and 0.3 mmA. After applying the various mechanical surface treatments, the changes in the surface and near-surface layer properties such as microhardness, residual stress-depth profiles, and surface roughness were determined. The microhardness, surface roughness, and the residual stresses increased proportionally with the almen intensity. Electropolitically polished conditions were used as reference in the mechanically surface treated specimens. A significant improvement was seen in the fatigue performance of the 0.1 mmA.

NASA - easyJet Collaboration on the Human Factors Monitoring Program (HFMP) Study

NASA Technical Reports Server (NTRS)

Srivistava, Ashok N.; Barton, Phil

2012-01-01

This is the first annual report jointly prepared by NASA and easyJet on the work performed under the agreement to collaborate on a study of the many factors entailed in flight - and cabin-crew fatigue and documenting the decreases in performance associated with fatigue. The objective of this Agreement is to generate reliable, automated procedures that improve understanding of the levels and characteristics of flight - and cabin-crew fatigue factors, both latent and proximate, whose confluence will likely result in unacceptable flight crew performance. This study entails the analyses of numerical and textual data collected during operational flights. NASA and easyJet are both interested in assessing and testing NASA s automated capabilities for extracting operationally significant information from very large, diverse (textual and numerical) databases, much larger than can be handled practically by human experts.

Single doses of Panax ginseng (G115) reduce blood glucose levels and improve cognitive performance during sustained mental activity.

PubMed

Reay, Jonathon L; Kennedy, David O; Scholey, Andrew B

2005-07-01

Single doses of the traditional herbal treatment Panax ginseng have recently been shown to elicit cognitive improvements in healthy young volunteers. The mechanisms by which ginseng improves cognitive performance are not known. However, they may be related to the glycaemic properties of some Panax species. Using a double-blind, placebo-controlled, balanced crossover design, 30 healthy young adults completed a 10 min test battery at baseline, and then six times in immediate succession commencing 60 min after the day's treatment (placebo, 200mg G115 or 400mg G115). The 10 min battery comprised a Serial Threes subtraction task (2 min); a Serial Sevens task (2 min); a Rapid Visual Information Processing task (5 min); then a 'mental fatigue' visual analogue scale. Blood glucose was measured prior to each day's treatment, and before, during and after the post-dose completions of the battery. Both the 200mg and 400mg treatments led to significant reductions in blood glucose levels at all three post-treatment measurements (p 0.005 in all cases). The most notable behavioural effects were associated with 200mg of ginseng and included significantly improved Serial Sevens subtraction task performance and significantly reduced subjective mental fatigue throughout all (with the exception of one time point in each case) of the post-dose completions of the 10 min battery (p 0.05). Overall these data suggest that Panax ginseng can improve performance and subjective feelings of mental fatigue during sustained mental activity. This effect may be related to the acute gluco-regulatory properties of the extract.

Shoulder girdle muscle activity and fatigue in traditional and improved design carpet weaving workstations.

PubMed

Allahyari, Teimour; Mortazavi, Narges; Khalkhali, Hamid Reza; Sanjari, Mohammad Ali

2016-01-01

Work-related musculoskeletal disorders in the neck and shoulder regions are common among carpet weavers. Working for prolonged hours in a static and awkward posture could result in an increased muscle activity and may lead to musculoskeletal disorders. Ergonomic workstation improvements can reduce muscle fatigue and the risk of musculoskeletal disorders. The aim of this study is to assess and to compare upper trapezius and middle deltoid muscle activity in 2 traditional and improved design carpet weaving workstations. These 2 workstations were simulated in a laboratory and 12 women carpet weavers worked for 3 h. Electromyography (EMG) signals were recorded during work in bilateral upper trapezius and bilateral middle deltoid. The root mean square (RMS) and median frequency (MF) values were calculated and used to assess muscle load and fatigue. Repeated measure ANOVA was performed to assess the effect of independent variables on muscular activity and fatigue. The participants were asked to report shoulder region fatigue on the Borg's Category-Ratio scale (Borg CR-10). Root mean square values in workstation A are significantly higher than in workstation B. Furthermore, EMG amplitude was higher in bilateral trapezius than in bilateral deltoid. However, muscle fatigue was not observed in any of the workstations. The results of the study revealed that muscle load in a traditional workstation was high, but fatigue was not observed. Further studies investigating other muscles involved in carpet weaving tasks are recommended. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

Closed-Loop Control for Sonic Fatigue Testing Systems

NASA Technical Reports Server (NTRS)

Rizzi, Stephen A.; Bossaert, Guido

2001-01-01

This article documents recent improvements to the acoustic control system of the Thermal Acoustic Fatigue Apparatus (TAFA), a progressive wave tube test facility at the NASA Langley Research Center, Hampton, VA. A brief summary of past acoustic performance is first given to serve as a basis of comparison with the new performance data using a multiple-input, closed-loop, narrow-band controller. Performance data in the form of test section acoustic power spectral densities and coherence are presented for a variety of input spectra including uniform, band-limited random and an expendable launch vehicle payload bay environment.

Resistance exercise improves physical fatigue in women with fibromyalgia: a randomized controlled trial.

PubMed

Ericsson, Anna; Palstam, Annie; Larsson, Anette; Löfgren, Monika; Bileviciute-Ljungar, Indre; Bjersing, Jan; Gerdle, Björn; Kosek, Eva; Mannerkorpi, Kaisa

2016-07-30

Fibromyalgia (FM) affects approximately 1-3 % of the general population. Fatigue limits the work ability and social life of patients with FM. A few studies of physical exercise have included measures of fatigue in FM, indicating that exercise can decrease fatigue levels. There is limited knowledge about the effects of resistance exercise on multiple dimensions of fatigue in FM. The present study is a sub-study of a multicenter randomized controlled trial in women with FM. The purpose of the present sub-study was to examine the effects of a person-centered progressive resistance exercise program on multiple dimensions of fatigue in women with FM, and to investigate predictors of the potential change in fatigue. A total of 130 women with FM (age 22-64 years) were included in this assessor-blinded randomized controlled multicenter trial examining the effects of person-centered progressive resistance exercise compared with an active control group. The intervention was performed twice a week for 15 weeks. Outcomes were five dimensions of fatigue measured with the Multidimensional Fatigue Inventory (MFI-20). Information about background was collected and the women also completed several health-related questionnaires. Multiple linear stepwise regression was used to analyze predictors of change in fatigue in the total population. A higher improvement was found at the post-treatment examination for change in the resistance exercise group, as compared to change in the active control group in the MFI-20 subscale of physical fatigue (resistance group Δ -1.7, SD 4.3, controls Δ 0.0, SD 2.7, p = 0.013), with an effect size of 0.33. Sleep efficiency was the strongest predictor of change in the MFI-20 subscale general fatigue (beta = -0.54, p = 0.031, R (2) = 0.05). Participating in resistance exercise (beta = 1.90, p = 0.010) and working fewer hours per week (beta = 0.84, p = 0.005) were independent significant predictors of change in physical fatigue (R (2) = 0.14). Person-centered progressive resistance exercise improved physical fatigue in women with FM when compared to an active control group. ClinicalTrials.gov NCT01226784 . Registered 21 October 2010.

Full-scale transmission testing to evaluate advanced lubricants

NASA Technical Reports Server (NTRS)

Lewicki, David G.; Decker, Harry J.; Shimski, John T.

1992-01-01

Experimental tests were performed on the OH-58A helicopter main rotor transmission in the NASA Lewis 500 hp helicopter transmission test stand. The testing was part of a lubrication program. The objectives are to develop and show a separate lubricant for gearboxes with improved performance in life and load carrying capacity. The goal was to develop a testing procedure to fail certain transmission components using a MIL-L-23699 based reference oil and then to run identical tests with improved lubricants and show improved performance. The tests were directed at parts that failed due to marginal lubrication from Navy field experience. These failures included mast shaft bearing micropitting, sun gear and planet bearing fatigue, and spiral bevel gear scoring. A variety of tests were performed and over 900 hrs of total run time accumulated for these tests. Some success was achieved in developing a testing procedure to produce sun gear and planet bearing fatigue failures. Only marginal success was achieved in producing mast shaft bearing micropitting and spiral bevel gear scoring.

Fracture properties and fatigue cracking resistance of asphalt binders.

DOT National Transportation Integrated Search

2012-03-01

Several different types of modifiers are increasingly bring used to improve the performance of asphalt binders or to : achieve desired mixture production characteristics (e.g., Warm Mix Asphalt). However, current Superpave : performance specification...

Modafinil treatment for fatigue in HIV+ patients: a pilot study.

PubMed

Rabkin, Judith G; McElhiney, Martin C; Rabkin, Richard; Ferrando, Stephen J

2004-12-01

Fatigue is widespread among human immunodeficiency virus-positive (HIV+) patients, yet few studies have assessed effective treatments. The authors conducted a pilot study to evaluate the efficacy of modafinil for fatigue in this clinical population. Response was evaluated after a 4-week open-label trial. Data were collected from February 2003 through January 2004. Responders were offered 8 additional weeks of modafinil. Inclusion criteria included written approval from the primary care physician, clinically significant fatigue, current use of anti-retroviral medications, and the absence of treatable medical conditions known to cause fatigue. Exclusion criteria included untreated major depression and current substance abuse. Major outcome measures were the Fatigue Severity Scale, Chalder Fatigue Scale, Hamilton Rating Scale for Depression, Beck Depression Inventory, and neuropsychological tests assessing verbal memory, speed of processing, and executive function. Immunologic and virologic measures were performed at baseline and week 4 to assess safety of treatment. All 30 patients who enrolled completed 4 weeks of treatment; 24 (80%) were rated as responders. Responders showed statistically significant improvement on all measures of fatigue, depressive symptoms, and executive function, while nonresponders did not. Mean values of CD4 cell count and HIV RNA viral load did not change. The most common side effect was headache, followed by irritability and feeling "hyper." This pilot study shows encouraging results for modafinil in alleviation of fatigue in HIV+ patients. In addition, depressive symptoms were substantially reduced. Improvements on measures of verbal memory and executive function were significant, but in the absence of a placebo control, the magnitude of effect due to practice cannot be determined.

Four Weeks of IV Iron Supplementation Reduces Perceived Fatigue and Mood Disturbance in Distance Runners

PubMed Central

Woods, Amy; Garvican-Lewis, Laura A.; Saunders, Philo U.; Lovell, Greg; Hughes, David; Fazakerley, Ruth; Anderson, Bev; Gore, Christopher J.; Thompson, Kevin G.

2014-01-01

Purpose To determine the effect of intravenous iron supplementation on performance, fatigue and overall mood in runners without clinical iron deficiency. Methods Fourteen distance runners with serum ferritin 30–100 µg·L−1 were randomly assigned to receive three blinded injections of intravenous ferric-carboxymaltose (2 ml, 100 mg, IRON) or normal saline (PLACEBO) over four weeks (weeks 0, 2, 4). Athletes performed a 3,000 m time trial and 10×400 m monitored training session on consecutive days at week 0 and again following each injection. Hemoglobin mass (Hbmass) was assessed via carbon monoxide rebreathing at weeks 0 and 6. Fatigue and mood were determined bi-weekly until week 6 via Total Fatigue Score (TFS) and Total Mood Disturbance (TMD) using the Brief Fatigue Inventory and Brunel Mood Scale. Data were analyzed using magnitude-based inferences, based on the unequal variances t-statistic and Cohen's Effect sizes (ES). Results Serum ferritin increased in IRON only (Week 0: 62.8±21.9, Week 4: 128.1±46.6 µg·L−1; p = 0.002) and remained elevated two weeks after the final injection (127.0±66.3 µg·L−1, p = 0.01), without significant changes in Hbmass. Supplementation had a moderate effect on TMD of IRON (ES -0.77) with scores at week 6 lower than PLACEBO (ES -1.58, p = 0.02). Similarly, at week 6, TFS was significantly improved in IRON vs. PLACEBO (ES –1.54, p = 0.05). There were no significant improvements in 3,000 m time in either group (Week 0 vs. Week 4; Iron: 625.6±55.5 s vs. 625.4±52.7 s; PLACEBO: 624.8±47.2 s vs. 639.1±59.7 s); but IRON reduced their average time for the 10×400 m training session at week 2 (Week 0: 78.0±6.6 s, Week 2: 77.2±6.3; ES–0.20, p = 0.004). Conclusion During 6 weeks of training, intravenous iron supplementation improved perceived fatigue and mood of trained athletes with no clinical iron deficiency, without concurrent improvements in oxygen transport capacity or performance. PMID:25247929

Elbow joint fatigue and bench-press training.

PubMed

Huang, Yen-Po; Chou, You-Li; Chen, Feng-Chun; Wang, Rong-Tyai; Huang, Ming-Jer; Chou, Paul Pei-Hsi

2014-01-01

Bench-press exercises are among the most common form of training exercise for the upper extremity because they yield a notable improvement in both muscle strength and muscle endurance. The literature contains various investigations into the effects of different bench-press positions on the degree of muscle activation. However, the effects of fatigue on the muscular performance and kinetics of the elbow joint are not understood fully. To investigate the effects of fatigue on the kinetics and myodynamic performance of the elbow joint in bench-press training. Controlled laboratory study. Motion research laboratory. A total of 18 physically healthy male students (age = 19.6 ± 0.8 years, height = 168.7 ± 5.5 cm, mass = 69.6 ± 8.6 kg) participated in the investigation. All participants were right-hand dominant, and none had a history of upper extremity injuries or disorders. Participants performed bench-press training until fatigued. Maximal possible number of repetitions, cycle time, myodynamic decline rate, elbow-joint force, and elbow-joint moment. We observed a difference in cycle time in the initial (2.1 ± 0.42 seconds) and fatigue (2.58 ± 0.46 seconds) stages of the bench-press exercise (P = .04). As the participants fatigued, we observed an increase in the medial-lateral force (P = .03) and internal-external moment (P ≤ .04) acting on the elbow joint. Moreover, a reduction in the elbow muscle strength was observed in the elbow extension-flexion (P ≤ .003) and forearm supination-pronation (P ≤ .001) conditions. The results suggest that performing bench-press exercises to the point of fatigue increases elbow-joint loading and may further increase the risk of injury. Therefore, when clinicians design bench-press exercise regimens for general athletic training, muscle strengthening, or physical rehabilitation, they should control carefully the maximal number of repetitions.

The role of insomnia in the treatment of chronic fatigue.

PubMed

Kallestad, Håvard; Jacobsen, Henrik B; Landrø, Nils Inge; Borchgrevink, Petter C; Stiles, Tore C

2015-05-01

The definition of Chronic Fatigue Syndrome (CFS) overlaps with definitions of insomnia, but there is limited knowledge about the role of insomnia in the treatment of chronic fatigue. To test if improvement of insomnia during treatment of chronic fatigue was associated with improved outcomes on 1) fatigue and 2) cortisol recovery span during a standardized stress exposure. Patients (n = 122) with chronic fatigue received a 3.5-week inpatient return-to-work rehabilitation program based on Acceptance and Commitment Therapy, and had been on paid sick leave>8 weeks due their condition. A physician and a psychologist examined the patients, assessed medication use, and SCID-I diagnoses. Patients completed self-report questionnaires measuring fatigue, pain, depression, anxiety, and insomnia before and after treatment. A subgroup (n = 25) also completed the Trier Social Stress Test for Groups (TSST-G) before and after treatment. Seven cortisol samples were collected during each test and cortisol spans for the TSST-G were calculated. A hierarchical regression analysis in nine steps showed that insomnia improvement predicted improvement in fatigue, independently of age, gender, improvement in pain intensity, depression and anxiety. A second hierarchical regression analysis showed that improvement in insomnia significantly predicted the cortisol recovery span after the TSST-G independently of improvement in fatigue. Improvement in insomnia severity had a significant impact on both improvement in fatigue and the ability to recover from a stressful situation. Insomnia severity may be a maintaining factor in chronic fatigue and specifically targeting this in treatment could increase treatment response. Copyright © 2014. Published by Elsevier Inc.

Patients receiving anti-TNF therapies experience clinically important improvements in RA-related fatigue: results from the British Society for Rheumatology Biologics Register for Rheumatoid Arthritis.

PubMed

Druce, Katie L; Jones, Gareth T; Macfarlane, Gary J; Basu, Neil

2015-06-01

Pro-inflammatory cytokines such as TNF-α are important in the pathogenesis of fatigue in conditions such as RA. This study aimed to determine whether fatigue improved in a cohort of RA patients with clinically relevant fatigue commencing anti-TNF-α therapy and, if so, to identify predictors of improvement. Participants recruited to a long-term observational cohort study (the British Society for Rheumatology Biologics Register for RA) provided information on fatigue using the 36-item Short Form Health Survey (SF-36) vitality subscale. The prevalence of severe baseline fatigue (SF-36 vitality ≤12.5) was calculated and improvements, considered as (i) absolute values and (ii) improvement from severe to non-severe fatigue (SF-36 vitality >12.5), were examined 6 months subsequently. A comprehensive set of putative predictors of fatigue improvement were evaluated using multivariable logistic regression. In 6835 participants the prevalence of severe baseline fatigue was 38.8%. Of those with severe fatigue, 70% reported clinically relevant improvement and 66% moved to the non-severe fatigue category (i.e. improvers). The mean change for improvers was three times the minimum clinically important difference for improvement (33.0 U). Independent baseline predictors of improvement were female sex [odds ratio (OR) 1.3 (95% CI 1.1, 1.7)], not being unemployed due to ill health [OR 1.5 (95% CI 1.2, 1.7)], low disability [OR 1.2 (95% CI 1.001, 1.5)], seropositivity [OR 1.2 (95% CI 0.98, 1.4)], not using steroids [OR 1.2 (95% CI 1.03, 1.5)], no history of hypertension [OR 1.4 (95% CI 1.1, 1.6)] or depression [OR 1.3 (95% CI 1.1, 1.5)] and good mental health [SF-36 mental health subscale >35; OR 1.4 (95% CI 1.2, 1.7)]. Fatigued RA patients reported substantial improvement in their fatigue after commencing anti-TNF-α therapy. Further, a number of clinical and psychosocial baseline factors identified those most likely to improve, supporting future stratified approaches to RA fatigue management. © The Author 2014. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Effects of environment and frequency on the fatigue behavior of the spallation neutron source (SNS) target container material - 316 LN stainless steel

NASA Astrophysics Data System (ADS)

Tian, Hongbo

As the candidate target container material of the new Spallation Neutron Source (SNS) being designed and constructed at the Oak Ridge National Laboratory (ORNL), Type 316 low-carbon nitrogen-added (LN) stainless steel (SS) will operate in an aggressive environment, subjected to intense fluxes of high-energy protons and neutrons while exposed to liquid mercury. The current project is oriented toward materials studies regarding the effects of test environment and frequency on the fatigue behavior of 316 LN SS. In order to study the structural applications of this material and improve the fundamental understanding of the fatigue damage mechanisms, fatigue tests were performed in air and mercury environments at various frequencies and R ratios (R = sigma min/sigmamax, sigmamin and sigmamax are the applied minimum and maximum stresses, respectively). Fatigue data were developed for the structural design and engineering applications of this material. Specifically, high-cycle fatigue tests, fatigue crack-propagation tests, and ultrahigh cycle fatigue tests up to 10 9 cycles were conducted in air and mercury with test frequencies from 10 Hz to 700 Hz. Microstructure characterizations were performed using optical microscopy (OM), scanning-electron microscopy (SEM), and transmission-electron microscopy (TEM). It was found that mercury doesn't seem to have a large impact on the crack-initiation behavior of 316 LN SS. However, the crack-propagation mechanisms in air and mercury are different in some test conditions. Transgranular cracks seem to be the main mechanism in air, and intergranular in mercury. A significant specimen self-heating effect was found during high-cycle faituge. Theoretical calculation was performed to predict temperature responses of the material subjected to cyclic deformation. The predicted cyclic temperature evolution seems to be in good agreement with the experimental results.

Effects of Volitional Spine Stabilization and Lower-Extremity Fatigue on the Knee and Ankle During Landing Performance in a Population With Recurrent Low Back Pain.

PubMed

Haddas, Ram; Sawyer, Steven F; Sizer, Phillip S; Brooks, Toby; Chyu, Ming-Chien; James, C Roger

2017-09-01

Recurrent lower back pain (rLBP) and neuromuscular fatigue are independently thought to increase the risk of lower extremity (LE) injury. Volitional preemptive abdominal contraction (VPAC) is thought to improve lumbar spine and pelvis control in individuals with rLBP. The effects of VPAC on fatigued landing performance in individuals with rLBP are unknown. To determine the effects of VPAC and LE fatigue on landing performance in a rLBP population. Cross-sectional pretest-posttest cohort control design. A clinical biomechanics laboratory. 32 rLBP (age 21.2 ± 2.7 y) but without current symptoms and 33 healthy (age 20.9 ± 2.3 y) subjects. (i) Volitional preemptive abdominal contraction using abdominal bracing and (ii) fatigue using submaximal free-weight squat protocol with 15% body weight until task failure was achieved. Knee and ankle angles, moments, electromyographic measurements from semitendinosus and vastus medialis muscles, and ground reaction force (GRF) were collected during 0.30 m drop-jump landings. The VPAC resulted in significantly earlier muscle onsets across all muscles with and without fatigue in both groups (mean ± SD, 0.063 ± 0.016 s earlier; P ≤ .001). Fatigue significantly delayed semitendinosus muscle onsets (0.033 ± 0.024 s later; P ≤ .001), decreased GRF (P ≤ .001), and altered landing kinematics in a variety of ways. The rLBP group exhibited delayed semitendinosus and vastus medialis muscle onsets (0.031 ± 0.028 s later; P ≤ .001) and 1.8° less knee flexion at initial contact (P ≤ .008). The VPAC decreases some of the detrimental effects of fatigue on landing biomechanics and thus may reduce LE injury risk in a rLBP population.

Effectiveness of core stability exercises and recovery myofascial release massage on fatigue in breast cancer survivors: a randomized controlled clinical trial.

PubMed

Cantarero-Villanueva, Irene; Fernández-Lao, Carolina; Del Moral-Avila, Rosario; Fernández-de-Las-Peñas, César; Feriche-Fernández-Castanys, María Belén; Arroyo-Morales, Manuel

2012-01-01

The purpose of the present paper was to evaluate the effects of an 8-week multimodal program focused on core stability exercises and recovery massage with DVD support for a 6-month period in physical and psychological outcomes in breast cancer survivors. A randomized controlled clinical trial was performed. Seventy-eight (n = 78) breast cancer survivors were assigned to experimental (core stability exercises plus massage-myofascial release) and control (usual health care) groups. The intervention period was 8 weeks. Mood state, fatigue, trunk curl endurance, and leg strength were determined at baseline, after the last treatment session, and at 6 months of followup. Immediately after treatment and at 6 months, fatigue, mood state, trunk curl endurance, and leg strength exhibited greater improvement within the experimental group compared to placebo group. This paper showed that a multimodal program focused on core stability exercises and massage reduced fatigue, tension, depression, and improved vigor and muscle strength after intervention and 6 months after discharge.

Constructing an adaptive care model for the management of disease-related symptoms throughout the course of multiple sclerosis--performance improvement CME.

PubMed

Miller, Aaron E; Cohen, Bruce A; Krieger, Stephen C; Markowitz, Clyde E; Mattson, David H; Tselentis, Helen N

2014-01-01

Symptom management remains a challenging clinical aspect of MS. To design a performance improvement continuing medical education (PI CME) activity for better clinical management of multiple sclerosis (MS)-related depression, fatigue, mobility impairment/falls, and spasticity. Ten volunteer MS centers participated in a three-stage PI CME model: A) baseline assessment; B) practice improvement CME intervention; C) reassessment. Expert faculty developed performance measures and activity intervention tools. Designated MS center champions reviewed patient charts and entered data into an online database. Stage C data were collected eight weeks after implementation of the intervention and compared with Stage A baseline data to measure change in performance. Aggregate data from the 10 participating MS centers (405 patient charts) revealed performance improvements in the assessment of all four MS-related symptoms. Statistically significant improvements were found in the documented assessment of mobility impairment/falls (p=0.003) and spasticity (p<0.001). For documentation of care plans, statistically significant improvements were reported for fatigue (p=0.007) and mobility impairment/falls (p=0.040); non-significant changes were noted for depression and spasticity. Our PI CME interventions demonstrated performance improvement in the management of MS-related symptoms. This PI CME model (available at www.achlpicme.org/ms/toolkit) offers a new perspective on enhancing symptom management in patients with MS.

The Development of Lightweight Commercial Vehicle Wheels Using Microalloying Steel

NASA Astrophysics Data System (ADS)

Lu, Hongzhou; Zhang, Lilong; Wang, Jiegong; Xuan, Zhaozhi; Liu, Xiandong; Guo, Aimin; Wang, Wenjun; Lu, Guimin

Lightweight wheels can reduce weight about 100kg for commercial vehicles, and it can save energy and reduce emission, what's more, it can enhance the profits for logistics companies. The development of lightweight commercial vehicle wheels is achieved by the development of new steel for rim, the process optimization of flash butt welding, and structure optimization by finite element methods. Niobium micro-alloying technology can improve hole expansion rate, weldability and fatigue performance of wheel steel, and based on Niobium micro-alloying technology, a special wheel steel has been studied whose microstructure are Ferrite and Bainite, with high formability and high fatigue performance, and stable mechanical properties. The content of Nb in this new steel is 0.025% and the hole expansion rate is ≥ 100%. At the same time, welding parameters including electric upsetting time, upset allowance, upsetting pressure and flash allowance are optimized, and by CAE analysis, an optimized structure has been attained. As a results, the weight of 22.5in×8.25in wheel is up to 31.5kg, which is most lightweight comparing the same size wheels. And its functions including bending fatigue performance and radial fatigue performance meet the application requirements of truck makers and logistics companies.

Psychophysiological Assessment of Fatigue in Commercial Aviation Operations

NASA Technical Reports Server (NTRS)

Hernandez, Norma; Cowings, Patricia; Toscano, William

2012-01-01

The overall goal of this study is to improve our understanding of crew work hours, workload, sleep, fatigue, and performance, and the relationships between these variables on actual flight deck performance. Specifically, this study will provide objective measures of physiology and performance, which may benefit investigators in identifying fatigue levels of operators in commercial aviation and provide a way to better design strategies to limit crew fatigue. This research was supported by an agreement between NASA Ames Research Center and easyJet Airline Company, Ltd., Luton, UK. Twenty commercial pilots volunteered to participant in the study that included 15 flight duty days. Participants wore a Zephyr Bioharness ambulatory physiological monitor each flight day, which measured their heart rate, respiration rate, skin temperature, activity and posture. In addition, pilots completed sleep log diaries, self-report scales of mood, sleepiness and workload, and a Performance Vigilance Task (PVT). All data were sent to NASA researchers for processing and analyses. Heart rate variability data of several subjects were subjected to a spectral analysis to examine power in specific frequency bands. Increased power in low frequency band was associated with reports of higher subjective sleepinesss in some subjects. Analyses of other participants data are currently underway.

Assessment of microalloying effects on the high temperature fatigue behavior of NiAl

NASA Technical Reports Server (NTRS)

Noebe, R. D.; Lerch, B. A.; Rao, K. B. S.

1995-01-01

Binary NiAl suffers from a lack of strength and poor creep properties at and above 1000 K. Poor creep resistance in turn affects low cycle fatigue (LCF) lives at low strain ranges due to the additional interactions of creep damage. One approach for improving these properties involved microalloying with either Zr or N. As an integral part of a much larger alloying program the low cycle fatigue behavior of Zr and N doped nickel aluminides produced by extrusion of prealloyed powders has been investigated. Strain controlled LCF tests were performed in air at 1000 K. The influence of these microalloying additions on the fatigue life and cyclic stress response of polycrystalline NiAl are discussed.

Analysis of physiological impact while reading stereoscopic radiographs

NASA Astrophysics Data System (ADS)

Unno, Yasuko Y.; Tajima, Takashi; Kuwabara, Takao; Hasegawa, Akira; Natsui, Nobutaka; Ishikawa, Kazuo; Hatada, Toyohiko

2011-03-01

A stereoscopic viewing technology is expected to improve diagnostic performance in terms of reading efficiency by adding one more dimension to the conventional 2D images. Although a stereoscopic technology has been applied to many different field including TV, movies and medical applications, physiological fatigue through reading stereoscopic radiographs has been concerned although no established physiological fatigue data have been provided. In this study, we measured the α-amylase concentration in saliva, heart rates and normalized tissue hemoglobin index (nTHI) in blood of frontal area to estimate physiological fatigue through reading both stereoscopic radiographs and the conventional 2D radiographs. In addition, subjective assessments were also performed. As a result, the pupil contraction occurred just after the reading of the stereoscopic images, but the subjective assessments regarding visual fatigue were nearly identical for the reading the conventional 2D and stereoscopic radiographs. The α-amylase concentration and the nTHI continued to decline while examinees read both 2D and stereoscopic images, which reflected the result of subjective assessment that almost half of the examinees reported to feel sleepy after reading. The subjective assessments regarding brain fatigue showed that there were little differences between 2D and stereoscopic reading. In summary, this study shows that the physiological fatigue caused by stereoscopic reading is equivalent to the conventional 2D reading including ocular fatigue and burden imposed on brain.

Effectiveness and cost-effectiveness of a self-management group program to improve social participation in patients with neuromuscular disease and chronic fatigue: protocol of the Energetic study.

PubMed

Veenhuizen, Yvonne; Cup, Edith H C; Groothuis, Jan T; Hendriks, Jan C M; Adang, Eddy M M; van Engelen, Baziel G M; Geurts, Alexander C H

2015-04-19

Chronic fatigue is present in more than 60% of the patients with a neuromuscular disease and can be their most disabling symptom. In combination with other impairments, fatigue often results in low levels of physical activity and decreased social participation, leading to high societal costs. 'Energetic' is a self-management group program aimed at improving social participation, physical endurance and alleviating fatigue in these patients. The primary aim of this study is to evaluate the effectiveness and cost-effectiveness of the Energetic program. A multicentered, assessor-blinded, two-armed randomized controlled trial is conducted with evaluations at inclusion and four, seven and fifteen months later. The study includes patients with a neuromuscular disease and chronic fatigue and, when present, their caregivers. The participants are randomized (ratio 1:1) to either an intervention group, receiving the Energetic program, or a control group, receiving usual care (i.e., no specific intervention). The Energetic program covers four months and includes four modules: 1) individually tailored aerobic exercise training; 2) education about aerobic exercise; 3) self-management training in applying energy conservation strategies; and 4) implementation and relapse prevention in daily life. Two months after cessation of the program a booster session is provided. The primary outcome is the perceived performance score of the Canadian Occupational Performance Measure (COPM). Secondary outcomes include the COPM-satisfaction score, and measures of fatigue, physical endurance, activity engagement, mood, and self-efficacy. Caregiver burden is also evaluated as a secondary outcome. Health-related quality of life and medical and societal costs are assessed to estimate cost-effectiveness of the program. The Energetic study is the first randomized controlled trial to evaluate the effectiveness and cost-effectiveness of a combined physical and self-management group training program for improving social participation, physical endurance and alleviating fatigue in patients with neuromuscular diseases. It will generate new insights in (cost-)effective rehabilitation strategies for these incurable conditions. Clinicaltrials.gov NCT02208687 .

Caffeine and exercise.

PubMed

Paluska, Scott A

2003-08-01

Caffeine is the most commonly consumed drug in the world, and athletes frequently use it as an ergogenic aid. It improves performance and endurance during prolonged, exhaustive exercise. To a lesser degree it also enhances short-term, high-intensity athletic performance. Caffeine improves concentration, reduces fatigue, and enhances alertness. Habitual intake does not diminish caffeine's ergogenic properties. Several mechanisms have been proposed to explain the physiologic effects of caffeine, but adenosine receptor antagonism most likely accounts for the primary mode of action. It is relatively safe and has no known negative performance effects, nor does it cause significant dehydration or electrolyte imbalance during exercise. Routine caffeine consumption may cause tolerance or dependence, and abrupt discontinuation produces irritability, mood shifts, headache, drowsiness, or fatigue. Major sport governing bodies ban excessive use of caffeine, but current monitoring techniques are inadequate, and ethical dilemmas persist regarding caffeine intake by athletes.

Testing Aerospace Gears for Bending Fatigue, Pitting, and Scuffing

NASA Technical Reports Server (NTRS)

Krantz, Timothy; Anderson, Cody; Shareef, Iqbal; Fetty, Jason

2017-01-01

This work was motivated by the goal to increase the power to weight ratio of rotorcraft drive systems. Experiments were conducted to establish the performance of gears made from an aerospace alloy used in production aircraft. Bending fatigue, pitting, and scuffing test procedures and results are documented. The data establishes a baseline for evaluation of new technologies. Recommendations are made to improve test procedures for future work.

Preseason changes in markers of lower body fatigue and performance in young professional rugby union players.

PubMed

Roe, Gregory A B; Darrall-Jones, Joshua D; Till, Kevin; Jones, Ben

2016-11-01

This study investigated the changes in measures of neuromuscular fatigue and physical performance in young professional rugby union players during a preseason training period. Fourteen young (age: 19.1 ± 1.2 years) professional rugby union players participated in the study. Changes in measures of lower body neuromuscular fatigue (countermovement jump (CMJ) mean power, mean force, flight-time) and physical performance (lower body strength, 40 m sprint velocity) were assessed during an 11-week preseason period using magnitude-based inferences. CMJ mean power was likely to very likely decreased during week 2 (-8.1 ± 5.5% to -12.5 ± 6.8%), and likely to almost certainly decreased from weeks 5 to 11 (-10 ± 4.3% to -14.7 ± 6.9%), while CMJ flight-time demonstrated likely to very likely decreases during weeks 2, and weeks 4-6 (-2.41 ± 1% to -3.3 ± 1.3%), and weeks 9-10 (-1.9 ± 0.9% to -2.2 ± 1.5%). Despite this, possible improvements in lower body strength (5.8 ± 2.7%) and very likely improvements in 40 m velocity (5.5 ± 3.6%) were made. Relationships between changes in CMJ metrics and lower body strength or 40 m sprint velocity were trivial or small (<0.22). Increases in lower body strength and 40 m velocity occurred over the course of an 11-week preseason despite the presence of neuromuscular fatigue (as measured by CMJ). The findings of this study question the usefulness of CMJ for monitoring fatigue in the context of strength and sprint velocity development. Future research is needed to ascertain the consequences of negative changes in CMJ in the context of rugby-specific activities to determine the usefulness of this test as a measure of fatigue in this population.

The effect of carbohydrate ingestion on performance during a simulated soccer match.

PubMed

Goedecke, Julia H; White, Nicholas J; Chicktay, Waheed; Mahomed, Hafsa; Durandt, Justin; Lambert, Michael I

2013-12-16

This study investigated how performance was affected after soccer players, in a postprandial state, ingested a 7% carbohydrate (CHO) solution compared to a placebo (0% CHO) during a simulated soccer match. Using a double-blind placebo-controlled design, 22 trained male league soccer players (age: 24 ± 7 years, wt: 73.4 ± 12.0 kg, VO2max: 51.8 ± 4.3 mL O2/kg/min) completed two trials, separated by 7 days, during which they ingested, in random order, 700 mL of either a 7% CHO or placebo drink during a simulated soccer match. Ratings of perceived exertion (RPE), agility, timed and run to fatigue were measured during the trials. Change in agility times was not altered by CHO vs. placebo ingestion (0.57 ± 1.48 vs. 0.66 ± 1.00, p = 0.81). Timed runs to fatigue were 381 ± 267 s vs. 294 ± 159 s for the CHO and placebo drinks, respectively (p = 0.11). Body mass modified the relationship between time to fatigue and drink ingestion (p = 0.02 for drink × body mass), such that lower body mass was associated with increased time to fatigue when the players ingested CHO, but not placebo. RPE values for the final stage of the simulated soccer match were 8.5 ± 1.7 and 8.6 ± 1.5 for the CHO and placebo drinks respectively (p = 0.87). The group data showed that the 7% CHO solution (49 g CHO) did not significantly improve performance during a simulated soccer match in league soccer players who had normal pre-match nutrition. However, when adjusting for body mass, increasing CHO intake was associated with improved time to fatigue during the simulated soccer match.

The Effect of Carbohydrate Ingestion on Performance during a Simulated Soccer Match

PubMed Central

Goedecke, Julia H.; White, Nicholas J.; Chicktay, Waheed; Mahomed, Hafsa; Durandt, Justin; Lambert, Michael I.

2013-01-01

Aim: This study investigated how performance was affected after soccer players, in a postprandial state, ingested a 7% carbohydrate (CHO) solution compared to a placebo (0% CHO) during a simulated soccer match. Methods: Using a double-blind placebo-controlled design, 22 trained male league soccer players (age: 24 ± 7 years, wt: 73.4 ± 12.0 kg, VO2max: 51.8 ± 4.3 mL O2/kg/min) completed two trials, separated by 7 days, during which they ingested, in random order, 700 mL of either a 7% CHO or placebo drink during a simulated soccer match. Ratings of perceived exertion (RPE), agility, timed and run to fatigue were measured during the trials. Results: Change in agility times was not altered by CHO vs. placebo ingestion (0.57 ± 1.48 vs. 0.66 ± 1.00, p = 0.81). Timed runs to fatigue were 381 ± 267 s vs. 294 ± 159 s for the CHO and placebo drinks, respectively (p = 0.11). Body mass modified the relationship between time to fatigue and drink ingestion (p = 0.02 for drink × body mass), such that lower body mass was associated with increased time to fatigue when the players ingested CHO, but not placebo. RPE values for the final stage of the simulated soccer match were 8.5 ± 1.7 and 8.6 ± 1.5 for the CHO and placebo drinks respectively (p = 0.87). Conclusions: The group data showed that the 7% CHO solution (49 g CHO) did not significantly improve performance during a simulated soccer match in league soccer players who had normal pre-match nutrition. However, when adjusting for body mass, increasing CHO intake was associated with improved time to fatigue during the simulated soccer match. PMID:24352094

The CF6 jet engine performance improvement: New front mount

NASA Technical Reports Server (NTRS)

Fasching, W. A.

1979-01-01

The New Front Mount was evaluated in component tests including stress, deflection/distortion and fatigue tests. The test results demonstrated a performance improvement of 0.1% in cruise sfc, 16% in compressor stall margin and 10% in compressor stator angle margin. The New Front Mount hardware successfully completed 35,000 simulated flight cycles endurance testing.

Improving EEG-Based Driver Fatigue Classification Using Sparse-Deep Belief Networks.

PubMed

Chai, Rifai; Ling, Sai Ho; San, Phyo Phyo; Naik, Ganesh R; Nguyen, Tuan N; Tran, Yvonne; Craig, Ashley; Nguyen, Hung T

2017-01-01

This paper presents an improvement of classification performance for electroencephalography (EEG)-based driver fatigue classification between fatigue and alert states with the data collected from 43 participants. The system employs autoregressive (AR) modeling as the features extraction algorithm, and sparse-deep belief networks (sparse-DBN) as the classification algorithm. Compared to other classifiers, sparse-DBN is a semi supervised learning method which combines unsupervised learning for modeling features in the pre-training layer and supervised learning for classification in the following layer. The sparsity in sparse-DBN is achieved with a regularization term that penalizes a deviation of the expected activation of hidden units from a fixed low-level prevents the network from overfitting and is able to learn low-level structures as well as high-level structures. For comparison, the artificial neural networks (ANN), Bayesian neural networks (BNN), and original deep belief networks (DBN) classifiers are used. The classification results show that using AR feature extractor and DBN classifiers, the classification performance achieves an improved classification performance with a of sensitivity of 90.8%, a specificity of 90.4%, an accuracy of 90.6%, and an area under the receiver operating curve (AUROC) of 0.94 compared to ANN (sensitivity at 80.8%, specificity at 77.8%, accuracy at 79.3% with AUC-ROC of 0.83) and BNN classifiers (sensitivity at 84.3%, specificity at 83%, accuracy at 83.6% with AUROC of 0.87). Using the sparse-DBN classifier, the classification performance improved further with sensitivity of 93.9%, a specificity of 92.3%, and an accuracy of 93.1% with AUROC of 0.96. Overall, the sparse-DBN classifier improved accuracy by 13.8, 9.5, and 2.5% over ANN, BNN, and DBN classifiers, respectively.

Improving EEG-Based Driver Fatigue Classification Using Sparse-Deep Belief Networks

PubMed Central

Chai, Rifai; Ling, Sai Ho; San, Phyo Phyo; Naik, Ganesh R.; Nguyen, Tuan N.; Tran, Yvonne; Craig, Ashley; Nguyen, Hung T.

2017-01-01

This paper presents an improvement of classification performance for electroencephalography (EEG)-based driver fatigue classification between fatigue and alert states with the data collected from 43 participants. The system employs autoregressive (AR) modeling as the features extraction algorithm, and sparse-deep belief networks (sparse-DBN) as the classification algorithm. Compared to other classifiers, sparse-DBN is a semi supervised learning method which combines unsupervised learning for modeling features in the pre-training layer and supervised learning for classification in the following layer. The sparsity in sparse-DBN is achieved with a regularization term that penalizes a deviation of the expected activation of hidden units from a fixed low-level prevents the network from overfitting and is able to learn low-level structures as well as high-level structures. For comparison, the artificial neural networks (ANN), Bayesian neural networks (BNN), and original deep belief networks (DBN) classifiers are used. The classification results show that using AR feature extractor and DBN classifiers, the classification performance achieves an improved classification performance with a of sensitivity of 90.8%, a specificity of 90.4%, an accuracy of 90.6%, and an area under the receiver operating curve (AUROC) of 0.94 compared to ANN (sensitivity at 80.8%, specificity at 77.8%, accuracy at 79.3% with AUC-ROC of 0.83) and BNN classifiers (sensitivity at 84.3%, specificity at 83%, accuracy at 83.6% with AUROC of 0.87). Using the sparse-DBN classifier, the classification performance improved further with sensitivity of 93.9%, a specificity of 92.3%, and an accuracy of 93.1% with AUROC of 0.96. Overall, the sparse-DBN classifier improved accuracy by 13.8, 9.5, and 2.5% over ANN, BNN, and DBN classifiers, respectively. PMID:28326009

Human fatigue expression recognition through image-based dynamic multi-information and bimodal deep learning

NASA Astrophysics Data System (ADS)

Zhao, Lei; Wang, Zengcai; Wang, Xiaojin; Qi, Yazhou; Liu, Qing; Zhang, Guoxin

2016-09-01

Human fatigue is an important cause of traffic accidents. To improve the safety of transportation, we propose, in this paper, a framework for fatigue expression recognition using image-based facial dynamic multi-information and a bimodal deep neural network. First, the landmark of face region and the texture of eye region, which complement each other in fatigue expression recognition, are extracted from facial image sequences captured by a single camera. Then, two stacked autoencoder neural networks are trained for landmark and texture, respectively. Finally, the two trained neural networks are combined by learning a joint layer on top of them to construct a bimodal deep neural network. The model can be used to extract a unified representation that fuses landmark and texture modalities together and classify fatigue expressions accurately. The proposed system is tested on a human fatigue dataset obtained from an actual driving environment. The experimental results demonstrate that the proposed method performs stably and robustly, and that the average accuracy achieves 96.2%.

Influence of dietary nitrate supplementation on physiological and cognitive responses to incremental cycle exercise.

PubMed

Thompson, Kevin G; Turner, Louise; Prichard, Jonathon; Dodd, Fiona; Kennedy, David O; Haskell, Crystal; Blackwell, James R; Jones, Andrew M

2014-03-01

Dietary inorganic nitrate supplementation causes physiological effects which may enhance exercise tolerance. However it is not known whether nitrate might alter cognitive function during exercise. In a double-blind, cross-over study, sixteen subjects ingested either nitrate-rich beetroot juice or a placebo and completed a continuous cycle exercise test involving 20min stages at 50% and 70% V˙O2peak and a final stage at 90% V˙O2peak until volitional exhaustion. Cognitive tasks were completed before, during and after exercise. In the dietary nitrate condition: plasma [nitrite] increased (p<0.01), systolic blood pressure decreased (p<0.05) and there was a trend for a reduced oxygen uptake at 50% V˙O2peak. Tissue oxygenation improved across exercise intensities and exercise tolerance was greater at 90% V˙O2peak (p<0.05). Rating of perceived exertion, energy levels and cognitive performance were similar between conditions with mental fatigue being evident from 70% V˙O2peak onwards (p<0.05). Dietary nitrate supplementation enhanced short-term endurance exercise performance with concomitant mental fatigue but did not improve cognitive performance post-fatigue. Copyright © 2014 Elsevier B.V. All rights reserved.

Surface-distributed low-frequency asynchronous stimulation delays fatigue of stimulated muscles.

PubMed

Maneski, Lana Z Popović; Malešević, Nebojša M; Savić, Andrej M; Keller, Thierry; Popović, Dejan B

2013-12-01

One important reason why functional electrical stimulation (FES) has not gained widespread clinical use is the limitation imposed by rapid muscle fatigue due to non-physiological activation of the stimulated muscles. We aimed to show that asynchronous low-pulse-rate (LPR) electrical stimulation applied by multipad surface electrodes greatly postpones the occurrence of muscle fatigue compared with conventional stimulation (high pulse rate, HPR). We compared the produced force vs. time of the forearm muscles responsible for finger flexion in 2 stimulation protocols, LPR (fL = 10 Hz) and HPR (fH = 40 Hz). Surface-distributed low-frequency asynchronous stimulation (sDLFAS) doubles the time interval before the onset of fatigue (104 ± 80%) compared with conventional synchronous stimulation. Combining the performance of multipad electrodes (increased selectivity and facilitated positioning) with sDLFAS (decreased fatigue) can improve many FES applications in both the lower and upper extremities. Copyright © 2013 Wiley Periodicals, Inc.

Effects of Quadriceps Muscle Fatigue on Stiff-Knee Gait in Patients with Hemiparesis

PubMed Central

Boudarham, Julien; Roche, Nicolas; Pradon, Didier; Delouf, Eric; Bensmail, Djamel; Zory, Raphael

2014-01-01

The relationship between neuromuscular fatigue and locomotion has never been investigated in hemiparetic patients despite the fact that, in the clinical context, patients report to be more spastic or stiffer after walking a long distance or after a rehabilitation session. The aim of this study was to evaluate the effects of quadriceps muscle fatigue on the biomechanical gait parameters of patients with a stiff-knee gait (SKG). Thirteen patients and eleven healthy controls performed one gait analysis before a protocol of isokinetic quadriceps fatigue and two after (immediately after and after 10 minutes of rest). Spatiotemporal parameters, sagittal knee and hip kinematics, rectus femoris (RF) and vastus lateralis (VL) kinematics and electromyographic (EMG) activity were analyzed. The results showed that quadriceps muscle weakness, produced by repetitive concentric contractions of the knee extensors, induced an improvement of spatiotemporal parameters for patients and healthy subjects. For the patient group, the increase in gait velocity and step length was associated with i) an increase of sagittal hip and knee flexion during the swing phase, ii) an increase of the maximal normalized length of the RF and VL and of the maximal VL lengthening velocity during the pre-swing and swing phases, and iii) a decrease in EMG activity of the RF muscle during the initial pre-swing phase and during the latter 2/3 of the initial swing phase. These results suggest that quadriceps fatigue did not alter the gait of patients with hemiparesis walking with a SKG and that neuromuscular fatigue may play the same functional role as an anti-spastic treatment such as botulinum toxin-A injection. Strength training of knee extensors, although commonly performed in rehabilitation, does not seem to be a priority to improve gait of these patients. PMID:24718087

Improvement in multiple dimensions of fatigue in patients with fibromyalgia treated with duloxetine: secondary analysis of a randomized, placebo-controlled trial.

PubMed

Arnold, Lesley M; Wang, Fujun; Ahl, Jonna; Gaynor, Paula J; Wohlreich, Madelaine M

2011-06-13

Fatigue is one of the most disabling symptoms associated with fibromyalgia that greatly impacts quality of life. Fatigue was assessed as a secondary objective in a 2-phase, 24-week study in outpatients with American College of Rheumatology-defined fibromyalgia. Patients were randomized to duloxetine 60-120 mg/d (N = 263) or placebo (N = 267) for the 12-week acute phase. At Week 12, all placebo-treated patients were switched to double-blind treatment with duloxetine for the extension phase. Fatigue was assessed at baseline and every 4 weeks with the Multidimensional Fatigue Inventory (MFI) scales: General Fatigue, Physical Fatigue, Mental Fatigue, Reduced Activity, and Reduced Motivation. Other assessments that may be associated with fatigue included Brief Pain Inventory (BPI) average pain, numerical scales to rate anxiety, depressed mood, bothered by sleep difficulties, and musculoskeletal stiffness. Treatment-emergent fatigue-related events were also assessed. Changes from baseline to Week 12, and from Week 12 to Week 24, were analyzed by mixed-effects model repeated measures analysis. At Week 12, duloxetine versus placebo significantly (all p < .05) reduced ratings on each MFI scale, BPI pain, anxiety, depressed mood, and stiffness. Improvement in ratings of being bothered by sleep difficulties was significant only at Weeks 4 and 8. At Week 24, mean changes in all measures indicated improvement was maintained for patients who received duloxetine for all 24 weeks (n = 176). Placebo-treated patients switched to duloxetine (n = 187) had significant within-group improvement in Physical Fatigue (Weeks 16, 20, and 24); General Fatigue (Weeks 20 and 24); Mental Fatigue (Week 20); and Reduced Activity (Weeks 20 and 24). These patients also experienced significant within-group improvement in BPI pain, anxiety, depressed mood, bothered by sleep difficulties, and stiffness. Overall, the most common (> 5% incidence) fatigue-related treatment-emergent adverse events were fatigue, somnolence, and insomnia. Treatment with duloxetine significantly improved multiple dimensions of fatigue in patients with fibromyalgia, and improvement was maintained for up to 24 weeks. ClinicalTrials.gov registry NCT00673452.

Computerized training improves verbal working memory in patients with myalgic encephalomyelitis/chronic fatigue syndrome: A pilot study.

PubMed

Maroti, Daniel; Westerberg, Annika Fryxell; Saury, Jean-Michel; Bileviciute-Ljungar, Indre

2015-08-18

Patients with myalgic encephalomyelitis/chronic fatigue syndrome experience cognitive difficulties. The aim of this study was to evaluate the effect of computerized training on working memory in this syndrome. Non-randomized (quasi-experimental) study with no-treatment control group and non-equivalent dependent variable design in a myalgic encephalomyelitis/chronic fatigue syndrome-cohort. Patients with myalgic encephalomyelitis/chronic fatigue syndrome who participated in a 6-month outpatient rehabilitation programme were included in the study. Eleven patients who showed signs of working memory deficit were recruited for additional memory training and 12 patients with no working memory deficit served as controls. Cognitive training with computerized working memory tasks of increasing difficulty was performed 30-45 min/day, 5 days/week over a 5-week period. Short-term and working memory tests (Digit Span - forward, backward, total) were used as primary outcome measures. Nine of the 11 patients were able to complete the training. Cognitive training increased working memory (p = 0.003) and general attention (p = 0.004) to the mean level. Short-term memory was also improved, but the difference was not statistically significant (p = 0.052) vs prior training. The control group did not show any significant improvement in primary outcome measures. Cognitive training may be a new treatment for patients with myalgic encephalomyelitis/chronic fatigue syndrome.

Modafinil for the Improvement of Patient Outcomes Following Traumatic Brain Injury.

PubMed

Borghol, Amne; Aucoin, Michael; Onor, Ifeanyichukwu; Jamero, Dana; Hawawini, Fadi

2018-04-01

Objective : The authors sought to assess the literature evidence on the efficacy of modafinil use in patients with fatigue or excessive daytime sleepiness (EDS) secondary to traumatic brain injury (TBI). Method of Research : A literature search of Medline and PubMed was performed using the EBSCOhost database. Primary literature, observational studies, meta-analyses, case reports, and systematic reviews were assessed for content regarding modafinil and psychostimulant use in patients with TBI. Of the 23 articles collected, three randomized, controlled studies, three observational studies, one case report, and two systematic reviews gave a description of modafinil use in TBI patients. Results and Conclusion : Modafinil is a central nervous system stimulant with well-established effectiveness in the treatment of narcolepsy and shift-work sleep disorder. There is conflicting evidence about the benefits of modafinil in the treatment of fatigue and EDS secondary to TBI. One randomized, controlled study states that modafinil does not significantly improve patient wakefulness, while another concludes that modafinil corrects EDS but not fatigue. An observational study provides evidence that modafinil increases alertness in fatigued patients with past medical history of brainstem diencephalic stroke or multiple sclerosis. Modafinil appears to have the potential to improve wakefulness in patients with TBI. A prospective, double-blinded, randomized, crossover trial of modafinil for the management of fatigue in ischemic stroke patients is currently being conducted, and further studies demonstrating consistent results are needed before making a conclusive decision.

Improvement of fatigue in patients with rheumatoid arthritis treated with biologics: relationship with sleep disorders, depression and clinical efficacy. A prospective, multicentre study.

PubMed

Genty, Marlène; Combe, Bernard; Kostine, Marie; Ardouin, Elodie; Morel, Jacques; Lukas, Cédric

2017-01-01

To assess predictive factors of improvement in related fatigue in rheumatoid arthritis (RA) patients newly receiving biologic therapy, and specifically the influence of the improvement of the quality of sleep. We conducted a multicentre prospective study in RA patients requiring initiation or change of biologic therapy. The improvement in fatigue, sleep disorders and depression was assessed respectively by the FACIT fatigue scale, Spiegel scale and Beck Depression Inventory at inclusion (M0) and 3 months (M3) after the beginning of treatment. Potential confounders were assessed and adjusted for. The association between evolution of fatigue and other characteristics were evaluated by univariate (χ2) then multivariate (logistic regression) analyses. We followed-up 99 patients. FACIT scores at M0 revealed frequently reported fatigue: 89%, high prevalence of sleep disorders: 95% and depression: 67%. Improvement of fatigue, sleep quality and depression was observed in 58.6%, 26.3% and 34.3% of cases, respectively. Significant factors associated with an improvement in fatigue at M3 were an elevated sedimentation rate at M0 (OR=5.7[2.0-16.0], p=0.001) and a favourable EULAR response at M3 (OR=4.8[1.6-14.8], p=0.006). Furthermore, a number of swollen joints > 5 at baseline (OR=0.3 [0.1-0.8]) and the use of psychotropic drugs (OR=0.2[0.04-0.9]) were predictive of an absence of improvement in fatigue. No significant association with the improvement in sleep disorders could be demonstrated. Fatigue in RA is improved by effective treatment, via decreasing disease activity. Improvement of sleep disorders is more likely a surrogate of therapeutic efficiency rather than an independent outcome.

Prevention of fatigue and insomnia in shift workers-a review of non-pharmacological measures.

PubMed

Richter, Kneginja; Acker, Jens; Adam, Sophia; Niklewski, Guenter

2016-01-01

Excessive fatigue and insomnia are common among shift workers and can lead to negative effects such as reduced work performance, processing errors, accidents at work, absenteeism, reduced quality of life, and symptoms of depression. Moreover, work in rotating shifts can be a risk factor for different somatic and psychiatric diseases and may contribute to poor health, especially in elder adults and women. This review aims to show non-pharmacological preventive measures against fatigue and insomnia in shift workers. Computerized literature searches in MedLine and in the Cochrane Library were performed with the following key words: shift work disorder, fatigue, insomnia, shift work, measures, treatment, therapy, strategies and coping. The search was limited to non-pharmacological studies that were conducted on human subjects and published as English-language articles in peer-reviewed journals since 1970. Additional studies were identified through the reference sections of relevant articles. Eighteen articles on fatigue in shift workers, including six original research articles with a total sample size of 3504 probands consisting of industrial workers, office employees, aircraft maintenance engineers, and non-shift workers working in simulated shifts, were analyzed, as well as seven articles on insomnia, including an original research article with a sample size of 26 media workers. Also, 4 reviews on shift work disorder were analyzed. The occurrence of fatigue and insomnia in shift workers associated with a working period is described as shift work disorder. Estimations on the prevalence of shift work disorder in shift workers vary between 5 % and about 20 %; about one in three shift workers is affected by insomnia and up to 90 % of shift workers report regular fatigue and sleepiness at the workplace. We concluded that there is a necessity for treatments to improve the sleep quality of the shift working population. The most common non-pharmacological recommendations to improve sleep quality and to reduce insomnia and fatigue were scheduling, bright light exposure, napping, psychoeducation for sleep hygiene, and cognitive-behavioral measures. Some important preventive coping strategies for fatigue associated with shift work such as napping and exposure to bright light have already been investigated and are generally approved. A few studies also provide good evidence for the efficacy of cognitive-behavioral techniques in the treatment of chronic primary and comorbid insomnia. These coping strategies summarized in this paper should be considered in the workplace health promotion programs of each work environment to improve working conditions for shift workers and to save money.

Task-relevant cognitive and motor functions are prioritized during prolonged speed-accuracy motor task performance.

PubMed

Solianik, Rima; Satas, Andrius; Mickeviciene, Dalia; Cekanauskaite, Agne; Valanciene, Dovile; Majauskiene, Daiva; Skurvydas, Albertas

2018-06-01

This study aimed to explore the effect of prolonged speed-accuracy motor task on the indicators of psychological, cognitive, psychomotor and motor function. Ten young men aged 21.1 ± 1.0 years performed a fast- and accurate-reaching movement task and a control task. Both tasks were performed for 2 h. Despite decreased motivation, and increased perception of effort as well as subjective feeling of fatigue, speed-accuracy motor task performance improved during the whole period of task execution. After the motor task, the increased working memory function and prefrontal cortex oxygenation at rest and during conflict detection, and the decreased efficiency of incorrect response inhibition and visuomotor tracking were observed. The speed-accuracy motor task increased the amplitude of motor-evoked potentials, while grip strength was not affected. These findings demonstrate that to sustain the performance of 2-h speed-accuracy task under conditions of self-reported fatigue, task-relevant functions are maintained or even improved, whereas less critical functions are impaired.

Post-exercise recovery of contractile function and endurance in humans and mice is accelerated by heating and slowed by cooling skeletal muscle.

PubMed

Cheng, Arthur J; Willis, Sarah J; Zinner, Christoph; Chaillou, Thomas; Ivarsson, Niklas; Ørtenblad, Niels; Lanner, Johanna T; Holmberg, Hans-Christer; Westerblad, Håkan

2017-12-15

We investigated whether intramuscular temperature affects the acute recovery of exercise performance following fatigue-induced by endurance exercise. Mean power output was better preserved during an all-out arm-cycling exercise following a 2 h recovery period in which the upper arms were warmed to an intramuscular temperature of ̴ 38°C than when they were cooled to as low as 15°C, which suggested that recovery of exercise performance in humans is dependent on muscle temperature. Mechanisms underlying the temperature-dependent effect on recovery were studied in intact single mouse muscle fibres where we found that recovery of submaximal force and restoration of fatigue resistance was worsened by cooling (16-26°C) and improved by heating (36°C). Isolated whole mouse muscle experiments confirmed that cooling impaired muscle glycogen resynthesis. We conclude that skeletal muscle recovery from fatigue-induced by endurance exercise is impaired by cooling and improved by heating, due to changes in glycogen resynthesis rate. Manipulation of muscle temperature is believed to improve post-exercise recovery, with cooling being especially popular among athletes. However, it is unclear whether such temperature manipulations actually have positive effects. Accordingly, we studied the effect of muscle temperature on the acute recovery of force and fatigue resistance after endurance exercise. One hour of moderate-intensity arm cycling exercise in humans was followed by 2 h recovery in which the upper arms were either heated to 38°C, not treated (33°C), or cooled to ∼15°C. Fatigue resistance after the recovery period was assessed by performing 3 × 5 min sessions of all-out arm cycling at physiological temperature for all conditions (i.e. not heated or cooled). Power output during the all-out exercise was better maintained when muscles were heated during recovery, whereas cooling had the opposite effect. Mechanisms underlying the temperature-dependent effect on recovery were tested in mouse intact single muscle fibres, which were exposed to ∼12 min of glycogen-depleting fatiguing stimulation (350 ms tetani given at 10 s interval until force decreased to 30% of the starting force). Fibres were subsequently exposed to the same fatiguing stimulation protocol after 1-2 h of recovery at 16-36°C. Recovery of submaximal force (30 Hz), the tetanic myoplasmic free [Ca 2+ ] (measured with the fluorescent indicator indo-1), and fatigue resistance were all impaired by cooling (16-26°C) and improved by heating (36°C). In addition, glycogen resynthesis was faster at 36°C than 26°C in whole flexor digitorum brevis muscles. We conclude that recovery from exhaustive endurance exercise is accelerated by raising and slowed by lowering muscle temperature. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

Technological Distractions (Part 2): A Summary of Approaches to Manage Clinical Alarms With Intent to Reduce Alarm Fatigue.

PubMed

Winters, Bradford D; Cvach, Maria M; Bonafide, Christopher P; Hu, Xiao; Konkani, Avinash; O'Connor, Michael F; Rothschild, Jeffrey M; Selby, Nicholas M; Pelter, Michele M; McLean, Barbara; Kane-Gill, Sandra L

2018-01-01

Alarm fatigue is a widely recognized safety and quality problem where exposure to high rates of clinical alarms results in desensitization leading to dismissal of or slowed response to alarms. Nonactionable alarms are thought to be especially problematic. Despite these concerns, the number of clinical alarm signals has been increasing as an everincreasing number of medical technologies are added to the clinical care environment. PubMed, SCOPUS, Embase, and CINAHL. We performed a systematic review of the literature focused on clinical alarms. We asked a primary key question; "what interventions have been attempted and resulted in the success of reducing alarm fatigue?" and 3-secondary key questions; "what are the negative effects on patients/families; what are the balancing outcomes (unintended consequences of interventions); and what human factor approaches apply to making an effective alarm?" Articles relevant to the Key Questions were selected through an iterative review process and relevant data was extracted using a standardized tool. We found 62 articles that had relevant and usable data for at least one key question. We found that no study used/developed a clear definition of "alarm fatigue." For our primary key question 1, the relevant studies focused on three main areas: quality improvement/bundled activities; intervention comparisons; and analysis of algorithm-based false and total alarm suppression. All sought to reduce the number of total alarms and/or false alarms to improve the positive predictive value. Most studies were successful to varying degrees. None measured alarm fatigue directly. There is no agreed upon valid metric(s) for alarm fatigue, and the current methods are mostly indirect. Assuming that reducing the number of alarms and/or improving positive predictive value can reduce alarm fatigue, there are promising avenues to address patient safety and quality problem. Further investment is warranted not only in interventions that may reduce alarm fatigue but also in defining how to best measure it.

Effect of fatigue on reaction time, response time, performance time, and kick impact in taekwondo roundhouse kick.

PubMed

Sant'Ana, Jader; Franchini, Emerson; da Silva, Vinicius; Diefenthaeler, Fernando

2017-06-01

Reaction time and response time are considered important abilities and can potentially affect combat performance. This study investigated the effect of a specific fatigue protocol on reaction time, response time, performance time, and kick impact. Seven male athletes reported to the laboratory on two different days. During day one, athletes performed a specific progressive taekwondo test, and on day two, a protocol for determining reaction time, response time, performance time, and kick impact before and after a time to exhaustion test at an intensity level corresponding to the maximal kick frequency obtained during the specific progressive taekwondo test. Muscle activation from rectus femoris and kick impact of the preferred limb were assessed. No differences were observed for response time and performance time. However, kick impact decreased (43 ± 27 to 13 ± 10 g, p < 0.01) while reaction time increased (145 ± 51 to 223 ± 133 ms, p < 0.05). Moderate correlation was observed between kick impact and response time (r = 0.565; p < 0.01), and kick impact and performance time (r = 0.494; p < 0.05). Results indicate that coaches and athletes may use taekwondo training programmes on coordination-based exercises leading to improve response time and to reduce fatigue effects in order to improve technique effectiveness and enhance the possibilities of scoring in a competitive situation.

Matching initial torque with different stimulation parameters influences skeletal muscle fatigue.

PubMed

Bickel, C Scott; Gregory, Chris M; Azuero, Andres

2012-01-01

A fundamental barrier to using electrical stimulation in the clinical setting is an inability to maintain torque production secondary to muscle fatigue. Electrical stimulation parameters are manipulated to influence muscle torque production, and they may also influence fatigability during repetitive stimulation. Our purpose was to determine the response of the quadriceps femoris to three different fatigue protocols using the same initial torque obtained by altering stimulator parameter settings. Participants underwent fatigue protocols in which either pulse frequency (lowHz), pulse duration (lowPD), or voltage (lowV) was manipulated to obtain an initial torque that equaled 25% of maximum voluntary isometric contraction. Muscle soreness was reported on a visual analog scale 48 h after each fatigue test. The lowHz protocol resulted in the least fatigue (25% +/- 14%); the lowPD (50% +/- 13%) and lowV (48% +/- 14%) protocols had similar levels of fatigue. The lowHz protocol resulted in significantly less muscle soreness than the higher frequency protocols. Stimulation protocols that use a lower frequency coupled with long pulse durations and high voltages result in lesser amounts of muscle fatigue and perceived soreness. The identification of optimal stimulation patterns to maximize muscle performance will reduce the effect of muscle fatigue and potentially improve clinical efficacy.

The Effect of Classroom Capacity on Vocal Fatigue as Quantified by the Vocal Fatigue Index.

PubMed

Banks, Russell E; Bottalico, Pasquale; Hunter, Eric J

2017-01-01

Previous research has concluded that teachers are at a higher-than-normal risk for voice issues that can cause occupational limitations. While some risk factors have been identified, there are still many unknowns. A survey was distributed electronically with 506 female teacher respondents. The survey included questions to quantify three aspects of vocal fatigue as captured by the Vocal Fatigue Index (VFI): (1) general tiredness of voice (performance), (2) physical discomfort associated with voicing (pain), and (3) improvement of symptoms with rest (recovery). The effect of classroom capacity on US teachers' self-reported experience of vocal fatigue was analyzed. The results indicated that a classroom's capacity significantly affected teachers' reported amounts of vocal fatigue, while a teacher's age also appeared to significantly affect the reported amount of vocal fatigue. A quadratic rather than linear effect was seen, with the largest age effect occurring at around 40-45 years in all three factors of the VFI. Further factors which may affect vocal fatigue must be explored in future research. By understanding what increases the risk for vocal fatigue, educators and school administrators can take precautions to mitigate the occupational risk of short- and long-term vocal health issues in school teachers. © 2017 S. Karger AG, Basel.

Effects of Relaxing Music on Mental Fatigue Induced by a Continuous Performance Task: Behavioral and ERPs Evidence.

PubMed

Guo, Wei; Ren, Jie; Wang, Biye; Zhu, Qin

2015-01-01

The purpose of this study was to investigate whether listening to relaxing music would help reduce mental fatigue and to maintain performance after a continuous performance task. The experiment involved two fatigue evaluation phases carried out before and after a fatigue inducing phase. A 1-hour AX-continuous performance test was used to induce mental fatigue in the fatigue-inducing phase, and participants' subjective evaluation on the mental fatigue, as well as their neurobehavioral performance in a Go/NoGo task, were measured before and after the fatigue-inducing phase. A total of 36 undergraduate students (18-22 years) participated in the study and were randomly assigned to the music group and control group. The music group performed the fatigue-inducing task while listening to relaxing music, and the control group performed the same task without any music. Our results revealed that after the fatigue-inducing phase, (a) the music group demonstrated significantly less mental fatigue than control group, (b) reaction time significantly increased for the control group but not for the music group, (c) larger Go-P3 and NoGo-P3 amplitudes were observed in the music group, although larger NoGo-N2 amplitudes were detected for both groups. These results combined to suggest that listening to relaxing music alleviated the mental fatigue associated with performing an enduring cognitive-motor task.

A caffeine-maltodextrin mouth rinse counters mental fatigue.

PubMed

Van Cutsem, Jeroen; De Pauw, Kevin; Marcora, Samuele; Meeusen, Romain; Roelands, Bart

2018-04-01

Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity that has negative implications on many aspects in daily life. Caffeine and carbohydrate ingestion have been shown to be able to reduce these negative effects of mental fatigue. Intake of these substances might however be less desirable in some situations (e.g., restricted caloric intake, Ramadan). Rinsing caffeine or glucose within the mouth has already been shown to improve exercise performance. Therefore, we sought to evaluate the effect of frequent caffeine-maltodextrin (CAF-MALT) mouth rinsing on mental fatigue induced by a prolonged cognitive task. Ten males (age 23 ± 2 years, physical activity 7.3 ± 4.3 h/week, low CAF users) performed two trials. Participants first completed a Flanker task (3 min), then performed a 90-min mentally fatiguing task (Stroop task), followed by another Flanker task. Before the start and after each 12.5% of the Stroop task (eight blocks), subjects received a CAF-MALT mouth rinse (MR: 0.3 g/25 ml CAF: 1.6g/25 ml MALT) or placebo (PLAC: 25 ml artificial saliva). Self-reported mental fatigue was lower in MR (p = 0.017) compared to PLAC. Normalized accuracy (accuracy first block = 100%) was higher in the last block of the Stroop in MR (p = 0.032) compared to PLAC. P2 amplitude in the dorsolateral prefrontal cortex (DLPFC) decreased over time only in PLAC (p = 0.017). Frequent mouth rinsing during a prolonged and demanding cognitive task reduces mental fatigue compared to mouth rinsing with artificial saliva.

Psychosocial correlates of fatigue in multiple sclerosis.

PubMed

Schwartz, C E; Coulthard-Morris, L; Zeng, Q

1996-02-01

To explore: (1) the interrelation among the neuropsychological, psychological, and psychosocial factors and fatigue as measured by the Multidimensional Assessment of Fatigue scale, and (2) the impact of fatigue on role performance. Clinical interview with neuropsychological testing and cross-sectional study by mail. Multiple sclerosis (MS) clinic registry of a large Boston teaching hospital. 139 MS patients representing a broad range of disability. The Multidimensional Assessment of Fatigue (MAF) scale, the Extended Disability Status Scale, the Sickness Impact Profile, Rao cognitive battery, the Trailmaking Test, depression, anxiety, and social activity limitations subscales from the Arthritis Impact Measurement Scales, and the Ryff Happiness Scale. Stepwise multiple regression analyses revealed that having a low sense of environmental mastery was the best psychosocial predictor of both global fatigue and fatigue-related distress, after adjusting for sociodemographic and medical factors. Further, people who reported being more depressed tended to report more severe fatigue. Neuropsychological performance was not associated with fatigue. Fatigue was found to limit social, work, and overall role performance, but not physical role performance. People who feel that they can choose or create environments suitable to their psychic or physical conditions report less global fatigue and less fatigue-related distress, and fatigue can have an important impact on role performance. The implications of these findings for designing fatigue management interventions are discussed.

Combined modality treatment of aromatherapy, footsoak, and reflexology relieves fatigue in patients with cancer.

PubMed

Kohara, Hiroyuki; Miyauchi, Takako; Suehiro, Yoko; Ueoka, Hiroshi; Takeyama, Hiroyasu; Morita, Tatsuya

2004-12-01

Fatigue is one of the most distressful symptoms experienced by patients with advanced cancer. Aromatherapy, footsoak, and reflexology are popular health care modality treatments in Japan, however, the effectiveness of each treatment for cancer-related fatigue has not been fully established. To investigate the effectiveness of combined modality treatment consisting of aromatherapy, footsoak, and reflexology against fatigue, an open study was performed in 20 terminally ill patients with cancer. After a patch test was performed, patients received aromatherapy that was accompanied with footsoak in warm water containing lavender essential oil for 3 minutes, followed by reflexology treatment with jojoba oil containing lavender for 10 min. Fatigue was evaluated using the Cancer Fatigue Scale (CFS) before, 1 hour after, and 4 hours after treatment. Total CFS scores improved significantly after this treatment (from 25.6 +/- 11.0 to 18.1 +/- 10.0, p < 0.001). Among three CFS subscales, physical and cognitive subscale scores were reduced significantly (11.3 +/- 6.1 to 6.7 +/- 6.1, p < 0.001; 4.5 +/- 3.2 to 2.4 +/- 2.4, p < 0.001). No adverse effects were experienced. Because all patients desired to continue this treatment, they received treatment eight times on average. Combined modality treatment consisting of aromatherapy, footsoak, and reflexology appears to be effective for alleviating fatigue in terminally ill cancer patients. To confirm safety and effectiveness of this combined modality treatment, further investigation including randomized treatment assignment is warranted.

Improvements in Depression and Changes in Fatigue: Results from the SLAM DUNC Depression Treatment Trial

PubMed Central

Bengtson, Angela M.; Gaynes, Bradley N.; McGuinness, Teena; Quinlivan, Evelyn B.; Ogle, Michelle; Heine, Amy; Thielman, Nathan M.; Pence, Brian W.

2016-01-01

Fatigue and depression are common co-morbid conditions among people with HIV infection. We analyzed a population of HIV-infected adults with depression, who were enrolled in a depression treatment trial, to examine the extent to which improvements in depression over time were associated with improvements in HIV-related fatigue. Data for this analysis come from a randomized controlled trial to evaluate the effectiveness of improved depression treatment on antiretroviral adherence. Fatigue was measured using the HIV-Related Fatigue Scale, and depressive symptoms were measured with the Hamilton Depression Rating Scale. Participants (n = 234) were on average nearly 44 years of age and predominantly male, black or African American, and unemployed. Individuals who experienced stronger depression response (i.e., greater improvement in depression score) had larger decreases in fatigue. However, even among those who demonstrated a full depression response, nearly three-quarters continued to have either moderate or severe fatigue at 6 and 12 months. PMID:26525221

Effect of aromatherapy via inhalation on the sleep quality and fatigue level in people undergoing hemodialysis.

PubMed

Muz, Gamze; Taşcı, Sultan

2017-10-01

The most common problems in hemodialysis patients are sleep disorders and fatigue. This randomized-controlled experimental study was conducted to determine the effect of aromatherapy applied by inhalation on sleep quality and fatigue level in hemodialysis patients. The study was completed in five hemodialysis centers settled in two provinces with 27 intervention group patients and 35 controls, being totally 62 patients, recruited with simple randomization. Ethical approval, informed consent from the individuals and institutional permission were obtained. Data were collected with a questionnaire form and Visual Analogue Scale (VAS) for fatigue, Piper fatigue scale, Pittsburgh Sleep Quality Index (PSQI), and follow-up forms for the patient and the researcher. Aromatherapy inhalation (sweet orange and lavender oil) was performed before going to bed every day for one month to the intervention group patients. No other application has been made to the control group patients except for standard hemodialysis treatment. All of the forms were performed at baseline and at follow-up at the end of the four weeks (baseline and last follow-up), VAS and Piper fatigue scale were performed during follow-ups at the end of every week (the first, second and third follow-ups). Data were statistically analyzed with Independent Samples t-test, one way analysis of variance, Pearson correlation analysis, chi-square test, Friedman and Mann Whitney U tests and Bonferroni test. p<0.05 was set as statistically significant in comparisons. Mean total and sub-dimension scores of VAS, Piper fatigue scale and PSQI (except for daytime sleepiness dysfunction sub-dimension) of the intervention and control groups at baseline were not significantly different (p>0.05). It was found that mean total and sub-dimension scores of VAS, Piper fatigue scale and PSQI of the intervention group significantly decreased in other follow-ups compared to the control group (p<0.05). Consequently, it was determined that aromatherapy applied by inhalation improved sleep quality, decreased fatigue level and severity in hemodialysis patients. Accordingly, aromatherapy prepared with sweet orange and lavender oil may be recommended to increase sleep quality and to decrease fatigue level of the hemodialysis patients. Copyright © 2017 Elsevier Inc. All rights reserved.

Influence of music on performance and psychophysiological responses during moderate-intensity exercise preceded by fatigue.

PubMed

Lopes-Silva, Joao P; Lima-Silva, Adriano E; Bertuzzi, Romulo; Silva-Cavalcante, Marcos D

2015-02-01

We examined the effects of listening to music on time to exhaustion and psychophysiological responses during moderate-intensity exercise performed in fatigued and non-fatigued conditions. Fourteen healthy men performed moderate-intensity exercise (60% Wmax) until exhaustion under four different conditions: with and without pre-fatigue (induced by 100 drop jumps) and listening and not listening to music. Time to exhaustion was lower in the fatigued than the non-fatigued condition regardless listening to music. Similarly, RPE was higher in the fatigued than the non-fatigued condition, but music had no effect. On the other hand, listening to music decreased the associative thoughts regardless of fatigue status. Heart rate was not influenced by any treatment. These results suggest that listening to music changes attentional focus but is not able to reverse fatigue-derived alteration of performance. Copyright © 2014 Elsevier Inc. All rights reserved.

Short-term effects of black pepper (Piper nigrum) and rosemary (Rosmarinus officinalis and Rosmarinus eriocalyx) on sustained attention and on energy and fatigue mood states in young adults with low energy.

PubMed

Lindheimer, Jacob B; Loy, Bryan D; O'Connor, Patrick J

2013-08-01

The purpose was to test whether a single dose of black pepper or rosemary produced short-term enhancements in sustained attention, motivation to perform cognitive tasks, or feelings of mental energy and fatigue. Outcomes were measured in 40 young adults with below average feelings of energy before and twice after they orally consumed capsules containing either black pepper (2.0 g), rosemary (1.7 g), or a placebo (3.1 g rice flour). Sustained attention was measured using a 16-min dual task, in which, single-digit numbers were presented every second on a screen and the participant performed both a primary task [detection of three successive, different odd digits] and a secondary task [detection of the number 6]. Feelings of energy and fatigue were measured using the vigor and fatigue subscales of the Profile of Mood States and visual analog scales (VAS). Analysis of variance showed nonsignificant condition (spice versus placebo)×time (T1, T2, & T3) effects for motivation, measured with a VAS, and the intensity of energy and fatigue feelings. Unadjusted effect sizes revealed that rosemary induced small, transient reductions in false alarm errors (d=0.21) and mental fatigue (d=0.40) at isolated time periods. Time-varying analysis of covariance, controlling for motivation to perform cognitive tasks, showed no significant effects on the primary or secondary task outcomes of correct responses (hits), errors (false alarms, misses), speed of response (reaction time), and signal detection sensitivity. It is concluded that black pepper and rosemary, consumed in a capsule form, in the doses used and while wearing a nose clip to block olfactory effects, do not induce consistent short-term improvements in sustained attention, motivation to perform cognitive tasks, or feelings of mental energy and fatigue in young adults with low energy.

Elbow Joint Fatigue and Bench-Press Training

PubMed Central

Huang, Yen-Po; Chou, You-Li; Chen, Feng-Chun; Wang, Rong-Tyai; Huang, Ming-Jer; Chou, Paul Pei-Hsi

2014-01-01

Context: Bench-press exercises are among the most common form of training exercise for the upper extremity because they yield a notable improvement in both muscle strength and muscle endurance. The literature contains various investigations into the effects of different bench-press positions on the degree of muscle activation. However, the effects of fatigue on the muscular performance and kinetics of the elbow joint are not understood fully. Objective: To investigate the effects of fatigue on the kinetics and myodynamic performance of the elbow joint in bench-press training. Design: Controlled laboratory study. Setting: Motion research laboratory. Patients or Other Participants: A total of 18 physically healthy male students (age = 19.6 ± 0.8 years, height = 168.7 ± 5.5 cm, mass = 69.6 ± 8.6 kg) participated in the investigation. All participants were right-hand dominant, and none had a history of upper extremity injuries or disorders. Intervention(s): Participants performed bench-press training until fatigued. Main Outcome Measure(s): Maximal possible number of repetitions, cycle time, myodynamic decline rate, elbow-joint force, and elbow-joint moment. Results: We observed a difference in cycle time in the initial (2.1 ± 0.42 seconds) and fatigue (2.58 ± 0.46 seconds) stages of the bench-press exercise (P = .04). As the participants fatigued, we observed an increase in the medial-lateral force (P = .03) and internal-external moment (P ≤ .04) acting on the elbow joint. Moreover, a reduction in the elbow muscle strength was observed in the elbow extension-flexion (P ≤ .003) and forearm supination-pronation (P ≤ .001) conditions. Conclusions: The results suggest that performing bench-press exercises to the point of fatigue increases elbow-joint loading and may further increase the risk of injury. Therefore, when clinicians design bench-press exercise regimens for general athletic training, muscle strengthening, or physical rehabilitation, they should control carefully the maximal number of repetitions. PMID:24533529

Characterization and analysis of surface notches on Ti-alloy plates fabricated by additive manufacturing techniques

NASA Astrophysics Data System (ADS)

Chan, Kwai S.

2015-12-01

Rectangular plates of Ti-6Al-4V with extra low interstitial (ELI) were fabricated by layer-by-layer deposition techniques that included electron beam melting (EBM) and laser beam melting (LBM). The surface conditions of these plates were characterized using x-ray micro-computed tomography. The depth and radius of surface notch-like features on the LBM and EBM plates were measured from sectional images of individual virtual slices of the rectangular plates. The stress concentration factors of individual surface notches were computed and analyzed statistically to determine the appropriate distributions for the notch depth, notch radius, and stress concentration factor. These results were correlated with the fatigue life of the Ti-6Al-4V ELI alloys from an earlier investigation. A surface notch analysis was performed to assess the debit in the fatigue strength due to the surface notches. The assessment revealed that the fatigue lives of the additively manufactured plates with rough surface topographies and notch-like features are dominated by the fatigue crack growth of large cracks for both the LBM and EBM materials. The fatigue strength reduction due to the surface notches can be as large as 60%-75%. It is concluded that for better fatigue performance, the surface notches on EBM and LBM materials need to be removed by machining and the surface roughness be improved to a surface finish of about 1 μm.

Effects of processing on the transverse fatigue properties of low-sulfur AISI 4140 steel

NASA Astrophysics Data System (ADS)

Collins, Sunniva R.; Michal, Gary M.

1993-12-01

The effects of inclusions due to steelmaking processes on the fatigue life of AISI 4140 have been investigated. The test matrix consisted of three commercially produced heats of AISI 4140 of comparable cleanliness: one was conventionally cast (CC), and two were inert gas-shielded/ bottom-poured (IGS). One of the IGS heats was calcium-treated to explore the effects of inclusion shape control (IGS/SC). All heats were hot-rolled and reduced over 95 pct to produce bar stock of 127 to 152 mm (5 to 6 in.) in diameter. Transverse axial specimens conforming to ASTM E466 were machined, quenched, and tempered to approximately 40 HRC, and they were fatigue tested in tension-tension cycling ( R = 0.1). Test results and statistical analyses of the stress-life data show that the IGS grade has several times the fatigue strength of the CC grade at 107 cycles. Lower-limit fatigue strengths calculated at a 99.9 pct probability were 518.5 MPa (75.2 ksi) for IGS vs 55.6 MPa (8.1 ksi) for the CC grade. The IGS/SC grade had the best performance at all stress and life levels. The results obtained indicate that fatigue performance can be improved by choosing a processing method that reduces the incidence of exogenous oxides and by controlling the shape of the sulfides.

The effects of cockpit environment on long-term pilot performance

NASA Technical Reports Server (NTRS)

Stave, A. M.

1977-01-01

A fixed-base helicopter simulator was used to examine pilot performance as influenced by noise, vibration, and fatigue. Subjects flew the simulator for periods ranging between three and eight hours while exposed to vibrations (at 17 Hz) ranging from 0.1 to 0.3 g, and noise stimuli varying between 74 (ambient) and 100 dB. Despite reports of extreme fatigue on these long flights, subject performance did not degrade. Within the limits of this study, performance tended to improve as environmental stress increased. However, subjects did suffer from lapses resulting in abnormally poor performance. These lapses are probably of short duration (seconds) and occur at unpredictable times. If such lapses occur in actual flight, they could provide an explanation for many so-called 'pilot error' accidents.

Fatigue resistance, electrochemical corrosion and biological response of Ti-15Mo with surface modified by amorphous TiO2 nanotubes layer.

PubMed

Campanelli, Leonardo C; Oliveira, Nilson T C; da Silva, Paulo Sergio C P; Bolfarini, Claudemiro; Palmieri, Annalisa; Cura, Francesca; Carinci, Francesco; Motheo, Artur J

2018-03-04

The objective of this work was a systemic evaluation of the anodizing treatment in a β-type Ti-15Mo alloy to grow a TiO 2 nanostructured layer for osseointegration improvement. The technical viability of the surface modification was assessed based on the resistance to mechanical fatigue, electrochemical corrosion, and biological response. By using an organic solution of NH 4 F in ethylene glycol, a well-organized array of 90 nm diameter nanotubes was obtained with a potential of 40 V for 6 h, while undefined nanotubes of 25 nm diameter were formed with a potential of 20 V for 1 h. Nevertheless, the production of the 90 nm diameter nanotubes was followed by micrometer pits that significantly reduced the fatigue performance. The undefined nanotubes of 25 nm diameter, besides the greater cell viability and improved osteoblastic cell differentiation in comparison to the as-polished surface, were not deleterious to the fatigue and corrosion properties. This result strengthens the necessity of an overall evaluation of the anodizing treatment, particularly the fatigue resistance, before suggesting it for the design of implants. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

A randomized controlled trial on the effects of combined aerobic-resistance exercise on muscle strength and fatigue, glycemic control and health-related quality of life of type 2 diabetes patients.

PubMed

Tomas-Carus, Pablo; Ortega-Alonso, Alfredo; Pietilainen, Kirsi H; Santos, Vitoria; Goncalves, Helena; Ramos, Jorge; Raimundo, Armando

2016-05-01

The aim of this paper was to evaluate the effects of a 12-weeks combined aerobic-resistance exercise therapy on fatigue and isokinetic muscle strength, glycemic control and health-related quality of life (HRQoL) in moderately affected type 2 diabetes (T2DM) patients. A randomized controlled trial design was employed. Forty-three T2DM patients were assigned to an exercise group (N.=22), performing 3 weekly sessions of 60 minutes of combined aerobic-resistance exercise for 12-weeks; or a no exercise control group (N.=21). Both groups were evaluated at a baseline and after 12-weeks of exercise therapy for: 1) muscle strength and fatigue by isokinetic dynamometry; 2) plasma glycated hemoglobin A1C (HbA1C); and 3) HRQoL utilizing the SF-36 questionnaire. The exercise therapy led to improvements in muscle fatigue in knee extensors (-55%) and increased muscle strength in knee flexors and extensors (+15 to +30%), while HbA1C decreased (-18%). In addition, the exercising patients showed sizeable improvements in HRQoL: physical function (+53%), vitality (+21%) and mental health (+40%). Twelve-weeks of combined aerobic-resistance exercise was highly effective to improve muscle strength and fatigue, glycemic control and several aspects of HRQoL in T2DM patients. These data encourage the use of aerobic and resistance exercise in the good clinical care of T2DM.

Randomized Evaluation of Cognitive-Behavioral Therapy and Graded Exercise Therapy for Post-Cancer Fatigue.

PubMed

Sandler, Carolina X; Goldstein, David; Horsfield, Sarah; Bennett, Barbara K; Friedlander, Michael; Bastick, Patricia A; Lewis, Craig R; Segelov, Eva; Boyle, Frances M; Chin, Melvin T M; Webber, Kate; Barry, Benjamin K; Lloyd, Andrew R

2017-07-01

Cancer-related fatigue is prevalent and disabling. When persistent and unexplained, it is termed post-cancer fatigue (PCF). Cognitive behavioral therapy (CBT) and graded exercise therapy (GET) may improve symptoms and functional outcomes. To evaluate the outcomes of a randomized controlled trial, which assigned patients with post-cancer fatigue to education, or 12 weeks of integrated cognitive-behavioral therapy (CBT) and graded exercise therapy (GET). Three months after treatment for breast or colon cancer, eligible patients had clinically significant fatigue, no comorbid medical or psychiatric conditions that explained the fatigue, and no evidence of recurrence. The CBT/GET arm included individually tailored consultations at approximately two weekly intervals. The education arm included a single visit with clinicians describing the principles of CBT/GET and a booklet. The primary outcome was clinically significant improvement in self-reported fatigue (Somatic and Psychological HEalth REport 0-12), designated a priori as greater than one SD of improvement in fatigue score. The secondary outcome was associated improvement in function (role limitation due to physical health problems-36-Item Short Form Health Survey 0-100) comparing baseline, end treatment (12 weeks), and follow-up (24 weeks). There were 46 patients enrolled, including 43 women (94%), with a mean age of 51 years. Fatigue severity improved in all subjects from a mean of 5.2 (±3.1) at baseline to 3.9 (±2.8) at 12 weeks, suggesting a natural history of improvement. Clinically significant improvement was observed in 7 of 22 subjects in the intervention group compared with 2 of 24 in the education group (P < 0.05, χ 2 ). These subjects also had improvement in functional status compared with nonresponders (P < 0.01, t-test). Combined CBT/GET improves fatigue and functional outcomes for a subset of patients with post-cancer fatigue. Further studies to improve the response rate and the magnitude of the benefit are warranted. Copyright © 2017 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.

Reliability Quantification of the Flexure: A Critical Stirling Convertor Component

NASA Technical Reports Server (NTRS)

Shah, Ashwin R.; Korovaichuk, Igor; Zampino, Edward J.

2004-01-01

Uncertainties in the manufacturing, fabrication process, material behavior, loads, and boundary conditions results in the variation of the stresses and strains induced in the flexures and its fatigue life. Past experience and the test data at material coupon levels revealed a significant amount of scatter of the fatigue life. Owing to these facts, the design of the flexure, using conventional approaches based on safety factor or traditional reliability based on similar equipment considerations does not provide a direct measure of reliability. Additionally, it may not be feasible to run actual long term fatigue tests due to cost and time constraints. Therefore it is difficult to ascertain material fatigue strength limit. The objective of the paper is to present a methodology and quantified results of numerical simulation for the reliability of flexures used in the Stirling convertor for their structural performance. The proposed approach is based on application of finite element analysis method in combination with the random fatigue limit model, which includes uncertainties in material fatigue life. Additionally, sensitivity of fatigue life reliability to the design variables is quantified and its use to develop guidelines to improve design, manufacturing, quality control and inspection design process is described.

Effects of Person-Centered Physical Therapy on Fatigue-Related Variables in Persons With Rheumatoid Arthritis: A Randomized Controlled Trial.

PubMed

Feldthusen, Caroline; Dean, Elizabeth; Forsblad-d'Elia, Helena; Mannerkorpi, Kaisa

2016-01-01

To examine effects of person-centered physical therapy on fatigue and related variables in persons with rheumatoid arthritis (RA). Randomized controlled trial. Hospital outpatient rheumatology clinic. Persons with RA aged 20 to 65 years (N=70): intervention group (n=36) and reference group (n=34). The 12-week intervention, with 6-month follow-up, focused on partnership between participant and physical therapist and tailored health-enhancing physical activity and balancing life activities. The reference group continued with regular activities; both groups received usual health care. Primary outcome was general fatigue (visual analog scale). Secondary outcomes included multidimensional fatigue (Bristol Rheumatoid Arthritis Fatigue Multi-Dimensional Questionnaire) and fatigue-related variables (ie, disease, health, function). At posttest, general fatigue improved more in the intervention group than the reference group (P=.042). Improvement in median general fatigue reached minimal clinically important differences between and within groups at posttest and follow-up. Improvement was also observed for anxiety (P=.0099), and trends toward improvements were observed for most multidimensional aspects of fatigue (P=.023-.048), leg strength/endurance (P=.024), and physical activity (P=.023). Compared with the reference group at follow-up, the intervention group improvement was observed for leg strength/endurance (P=.001), and the trends toward improvements persisted for physical (P=.041) and living-related (P=.031) aspects of fatigue, physical activity (P=.019), anxiety (P=.015), self-rated health (P=.010), and self-efficacy (P=.046). Person-centered physical therapy focused on health-enhancing physical activity and balancing life activities showed significant benefits on fatigue in persons with RA. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Experimental Evaluation of Fatigue Crack Initiation from Corroded Hemispherical Notches in Aerospace Structural Materials

NASA Technical Reports Server (NTRS)

Garcia, Daniel B.; Forman, Royce; Shindo, David

2010-01-01

A test program was developed and executed to evaluate the influence of corroded hemispherical notches on the fatigue crack initiation and propagation in aluminum 7075-T7351, 4340 steel, and D6AC steel. Surface enhancements such as shot peening and laser shock peening were also incorporated as part of the test effort with the intent of improving fatigue performance. In addition to the testing, fracture mechanics and endurance limit based analysis methods were evaluated to characterize the results with the objective of challenging typical assumptions used in modeling fatigue cracks from corrosion pits. The results specifically demonstrate that the aluminum and steel alloys behave differently with respect to fatigue crack initiation from hemispherical corrosion pits. The aluminum test results were bounded by the fracture mechanics and endurance limit models while exhibiting a general insensitivity to the residual stress field generated by shot peening. The steel specimens were better characterized by the endurance limit fatigue properties and did exhibit sensitivities to residual stresses from the shot peening and laser shock peening

[Effects of self-foot reflexology on stress, fatigue and blood circulation in premenopausal middle-aged women].

PubMed

Jang, Soo Hyun; Kim, Kye Ha

2009-10-01

This study was to examine the effects of self-foot reflexology on stress, fatigue and blood circulation in premenopausal middle-aged women. A quasi-experimental nonequivalent control group, pretest-posttest design was used. Participants were 59 premenopausal, middle-aged women in their 40s and 60s living in G city: 30 in the experiment group and 29 in the control group. Data were collected from May to August 2008. Self-foot reflexology was performed three times a week for 6 weeks for 40 min at each session. The results showed that self-foot reflexology was effective in reducing perceived stress and fatigue and helped blood circulation in premenopausal middle-aged women. Self-foot reflexology may be an effective nursing intervention in reducing perceived stress and fatigue and in improving blood circulation.

A 3-week multimodal intervention involving high-intensity interval training in female cancer survivors: a randomized controlled trial.

PubMed

Schmitt, Joachim; Lindner, Nathalie; Reuss-Borst, Monika; Holmberg, Hans-Christer; Sperlich, Billy

2016-02-01

To compare the effects of a 3-week multimodal rehabilitation involving supervised high-intensity interval training (HIIT) on female breast cancer survivors with respect to key variables of aerobic fitness, body composition, energy expenditure, cancer-related fatigue, and quality of life to those of a standard multimodal rehabilitation program. A randomized controlled trial design was administered. Twenty-eight women, who had been treated for cancer were randomly assigned to either a group performing exercise of low-to-moderate intensity (LMIE; n = 14) or a group performing high-intensity interval training (HIIT; n = 14) as part of a 3-week multimodal rehabilitation program. No adverse events related to the exercise were reported. Work economy improved following both HIIT and LMIE, with improved peak oxygen uptake following LMIE. HIIT reduced mean total body fat mass with no change in body mass, muscle or fat-free mass (best P < 0.06). LMIE increased muscle and total fat-free body mass. Total energy expenditure (P = 0.45) did not change between the groups, whereas both improved quality of life to a similar high extent and lessened cancer-related fatigue. This randomized controlled study demonstrates that HIIT can be performed by female cancer survivors without adverse health effects. Here, HIIT and LMIE both improved work economy, quality of life and cancer-related fatigue, body composition or energy expenditure. Since the outcomes were similar, but HIIT takes less time, this may be a time-efficient strategy for improving certain aspects of the health of female cancer survivors. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

High Performance Skiing. How to Become a Better Alpine Skier.

ERIC Educational Resources Information Center

Yacenda, John

This book is intended for people who desire to improve their skiing by exploring high performance techniques leading to: (1) more consistent performance; (2) less fatigue and more endurance; (3) greater strength and flexibility; (4) greater versatility; (5) greater confidence in all skiing conditions; and (6) the knowledge to participate in…

Intermittent Theta Burst Over M1 May Increase Peak Power of a Wingate Anaerobic Test and Prevent the Reduction of Voluntary Activation Measured with Transcranial Magnetic Stimulation

PubMed Central

Giboin, Louis-Solal; Thumm, Patrick; Bertschinger, Raphael; Gruber, Markus

2016-01-01

Despite the potential of repetitive transcranial magnetic stimulation (rTMS) to improve performances in patients suffering from motor neuronal afflictions, its effect on motor performance enhancement in healthy subjects during a specific sport task is still unknown. We hypothesized that after an intermittent theta burst (iTBS) treatment, performance during the Wingate Anaerobic Test (WAnT) will increase and supraspinal fatigue following the exercise will be lower in comparison to a control treatment. Ten subjects participated in two randomized experiments consisting of a WAnT 5 min after either an iTBS or a control treatment. We determined voluntary activation (VA) of the right knee extensors with TMS (VATMS) and with peripheral nerve stimulation (VAPNS) of the femoral nerve, before and after the WAnT. T-tests were applied to the WAnT results and a two way within subject ANOVA was applied to VA results. The iTBS treatment increased the peak power and the maximum pedalling cadence and suppressed the reduction of VATMS following the WAnT compared to the control treatment. No behavioral changes related to fatigue (mean power and fatigue index) were observed. These results indicate for the first time that iTBS could be used as a potential intervention to improve anaerobic performance in a sport specific task. PMID:27486391

Intermittent Theta Burst Over M1 May Increase Peak Power of a Wingate Anaerobic Test and Prevent the Reduction of Voluntary Activation Measured with Transcranial Magnetic Stimulation.

PubMed

Giboin, Louis-Solal; Thumm, Patrick; Bertschinger, Raphael; Gruber, Markus

2016-01-01

Despite the potential of repetitive transcranial magnetic stimulation (rTMS) to improve performances in patients suffering from motor neuronal afflictions, its effect on motor performance enhancement in healthy subjects during a specific sport task is still unknown. We hypothesized that after an intermittent theta burst (iTBS) treatment, performance during the Wingate Anaerobic Test (WAnT) will increase and supraspinal fatigue following the exercise will be lower in comparison to a control treatment. Ten subjects participated in two randomized experiments consisting of a WAnT 5 min after either an iTBS or a control treatment. We determined voluntary activation (VA) of the right knee extensors with TMS (VATMS) and with peripheral nerve stimulation (VAPNS) of the femoral nerve, before and after the WAnT. T-tests were applied to the WAnT results and a two way within subject ANOVA was applied to VA results. The iTBS treatment increased the peak power and the maximum pedalling cadence and suppressed the reduction of VATMS following the WAnT compared to the control treatment. No behavioral changes related to fatigue (mean power and fatigue index) were observed. These results indicate for the first time that iTBS could be used as a potential intervention to improve anaerobic performance in a sport specific task.

Description of a multifaceted intervention programme for fatigue after acquired brain injury: a pilot study.

PubMed

Stubberud, Jan; Edvardsen, Espen; Schanke, Anne-Kristine; Lerdal, Anners; Kjeverud, Anita; Schillinger, Andreas; Løvstad, Marianne

2017-07-05

The purpose of this pilot study was to describe and explore a group-based multifaceted intervention for patients with fatigue after acquired brain injury (ABI). We hypothesised that post-intervention changes would result in reduced fatigue, in addition to improved emotional health, sleep and attentional control. Eight subjects with traumatic brain injury (n = 3) and cerebrovascular insults (n = 5) were included. Inclusion was based upon the presence of fatigue complaints. The participants received 36 hours of intervention. Changes related to fatigue, emotional health and sleep was assessed with self-rating measures. Additionally, a neuropsychological test (Conners' Continuous Performance Test II) was included as a measure of attentional control. All subjects were assessed at baseline, post-intervention, and at 3 and 9 months follow-up. Findings indicated reduced fatigue levels (post-intervention and 3 months follow-up), anxiety (9 months follow-up), and daytime sleepiness (3 and 9 months follow-up). Pilot results suggest that multifaceted group-based interventions may have the potential to alleviate symptoms of fatigue, anxiety and sleepiness after ABI. At an individual level, a low load of psychological distress, insomnia symptoms, dysexecutive symptoms, in addition to a strong sense of self-efficacy, may be central in order to reduce levels of fatigue.

Impact of Fatigue in Rheumatic Diseases in the Work Environment: A Qualitative Study

PubMed Central

Connolly, Deirdre; Fitzpatrick, Clodagh; O’Toole, Lynn; Doran, Michele; O’Shea, Finbar

2015-01-01

Fatigue is a symptom of arthritis that causes difficulty at work. An improved understanding of this symptom could assist its management in the work environment. The aim of this study was to explore people with rheumatic diseases’ experiences of fatigue in work. A qualitative descriptive design was used with semi-structured interviews and a constant comparative method of data analysis. There were 18 participants, the majority of them female with Rheumatoid Arthritis (RA) and working full-time. Three themes were identified: “Impact of fatigue on work performance” with cognition, mood and physical abilities being the main difficulties reported. In the second theme “Disclosure at Work” participants discussed disclosing their disease to employers but reported a lack of understanding of fatigue from colleagues. The final theme “work-based fatigue management strategies” included cognitive strategies and energy management techniques, which were mainly self-taught. In this study, fatigue was reported to impact on many areas of work performance with limited understanding from colleagues and employers. Interventions from health professionals to assist with development of work-related self-management skills are required to assist with symptom management in the work place. Such interventions should include education to employers and colleagues on the nature of fatigue in Rheumatic diseases. PMID:26516896

Assessment of the microstructure and torsional fatigue performance of an induction hardened vanadium microalloyed medium-carbon steel

NASA Astrophysics Data System (ADS)

Rothleutner, Lee M.

Vanadium microalloying of medium-carbon bar steels is a common practice in industry for a number of hot rolled as well as forged and controlled-cooled components. However, use of vanadium microalloyed steels has expanded into applications beyond their originally designed controlled-cooled processing scheme. Applications such as transmission shafts often require additional heat-treatments such as quench and tempering and/or induction hardening to meet packaging or performance requirements. As a result, there is uncertainty regarding the influence of vanadium on the properties of heat-treated components, specifically the effect of rapid heat-treating such as induction hardening. In the current study, the microstructural evolution and torsional fatigue behavior of induction hardened 1045 and 10V45 (0.08 wt pct V) steels were examined. Torsional fatigue specimens specifically designed for this research were machined from the as-received, hot rolled bars and induction hardened using both scanning (96 kHz/72 kW) and single-shot (31 kHz/128 kW) methods. Four conditions were evaluated, three scan hardened to 25, 32, and 44 pct nominal effective case depths and one single-shot hardened to 44 pct. Torsional fatigue tests were conducted at a stress ratio of 0.1 and shear stress amplitudes of 550, 600, and 650 MPa. Physical simulations using the thermal profiles from select induction hardened conditions were conducted in the GleebleRTM 3500 to augment microstructural analysis of torsional fatigue specimens. Thermal profiles were calculated by a collaborating private company using electro-thermal finite element analysis. Residual stresses were evaluated for all conditions using a strain gage hole drilling technique. The results showed that vanadium microalloying has an influence on the microstructure in the highest hardness region of the induction-hardened case as well as the total case region. Vanadium microalloyed conditions consistently exhibited a greater amount of non-martensitic transformation products in the induction-hardened case. In the total case region, vanadium reduced the total case depth by inhibiting austenite formation at low austenitizing temperatures; however, the non-martensitic constituents in the case microstructure and the reduced total case depth of the vanadium microalloyed steel did not translate directly to a degradation of torsional fatigue properties. In general, vanadium microalloying was not found to affect torsional fatigue performance significantly with one exception. In the 25 pct effective case depth condition, the 10V45 steel had a ~75 pct increase in fatigue life at all shear stress amplitudes when compared to the 1045 steel. The improved fatigue performance is likely a result of the significantly higher case hardness this condition exhibited compared to all other conditions. The direct influence of vanadium on the improved fatigue life of the 25 pct effective case depth condition is confounded with the slightly higher carbon content of the 10V45 steel. In addition, the 10V45 conditions showed a consistently higher case hardness than the in 1045 conditions. The increased hardness of the 10V45 steel did not increase the compressive residual stresses at the surface. Induction hardening parameters were more closely related to changes in residual stress than vanadium microalloying additions. Torsional fatigue data from the current study as well as from literature were used to develop an empirical multiple linear regression model that accounts for case depth as well as carbon content when predicting torsional fatigue life of induction hardened medium-carbon steels.

Cognitive and Physical Fatigue Tasks Enhance Pain, Cognitive Fatigue and Physical Fatigue in People with Fibromyalgia

PubMed Central

Dailey, Dana L; Keffala, Valerie J; Sluka, Kathleen A

2014-01-01

Objective Fibromyalgia is a condition characterized by chronic widespread muscle pain and fatigue. The primary objective of this study was to determine if pain, perceived cognitive fatigue, and perceived physical fatigue were enhanced in participants with fibromyalgia compared to healthy controls during a cognitive fatigue task, a physical fatigue task and a dual fatigue task. Methods Twenty four people with fibromyalgia and 33 healthy controls completed pain, fatigue and function measures. A cognitive fatigue task (Controlled Oral Word Association Test) and physical fatigue task (Valpar peg test) were done individually and combined for a dual fatigue task. Resting pain, perceived cognitive fatigue and perceived physical fatigue were assessed during each task using visual analogue scales. Function was assessed with shoulder range of motion and grip. Results People with fibromyalgia had significantly higher increases in pain, cognitive fatigue and physical fatigue when compared to healthy controls after completion of a cognitive fatigue task, a physical fatigue task, or a dual fatigue task (p<0.01). People with fibromyalgia performed equivalently on measures of physical performance and cognitive performance on the physical and cognitive fatigue tasks, respectively. Conclusions These data show that people with fibromyalgia show larger increases in pain, perceived cognitive fatigue and perceived physical fatigue to both cognitive and physical fatigue tasks compared to healthy controls. The increases in pain and fatigue during cognitive and physical fatigue tasks could influence subject participation in daily activities and rehabilitation. PMID:25074583

Environmental Barrier Coating Development for SiC/SiC Ceramic Matrix Composites: Recent Advances and Future Directions

NASA Technical Reports Server (NTRS)

Zhu, Dongming

2016-01-01

This presentation briefly reviews the SiC/SiC major environmental and environment-fatigue degradations encountered in simulated turbine combustion environments, and thus NASA environmental barrier coating system evolution for protecting the SiC/SiC Ceramic Matrix Composites for meeting the engine performance requirements. The presentation will review several generations of NASA EBC materials systems, EBC-CMC component system technologies for SiC/SiC ceramic matrix composite combustors and turbine airfoils, highlighting the temperature capability and durability improvements in simulated engine high heat flux, high pressure, high velocity, and with mechanical creep and fatigue loading conditions. This paper will also focus on the performance requirements and design considerations of environmental barrier coatings for next generation turbine engine applications. The current development emphasis is placed on advanced NASA candidate environmental barrier coating systems for SiC/SiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. The efforts have been also directed to developing prime-reliant, self-healing 2700F EBC bond coat; and high stability, lower thermal conductivity, and durable EBC top coats. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, erosion-impact resistance, and long-term fatigue-environment system durability performance will be described. The research and development opportunities for turbine engine environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling will be briefly discussed.

N-acetylcysteine inhibits muscle fatigue in humans.

PubMed Central

Reid, M B; Stokić, D S; Koch, S M; Khawli, F A; Leis, A A

1994-01-01

N-acetylcysteine (NAC) is a nonspecific antioxidant that selectively inhibits acute fatigue of rodent skeletal muscle stimulated at low (but not high) tetanic frequencies and that decreases contractile function of unfatigued muscle in a dose-dependent manner. The present experiments test the hypothesis that NAC pretreatment can inhibit acute muscular fatigue in humans. Healthy volunteers were studied on two occasions each. Subjects were pretreated with NAC 150 mg/kg or 5% dextrose in water by intravenous infusion. The subject then sat in a chair with surface electrodes positioned over the motor point of tibialis anterior, an ankle dorsiflexor of mixed-fiber composition. The muscle was stimulated to contract electrically (40-55 mA, 0.2-ms pulses) and force production was measured. Function of the unfatigued muscle was assessed by measuring the forces produced during maximal voluntary contractions (MVC) of ankle dorsiflexor muscle groups and during electrical stimulation of tibialis anterior at 1, 10, 20, 40, 80, and 120 Hz (protocol 1). Fatigue was produced using repetitive tetanic stimulations at 10 Hz (protocol 1) or 40 Hz (protocol 2); intermittent stimulations subsequently were used to monitor recovery from fatigue. The contralateral leg then was studied using the same protocol. Pretreatment with NAC did not alter the function of unfatigued muscle; MVC performance and the force-frequency relationship of tibialis anterior were unchanged. During fatiguing contractions stimulated at 10 Hz, NAC increased force output by approximately 15% (P < 0.0001), an effect that was evident after 3 min of repetitive contraction (P < 0.0125) and persisted throughout the 30-min protocol. NAC had no effect on fatigue induced using 40 Hz stimuli or on recovery from fatigue. N-acetylcysteine pretreatment can improve performance of human limb muscle during fatiguing exercise, suggesting that oxidative stress plays a causal role in the fatigue process and identifying antioxidant therapy as a novel intervention that may be useful clinically. PMID:7989604

Fatigue life characterization of Superpave mixtures at the Virginia Smart Road.

DOT National Transportation Integrated Search

2005-01-01

Laboratory fatigue testing was performed on six Superpave HMA mixtures in use at the Virginia Smart Road. Evaluation of the applied strain and resulting fatigue life was performed to fit regressions to predict the fatigue performance of each mixture....

Mental versus physical fatigue after subarachnoid hemorrhage: differential associations with outcome.

PubMed

Buunk, Anne M; Groen, Rob J M; Wijbenga, Rianne A; Ziengs, Aaltje L; Metzemaekers, Jan D M; van Dijk, J Marc C; Spikman, Jacoba M

2018-06-20

Fatigue is a major consequence of subarachnoid hemorrhage (SAH), but the specific characteristics are unclear. Our objective was to investigate the nature of post-SAH fatigue (mental or physical) and to determine the relationship with functional outcome in the chronic stage. Also, the possible influence of mood disorders and acute SAH-related factors (SAH type and external cerebrospinal fluid (CSF) drainage) on the presence of fatigue was investigated. Patients with an aneurysmal SAH (aSAH) or angiographically negative SAH (anSAH) were assessed 3 to 10 years post-SAH (N = 221). Questionnaires were used to investigate mental and physical fatigue and mood. Functional outcome was examined with the Glasgow Outcome Scale Extended (GOSE). Between-group comparisons and binary logistic regression analysis were performed. Frequencies of mental and physical fatigue were 48.4% and 38.5% respectively, with prevalence of mental fatigue being significantly higher. A two-way ANOVA with SAH type and external CSF drainage as independent variables and mental fatigue as dependent variable, showed a significant main effect of CSF drainage only (p < 0.001). Only mental fatigue explained a significant part of the variance in long-term functional outcome (Model χ 2 = 52.99, p < 0.001; Nagelkerke R² = 0.32). Mental fatigue after SAH is a serious burden to the patient and is associated with impaired long-term functional outcome. Distinguishing different aspects of fatigue is relevant as mental post-SAH fatigue might be a target for treatment aimed to improve long-term outcome. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

PubMed Central

Daneshmandi, H.; Ghaem, H.; Alhamd, M.; Fakherpour, A.

2017-01-01

Summary Introduction. Work-related Musculoskeletal Disorders (WMSDs) can impact on fatigue and productivity of office workers. This study aimed to investigate the effect of musculoskeletal problems on fatigue and productivity among office personnel. Methods. This study was performed on 101 Iranian office workers. Data were gathered through a demographic questionnaire, Nordic Musculoskeletal Questionnaire, Numeric Rating Scale, Persian version of Multidimensional Assessment of Fatigue Scale, and Persian version of Health and Work Questionnaire. Results. The results revealed that the highest prevalence rates of musculoskeletal symptoms in the past week were related to neck (41.6%), lower back (41.6%), and shoulders (40.6%). The mean score of discomfort/pain was 1.67, 1.55, and 1.31 in the neck, lower back, and shoulders, respectively. Additionally, the severity of discomfort/pain in neck, shoulders, lower back, and thighs was correlated to total fatigue. The severity of discomfort/pain in neck, lower back, buttock, and thighs was also correlated to the concentration/focus subscale of productivity. Conclusions. Improvement of working conditions is suggested to reduce musculoskeletal problems and fatigue and enhance productivity. PMID:29123372

Life prediction technologies for aeronautical propulsion systems

NASA Technical Reports Server (NTRS)

Mcgaw, Michael A.

1987-01-01

Fatigue and fracture problems continue to occur in aeronautical gas turbine engines. Components whose useful life is limited by these failure modes include turbine hot-section blades, vanes and disks. Safety considerations dictate that catastrophic failures be avoided, while economic considerations dictate that noncatastrophic failures occur as infrequently as possible. The design decision is therefore in making the tradeoff between engine performance and durability. The NASA Lewis Research Center has contributed to the aeropropulsion industry in the areas of life prediction technology for 30 years, developing creep and fatigue life prediction methodologies for hot-section materials. Emphasis is placed on the development of methods capable of handling both thermal and mechanical fatigue under severe environments. Recent accomplishments include the development of more accurate creep-fatigue life prediction methods such as the total strain version of Lewis' Strainrange Partitioning (SRP) and the HOST-developed Cyclic Damage Accumulation (CDA) model. Other examples include the Double Damage Curve Approach (DDCA), which provides greatly improved accuracy for cumulative fatigue design rules.

New PDC cutters improve drilling efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mensa-Wilmot, G.

1997-10-27

New polycrystalline diamond compact (PDC) cutters increase penetration rates and cumulative footage through improved abrasion, impact, interface strength, thermal stability, and fatigue characteristics. Studies of formation characterization, vibration analysis, hydraulic layouts, and bit selection continue to improve and expand PDC bit applications. The paper discusses development philosophy, performance characteristics and requirements, Types A, B, and C cutters, and combinations.

Cognitive behavioural therapy for MS-related fatigue explained: A longitudinal mediation analysis.

PubMed

van den Akker, L E; Beckerman, H; Collette, E H; Knoop, H; Bleijenberg, G; Twisk, J W; Dekker, J; de Groot, V

2018-03-01

Cognitive behavioural therapy (CBT) effectively reduces fatigue directly following treatment in patients with Multiple Sclerosis (MS), but little is known about the process of change during and after CBT. Additional analysis of a randomized clinical trial. To investigate which psychological factors mediate change in fatigue during and after CBT. TREFAMS-CBT studied the effectiveness of a 16-week CBT treatment for MS-related fatigue. Ninety-one patients were randomized (44 to CBT, 47 to the MS-nurse consultations). Mediation during CBT treatment was studied using assessments at baseline, 8 and 16weeks. Mediation of the change in fatigue from post-treatment to follow-up was studied separately using assessments at 16, 26 and 52weeks. Proposed mediators were: changes in illness cognitions, general self-efficacy, coping styles, daytime sleepiness, concentration and physical activity, fear of disease progression, fatigue perceptions, depression and physical functioning. Mediators were separately analysed according to the product-of-coefficients approach. Confidence intervals were calculated with a bootstrap procedure. During treatment the decrease in fatigue brought on by CBT was mediated by improved fatigue perceptions, increased physical activity, less sleepiness, less helplessness, and improved physical functioning. Post-treatment increases in fatigue levels were mediated by reduced physical activity, reduced concentration, and increased sleepiness. These results suggests that focusing on improving fatigue perceptions, perceived physical activity, daytime sleepiness, helplessness, and physical functioning may further improve the effectiveness of CBT for fatigue in patients with MS. Maintenance of treatment effects may be obtained by focusing on improving physical activity, concentration and sleepiness. Copyright © 2018 Elsevier Inc. All rights reserved.

Performance of FRCM strengthened beams subject to fatigue.

DOT National Transportation Integrated Search

2017-05-31

Fabric Reinforced Cementitious Matrix (FRCM) systems have been developed to strengthen or rehabilitate existing concrete and masonry structures subject to damage, steel reinforcement corrosion or requiring resistance capacity improvements due to incr...

Transmission Bearing Damage Detection Using Decision Fusion Analysis

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Lewicki, David G.; Decker, Harry J.

2004-01-01

A diagnostic tool was developed for detecting fatigue damage to rolling element bearings in an OH-58 main rotor transmission. Two different monitoring technologies, oil debris analysis and vibration, were integrated using data fusion into a health monitoring system for detecting bearing surface fatigue pitting damage. This integrated system showed improved detection and decision-making capabilities as compared to using individual monitoring technologies. This diagnostic tool was evaluated by collecting vibration and oil debris data from tests performed in the NASA Glenn 500 hp Helicopter Transmission Test Stand. Data was collected during experiments performed in this test rig when two unanticipated bearing failures occurred. Results show that combining the vibration and oil debris measurement technologies improves the detection of pitting damage on spiral bevel gears duplex ball bearings and spiral bevel pinion triplex ball bearings in a main rotor transmission.

Short-duration beta-alanine supplementation increases training volume and reduces subjective feelings of fatigue in college football players.

PubMed

Hoffman, Jay R; Ratamess, Nicholas A; Faigenbaum, Avery D; Ross, Ryan; Kang, Jie; Stout, Jeffrey R; Wise, John A

2008-01-01

The purpose of this study was to examine the effect of 30 days of beta-alanine supplementation in collegiate football players on anaerobic performance measures. Subjects were randomly divided into a supplement (beta-alanine group [BA], 4.5 g x d(-1) of beta-alanine) or placebo (placebo group [P], 4.5 g x d(-1) of maltodextrin) group. Supplementation began 3 weeks before preseason football training camp and continued for an additional 9 days during camp. Performance measures included a 60-second Wingate anaerobic power test and 3 line drills (200-yd shuttle runs with a 2-minute rest between sprints) assessed on day 1 of training camp. Training logs recorded resistance training volumes, and subjects completed questionnaires on subjective feelings of soreness, fatigue, and practice intensity. No difference was seen in fatigue rate in the line drill, but a trend (P = .07) was observed for a lower fatigue rate for BA compared with P during the Wingate anaerobic power test. A significantly higher training volume was seen for BA in the bench press exercise, and a trend (P = .09) for a greater training volume was seen for all resistance exercise sessions. In addition, subjective feelings of fatigue were significantly lower for BA than P. In conclusion, despite a trend toward lower fatigue rates during 60 seconds of maximal exercise, 3 weeks of beta-alanine supplementation did not result in significant improvements in fatigue rates during high-intensity anaerobic exercise. However, higher training volumes and lower subjective feelings of fatigue in BA indicated that as duration of supplementation continued, the efficacy of beta-alanine supplementation in highly trained athletes became apparent.

Effect of Dynamic Light Application on Cognitive Performance and Well-being of Intensive Care Nurses.

PubMed

Simons, Koen S; Boeijen, Enzio R K; Mertens, Marlies C; Rood, Paul; de Jager, Cornelis P C; van den Boogaard, Mark

2018-05-01

Exposure to bright light has alerting effects. In nurses, alertness may be decreased because of shift work and high work pressure, potentially reducing work performance and increasing the risk for medical errors. To determine whether high-intensity dynamic light improves cognitive performance, self-reported depressive signs and symptoms, fatigue, alertness, and well-being in intensive care unit nurses. In a single-center crossover study in an intensive care unit of a teaching hospital in the Netherlands, 10 registered nurses were randomly divided into 2 groups. Each group worked alternately for 3 to 4 days in patients' rooms with dynamic light and 3 to 4 days in control lighting settings. High-intensity dynamic light was administered through ceiling-mounted fluorescent tubes that delivered bluish white light up to 1700 lux during the daytime, versus 300 lux in control settings. Cognitive performance, self-reported depressive signs and symptoms, fatigue, and well-being before and after each period were assessed by using validated cognitive tests and questionnaires. Cognitive performance, self-reported depressive signs and symptoms, and fatigue did not differ significantly between the 2 light settings. Scores of subjective well-being were significantly lower after a period of working in dynamic light. Daytime lighting conditions did not affect intensive care unit nurses' cognitive performance, perceived depressive signs and symptoms, or fatigue. Perceived quality of life, predominantly in the psychological and environmental domains, was lower for nurses working in dynamic light. © 2018 American Association of Critical-Care Nurses.

Reduced Dual-Task Performance in MS Patients Is Further Decreased by Muscle Fatigue.

PubMed

Wolkorte, Ria; Heersema, Dorothea J; Zijdewind, Inge

2015-06-01

Multiple sclerosis (MS) can be accompanied by motor, cognitive, and sensory impairments. Additionally, MS patients often report fatigue as one of their most debilitating symptoms. It is, therefore, expected that MS patients will have difficulties in performing cognitive-motor dual tasks (DTs), especially in a fatiguing condition. To determine whether MS patients are more challenged by a DT than controls in a fatiguing and less-fatiguing condition and whether DT performance is associated with perceived fatigue. A group of 19 MS patients and 19 age-, sex-, and education-matched controls performed a cognitive task (2-choice reaction time task) separately or concurrent with a low-force or a high-force motor task (index finger abduction at 10% or 30% maximal voluntary contraction). MS patients performed less well on a cognitive task than controls. Cognitive task performance under DT conditions decreased more for MS patients. Moreover, under high-force DT conditions, cognitive performance declined in both groups but to a larger degree for MS patients. Besides a decline in cognitive task performance, MS patients also showed a stronger decrease in motor performance under high-force DT conditions. DT costs were positively related to perceived fatigue as measured by questionnaires. Compared with controls, MS patients performed less well on DTs as demonstrated by a reduction in both cognitive and motor performances. This performance decrease was stronger under fatiguing conditions and was related to the sense of fatigue of MS patients. These data illustrate problems that MS patients may encounter in daily life because of their fatigue. © The Author(s) 2014.

Breaking up workplace sitting time with intermittent standing bouts improves fatigue and musculoskeletal discomfort in overweight/obese office workers.

PubMed

Thorp, Alicia A; Kingwell, Bronwyn A; Owen, Neville; Dunstan, David W

2014-11-01

To examine whether the introduction of intermittent standing bouts during the workday using a height-adjustable workstation can improve subjective levels of fatigue, musculoskeletal discomfort and work productivity relative to seated work. Overweight/obese office workers (n=23; age 48.2±7.9 years, body mass index 29.6±4 kg/m(2)) undertook two, 5-day experimental conditions in an equal, randomised (1:1) order. In a simulated office environment, participants performed their usual occupational tasks for 8 h/day in a: seated work posture (SIT condition); or interchanging between a standing and seated work posture every 30 min using an electric, height-adjustable workstation (STAND-SIT condition). Self-administered questionnaires measuring fatigue, musculoskeletal discomfort and work productivity were performed on day 5 of each experimental condition. Participants' total fatigue score was significantly higher during the SIT condition (mean 67.8 (95% CI 58.8 to 76.7)) compared with the STAND-SIT condition (52.7 (43.8 to 61.5); p<0.001). Lower back musculoskeletal discomfort was significantly reduced during the STAND-SIT condition compared with the SIT condition (31.8% reduction; p=0.03). Despite concentration/focus being significantly higher during the SIT condition (p=0.006), there was a trend towards improved overall work productivity in favour of the STAND-SIT condition (p=0.053). Transitioning from a seated to a standing work posture every 30 min across the workday, relative to seated work, led to a significant reduction in fatigue levels and lower back discomfort in overweight/obese office workers, while maintaining work productivity. Future investigations should be directed at understanding whether sustained use of height-adjustable workstations promote concentration and productivity at work. ACTRN12611000632998. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Rhodiola rosea in stress induced fatigue--a double blind cross-over study of a standardized extract SHR-5 with a repeated low-dose regimen on the mental performance of healthy physicians during night duty.

PubMed

Darbinyan, V; Kteyan, A; Panossian, A; Gabrielian, E; Wikman, G; Wagner, H

2000-10-01

The aim of this study was to investigate the effect of repeated low-dose treatment with a standardized extract SHR/5 of rhizome Rhodiola rosea L, (RRE) on fatigue during night duty among a group of 56 young, healthy physicians. The effect was measured as total mental performance calculated as Fatigue Index. The tests chosen reflect an overall level of mental fatigue, involving complex perceptive and cognitive cerebral functions, such as associative thinking, short-term memory, calculation and ability of concentration, and speed of audio-visual perception. These parameters were tested before and after night duty during three periods of two weeks each: a) a test period of one RRE/placebo tablet daily, b) a washout period and c) a third period of one placebo/RRE tablet daily, in a double-blind cross-over trial. The perceptive and cognitive cerebral functions mentioned above were investigated using 5 different tests. A statistically significant improvement in these tests was observed in the treatment group (RRE) during the first two weeks period. No side-effects were reported for either treatment noted. These results suggest that RRE can reduce general fatigue under certain stressful conditions.

Electromechanical fatigue in IPMC under dynamic energy harvesting conditions

NASA Astrophysics Data System (ADS)

Krishnaswamy, Arvind; Roy Mahapatra, D.

2011-04-01

Ionic polymer-metal composites (IPMCs) are an interesting subset of smart, multi-functional materials that have shown promises in energy conversion technologies. Being electromechanically coupled, IPMCs can function as dynamic actuators and sensors, transducers for energy conversion and harvesting, as well as artificial muscles for medical and industrial applications. Like all natural materials, even IPMCs undergo fatigue under dynamic load conditions. Here, we investigate the electromechanical fatigue induced in the IPMCs due to the application of cyclic mechanical bending deformation under hydrodynamic energy harvesting condition. Considering the viscoelastic nature of the IPMC, we employ an analytical approach to modeling electromechanical fatigue primarily under the cyclic stresses induced in the membrane. The polymer-metal composite undergoes cyclic softening throughout the fatigue life without attaining a saturated state of charge migration. However, it results in (1) degradation of electromechanical performance; (2) nucleation and growth of microscopic cracks in the metal electrodes; (3) delamination of metal electrodes at the polymer-electrode interface. To understand these processes, we employ a phenomenological approach based on experimentally measured relaxation properties of the IPMC membrane. Electromechanical performance improves significantly with self-healing like properties for a certain range of relaxation time. This is due to reorientation of the backbone polymer chains which eventually leads to a regenerative process with increased charge transport.

Effect of Coriolus versicolor Mycelia Extract on Exercise Performance and Physical Fatigue in Mice.

PubMed

Ho, Chun-Sheng; Tung, Yu-Tang; Kung, Woon-Man; Huang, Wen-Ching; Leung, Wing-Ki; Huang, Chi-Chang; Wu, Jyh-Horng

2017-01-01

In this study, Coriolus versicolor mycelia (CVM) was evaluated the ergogenic and anti-fatigue activities. Male ICR mice were divided into four groups ( n = 8/group) to receive vehicle or CVM by oral gavage for 4 weeks at 0, 615, 1230 or 3075 mg/kg/day, which were respectively designated the vehicle, CVM-1X, CVM-2X and CVM-5X groups. Forelimb grip strength, endurance swimming time, and levels of physical fatigue-associated parameters serum lactate, ammonia, glucose and creatine kinase (CK) after physical challenge were performed to evaluate exercise performance and anti-fatigue activity. Results revealed that the forelimb grip strength of mice in group CVM-1X, CVM-2X and CVM-5X were significantly increased by 1.20-, 1.18- and 1.23-fold, respectively, compared to the vehicle group. After the 15 minute swimming exercise, the levels of serum lactate of CVM-1X, CVM-2X and CVM-5X groups were significantly lower than the vehicle control group by 29%, 23% and 31%, respectively. The levels of ammonia in CVM-1X, CVM-2X and CVM-5X groups were significantly lowered by 22%, 25% and 41%, respectively, compared to the vehicle control group. In addition, the levels of serum CK in CVM-2X and CVM-5X groups were significantly lowered by 13% and 11%, respectively, compared to the vehicle control group. Accordingly, the supplementation with CVM has beneficial effects on performance improvement and anti-fatigue activity, and thus has great potential as a source for natural health products.

Effect of Coriolus versicolor Mycelia Extract on Exercise Performance and Physical Fatigue in Mice

PubMed Central

Ho, Chun-Sheng; Tung, Yu-Tang; Kung, Woon-Man; Huang, Wen-Ching; Leung, Wing-Ki; Huang, Chi-Chang; Wu, Jyh-Horng

2017-01-01

In this study, Coriolus versicolor mycelia (CVM) was evaluated the ergogenic and anti-fatigue activities. Male ICR mice were divided into four groups (n = 8/group) to receive vehicle or CVM by oral gavage for 4 weeks at 0, 615, 1230 or 3075 mg/kg/day, which were respectively designated the vehicle, CVM-1X, CVM-2X and CVM-5X groups. Forelimb grip strength, endurance swimming time, and levels of physical fatigue-associated parameters serum lactate, ammonia, glucose and creatine kinase (CK) after physical challenge were performed to evaluate exercise performance and anti-fatigue activity. Results revealed that the forelimb grip strength of mice in group CVM-1X, CVM-2X and CVM-5X were significantly increased by 1.20-, 1.18- and 1.23-fold, respectively, compared to the vehicle group. After the 15 minute swimming exercise, the levels of serum lactate of CVM-1X, CVM-2X and CVM-5X groups were significantly lower than the vehicle control group by 29%, 23% and 31%, respectively. The levels of ammonia in CVM-1X, CVM-2X and CVM-5X groups were significantly lowered by 22%, 25% and 41%, respectively, compared to the vehicle control group. In addition, the levels of serum CK in CVM-2X and CVM-5X groups were significantly lowered by 13% and 11%, respectively, compared to the vehicle control group. Accordingly, the supplementation with CVM has beneficial effects on performance improvement and anti-fatigue activity, and thus has great potential as a source for natural health products. PMID:29104465

Up-Down Hand Position Switch May Delay the Fatigue of Non-Dominant Hand Position Rescuers and Improve Chest Compression Quality during Cardiopulmonary Resuscitation: A Randomized Crossover Manikin Study

PubMed Central

Xu, Bing; Wang, Huang-Lei; Xiong, Dan; Sheng, Li-Pin; Yang, Qi-Sheng; Jiang, Shan; Xu, Peng; Chen, Zhi-Qiao; Zhao, Yan

2015-01-01

Previous studies have shown improved external chest compression (ECC) quality and delayed rescuer fatigue when the dominant hand (DH) was in contact with the sternum. However, many rescuers prefer placing the non-dominant hand (NH) in contact with the sternum during ECC. We aimed to investigate the effects of up-down hand position switch on the quality of ECC and the fatigue of rescuers during cardiopulmonary resuscitation (CPR). After completion of a review of the standard adult basic life support (BLS) course, every candidate performed 10 cycles of single adult CPR twice on an adult manikin with either a constant hand position (CH) or a switched hand position (SH) in random order at 7-day intervals. The rescuers’ general characteristics, hand positions, physiological signs, fatigue appearance and ECC qualities were recorded. Our results showed no significant differences in chest compression quality for the DH position rescuers between the CH and SH sessions (p>0.05, resp.). And also no significant differences were found for Borg score (p = 0.437) or cycle number (p = 0.127) of fatigue appearance after chest compressions between the two sessions. However, for NH position rescuers, the appearance of fatigue was delayed (p = 0.046), with a lower Borg score in the SH session (12.67 ± 2.03) compared to the CH session (13.33 ± 1.95) (p = 0.011). Moreover, the compression depth was significantly greater in the SH session (39.3 ± 7.2 mm) compared to the CH session (36.3 ± 8.1 mm) (p = 0.015). Our data suggest that the up-down hand position switch during CPR may delay the fatigue of non-dominant hand position rescuers and improve the quality of chest compressions. PMID:26267353

Lower rate-pressure product during submaximal walking: a link to fatigue improvement following a physical activity intervention among breast cancer survivors.

PubMed

Carter, Stephen J; Hunter, Gary R; McAuley, Edward; Courneya, Kerry S; Anton, Philip M; Rogers, Laura Q

2016-10-01

Research showing a link between exercise-induced changes in aerobic fitness and reduced fatigue after a cancer diagnosis has been inconsistent. We evaluated associations of fatigue and rate-pressure product (RPP), a reliable index of myocardial oxygen demand, at rest and during submaximal walking following a physical activity intervention among post-primary treatment breast cancer survivors (BCS). Secondary analyses of 152 BCS in a randomized controlled trial testing a physical activity intervention (INT) versus usual care (UC) were performed. The INT group completed counseling/group discussions along with supervised exercise sessions tapered to unsupervised exercise. Evaluations were made at baseline and immediately post-intervention (M3) on measures of physical activity (accelerometry), graded walk test, and average fatigue over the previous 7 days. RPP was calculated by dividing the product of heart rate and systolic blood pressure by 100. Resting and submaximal RPPs were significantly improved in both groups at M3; however, the magnitude of change (∆) was greater in the INT group from stage 1 (∆RPP1; INT -13 ± 17 vs. UC -7 ± 18; p = 0.03) through stage 4 (∆RPP4; INT -21 ± 26 vs. UC -9 ± 24; p < 0.01) of the walk test. The INT group reported significantly reduced fatigue (INT -0.7 ± 2.0 vs. UC +0.1 ± 2.0; p = 0.02) which was positively associated with ∆RPP during stages 2-4 of the walk test but not ∆aerobic fitness. Lower RPP during submaximal walking was significantly associated with reduced fatigue in BCS. Exercise/physical activity training programs that lower the physiological strain during submaximal walking may produce the largest improvements in reported fatigue.

Biomarkers of Fatigue: Ranking Mental Fatigue Susceptibility

DTIC Science & Technology

2010-12-10

expected declines in performance during the 36-hour, 15-minute period of sleep deprivation without caffeine. The simple change from baseline results...rankings for fatigue resistance were then determined via a percent- change rule similar to that used in Chaiken, Harville, Harrison, Fischer, Fisher...and Whitmore (2008). This rule ranks subjects on percent change of cognitive performance from a baseline performance (before fatigue) to a fatigue

Influence of Exergaming on the Perception of Cancer-Related Fatigue.

PubMed

da Silva Alves, Ricardo; Iunes, Denise Hollanda; Pereira, Isabela Carvalho; Borges, Juliana Bassalobre Carvalho; Nogueira, Denismar Alves; Silva, Andreia Maria; Lobato, Daniel Ferreira Moreira; Carvalho, Leonardo Cesar

2017-04-01

Exercise is recommended for cancer patients to reduce fatigue and improve quality of life. This study's aim is to evaluate the influence of an exergaming protocol on cancer-related fatigue, muscle fatigue, and muscle strength in cancer patients. We conducted a quasi-experimental control study using exergaming in all groups through an Xbox360 Kinect™ console, two to three times per week, for 20 sessions. Three groups were created: cancer patients in chemotherapy and/or radiotherapy group (CRG; n:15), cancer patients after chemotherapy and/or radiotherapy (CAG; n:15), and a control group (CG; n:15). They were assessed for cancer-related fatigue using the fatigue subscale of the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) questionnaire. To assess dorsiflexor and plantar flexor muscle functioning, we used median frequency (MDF) of the surface electromyography and muscle strength using a dynamometer. The assessments were performed preintervention (EV0), after 10 sessions (EV1), and after 20 sessions (EV2). With an exergaming protocol, CRG and CAG showed a reduction in related fatigue compared with CG (P < 0.01). The CRG group saw an increase in maximal voluntary isometric contraction in right plantar flexor muscles and dorsiflexor muscles, as well as an increase in the MDF of both medial gastrocnemius muscles and the left tibialis anterior muscle of the CAG. For other analyses done, the differences were observed during exergaming. Exergaming demonstrated efficacy in reducing cancer patients' fatigue, including muscle fatigue, and increasing muscle strength in patients' legs.

The impact of fatigue on the non-technical skills performance of critical care air ambulance clinicians.

PubMed

Myers, J A; Powell, D M C; Aldington, S; Sim, D; Psirides, A; Hathaway, K; Haney, M F

2017-11-01

The relationship between fatigue-related risk and impaired clinical performance is not entirely clear. Non-technical factors represent an important component of clinical performance and may be sensitive to the effects of fatigue. The hypothesis was that the sum score of overall non-technical performance is degraded by fatigue. Nineteen physicians undertook two different simulated air ambulance missions, once when rested, and once when fatigued (randomised crossover design). Trained assessors blinded to participants' fatigue status performed detailed structured assessments based on expected behaviours in four non-technical skills domains: teamwork, situational awareness, task management, and decision making. Participants also provided self-ratings of their performance. The primary endpoint was the sum score of overall non-technical performance. The main finding, the overall non-technical skills performance rating of the clinicians, was better in rested than fatigued states (mean difference with 95% CI, 2.8 [2.2-3.4]). The findings remained consistent across individual non-technical skills domains; also when controlling for an order effect and examining the impact of a number of possible covariates. There was no difference in self-ratings of clinical performance between rested and fatigued states. Non-technical performance of critical care air transfer clinicians is degraded when they are fatigued. Fatigued clinicians may fail to recognise the degree to which their performance is compromised. These findings represent risk to clinical care quality and patient safety in the dynamic and isolated environment of air ambulance transfer. © 2017 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

The Effect of Nutrition Therapy and Exercise on Cancer-Related Fatigue and Quality of Life in Men with Prostate Cancer: A Systematic Review

PubMed Central

Baguley, Brenton J.; Bolam, Kate A.; Wright, Olivia R. L.

2017-01-01

Background: Improvements in diet and/or exercise are often advocated during prostate cancer treatment, yet the efficacy of, and optimal nutrition and exercise prescription for managing cancer-related fatigue and quality of life remains elusive. The aim of this study is to systematically review the effects of nutrition and/or exercise on cancer-related fatigue and/or quality of life. Methods: A literature search was conducted in six electronic databases. The Delphi quality assessment list was used to evaluate the methodological quality of the literature. The study characteristics and results were summarized in accordance with the review’s Population, Intervention, Control, Outcome (PICO) criteria. Results: A total of 20 articles (one diet only, two combined diet and exercise, and seventeen exercise only studies) were included in the review. Soy supplementation improved quality of life, but resulted in several adverse effects. Prescribing healthy eating guidelines with combined resistance training and aerobic exercise improved cancer-related fatigue, yet its effect on quality of life was inconclusive. Combined resistance training with aerobic exercise showed improvements in cancer-related fatigue and quality of life. In isolation, resistance training appears to be more effective in improving cancer-related fatigue and quality of life than aerobic exercise. Studies that utilised an exercise professional to supervise the exercise sessions were more likely to report improvements in both cancer-related fatigue and quality of life than those prescribing unsupervised or partially supervised sessions. Neither exercise frequency nor duration appeared to influence cancer-related fatigue or quality of life, with further research required to explore the potential dose-response effect of exercise intensity. Conclusion: Supervised moderate-hard resistance training with or without moderate-vigorous aerobic exercise appears to improve cancer-related fatigue and quality of life. Targeted physiological pathways suggest dietary intervention may alleviate cancer-related fatigue and improve quality of life, however the efficacy of nutrition management with or without exercise prescription requires further exploration. PMID:28895922

The Effect of Nutrition Therapy and Exercise on Cancer-Related Fatigue and Quality of Life in Men with Prostate Cancer: A Systematic Review.

PubMed

Baguley, Brenton J; Bolam, Kate A; Wright, Olivia R L; Skinner, Tina L

2017-09-12

Improvements in diet and/or exercise are often advocated during prostate cancer treatment, yet the efficacy of, and optimal nutrition and exercise prescription for managing cancer-related fatigue and quality of life remains elusive. The aim of this study is to systematically review the effects of nutrition and/or exercise on cancer-related fatigue and/or quality of life. A literature search was conducted in six electronic databases. The Delphi quality assessment list was used to evaluate the methodological quality of the literature. The study characteristics and results were summarized in accordance with the review's Population, Intervention, Control, Outcome (PICO) criteria. A total of 20 articles (one diet only, two combined diet and exercise, and seventeen exercise only studies) were included in the review. Soy supplementation improved quality of life, but resulted in several adverse effects. Prescribing healthy eating guidelines with combined resistance training and aerobic exercise improved cancer-related fatigue, yet its effect on quality of life was inconclusive. Combined resistance training with aerobic exercise showed improvements in cancer-related fatigue and quality of life. In isolation, resistance training appears to be more effective in improving cancer-related fatigue and quality of life than aerobic exercise. Studies that utilised an exercise professional to supervise the exercise sessions were more likely to report improvements in both cancer-related fatigue and quality of life than those prescribing unsupervised or partially supervised sessions. Neither exercise frequency nor duration appeared to influence cancer-related fatigue or quality of life, with further research required to explore the potential dose-response effect of exercise intensity. Supervised moderate-hard resistance training with or without moderate-vigorous aerobic exercise appears to improve cancer-related fatigue and quality of life. Targeted physiological pathways suggest dietary intervention may alleviate cancer-related fatigue and improve quality of life, however the efficacy of nutrition management with or without exercise prescription requires further exploration.

Feasibility and changes in symptoms and functioning following inpatient cancer rehabilitation.

PubMed

Bertheussen, Gro F; Kaasa, Stein; Hokstad, Anne; Sandmæl, Jon Arne; Helbostad, Jorunn L; Salvesen, Øyvind; Oldervoll, Line M

2012-11-01

The aim was to assess feasibility of a 3 + 1 week inpatient rehabilitation program for cancer survivors, to explore characteristics of the attending participants and examine changes in work status, symptoms and functioning, level of fatigue, exercise and physical performance following rehabilitation. This was an open intervention study involving cancer survivors having completed primary cancer treatment. The multidisiplinary program consisted of physical training, patient education and group sessions. Participant were assessed at primary stay (T0), at follow-up stay 8-12 weeks later (T1), and six months after T1 (T2). Symptoms and functioning were assessed by the European Organization for Research and Treatment Core Quality-of-Life Questionnaire, physical fatigue by Fatigue Questionnaire, physical exercise by The Nord- Trøndelag Health Study Physical Activity Questionnaire and physical performance by aerobic capacity (VO(2max)), 30 second Sit-to-stand (STS) and Maximum Step Length (MSL). Linear mixed models were used in analyses. One hundred and thirty-four of 163 included participants (82%) completed both rehabilitation stays and returned questionaires at T2. The majority of completers were females (81%), breast cancer survivors (60%), highly educated and with mean age of 52.8 years (SD of 8.1). Participants had higher level of symptoms and fatigue and lower functioning at admission compared to a Norwegian reference population. However, they reported higher physical exercise level and 47% reported improved work status from T0 to T2. Symptoms and functioning, fatigue, physical exercise and physical performance improved significantly from T0 to T1 and were maintained at T2. The rehabilitation program was feasible and symptoms and functioning normalized following rehabilitation. The program mainly recruited well-educated breast cancer survivors, reporting relative high level of physical exercise. More focus should be put on recruiting and selecting those who need comprehensive inpatient rehabilitation and also compare the effects of inpatient with outpatient rehabilitation programs.

Quality-of-life assessment in gynecologic surgery.

PubMed

Rock, J A

2001-05-01

More than 90% of gynecologic surgery is performed for nonmalignant conditions, with a major objective of improving the patient's health-related quality of life (QOL). Clinical studies and patient surveys demonstrate that fatigue, diminished energy levels, increased need for rest, delayed time to return to work, difficulty performing daily routines, and difficulty caring for family and home persist for weeks to months or more following surgery. The social and economic implications of these outcomes provide a rationale for improving the QOL of gynecologic patients in the early weeks of recovery from surgery. Persistent and debilitating fatigue, which can lead to diminished QOL, is even more common than pain following hysterectomy. Global and specific subjective self-assessment instruments have been developed to measure fatigue as well as QOL parameters in postoperative gynecologic surgery patients. In addition, a QOL instrument combining both subjective self-assessment scales and objective measures of hemoglobin, hematocrit and muscle strength has been validated in postoperative orthopedic patients and may also have application in gynecologic surgery patients. Collectively, these various instruments may be useful in the assessment of recuperative power and vitality during early postoperative recovery in patients undergoing gynecologic surgery.

The Effect of Moderate and High-Intensity Fatigue on Groundstroke Accuracy in Expert and Non-Expert Tennis Players

PubMed Central

Lyons, Mark; Al-Nakeeb, Yahya; Hankey, Joanne; Nevill, Alan

2013-01-01

Exploring the effects of fatigue on skilled performance in tennis presents a significant challenge to the researcher with respect to ecological validity. This study examined the effects of moderate and high-intensity fatigue on groundstroke accuracy in expert and non-expert tennis players. The research also explored whether the effects of fatigue are the same regardless of gender and player’s achievement motivation characteristics. 13 expert (7 male, 6 female) and 17 non-expert (13 male, 4 female) tennis players participated in the study. Groundstroke accuracy was assessed using the modified Loughborough Tennis Skills Test. Fatigue was induced using the Loughborough Intermittent Tennis Test with moderate (70%) and high-intensities (90%) set as a percentage of peak heart rate (attained during a tennis-specific maximal hitting sprint test). Ratings of perceived exertion were used as an adjunct to the monitoring of heart rate. Achievement goal indicators for each player were assessed using the 2 x 2 Achievement Goals Questionnaire for Sport in an effort to examine if this personality characteristic provides insight into how players perform under moderate and high-intensity fatigue conditions. A series of mixed ANOVA’s revealed significant fatigue effects on groundstroke accuracy regardless of expertise. The expert players however, maintained better groundstroke accuracy across all conditions compared to the novice players. Nevertheless, in both groups, performance following high-intensity fatigue deteriorated compared to performance at rest and performance while moderately fatigued. Groundstroke accuracy under moderate levels of fatigue was equivalent to that at rest. Fatigue effects were also similar regardless of gender. No fatigue by expertise, or fatigue by gender interactions were found. Fatigue effects were also equivalent regardless of player’s achievement goal indicators. Future research is required to explore the effects of fatigue on performance in tennis using ecologically valid designs that mimic more closely the demands of match play. Key Points Groundstroke accuracy under moderate-intensity fatigue is equivalent to performance at rest. Groundstroke accuracy declines significantly in both expert (40.3% decline) and non-expert (49.6%) tennis players following high-intensity fatigue. Expert players are more consistent, hit more accurate shots and fewer out shots across all fatigue intensities. The effects of fatigue on groundstroke accuracy are the same regardless of gender and player’s achievement goal indicators. PMID:24149809

Customized mandibular reconstruction plates improve mechanical performance in a mandibular reconstruction model

PubMed Central

Gutwald, Ralf; Jaeger, Raimund; Lambers, Floor M.

2017-01-01

Abstract The purpose of this paper was to analyze the biomechanical performance of customized mandibular reconstruction plates with optimized strength. The best locations for increasing bar widths were determined with a sensitivity analysis. Standard and customized plates were mounted on mandible models and mechanically tested. Maximum stress in the plate could be reduced from 573 to 393 MPa (−31%) by increasing bar widths. The median fatigue limit was significantly greater (p < 0.001) for customized plates (650 ± 27 N) than for standard plates (475 ± 27 N). Increasing bar widths at case-specific locations was an effective strategy for increasing plate fatigue performance. PMID:27887036

Interferon-free therapy in hepatitis C virus (HCV) monoinfected and HCV/HIV coinfected patients: effect on cognitive function, fatigue, and mental health.

PubMed

Kleefeld, Felix; Heller, Sophie; Ingiliz, Patrick; Jessen, Heiko; Petersen, Anders; Kopp, Ute; Kraft, Antje; Hahn, Katrin

2018-05-21

The efficacy and safety of interferon-free therapies for hepatitis C virus (HCV) infection have been reported. Considering the accumulating evidence for a direct central nervous system infection by HCV, we aim to evaluate the effect of direct acting antivirals (DAA) therapy on cognitive function in HCV patients. We conducted a longitudinal analysis of the cognitive performance of 22 patients (8 HCV+, 14 HCV+/HIV+) who completed neuropsychological testing at baseline and at week 12 after DAA therapy. In 20 patients, we analyzed specific attention parameters derived from an experimental testing based on the Theory of Visual Attention (TVA). Depression, fatigue, and mental health were assessed as patient reported outcomes. At baseline, 54.5% of the patients met the criteria for cognitive impairment and 40% showed impairment in TVA parameters. Follow-up analysis revealed significant improvements in the domains of visual memory/learning, executive functions, verbal fluency, processing speed, and motor skills but not in verbal learning and attention/working memory. We did not observe significant improvement in visual attention measured by TVA. Fatigue and mental health significantly improved at follow-up. Our findings indicate that successful DAA treatment leads to cognitive improvements in several domains measured by standard neuropsychological testing. The absence of improvement in TVA parameters and of significant improvement in the domain of attention/working memory might reflect the persistence of specific cognitive deficits after HCV eradication. In summary, DAA treatment seems to have a positive effect on some cognitive domains and leads to an improvement in mental health and fatigue in HCV-infected patients.

Muscle contractile characteristics: relationship to high-intensity exercise.

PubMed

Morris, Martyn G; Dawes, Helen; Howells, Ken; Scott, Oona M; Cramp, Mary; Izadi, Hooshang

2010-09-01

We investigated the relationship between muscle contractile characteristics, collected using percutaneous electrical stimulation, and high-intensity exercise performance. Seventeen participants performed a muscle performance test for the calculation of rate of torque development (RTD), rate of relaxation (RR(1/2)), rate of fatigue and fatigue resistance. On a second visit the participants completed a Wingate cycle ergometer test with peak power, mean power, fatigue index and fatigue rate calculated. The muscle fatigue index related significantly to the WAnT fatigue index and fatigue rate (p < 0.01). The change in rate of torque development (%DeltaRTD) was also related significantly to the fatigue rate (W/s) during the WAnT. Subjects displaying the greatest reduction in RTD had the greatest fatigue rate during the WAnT and greater fatigue during the electrical stimulation protocol. There were no significant relationships between peak (r 0.36; p > 0.01) or mean power (r -0.11, p > 0.01) with any of the muscle performance measures. These findings demonstrate that muscle contractile characteristics, elicited during standardised in vivo electrical stimulation, relate to performance during a Wingate anaerobic test. They suggest that muscle contraction characteristics play an important role in high-intensity exercise performance and indicate that electrical stimulation protocols can be a useful additional tool to explore muscle contraction characteristics in relation to exercise performance and trainability.

Spring performance tester for miniature extension springs

DOEpatents

Salzbrenner, Bradley; Boyce, Brad

2017-05-16

A spring performance tester and method of testing a spring are disclosed that has improved accuracy and precision over prior art spring testers. The tester can perform static and cyclic testing. The spring tester can provide validation for product acceptance as well as test for cyclic degradation of springs, such as the change in the spring rate and fatigue failure.

Fatigue and Sleep Among Employees With Prospective Increase in Work Time Control: A 1-Year Observational Study With Objective Assessment.

PubMed

Kubo, Tomohide; Takahashi, Masaya; Liu, Xinxin; Ikeda, Hiroki; Togo, Fumiharu; Shimazu, Akihito; Tanaka, Katsutoshi; Kamata, Naoki; Kubo, Yoshiko; Uesugi, Junko

2016-11-01

This observational study aimed to determine how 1-year changes in work time control (WTC) have an impact upon objectively measured fatigue and sleep among employees. Thirty-nine employees were divided into two groups according to whether or not their WTC increased from baseline to 1 year later. Psychomotor vigilance task (PVT) and wrist actigraphy were used to objectively measure fatigue and sleep, respectively. Self-reported outcomes were also measured. The increased WTC group showed gradual improvements in PVT performance and sleep quality over the course of the follow-up period compared with the not-increased WTC group. Between-group differences were statistically significant for PVT lapses and tended to be significant for PVT speed after 1 year. A progressive increase in WTC could play a crucial role in reducing fatigue and promoting sleep among employees.

Classification of driver fatigue in an electroencephalography-based countermeasure system with source separation module.

PubMed

Rifai Chai; Naik, Ganesh R; Tran, Yvonne; Sai Ho Ling; Craig, Ashley; Nguyen, Hung T

2015-08-01

An electroencephalography (EEG)-based counter measure device could be used for fatigue detection during driving. This paper explores the classification of fatigue and alert states using power spectral density (PSD) as a feature extractor and fuzzy swarm based-artificial neural network (ANN) as a classifier. An independent component analysis of entropy rate bound minimization (ICA-ERBM) is investigated as a novel source separation technique for fatigue classification using EEG analysis. A comparison of the classification accuracy of source separator versus no source separator is presented. Classification performance based on 43 participants without the inclusion of the source separator resulted in an overall sensitivity of 71.67%, a specificity of 75.63% and an accuracy of 73.65%. However, these results were improved after the inclusion of a source separator module, resulting in an overall sensitivity of 78.16%, a specificity of 79.60% and an accuracy of 78.88% (p <; 0.05).

The effects of nighttime napping on sleep, sleep inertia, and performance during simulated 16 h night work: a pilot study.

PubMed

Oriyama, Sanae; Miyakoshi, Yukiko

2018-03-27

This study aimed to elucidate the effects of two naps taken at night on morning waking state and performance. The participants were 12 women. The experiment was performed in a laboratory over 2 days (16:00-09:00). In this crossover comparative study, three experimental nap conditions were used (naps from 22:30 to 00:00 and from 02:30 to 03:00 (22:30-NAP), 00:30 to 02:00 and 04:30 to 05:00 (00:30-NAP), and no naps (NO-NAP), respectively). Measurement items were a Visual Analog Scale for sleepiness and fatigue, the Psychomotor Vigilance Test (PVT), and single-digit addition calculations (10 min) every hour for 18 h from 16:00 to 09:00, excluding nap times. Sleep inertia and sleepiness were noted directly after napping. Less sleepiness and fatigue were noted in the nap groups between 06:00 and 09:00 in the morning than in the NO-NAP condition and PVT response times were faster. Since participants in the nap groups were able to conduct more single-digit addition calculations, the performance of these groups appeared to be superior to that of the NO-NAP condition. Furthermore, the performance of calculations was significantly better in the 00:30-NAP than in the 22:30-NAP. Taking two naps during a simulated night shift helps improve sleepiness and fatigue and maintain performance. Taking a nap in the early morning appears to be promising for improving the waking state.

Neuroprotective mechanism of losartan and its interaction with nimesulide against chronic fatigue stress.

PubMed

Kumar, Anil; Singh, Barinder; Mishra, Jitendriya; Sah, Sangeeta Pilkhwal; Pottabathini, Raghavender

2015-12-01

Potential role of angiotensin-II and cyclooxygenase have been suggested in the pathophysiology of chronic fatigue stress. The present study has been designed to evaluate the neuroprotective effect of losartan and its interaction with nimesulide against chronic fatigue stress and related complications in mice. In the present study, male Laca mice (20-30 g) were subjected to running wheel activity test session (RWATS) for 6 min daily for 21 days. Losartan, nimesulide and their combinations were administered daily for 21 days, 45 min before being subjected to RWATS. Various behavioral and biochemical and neuroinflammatory mediators were assessed subsequently. 21 days RWATS treatment significantly decreased number of wheel rotations/6 min indicating fatigue stress like behaviors as compared to naive group. 21 days treatment with losartan (10 and 20 mg/kg, ip), nimesulide (5 and 10 mg/kg, po) and their combinations significantly improved behavior [increased number of wheel rotations, reversal of post-exercise fatigue, locomotor activity, antianxiety-like behavior (number of entries, latency to enter and time spent in mirror chamber), and memory performance (transfer latency in plus-maze performance task)], biochemical parameters (reduced serum corticosterone, brain lipid peroxidation, nitrite concentration, acetylcholinesterase activity, restored reduced glutathione levels and catalase activity) as compared to RWATS control. Besides, TNF-α, CRP levels were significantly attenuated by these drugs and their combinations as compared to control. The present study highlights the role of cyclooxygenase modulation in the neuroprotective effect of losartan against chronic fatigue stress-induced behavioral, biochemical and cellular alterations in mice.

Cumulative fatigue damage behavior of MAR M-247

NASA Technical Reports Server (NTRS)

Mcgaw, Michael A.; Halford, Gary R.; Kalluri, Sreeramesh

1991-01-01

The objective was to examine the room temperature fatigue and nonlinear cumulative fatigue damage behavior of the cast nickel-based superalloy, MAR M-247. The fatigue test matrix consisted of single-level, fully reversed fatigue experiments. Two series of tests were performed: one of the two baseline fatigue LCF (Low-Cycle Fatigue) life levels was used in the first loading block, and the HCF (High-Cycle Fatigue) baseline loading level was used in the second block in each series. For each series, duplicate tests were performed at each applied LCF life fraction.

High temperature, low-cycle fatigue of copper-base alloys for rocket nozzles. Part 2: Strainrange partitioning and low-cycle fatigue results at 538 deg C

NASA Technical Reports Server (NTRS)

Conway, J. B.; Stentz, R. H.; Berling, J. T.

1976-01-01

Low-cycle fatigue tests of 1/2 Hard AMZIRC Copper and NARloy Z were performed in argon at 538 C to determine partitioned strain range versus life relationships. Strain-controlled low-cycle fatigue tests of a Zr-Cr-Mg copper-base alloy were also performed. Strain ranges, lower than those employed in previous tests, were imposed in order to extend the fatigue life curve out to approximately 400,000 cycles. An experimental copper alloy and an experimental silver alloy were also studied. Tensile tests were performed in air at room temperature and in argon at 538 C. Strain-controlled low-cycle fatigue tests were performed at 538 C in argon to define the fatigue life over the regime from 300 to 3,000 cycles. For the silver alloy, three additional heat treatments were introduced, and a limited evaluation of the short-term tensile and low-cycle fatigue behavior at 538 C was performed.

Fatigue, Work Schedules, and Perceived Performance in Bedside Care Nurses.

PubMed

Sagherian, Knar; Clinton, Michael E; Abu-Saad Huijer, Huda; Geiger-Brown, Jeanne

2017-07-01

Hospital nurses are expected to maintain optimal work performance; yet, fatigue can threaten safe practice and result in unfavorable patient outcomes. This descriptive cross-sectional study explored the association between fatigue, work schedules, and perceived work performance among nurses. The study sample included 77 bedside nurses who were mostly female, single, and between 20 and 29 years of age. The majority worked 8-hour shifts and overtime. Nurses who worked during off days reported significantly higher chronic fatigue compared with those nurses who took time off. Nurses who reported feeling refreshed after sleep had significantly less chronic and acute fatigue and more intershift recovery. Nurses with acute and chronic fatigue perceived poorer physical performance. Also, nurses who reported chronic fatigue perceived they were less alert and less able to concentrate when providing patient care. Less effective communication was also associated with acute and chronic fatigue. In conclusion, fatigue has safety implications for nurses' practice that should be monitored by nursing management.

Effect of La and W dopants on dielectric and ferroelectric properties of PZT thin films prepared by sol-gel process

NASA Astrophysics Data System (ADS)

Xiao, Mi; Zhang, Zebin; Zhang, Weikang; Zhang, Ping

2018-01-01

La or W-doped lead zirconate titanate thin films (PLZT or PZTW) were prepared on platinized silicon substrates by sol-gel process. The effects of La or W dopant on the phase development, microstructure, dielectric and ferroelectric characteristics of films were studied. For PLZT films, the optimum doping concentration was found to be 2 mol%. While for PZTW films, the dielectric and ferroelectric properties were found to be improved as the doping concentration increased. The fatigue properties of PLZT and PZTW thin films were also investigated, the results showed that A- or B-site donor doping could improve the fatigue properties of PZT thin films. The theory of oxygen vacancy was used to explain the performance improvement caused by donor doping.

Rituximab is Ineffective for Treatment of Fatigue in Primary Biliary Cholangitis: A phase-2 Randomised Controlled Trial.

PubMed

Khanna, Amardeep; Jopson, Laura; Howel, Denise; Bryant, Andrew; Blamire, Andrew; Newton, Julia L; Jones, David E

2018-05-23

Primary Biliary Cholangitis (PBC) is a chronic cholestatic liver disease. Half of patients experience debilitating fatigue which is currently untreatable. Previous studies have shown muscle bioenergetic abnormalities in PBC, including increased muscle acidosis with exercise linked to the anti-mitochondrial antibody (AMA) diagnostic of the disease, and reduced anaerobic threshold. In this study we addressed the hypothesis that fatigue in PBC is driven by muscle bioenergetic abnormality related to AMA, and that AMA reduction with B-cell depletion therapy will improve fatigue. In our single-centred Phase II randomised controlled trial (RCT) 57 participants aged ≥18 years with PBC and moderate or severe fatigue were randomized to receive 2 doses of either rituximab (1000mg) or saline (placebo). The primary outcome measure was fatigue severity assessed using the PBC-40 fatigue domain at 3 months. Secondary outcomes measures included patient-reported outcomes, immunological and bioenergetics disease parameters. Experimental outcomes included biochemical markers of disease severity. Improvement in fatigue score at 3 months was seen in both arms, with no significant difference (adjusted mean difference -0.9 95%CI -4.6 to 3.1). Little difference was observed in other patient reported outcomes or physical activity. Significant anaerobic threshold improvement was seen in the Rituximab group only but this was not associated with fatigue improvement. No treatment-emergent SAEs were seen. Rituximab was safe over the 12 month study period but showed no evidence of effectiveness for the treatment of fatigue in PBC. Anaerobic threshold improvement was seen; potentially linking AMA with muscle bioenergetics dysfunction, however, this was not related to improvement in fatigue. Rituximab had some evidence of a beneficial effect on alkaline phosphatase levels in this largely UDCA-responding, early disease stage cohort. This article is protected by copyright. All rights reserved. © 2018 by the American Association for the Study of Liver Diseases.

Small-crack effects in high-strength aluminum alloys

NASA Technical Reports Server (NTRS)

Newman, J. C., Jr.; Wu, X. R.; Venneri, S. L.; Li, C. G.

1994-01-01

The National Aeronautics and Space Administration and the Chinese Aeronautical Establishment participated in a Fatigue and Fracture Mechanics Cooperative Program. The program objectives were to identify and characterize crack initiation and growth of small cracks (10 microns to 2 mm long) in commonly used US and PRC aluminum alloys, to improve fracture mechanics analyses of surface- and corner-crack configurations, and to develop improved life-prediction methods. Fatigue and small-crack tests were performed on single-edgenotch tension (SENT) specimens and large-crack tests were conducted on center-crack tension specimens for constant-amplitude (stress ratios of -1, 0, and 0.5) and Mini-TWIST spectrum loading. The plastic replica method was used to monitor the initiation and growth of small fatigue cracks at the semicircular notch. Crack growth results from each laboratory on 7075-T6 bare and LC9cs clad aluminum alloys agreed well and showed that fatigue life was mostly crack propagation from a material defect (inclusion particles or void) or from the cladding layer. Finite-element and weight-function methods were used to determine stress intensity factors for surface and corner cracks in the SENT specimens. Equations were then developed and used in a crack growth and crack-closure model to correlate small- and large-crack data and to make life predictions for various load histories. The cooperative program produced useful experimental data and efficient analysis methods for improving life predictions. The results should ultimately improve aircraft structural reliability and safety.

Experimental Study on Fatigue Performance of Foamed Lightweight Soil

NASA Astrophysics Data System (ADS)

Qiu, Youqiang; Yang, Ping; Li, Yongliang; Zhang, Liujun

2017-12-01

In order to study fatigue performance of foamed lightweight soil and forecast its fatigue life in the supporting project, on the base of preliminary tests, beam fatigue tests on foamed lightweight soil is conducted by using UTM-100 test system. Based on Weibull distribution and lognormal distribution, using the mathematical statistics method, fatigue equations of foamed lightweight soil are obtained. At the same time, according to the traffic load on real road surface of the supporting project, fatigue life of formed lightweight soil is analyzed and compared with the cumulative equivalent axle loads during the design period of the pavement. The results show that even the fatigue life of foamed lightweight soil has discrete property, the linear relationship between logarithmic fatigue life and stress ratio still performs well. Especially, the fatigue life of Weibull distribution is more close to that derived from the lognormal distribution, in the instance of 50% guarantee ratio. In addition, the results demonstrated that foamed lightweight soil as subgrade filler has good anti-fatigue performance, which can be further adopted by other projects in the similar research domain.

Controlled-frequency breath swimming improves swimming performance and running economy.

PubMed

Lavin, K M; Guenette, J A; Smoliga, J M; Zavorsky, G S

2015-02-01

Respiratory muscle fatigue can negatively impact athletic performance, but swimming has beneficial effects on the respiratory system and may reduce susceptibility to fatigue. Limiting breath frequency during swimming further stresses the respiratory system through hypercapnia and mechanical loading and may lead to appreciable improvements in respiratory muscle strength. This study assessed the effects of controlled-frequency breath (CFB) swimming on pulmonary function. Eighteen subjects (10 men), average (standard deviation) age 25 (6) years, body mass index 24.4 (3.7) kg/m(2), underwent baseline testing to assess pulmonary function, running economy, aerobic capacity, and swimming performance. Subjects were then randomized to either CFB or stroke-matched (SM) condition. Subjects completed 12 training sessions, in which CFB subjects took two breaths per length and SM subjects took seven. Post-training, maximum expiratory pressure improved by 11% (15) for all 18 subjects (P < 0.05) while maximum inspiratory pressure was unchanged. Running economy improved by 6 (9)% in CFB following training (P < 0.05). Forced vital capacity increased by 4% (4) in SM (P < 0.05) and was unchanged in CFB. These findings suggest that limiting breath frequency during swimming may improve muscular oxygen utilization during terrestrial exercise in novice swimmers. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Modelling and Laboratory Studies on the Adhesion Fatigue Performance for Thin-Film Asphalt and Aggregate System

PubMed Central

Wang, Dongsheng; Feng, Decheng

2014-01-01

Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more important effect on the adhesion performance comparing with aggregate. Basalt, which is regarded as hydrophobic aggregates with low silica content, has better adhesion performance to asphalt binder when compared with granite. The effects of aging on the adhesion fatigue performance are different for PG64-22 and rubber asphalt. Long-term aging is found to reduce the adhesion fatigue lives for rubber asphalt and aggregate system, while the effect of long-term aging for aggregate and PG64-22 binder system is positive. Generally the increased stress amplitude and test temperature could induce greater damage and lead to less fatigue lives for adhesion test system. PMID:25054187

Modelling and laboratory studies on the adhesion fatigue performance for thin-film asphalt and aggregate system.

PubMed

Wang, Dongsheng; Yi, Junyan; Feng, Decheng

2014-01-01

Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more important effect on the adhesion performance comparing with aggregate. Basalt, which is regarded as hydrophobic aggregates with low silica content, has better adhesion performance to asphalt binder when compared with granite. The effects of aging on the adhesion fatigue performance are different for PG64-22 and rubber asphalt. Long-term aging is found to reduce the adhesion fatigue lives for rubber asphalt and aggregate system, while the effect of long-term aging for aggregate and PG64-22 binder system is positive. Generally the increased stress amplitude and test temperature could induce greater damage and lead to less fatigue lives for adhesion test system.

A home-based exercise program to improve function, fatigue, and sleep quality in patients with Stage IV lung and colorectal cancer: a randomized controlled trial.

PubMed

Cheville, Andrea L; Kollasch, Jenny; Vandenberg, Justin; Shen, Tiffany; Grothey, Axel; Gamble, Gail; Basford, Jeffrey R

2013-05-01

Exercise benefits patients with cancer, but studies of home-based approaches, particularly among those with Stage IV disease, remain small and exploratory. To conduct an adequately powered trial of a home-based exercise intervention that can be facilely integrated into established delivery and reimbursement structures. Sixty-six adults with Stage IV lung or colorectal cancer were randomized, in an eight-week trial, to usual care or incremental walking and home-based strength training. The exercising participants were instructed during a single physiotherapy visit and subsequently exercised four days or more per week; training and step-count goals were advanced during bimonthly telephone calls. The primary outcome measure was mobility assessed with the Ambulatory Post Acute Care Basic Mobility Short Form. Secondary outcomes included ratings of pain and sleep quality as well as the ability to perform daily activities (Ambulatory Post Acute Care Daily Activities Short Form), quality of life (Functional Assessment of Cancer Therapy-General), and fatigue (Functional Assessment of Cancer Therapy-Fatigue). Three participants dropped out and seven died (five in the intervention and two in the control group, P=0.28). At Week 8, the intervention group reported improved mobility (P=0.01), fatigue (P=0.02), and sleep quality (P=0.05) compared with the usual care group, but did not differ on the other measures. A home-based exercise program seems capable of improving the mobility, fatigue, and sleep quality of patients with Stage IV lung and colorectal cancer. Copyright © 2013. Published by Elsevier Inc.

Cyclic Creep and Recovery Behavior of Nextel(Trademark) 720/Alumina Ceramic Matrix Composite at 1200deg C in Air and in Steam Environments

DTIC Science & Technology

2007-09-01

steam. The creep and recovery periods ranged from 3 min to 30 h. The laboratory air tests significantly exceeded the life of the monotonic creep ...orders of magnitude improvement in the creep life and rate. The presence of steam greatly reduced the performance of the material. The results in...steam. Mehrman also reported that prior fatigue subsequently improved in air but creep performance but in steam creep performance remained poor

The Effects of Mental Fatigue on Physical Performance: A Systematic Review.

PubMed

Van Cutsem, Jeroen; Marcora, Samuele; De Pauw, Kevin; Bailey, Stephen; Meeusen, Romain; Roelands, Bart

2017-08-01

Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity. It has recently been suggested that mental fatigue can affect physical performance. Our objective was to evaluate the literature on impairment of physical performance due to mental fatigue and to create an overview of the potential factors underlying this effect. Two electronic databases, PubMed and Web of Science (until 28 April 2016), were searched for studies designed to test whether mental fatigue influenced performance of a physical task or influenced physiological and/or perceptual responses during the physical task. Studies using short (<30 min) self-regulatory depletion tasks were excluded from the review. A total of 11 articles were included, of which six were of strong and five of moderate quality. The general finding was a decline in endurance performance (decreased time to exhaustion and self-selected power output/velocity or increased completion time) associated with a higher than normal perceived exertion. Physiological variables traditionally associated with endurance performance (heart rate, blood lactate, oxygen uptake, cardiac output, maximal aerobic capacity) were unaffected by mental fatigue. Maximal strength, power, and anaerobic work were not affected by mental fatigue. The duration and intensity of the physical task appear to be important factors in the decrease in physical performance due to mental fatigue. The most important factor responsible for the negative impact of mental fatigue on endurance performance is a higher perceived exertion.

Advanced Environmental Barrier Coating and SA Tyrannohex SiC Composites Integration for Improved Thermomechanical and Environmental Durability

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Halbig, Michael; Singh, Mrityunjay

2018-01-01

The development of 2700 degF capable environmental barrier coating (EBC) systems, particularly, the Rare Earth "Hafnium" Silicon bond coat systems, have significantly improved the temperature capability and environmental stability of SiC/SiC Ceramic Matrix Composite Systems. We have specifically developed the advanced 2700 degF EBC systems, integrating the EBC to the high temperature SA Tyrannohex SiC fiber composites, for comprehensive performance and durability evaluations for potential turbine engine airfoil component applications. The fundamental mechanical properties, environmental stability and thermal gradient cyclic durability performance of the EBC - SA Tyrannohex composites were investigated. The paper will particularly emphasize the high pressure combustion rig recession, cyclic thermal stress resistance and thermomechanical low cycle fatigue testing of uncoated and environmental barrier coated Tyrannohex SiC SA composites in these simulated turbine engine combustion water vapor, thermal gradients, and mechanical loading conditions. We have also investigated high heat flux and flexural fatigue degradation mechanisms, determined the upper limits of operating temperature conditions for the coated SA composite material systems in thermomechanical fatigue conditions. Recent progress has also been made by using the self-healing rare earth-silicon based EBCs, thus enhancing the SA composite hexagonal fiber columns bonding for improved thermomechanical and environmental durability in turbine engine operation environments. More advanced EBC- composite systems based on the new EBC-Fiber Interphases will also be discussed.

Patients with primary biliary cholangitis and fatigue present with depressive symptoms and selected cognitive deficits, but with normal attention performance and brain structure.

PubMed

Zenouzi, Roman; von der Gablentz, Janina; Heldmann, Marcus; Göttlich, Martin; Weiler-Normann, Christina; Sebode, Marcial; Ehlken, Hanno; Hartl, Johannes; Fellbrich, Anja; Siemonsen, Susanne; Schramm, Christoph; Münte, Thomas F; Lohse, Ansgar W

2018-01-01

In primary biliary cholangitis (PBC) fatigue is a major clinical challenge of unknown etiology. By demonstrating that fatigue in PBC is associated with an impaired cognitive performance, previous studies have pointed out the possibility of brain abnormalities underlying fatigue in PBC. Whether structural brain changes are present in PBC patients with fatigue, however, is unclear. To evaluate the role of structural brain abnormalities in PBC patients severely affected from fatigue we, therefore, performed a case-control cerebral magnetic resonance imaging (cMRI) study and correlated changes of white and grey brain matter with the cognitive and attention performance. 20 female patients with PBC and 20 female age-matched controls were examined in this study. The assessment of fatigue, psychological symptoms, cognitive and attention performance included clinical questionnaires, established cognition tests and a computerized test battery of attention performance. T1-weighted cMRI and diffusion tensor imaging (DTI) scans were acquired with a 3 Tesla scanner. Structural brain alterations were investigated with voxel-based morphometry (VBM) and DTI analyses. Results were correlated to the cognitive and attention performance. Compared to healthy controls, PBC patients had significantly higher levels of fatigue and associated psychological symptoms. Except for an impairment of verbal fluency, no cognitive or attention deficits were found in the PBC cohort. The VBM and DTI analyses revealed neither major structural brain abnormalities in the PBC cohort nor correlations with the cognitive and attention performance. Despite the high burden of fatigue and selected cognitive deficits, the attention performance of PBC patients appears to be comparable to healthy people. As structural brain alterations do not seem to be present in PBC patients with fatigue, fatigue in PBC must be regarded as purely functional. Future studies should evaluate, whether functional brain changes underlie fatigue in PBC.

Resveratrol improves exercise performance and skeletal muscle oxidative capacity in heart failure.

PubMed

Sung, Miranda M; Byrne, Nikole J; Robertson, Ian M; Kim, Ty T; Samokhvalov, Victor; Levasseur, Jody; Soltys, Carrie-Lynn; Fung, David; Tyreman, Neil; Denou, Emmanuel; Jones, Kelvin E; Seubert, John M; Schertzer, Jonathan D; Dyck, Jason R B

2017-04-01

We investigated whether treatment of mice with established pressure overload-induced heart failure (HF) with the naturally occurring polyphenol resveratrol could improve functional symptoms of clinical HF such as fatigue and exercise intolerance. C57Bl/6N mice were subjected to either sham or transverse aortic constriction surgery to induce HF. Three weeks postsurgery, a cohort of mice with established HF (%ejection fraction <45) was administered resveratrol (~450 mg·kg -1 ·day -1 ) or vehicle for 2 wk. Although the percent ejection fraction was similar between both groups of HF mice, those mice treated with resveratrol had increased total physical activity levels and exercise capacity. Resveratrol treatment was associated with altered gut microbiota composition, increased skeletal muscle insulin sensitivity, a switch toward greater whole body glucose utilization, and increased basal metabolic rates. Although muscle mass and strength were not different between groups, mice with HF had significant declines in basal and ADP-stimulated O 2 consumption in isolated skeletal muscle fibers compared with sham mice, which was completely normalized by resveratrol treatment. Overall, resveratrol treatment of mice with established HF enhances exercise performance, which is associated with alterations in whole body and skeletal muscle energy metabolism. Thus, our preclinical data suggest that resveratrol supplementation may effectively improve fatigue and exercise intolerance in HF patients. NEW & NOTEWORTHY Resveratrol treatment of mice with heart failure leads to enhanced exercise performance that is associated with altered gut microbiota composition, increased whole body glucose utilization, and enhanced skeletal muscle metabolism and function. Together, these preclinical data suggest that resveratrol supplementation may effectively improve fatigue and exercise intolerance in heart failure via these mechanisms. Copyright © 2017 the American Physiological Society.

Muscle-Cooling Intervention to Reduce Fatigue and Fatigue-Induced Tremor in Novice and Experienced Surgeons: A Preliminary Investigation.

PubMed

Jensen, Lauren; Dancisak, Michael; Korndorffer, James

2016-10-01

A localized, intermittent muscle-cooling protocol was implemented to determine cooling garment efficacy in reducing upper extremity muscular fatigue and tremor in novice ( n  = 10) and experienced surgeons ( n  = 9). Subjects wore a muscle-cooling garment while performing multiple trials of a forearm exercise and paired suturing task to induce muscular fatigue and exercise-induced tremor. A reduction in tremor amplitude and an extension in time to fatigue were expected with muscle cooling as compared with control trials. Each subject completed an intervention session (5°C cooling condition) and a control session (32°C or thermal neutral condition). A paired samples t test indicated that tremor amplitude was significantly reduced ( t [8] = 1.89458; p  < 0.05) in experienced surgeons in two dimensions (up and down, and back and forth). Tremor amplitude was reduced in novice surgeons but the effect was not significant. Time to fatigue and suture time improved in both cohorts with muscle cooling, but the effect did not reach significance. Results from the pilot work suggest muscle cooling as an intervention for reduction of fatigue and tremor is very promising, warranting further investigation. Surgical specialties that require prolonged procedures might benefit more from this intervention.

Managing the impact of posttreatment fatigue on the family: breast cancer survivors share their experiences.

PubMed

Oktay, Julianne S; Bellin, Melissa H; Scarvalone, Susan; Appling, Sue; Helzlsouer, Kathy J

2011-06-01

With improvements in both early detection and treatments for breast cancer, the number of survivors has increased dramatically in recent decades. One of the most common lingering symptoms posttreatment for cancer survivors is chronic fatigue. Based on family stress theory and Rolland's typology of illness, this qualitative study extends our understanding of the impact of persistent posttreatment fatigue on families and how breast cancer survivors manage the family issues that arise because of this chronic stressor. Participants included 35 female survivors of breast cancer (mean age = 54 years) who experienced fatigue after the completion of active cancer treatment, with the exception of long-term hormonal therapy. Data were generated from (a) observations of group sessions from a randomized controlled fatigue intervention designed to reduce fatigue in breast cancer survivors, (b) individual in-depth interviews, and (c) family sessions. Qualitative analysis revealed two broad themes that illustrate how the survivors manage the impact of fatigue on their families: Interpreting the meaning of the fatigue and Dealing with the inability to perform family roles. Study findings describe the difficulties in family adaptation when the family is not able to assign a clear meaning to a chronic symptom posttreatment and build upon family stress theory by highlighting interrelationships among communication patterns and role shifts in the family system. ©2011 APA

Fatigue of a 3D Orthogonal Non-crimp Woven Polymer Matrix Composite at Elevated Temperature

NASA Astrophysics Data System (ADS)

Wilkinson, M. P.; Ruggles-Wrenn, M. B.

2017-12-01

Tension-tension fatigue behavior of two polymer matrix composites (PMCs) was studied at elevated temperature. The two PMCs consist of the NRPE polyimide matrix reinforced with carbon fibers, but have different fiber architectures: the 3D PMC is a singly-ply non-crimp 3D orthogonal weave composite and the 2D PMC, a laminated composite reinforced with 15 plies of an eight harness satin weave (8HSW) fabric. In order to assess the performance and suitability of the two composites for use in aerospace components designed to contain high-temperature environments, mechanical tests were performed under temperature conditions simulating the actual operating conditions. In all elevated temperature tests performed in this work, one side of the test specimen was at 329 °C while the other side was open to ambient laboratory air. The tensile stress-strain behavior of the two composites was investigated and the tensile properties measured for both on-axis (0/90) and off-axis (±45) fiber orientations. Elevated temperature had little effect on the on-axis tensile properties of the two composites. The off-axis tensile strength of both PMCs decreased slightly at elevated temperature. Tension-tension fatigue tests were conducted at elevated temperature at a frequency of 1.0 Hz with a ratio of minimum stress to maximum stress of R = 0.05. Fatigue run-out was defined as 2 × 105 cycles. Both strain accumulation and modulus evolution during cycling were analyzed for each fatigue test. The laminated 2D PMC exhibited better fatigue resistance than the 3D composite. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. Post-test examination under optical microscope revealed severe delamination in the laminated 2D PMC. The non-crimp 3D orthogonal weave composite offered improved delamination resistance.

Music Improves Subjective Feelings Leading to Cardiac Autonomic Nervous Modulation: A Pilot Study

PubMed Central

Kume, Satoshi; Nishimura, Yukako; Mizuno, Kei; Sakimoto, Nae; Hori, Hiroshi; Tamura, Yasuhisa; Yamato, Masanori; Mitsuhashi, Rika; Akiba, Keigo; Koizumi, Jun-ichi; Watanabe, Yasuyoshi; Kataoka, Yosky

2017-01-01

It is widely accepted that listening to music improves subjective feelings and reduces fatigue sensations, and different kinds of music lead to different activations of these feelings. Recently, cardiac autonomic nervous modulation has been proposed as a useful objective indicator of fatigue. However, scientific considerations of the relation between feelings of fatigue and cardiac autonomic nervous modulation while listening to music are still lacking. In this study, we examined which subjective feelings of fatigue are related to participants' cardiac autonomic nervous function while they listen to music. We used an album of comfortable and relaxing environmental music, with blended sounds from a piano and violin as well as natural sound sources. We performed a crossover trial of environmental music and silent sessions for 20 healthy subjects, 12 females, and 8 males, after their daily work shift. We measured changes in eight types of subjective feelings, including healing, fatigue, sleepiness, relaxation, and refreshment, using the KOKORO scale, a subjective mood measurement system for self-reported feelings. Further, we obtained measures of cardiac autonomic nervous function on the basis of heart rate variability before and after the sessions. During the music session, subjective feelings significantly shifted toward healing and a secure/relaxed feeling and these changes were greater than those in the silent session. Heart rates (ΔHR) in the music session significantly decreased compared with those in the silent session. Other cardiac autonomic parameters such as high-frequency (HF) component and the ratio of low-frequency (LF) and HF components (LF/HF) were similar in the two sessions. In the linear regression analysis of the feelings with ΔHR and changes in LF/HF (ΔLF/HF), increases and decreases in ΔHR were correlated to the feeling axes of Fatigue-Healing and Anxiety/Tension–Security/Relaxation, whereas those in ΔLF/HF were related to the feeling axes of Sleepiness–Wakefulness and Gloomy–Refreshed. This indicated that listening to music improved the participants' feelings of fatigue and decreased their heart rates. However, it did not reduce the cardiac LF/HF, suggesting that cardiac LF/HF might show a delayed response to fatigue. Thus, we demonstrated changes in cardiac autonomic nervous functions based on feelings of fatigue. PMID:28344545

Music Improves Subjective Feelings Leading to Cardiac Autonomic Nervous Modulation: A Pilot Study.

PubMed

Kume, Satoshi; Nishimura, Yukako; Mizuno, Kei; Sakimoto, Nae; Hori, Hiroshi; Tamura, Yasuhisa; Yamato, Masanori; Mitsuhashi, Rika; Akiba, Keigo; Koizumi, Jun-Ichi; Watanabe, Yasuyoshi; Kataoka, Yosky

2017-01-01

It is widely accepted that listening to music improves subjective feelings and reduces fatigue sensations, and different kinds of music lead to different activations of these feelings. Recently, cardiac autonomic nervous modulation has been proposed as a useful objective indicator of fatigue. However, scientific considerations of the relation between feelings of fatigue and cardiac autonomic nervous modulation while listening to music are still lacking. In this study, we examined which subjective feelings of fatigue are related to participants' cardiac autonomic nervous function while they listen to music. We used an album of comfortable and relaxing environmental music, with blended sounds from a piano and violin as well as natural sound sources. We performed a crossover trial of environmental music and silent sessions for 20 healthy subjects, 12 females, and 8 males, after their daily work shift. We measured changes in eight types of subjective feelings, including healing, fatigue, sleepiness, relaxation, and refreshment, using the KOKORO scale, a subjective mood measurement system for self-reported feelings. Further, we obtained measures of cardiac autonomic nervous function on the basis of heart rate variability before and after the sessions. During the music session, subjective feelings significantly shifted toward healing and a secure/relaxed feeling and these changes were greater than those in the silent session. Heart rates (ΔHR) in the music session significantly decreased compared with those in the silent session. Other cardiac autonomic parameters such as high-frequency (HF) component and the ratio of low-frequency (LF) and HF components (LF/HF) were similar in the two sessions. In the linear regression analysis of the feelings with ΔHR and changes in LF/HF (ΔLF/HF), increases and decreases in ΔHR were correlated to the feeling axes of Fatigue-Healing and Anxiety/Tension-Security/Relaxation, whereas those in ΔLF/HF were related to the feeling axes of Sleepiness-Wakefulness and Gloomy-Refreshed. This indicated that listening to music improved the participants' feelings of fatigue and decreased their heart rates. However, it did not reduce the cardiac LF/HF, suggesting that cardiac LF/HF might show a delayed response to fatigue. Thus, we demonstrated changes in cardiac autonomic nervous functions based on feelings of fatigue.

High Cycle Fatigue Performance in Laser Shock Peened TC4 Titanium Alloys Subjected to Foreign Object Damage

NASA Astrophysics Data System (ADS)

Luo, Sihai; Nie, Xiangfan; Zhou, Liucheng; Li, Yiming; He, Weifeng

2018-03-01

During their service, titanium alloys are likely to suffer from the foreign object damage (FOD), resulting in a decrease in their fatigue strength. Laser shock peening (LSP) has been proved to effectively increase the damage tolerance of military engine components by introducing a magnitude compressive residual stress in the near-surface layer of alloys. In this paper, smooth specimens of a TC4 titanium alloy were used and treated by LSP and subsequently exposed to FOD, which was simulated by firing a steel sphere with a nominal velocity of 300 m/s, at 90° with the leading edge of the LSP-treated region using a light gas gun. All impacted specimens were then subjected to fatigue loading. The results showed that LSP could effectively improve the fatigue strength of the damaged specimens. The effect of LSP on the fatigue strength was assessed through fracture observations, microhardness tests and residual stress analyses. The residual stresses due to the plastic deformation caused by LSP and the FOD impact, which were found to play a crucial role on the fatigue strength, were determined using the commercial software ABAQUS.

Effectiveness of Shot Peening In Suppressing Fatigue Cracking At Non-Metallic Inclusions In Udimet(Registered Trademark)720

NASA Technical Reports Server (NTRS)

Barrie, Robert L.; Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; Prescenzi, Anthony; Biles, T.; Bonacuse, P. J.

2006-01-01

The fatigue lives of modern powder metallurgy disk alloys can be reduced over an order of magnitude by cracking at inherent non-metallic inclusions. The objective of this work was to study the effectiveness of shot peening in suppressing LCF crack initiation and growth at surface nonmetallic inclusions. Inclusions were carefully introduced at elevated levels during powder metallurgy processing of the nickel-base disk superalloy Udimet 720. Multiple strain-controlled fatigue tests were then performed on machined specimens with and without shot peened test sections at 427 C and 650 C. The low cycle fatigue lives and failure initiation sites varied as functions of inclusion content, shot peening, and fatigue conditions. A large majority of the failures in as-machined specimens with the introduced inclusions occurred at cracks initiating from inclusions intersecting the specimen surface. These inclusions reduced fatigue life by up to 100X, when compared to lives of material without inclusions residing at specimen surface. Large inclusions produced the greatest reductions in life for tests at low strain ranges and high strain ratios. Shot peening improved life in many cases by reducing the most severe effects of inclusions.

Evaluation of the effect of progressive relaxation exercises on fatigue and sleep quality in patients with multiple sclerosis.

PubMed

Dayapoğlu, Nuray; Tan, Mehtap

2012-10-01

Fatigue and sleep problems are very commonly observed in patients with multiple sclerosis (MS). The Progressive Muscle Relaxation Technique (PMRT), used as one of the alternative methods in recent years, is reported to have benefits such as facilitating sleep and reducing sensitivity against fatigue. This research was conducted to investigate the effect of PMRT on fatigue and sleep quality in patients with MS. This research was performed as a single-group pretest/post-test pretrial model. The research was conducted between March 2008 and December 2009 in the neurology polyclinic. The study was conducted with 32 patients who met the research criteria and agreed to participate in the study. A Personal Information Form was used as a data collection tool, Fatigue Severity Scale was used for measuring fatigue, and the Pittsburgh Sleep Quality Index was used for evaluating the sleep quality. PMRT was applied to the sample group once a day for 6 weeks. Percentage, paired t-test, and Pearson's correlation analysis were used in the assessment of data. It was determined that PMRT decreased patients' fatigue level and improved their sleep quality, and this difference was observed to be statistically significant. Moreover, patients' fatigue level increased as their sleep quality decreased. This study supports the effect of PMRT on fatigue and sleep quality in patients with MS, and it is recommended that further studies be conducted on this subject in the future.

Acute effects of jaw clenching using a customized mouthguard on anaerobic ability and ventilatory flows.

PubMed

Morales, Jose; Buscà, Bernat; Solana-Tramunt, Mònica; Miró, Adrià

2015-12-01

The latest findings on the ergogenic effects of a dentistry-design, bite-aligning mouthpiece require additional research to assess its impact on anaerobic ability and ventilatory parameters. This paper was aimed at determining the ergogenic acute effects of wearing a custom-made mouthpiece on oral airflow dynamics, 30-s Wingate Anaerobic Test performance parameters. Twenty-eight healthy and physically-active male subjects (age: 24.50 ± 3.32, height: 181.34 ± 7.4, weight: 78.14 ± 8.21), were voluntarily studied. The subjects were first briefed on the test protocols, and then performed the 30s Wingate test and Spirometer test. The experimental trials were performed in a random counterbalanced order. We evaluate maximum expiratory volume (VEmax L min(-1)), mean power (W kg(-1)), peak power (W kg(-1)), time to peak (s), rate to fatigue (Ws(-1)) and lactate production (mMol L(-1)), rate of perceived exertion (RPE). There were significant differences between mouthguard and no-mouthguard conditions in mean power (W kg(-1)), peak power (W kg(-1)), time to peak (s), and rate to fatigue (Ws(-1)) for the 30-s Wingate Anaerobic Test. Significantly lower lactate production (mMol L(-1)) was observed, in mouthguard condition but no significant differences were found in RPE. In airflow dynamics, the VEmax L min(-1) was significantly higher when comparing the mouthguard and the no mouthguard conditions in both forced and unforced conditions. In conclusion, wearing a customized mouthguard improves anaerobic ability and increases forced expiratory volume. This study will help practitioners improve athlete's performance in anaerobic activities where high intensity action might provoke jaw-clenching, contributing in reductions of lactate and fatigue, and improving ventilatory parameters. Copyright © 2015 Elsevier B.V. All rights reserved.

Impact of Dietary Antioxidants on Sport Performance: A Review.

PubMed

Braakhuis, Andrea J; Hopkins, Will G

2015-07-01

Many athletes supplement with antioxidants in the belief this will reduce muscle damage, immune dysfunction and fatigue, and will thus improve performance, while some evidence suggests it impairs training adaptations. Here we review the effect of a range of dietary antioxidants and their effects on sport performance, including vitamin E, quercetin, resveratrol, beetroot juice, other food-derived polyphenols, spirulina and N-acetylcysteine (NAC). Older studies suggest vitamin E improves performance at altitude, with possible harmful effects on sea-level performance. Acute intake of vitamin E is worthy of further consideration, if plasma levels can be elevated sufficiently. Quercetin has a small beneficial effect for exercise of longer duration (>100 min), but it is unclear whether this benefits athletes. Resveratrol benefits trained rodents; more research is needed in athletes. Meta-analysis of beetroot juice studies has revealed that the nitrate component of beetroot juice had a substantial but unclear effect on performance when averaged across athletes, non-athletes and modes of exercise (single dose 1.4 ± 2.0%, double dose 0.5 ± 1.9%). The effect of addition of polyphenols and other components to beetroot juice was trivial but unclear (single dose 0.4 ± 3.2%, double dose -0.5 ± 3.3%). Other food-derived polyphenols indicate a range of performance outcomes from a large improvement to moderate impairment. Limited evidence suggests spirulina enhances endurance performance. Intravenous NAC improved endurance cycling performance and reduced muscle fatigue. On the basis of vitamin E and NAC studies, acute intake of antioxidants is likely to be beneficial. However, chronic intakes of most antioxidants have a harmful effect on performance.

Translating Fatigue to Human Performance.

PubMed

Enoka, Roger M; Duchateau, Jacques

2016-11-01

Despite flourishing interest in the topic of fatigue-as indicated by the many presentations on fatigue at the 2015 Annual Meeting of the American College of Sports Medicine-surprisingly little is known about its effect on human performance. There are two main reasons for this dilemma: 1) the inability of current terminology to accommodate the scope of the conditions ascribed to fatigue, and 2) a paucity of validated experimental models. In contrast to current practice, a case is made for a unified definition of fatigue to facilitate its management in health and disease. On the basis of the classic two-domain concept of Mosso, fatigue is defined as a disabling symptom in which physical and cognitive function is limited by interactions between performance fatigability and perceived fatigability. As a symptom, fatigue can only be measured by self-report, quantified as either a trait characteristic or a state variable. One consequence of such a definition is that the word fatigue should not be preceded by an adjective (e.g., central, mental, muscle, peripheral, and supraspinal) to suggest the locus of the changes responsible for an observed level of fatigue. Rather, mechanistic studies should be performed with validated experimental models to identify the changes responsible for the reported fatigue. As indicated by three examples (walking endurance in old adults, time trials by endurance athletes, and fatigue in persons with multiple sclerosis) discussed in the review, however, it has proven challenging to develop valid experimental models of fatigue. The proposed framework provides a foundation to address the many gaps in knowledge of how laboratory measures of fatigue and fatigability affect real-world performance.

Design, fabrication, and test of a steel spar wind turbine blade

NASA Technical Reports Server (NTRS)

Sullivan, T. L.; Sirocky, P. J., Jr.; Viterna, L. A.

1979-01-01

The design and fabrication of wind turbine blades based on 60 foot steel spars are discussed. Performance and blade load information is given and compared to analytical prediction. In addition, performance is compared to that of the original MOD-O aluminum blades. Costs for building the two blades are given, and a projection is made for the cost in mass production. Design improvements to reduce weight and improve fatigue life are suggested.

Cancer-related fatigue management: evaluation of a patient education program with a large-scale randomised controlled trial, the PEPs fatigue study.

PubMed

Bourmaud, A; Anota, A; Moncharmont, C; Tinquaut, F; Oriol, M; Trillet-Lenoir, V; Bajard, A; Parnalland, S; Rotonda, C; Bonnetain, F; Pérol, D; Chauvin, F

2017-03-28

To assess the efficacy of a patient educational program built according to guidelines that aims at reducing cancer-related fatigue (CRF). Randomised controlled trial, multicentre, comparing a patient education program, vs the standard of care. Patients were adult cancer outpatients with any tumour site. The primary outcome was fatigue severity assessed with a visual analogical scale (VAS), between the day of randomisation and week 7. Secondary outcomes were fatigue assessed with other scales, health-related quality of life, anxiety and depression. The time to fatigue severity deterioration was assessed. Analyses were performed in a modified intent-to-treat way, that is, including all patients with at least one baseline and 1 week 7 score. A total of 212 patients were included. Fatigue severity assessment was made on 79 patients in the experimental group and 65 in the control group. Between randomisation and week 7, the fatigue (VAS) improved by 0.96 (2.85) points in the experimental group vs 1.63 (2.63) points in the control group (P=0.15). No differences with the secondary outcomes were highlighted between two groups. No other factors were found to be associated with fatigue severity deterioration. Despite rigorous methodology, this study failed to highlight the program efficacy in fatigue reduction for cancer patients. Other assessment tools should be developed to measure the effect of the program on CRF and behaviour. The implementation of the program should also be explored in order to identify its mechanisms and longer-term impact.

The onset and evolution of fatigue-induced abnormal grain growth in nanocrystalline Ni–Fe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furnish, T. A.; Mehta, A.; Van Campen, D.

Conventional structural metals suffer from fatigue-crack initiation through dislocation activity which forms persistent slip bands leading to notch-like extrusions and intrusions. Ultrafine-grained and nanocrystalline metals can potentially exhibit superior fatigue-crack initiation resistance by suppressing these cumulative dislocation activities. Prior studies on these metals have confirmed improved high-cycle fatigue performance. In the case of nano-grained metals, analyses of subsurface crack initiation sites have indicated that the crack nucleation is associated with abnormally large grains. But, these post-mortem analyses have led to only speculation about when abnormal grain growth occurs (e.g., during fatigue, after crack initiation, or during crack growth). In thismore » study, a recently developed synchrotron X-ray diffraction technique was used to detect the onset and progression of abnormal grain growth during stress-controlled fatigue loading. Our study provides the first direct evidence that the grain coarsening is cyclically induced and occurs well before final fatigue failure—our results indicate that the first half of the fatigue life was spent prior to the detectable onset of abnormal grain growth, while the second half was spent coarsening the nanocrystalline structure and cyclically deforming the abnormally large grains until crack initiation. Post-mortem fractography, coupled with cycle-dependent diffraction data, provides the first details regarding the kinetics of this abnormal grain growth process during high-cycle fatigue testing. Finally, precession electron diffraction images collected in a transmission electron microscope after the in situ fatigue experiment also confirm the X-ray evidence that the abnormally large grains contain substantial misorientation gradients and sub-grain boundaries.« less

The onset and evolution of fatigue-induced abnormal grain growth in nanocrystalline Ni–Fe

DOE PAGES

Furnish, T. A.; Mehta, A.; Van Campen, D.; ...

2016-10-11

Conventional structural metals suffer from fatigue-crack initiation through dislocation activity which forms persistent slip bands leading to notch-like extrusions and intrusions. Ultrafine-grained and nanocrystalline metals can potentially exhibit superior fatigue-crack initiation resistance by suppressing these cumulative dislocation activities. Prior studies on these metals have confirmed improved high-cycle fatigue performance. In the case of nano-grained metals, analyses of subsurface crack initiation sites have indicated that the crack nucleation is associated with abnormally large grains. But, these post-mortem analyses have led to only speculation about when abnormal grain growth occurs (e.g., during fatigue, after crack initiation, or during crack growth). In thismore » study, a recently developed synchrotron X-ray diffraction technique was used to detect the onset and progression of abnormal grain growth during stress-controlled fatigue loading. Our study provides the first direct evidence that the grain coarsening is cyclically induced and occurs well before final fatigue failure—our results indicate that the first half of the fatigue life was spent prior to the detectable onset of abnormal grain growth, while the second half was spent coarsening the nanocrystalline structure and cyclically deforming the abnormally large grains until crack initiation. Post-mortem fractography, coupled with cycle-dependent diffraction data, provides the first details regarding the kinetics of this abnormal grain growth process during high-cycle fatigue testing. Finally, precession electron diffraction images collected in a transmission electron microscope after the in situ fatigue experiment also confirm the X-ray evidence that the abnormally large grains contain substantial misorientation gradients and sub-grain boundaries.« less

Cancer-related fatigue management: evaluation of a patient education program with a large-scale randomised controlled trial, the PEPs fatigue study

PubMed Central

Bourmaud, A; Anota, A; Moncharmont, C; Tinquaut, F; Oriol, M; Trillet-Lenoir, V; Bajard, A; Parnalland, S; Rotonda, C; Bonnetain, F; Pérol, D; Chauvin, F

2017-01-01

Background: To assess the efficacy of a patient educational program built according to guidelines that aims at reducing cancer-related fatigue (CRF). Methods: Randomised controlled trial, multicentre, comparing a patient education program, vs the standard of care. Patients were adult cancer outpatients with any tumour site. The primary outcome was fatigue severity assessed with a visual analogical scale (VAS), between the day of randomisation and week 7. Secondary outcomes were fatigue assessed with other scales, health-related quality of life, anxiety and depression. The time to fatigue severity deterioration was assessed. Analyses were performed in a modified intent-to-treat way, that is, including all patients with at least one baseline and 1 week 7 score. Results: A total of 212 patients were included. Fatigue severity assessment was made on 79 patients in the experimental group and 65 in the control group. Between randomisation and week 7, the fatigue (VAS) improved by 0.96 (2.85) points in the experimental group vs 1.63 (2.63) points in the control group (P=0.15). No differences with the secondary outcomes were highlighted between two groups. No other factors were found to be associated with fatigue severity deterioration. Conclusions: Despite rigorous methodology, this study failed to highlight the program efficacy in fatigue reduction for cancer patients. Other assessment tools should be developed to measure the effect of the program on CRF and behaviour. The implementation of the program should also be explored in order to identify its mechanisms and longer-term impact. PMID:28196066

An Investigation of the Combined Effect of Stress, Fatigue and Workload on Human Performance: Position Paper

NASA Technical Reports Server (NTRS)

Mock, Jessica

2005-01-01

Stress, fatigue, and workload affect worker performance. NSF reported that 61% of respondents state losing concentration at work while 79% occasionally or frequently made errors as a result of being fatigued. Shift work, altered work schedules, long hours of continuous wakefulness, and sleep loss can create sleep and circadian disruptions that degrade waking fundions causing stress and fatigue. Review of the literature has proven void of information that links the combined effects of fatigue, stress, and workload to human performance. This paper will address which occupational factors within stress, fatigue, and workload were identified as occupational contributors to performance changes. The results of this research will be apglied to underlying models and algorithms that will help predict performance changes in control room operators.

The Nature of Fatigue in Chronic Fatigue Syndrome.

PubMed

Olson, Karin; Zimka, Oksana; Stein, Eleanor

2015-10-01

In this article, we report the findings of our study on the nature of fatigue in patients diagnosed with chronic fatigue syndrome. Using ethnoscience as a design, we conducted a series of unstructured interviews and card sorts to learn more about how people with chronic fatigue syndrome describe fatigue. Participants (N = 14) described three distinct domains: tiredness, fatigue, and exhaustion. Most participants experienced tiredness prior to diagnosis, fatigue during daily life, and exhaustion after overexertion. We also discuss participants' ability to adapt to a variety of stressors and prevent shifts to exhaustion, and relate our findings to stress theory and other current research. Primary strategies that promoted adaptation to stressors included pacing and extended rest periods. These findings can aid health care professionals in detecting impending shifts between tiredness, fatigue, and exhaustion and in improving adaptive strategies, thereby improving quality of life. © The Author(s) 2015.

Effects of Warm-Up and Fatigue on Knee Joint Position Sense and Jump Performance.

PubMed

Romero-Franco, N; Jiménez-Reyes, P

2017-01-01

The purpose of this study was to evaluate the effects of a warm-up and fatigue protocol on the vertical jump and knee joint position sense of sprinters. Thirty-two sprinters were randomly allocated to either a control group (CONT) or a plyometric group (PLYO) that performed a warm-up, followed by a high-intensity plyometric protocol. Absolute (AAE), relative (RAE), and variable (VAE) angular errors and vertical jump were evaluated before and after the warm-up, as well as after the plyometric protocol and again 5 min later. After the warm-up, athletes improved RAE and jump performance. After the plyometric protocol, scores on the RAE, VAE, and the vertical jump performance worsened compared to the control group and to the values obtained after the warm-up. Five minutes later, RAE and vertical jump continued to be impaired. AAE did not show significant differences. The vertical jump is improved after the warm-up, although it is deteriorated after high-intensity plyometry. Regarding knee proprioception, the lack of impairments in the AAE make unclear the effects of the plyometric exercises on knee proprioception.

Development of a full-scale transmission testing procedure to evaluate advanced lubricants

NASA Technical Reports Server (NTRS)

Lewicki, David G.; Decker, Harry J.; Shimski, John T.

1992-01-01

Experimental tests were performed on the OH-58A helicopter main rotor transmission in the NASA Lewis 500-hp Helicopter Transmission Test Stand. The testing was part of a joint Navy/NASA/Army lubrication program. The objective of the program was to develop a separate lubricant for gearboxes and demonstrate an improved performance in life and load-carrying capacity. The goal of the experiments was to develop a testing procedure to fail certain transmission components using a MIL-L-23699 base reference oil, then run identical tests with improved lubricants and demonstrate performance. The tests were directed at failing components that the Navy has had problems with due to marginal lubrication. These failures included mast shaft bearing micropitting, sun gear and planet bearing fatigue, and spiral bevel gear scoring. A variety of tests were performed and over 900 hours of total run time accumulated for these tests. Some success was achieved in developing a testing procedure to produce sun gear and planet bearing fatigue failures. Only marginal success was achieved in producing mast shaft bearing micropitting and spiral bevel gear scoring.

Cognitive Fatigue Facilitates Procedural Sequence Learning.

PubMed

Borragán, Guillermo; Slama, Hichem; Destrebecqz, Arnaud; Peigneux, Philippe

2016-01-01

Enhanced procedural learning has been evidenced in conditions where cognitive control is diminished, including hypnosis, disruption of prefrontal activity and non-optimal time of the day. Another condition depleting the availability of controlled resources is cognitive fatigue (CF). We tested the hypothesis that CF, eventually leading to diminished cognitive control, facilitates procedural sequence learning. In a two-day experiment, 23 young healthy adults were administered a serial reaction time task (SRTT) following the induction of high or low levels of CF, in a counterbalanced order. CF was induced using the Time load Dual-back (TloadDback) paradigm, a dual working memory task that allows tailoring cognitive load levels to the individual's optimal performance capacity. In line with our hypothesis, reaction times (RT) in the SRTT were faster in the high- than in the low-level fatigue condition, and performance improvement was higher for the sequential than the motor components. Altogether, our results suggest a paradoxical, facilitating impact of CF on procedural motor sequence learning. We propose that facilitated learning in the high-level fatigue condition stems from a reduction in the cognitive resources devoted to cognitive control processes that normally oppose automatic procedural acquisition mechanisms.

Physical Activity and Symptoms in Pulmonary Arterial Hypertension.

PubMed

Matura, Lea Ann; Shou, Haochang; Fritz, Jason S; Smith, K Akaya; Vaidya, Anjali; Pinder, Diane; Archer-Chicko, Christine; Dubow, Danielle; Palevsky, Harold I; Sommers, Marilyn S; Kawut, Steven M

2016-07-01

Fatigue is a common symptom in patients with pulmonary arterial hypertension (PAH); however, the impact of fatigue on daily physical activity in PAH is unknown. Accelerometry is a validated measure for assessing physical activity. We hypothesized that patients with PAH reporting higher levels of fatigue would have lower daily physical activity measured by accelerometry. We performed a prospective cohort study of 15 women with PAH. On day 1, subjects completed the Multidimensional Fatigue Inventory (MFI), the United States Cambridge Pulmonary Hypertension Outcome Review (US CAMPHOR), and a 6-min walk test. Subjects wore the accelerometer on their dominant hip and completed an activity diary for 7 days. On day 15, subjects repeated the MFI and the US CAMPHOR, and then wore the accelerometer and completed an activity diary for an additional 7 days. All multivariate analyses were adjusted for age, BMI, and PAH type. The mean age was 50.5 years, and 53% had idiopathic or heritable PAH. During the 2 weeks, subjects were mostly sedentary (85% of the time), although 10% of their time was spent performing low-level activity. Lower average daily counts were associated with worse self-reported energy levels, whereas less day-to-day physical activity variability was associated with more self-reported mental fatigue, physical fatigue, and total activity. Higher percentage of activity bouts was also associated with worse energy. Women with PAH may spend most of their time being sedentary, and lower self-reported energy levels are associated with less daily activity. Interventions to improve symptoms such as fatigue may also increase physical activity levels in PAH. Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

Effect of an oral supplementation with a proprietary melon juice concentrate (Extramel®) on stress and fatigue in healthy people: a pilot, double-blind, placebo-controlled clinical trial

PubMed Central

Milesi, Marie-Anne; Lacan, Dominique; Brosse, Hervé; Desor, Didier; Notin, Claire

2009-01-01

Background Recent studies have demonstrated a correlation between perceived stress and oxidative stress. As SOD is the main enzyme of the enzymatic antioxidant defence system of the body, we evaluated the effect of an oral daily intake of a proprietary melon juice concentrate rich in SOD (EXTRAMEL®) on the signs and symptoms of stress and fatigue in healthy volunteers. Methods This randomized, double blind, placebo controlled clinical study was conducted with seventy healthy volunteers aged between 30 and 55 years, who feel daily stress and fatigue. They took the dietary supplement based on the melon juice concentrate (10 mg Extramel® corresponding to 140 IU SOD per capsule) or a placebo one time daily during 4 weeks. Stress and fatigue were measured using four observational psychometric scales: FARD, PSS-14, SF-12 and Epworth scale. The study was conducted by Isoclin, a clinical research organization, located in Poitiers, France. Results No adverse effect was noted. The supplementation with the proprietary melon juice concentrate bringing 140 IU SOD/day significantly improved signs and symptoms of stress and fatigue linked to performance, physical (pain, sleep troubles), cognitive (concentration, weariness, sleep troubles) or behavioural (attitude, irritability, difficulty of contact) compared to the placebo. In the same way, quality of life and perceived stress were significantly improved with SOD supplementation. Conclusion This pilot study showed that an oral supplementation with a proprietary melon juice concentrate rich in SOD may have a positive effect on several signs and symptoms of perceived stress and fatigue. PMID:19754931

Mental Fatigue Impairs Soccer-Specific Physical and Technical Performance.

PubMed

Smith, Mitchell R; Coutts, Aaron J; Merlini, Michele; Deprez, Dieter; Lenoir, Matthieu; Marcora, Samuele M

2016-02-01

To investigate the effects of mental fatigue on soccer-specific physical and technical performance. This investigation consisted of two separate studies. Study 1 assessed the soccer-specific physical performance of 12 moderately trained soccer players using the Yo-Yo Intermittent Recovery Test, Level 1 (Yo-Yo IR1). Study 2 assessed the soccer-specific technical performance of 14 experienced soccer players using the Loughborough Soccer Passing and Shooting Tests (LSPT, LSST). Each test was performed on two occasions and preceded, in a randomized, counterbalanced order, by 30 min of the Stroop task (mentally fatiguing treatment) or 30 min of reading magazines (control treatment). Subjective ratings of mental fatigue were measured before and after treatment, and mental effort and motivation were measured after treatment. Distance run, heart rate, and ratings of perceived exertion were recorded during the Yo-Yo IR1. LSPT performance time was calculated as original time plus penalty time. LSST performance was assessed using shot speed, shot accuracy, and shot sequence time. Subjective ratings of mental fatigue and effort were higher after the Stroop task in both studies (P < 0.001), whereas motivation was similar between conditions. This mental fatigue significantly reduced running distance in the Yo-Yo IR1 (P < 0.001). No difference in heart rate existed between conditions, whereas ratings of perceived exertion were significantly higher at iso-time in the mental fatigue condition (P < 0.01). LSPT original time and performance time were not different between conditions; however, penalty time significantly increased in the mental fatigue condition (P = 0.015). Mental fatigue also impaired shot speed (P = 0.024) and accuracy (P < 0.01), whereas shot sequence time was similar between conditions. Mental fatigue impairs soccer-specific running, passing, and shooting performance.

Assessment of physical fatigability and fatigue perception in myasthenia gravis.

PubMed

Jordan, Berit; Mehl, Theresa; Schweden, Tabea L K; Menge, Uwe; Zierz, Stephan

2017-05-01

Fatigue includes both performance fatigability and fatigue perception. In 32 stable patients with generalized myasthenia gravis (MG) and 17 controls, time-dependent physical performance was assessed by the arm movement test (AMT) and 6-minute walk test (6MWT). MG patients presented with low quantitative MG scores (mean 0.5, SD 0.5) and without pathologic decrement. Fatigability was based on calculation of linear trend (LT) reflecting dynamic performance within subsequent constant time intervals. Perception of physical fatigue was analyzed using fatigue questionnaires. MG patients showed a negative LT in both AMT and 6MWT, significantly differing from stable performance in controls. LT inversely correlated with elevation of acetylcholine receptor antibodies (r = -0.59, P < 0.005) but not with quantitative MG score and fatigue perception. LT allows quantification of fatigability as an objective measurement of decline in individual performance, even in patients without obvious neuromuscular deficits in routine testing. The missing correlation of experienced fatigue supports the multidimensional fatigue model. Muscle Nerve 55: 657-663, 2017. © 2016 Wiley Periodicals, Inc.

Fatigue methodology III; Proceedings of the AHS National Technical Specialists' Meeting on Advanced Rotorcraft Structures, Scottsdale, AZ, Oct. 3-5, 1989

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1989-01-01

Papers on rotorcraft and fatigue methodology are presented, covering topics such as reliability design for rotorcraft, a comparison between theory and fatigue test data on stress concentration factors, the retirement lives of rolling element bearings, hydrogen embrittlement risk analysis for high hardness steel parts, and rotating system load monitoring with minimum fixed system instrumentation. Additional topics include usage data collection to improve structural integrity of operational helicopters, usage monitory of military helicopters, improvements to the fatigue substantiation of the H-60 composite tail rotor blade, helicopter surviellance programs, and potential application of automotive fatigue technology in rotorcraft design. Also, consideration ismore » given to fatigue evaluation of C/MH-53 E main rotor damper threaded joints, SH-2F airframe fatigue test program, a ply termination concept for improving fracture and fatigue strength of composite laminates, the analysis and testing of composite panels subject to muzzle blast effects, the certification plan for an all-composite main rotor flexbeam, and the effects of stacking sequence on the flexural strength of composite beams.« less

On-line crack prognosis in attachment lug using Lamb wave-deterministic resampling particle filter-based method

NASA Astrophysics Data System (ADS)

Yuan, Shenfang; Chen, Jian; Yang, Weibo; Qiu, Lei

2017-08-01

Fatigue crack growth prognosis is important for prolonging service time, improving safety, and reducing maintenance cost in many safety-critical systems, such as in aircraft, wind turbines, bridges, and nuclear plants. Combining fatigue crack growth models with the particle filter (PF) method has proved promising to deal with the uncertainties during fatigue crack growth and reach a more accurate prognosis. However, research on prognosis methods integrating on-line crack monitoring with the PF method is still lacking, as well as experimental verifications. Besides, the PF methods adopted so far are almost all sequential importance resampling-based PFs, which usually encounter sample impoverishment problems, and hence performs poorly. To solve these problems, in this paper, the piezoelectric transducers (PZTs)-based active Lamb wave method is adopted for on-line crack monitoring. The deterministic resampling PF (DRPF) is proposed to be used in fatigue crack growth prognosis, which can overcome the sample impoverishment problem. The proposed method is verified through fatigue tests of attachment lugs, which are a kind of important joint component in aerospace systems.

Dietary supplementation with a superoxide dismutase-melon concentrate reduces stress, physical and mental fatigue in healthy people: a randomised, double-blind, placebo-controlled trial.

PubMed

Carillon, Julie; Notin, Claire; Schmitt, Karine; Simoneau, Guy; Lacan, Dominique

2014-06-19

We aimed to investigate effects of superoxide dismutase (SOD)-melon concentrate supplementation on psychological stress, physical and mental fatigue in healthy people. A randomized, double-blind, placebo-controlled trial was performed on 61 people divided in two groups: active supplement (n = 32) and placebo (n = 29) for 12 weeks. Volunteers were given one small hard capsule per day. One capsule contained 10 mg of SOD-melon concentrate (140 U of SOD) and starch for the active supplement and starch only for the placebo. Stress and fatigue were evaluated using four psychometric scales: PSS-14; SF-36; Stroop tests and Prevost scale. The supplementation with SOD-melon concentrate significantly decreased perceived stress, compared to placebo. Moreover, quality of life was improved and physical and mental fatigue were reduced with SOD-melon concentrate supplementation. SOD-melon concentrate supplementation appears to be an effective and natural way to reduce stress and fatigue. trial approved by the ethical committee of Poitiers (France), and the ClinicalTrials.gov Identifier is NCT01767922.

Driver fatigue and highway driving: a simulator study.

PubMed

Ting, Ping-Huang; Hwang, Jiun-Ren; Doong, Ji-Liang; Jeng, Ming-Chang

2008-06-09

Long duration of driving is a significant cause of fatigue-related accidents on motorways or major roadways. The fatigue caused by driving for extended periods acutely impairs driver alertness and performance and can compromise transportation safety. This study quantitatively measured the progression of driver fatigue and identified the conservative safe duration of continuous highway driving. Thirty young male subjects were analyzed during 90 min of laboratory-simulated highway driving. Sleepiness ratings (SSS) and reaction time (RT) tests were used to assess impairment of driver alertness and vigilance. Additionally, various measures of driving performance recorded throughout the experiment were used to measure temporal deterioration of driver performance from alert to fatigued using principal component analysis (PCA). The analytical results revealed that SSS scores, reaction times (RTs) and unstable driving performance significantly increased over time, indicating that excessive driving time is a significant fatigue factor and potential cause of fatigue-related accidents. Moreover, the analytical results indicated that 80 min was the safe limit for monotonous highway driving. Based on the experimental findings of this study, public awareness of the adverse affects of driver fatigue during long-distance driving should be enhanced. This study provides explicit information of fatigue development that can be used to prevent fatigue-related accidents.

Reduced Electromyographic Fatigue Threshold after Performing a Cognitive Fatiguing Task.

PubMed

Ferris, Justine R; Tomlinson, Mary A; Ward, Tayler N; Pepin, Marie E; Malek, Moh H

2018-02-22

Cognitive fatigue tasks performed prior to exercise may reduce exercise capacity. The electromyographic fatigue threshold (EMGFT) is the highest exercise intensity that can be maintained without significant increase in the EMG amplitude versus time relationship. To date, no studies have examined the effect of cognitive fatigue on the estimation of the EMGFT. The purpose of this study, therefore, was to determine whether or not cognitive fatigue prior to performing exercise reduces the estimated EMGFT. Eight healthy college-aged men were recruited from a university student population and visited the laboratory on multiple occasions. In a randomized order, subjects performed either the cognitive fatigue task (AX Continuous Performance Test; AX-CPT) for 60 min on one visit (experimental condition) or watched a video on trains for 60 min on the other visit (control condition). After each condition, subjects performed the incremental single-leg knee-extensor ergometry test while the EMG amplitude was recorded from the rectus femoris muscle and heart rate was monitored throughout. Thereafter, the EMGFT was calculated for each participant for each visit and compared using paired samples t-test. For exercise outcomes, there were no significant mean differences for maximal power output between the two conditions (control: 51 ± 5 vs. fatigue: 50 ± 3 W), but a significant decrease in EMGFT between the two conditions (control: 31 ± 3 vs. fatigue: 24 ± 2 W; p = 0.013). Moreover, maximal heart rate was significantly different between the two conditions (control: 151 ± 5 vs. fatigue: 132 ± 6; p = 0.027). These results suggest that performing the cognitive fatiguing task reduces the EMGFT with a corresponding reduction in maximal heart rate response.

NASA-ONERA Collaboration on Human Factors in Aviation Accidents and Incidents

NASA Technical Reports Server (NTRS)

Srivastava, Ashok N.; Fabiani, Patrick

2012-01-01

This is the first annual report jointly prepared by NASA and ONERA on the work performed under the agreement to collaborate on a study of the human factors entailed in aviation accidents and incidents, particularly focused on the consequences of decreases in human performance associated with fatigue. The objective of this agreement is to generate reliable, automated procedures that improve understanding of the levels and characteristics of flight-crew fatigue factors whose confluence will likely result in unacceptable crew performance. This study entails the analyses of numerical and textual data collected during operational flights. NASA and ONERA are collaborating on the development and assessment of automated capabilities for extracting operationally significant information from very large, diverse (textual and numerical) databases; much larger than can be handled practically by human experts.

Effects of Napping During Shift Work on Sleepiness and Performance in Emergency Medical Services Personnel and Similar Shift Workers: A Systematic Review and Meta-Analysis.

PubMed

Martin-Gill, Christian; Barger, Laura K; Moore, Charity G; Higgins, J Stephen; Teasley, Ellen M; Weiss, Patricia M; Condle, Joseph P; Flickinger, Katharyn L; Coppler, Patrick J; Sequeira, Denisse J; Divecha, Ayushi A; Matthews, Margaret E; Lang, Eddy S; Patterson, P Daniel

2018-02-15

Scheduled napping during work shifts may be an effective way to mitigate fatigue-related risk. This study aimed to critically review and synthesize existing literature on the impact of scheduled naps on fatigue-related outcomes for EMS personnel and similar shift worker groups. A systematic literature review was performed of the impact of a scheduled nap during shift work on EMS personnel or similar shift workers. The primary (critical) outcome of interest was EMS personnel safety. Secondary (important) outcomes were patient safety; personnel performance; acute states of fatigue, alertness, and sleepiness; indicators of sleep duration and/or quality; employee retention/turnover; indicators of long-term health; and cost to the system. Meta-analyses were performed to evaluate the impact of napping on a measure of personnel performance (the psychomotor vigilance test [PVT]) and measures of acute fatigue. Of 4,660 unique records identified, 13 experimental studies were determined relevant and summarized. The effect of napping on reaction time measured at the end of shift was small and non-significant (SMD 0.12, 95% CI -0.13 to 0.36; p = 0.34). Napping during work did not change reaction time from the beginning to the end of the shift (SMD -0.01, 95% CI -25.0 to 0.24; p = 0.96). Naps had a moderate, significant effect on sleepiness measured at the end of shift (SMD 0.40, 95% CI 0.09 to 0.72; p = 0.01). The difference in sleepiness from the start to the end of shift was moderate and statistically significant (SMD 0.41, 95% CI 0.09 to 0.72; p = 0.01). Reviewed literature indicated that scheduled naps at work improved performance and decreased fatigue in shift workers. Further research is required to identify the optimal timing and duration of scheduled naps to maximize the beneficial outcomes.

Mediators of the effects on fatigue of pragmatic rehabilitation for chronic fatigue syndrome.

PubMed

Wearden, Alison J; Emsley, Richard

2013-10-01

To examine potential mediators of the effect of pragmatic rehabilitation on improvements in fatigue following a randomized controlled trial for patients with chronic fatigue syndrome (CFS/ME) in primary care (IRCTN 74156610). Patients fulfilled the Oxford criteria for CFS. Ninety-five patients were randomized to pragmatic rehabilitation and 100 to general practitioner (GP) treatment as usual. The outcome was the Chalder fatigue scale score (0123 scoring) at end of treatment (20 weeks) and 1-year follow up (70 weeks). First, the effect of treatment on potential mediators was assessed. Then fatigue was regressed on significant mediators, treatment allocation, and baseline measures of fatigue and significant mediators. Reduction in limiting activities at 20 weeks mediated the positive effect of pragmatic rehabilitation on fatigue at 70 weeks (mediated effect size = -2.64, SE = 0.81, p = .001, proportion of effect mediated = 82.0%). Reduction in catastrophizing at 20 weeks mediated the positive effect of pragmatic rehabilitation on fatigue at 70 weeks (mediated effect size = -1.39, SE = 0.61, p = .023, proportion of effect mediated = 43.2%). Reductions in 70-week measures of fear avoidance, embarrassment avoidance, limiting activities, and all-or-nothing behavior all mediated improvement in fatigue at 70 weeks, although the causal direction of these cross-sectional effects cannot be determined. There were no between-group differences on measures of exercise capacity (a timed step test). Improvements in fatigue following pragmatic rehabilitation are related to changes in behavioral responses to and beliefs about fatigue.

The effect of rhythmic-cued motor imagery on walking, fatigue and quality of life in people with multiple sclerosis: A randomised controlled trial.

PubMed

Seebacher, Barbara; Kuisma, Raija; Glynn, Angela; Berger, Thomas

2017-02-01

Motor imagery and rhythmic auditory stimulation are physiotherapy strategies for walking rehabilitation. To investigate the effect of motor imagery combined with rhythmic cueing on walking, fatigue and quality of life (QoL) in people with multiple sclerosis (MS). Individuals with MS and Expanded Disability Status Scale scores of 1.5-4.5 were randomised into one of three groups: 17 minutes of motor imagery, six times per week, for 4 weeks, with music (A) or metronome cues (B), both with verbal cueing, and (C) controls. Primary outcomes were walking speed (Timed 25-Foot Walk) and distance (6-Minute Walk Test). Secondary outcomes were walking perception (Multiple Sclerosis Walking Scale-12), fatigue (Modified Fatigue Impact Scale) and QoL (Short Form-36 Health Survey, Multiple Sclerosis Impact Scale-29, Euroquol-5D-3L Questionnaire). Of the 112 participants randomised, 101 completed the study. Compared to controls, both interventions significantly improved walking speed, distance and perception. Significant improvements in cognitive but not psychosocial fatigue were seen in the intervention groups, and physical fatigue improved only in the music-based group. Both interventions improved QoL; however, music-cued motor imagery was superior at improving health-related QoL. Rhythmic-cued motor imagery improves walking, fatigue and QoL in people with MS, with music-cued motor imagery being more effective.

Proposed Performance Measures and Strategies for Implementation of the Fatigue Risk Management Guidelines for Emergency Medical Services.

PubMed

Martin-Gill, Christian; Higgins, J Stephen; Van Dongen, Hans P A; Buysse, Daniel J; Thackery, Ronald W; Kupas, Douglas F; Becker, David S; Dean, Bradley E; Lindbeck, George H; Guyette, Francis X; Penner, Josef H; Violanti, John M; Lang, Eddy S; Patterson, P Daniel

2018-02-15

Performance measures are a key component of implementation, dissemination, and evaluation of evidence-based guidelines (EBGs). We developed performance measures for Emergency Medical Services (EMS) stakeholders to enable the implementation of guidelines for fatigue risk management in the EMS setting. Panelists associated with the Fatigue in EMS Project, which was supported by the National Highway Traffic Safety Administration (NHTSA), used an iterative process to develop a draft set of performance measures linked to 5 recommendations for fatigue risk management in EMS. We used a cross-sectional survey design and the Content Validity Index (CVI) to quantify agreement among panelists on the wording and content of draft measures. An anonymous web-based tool was used to solicit the panelists' perceptions of clarity and relevance of draft measures. Panelists rated the clarity and relevance separately for each draft measure on a 4-point scale. CVI scores ≥0.78 for clarity and relevance were specified a priori to signify agreement and completion of measurement development. Panelists judged 5 performance measures for fatigue risk management as clear and relevant. These measures address use of fatigue and/or sleepiness survey instruments, optimal duration of shifts, access to caffeine as a fatigue countermeasure, use of napping during shift work, and the delivery of education and training on fatigue risk management for EMS personnel. Panelists complemented performance measures with suggestions for implementation by EMS agencies. Performance measures for fatigue risk management in the EMS setting will facilitate the implementation and evaluation of the EBG for Fatigue in EMS.

Translating Fatigue to Human Performance

PubMed Central

Enoka, Roger M.; Duchateau, Jacques

2016-01-01

Despite flourishing interest in the topic of fatigue—as indicated by the many presentations on fatigue at the 2015 annual meeting of the American College of Sports Medicine—surprisingly little is known about its impact on human performance. There are two main reasons for this dilemma: (1) the inability of current terminology to accommodate the scope of the conditions ascribed to fatigue, and (2) a paucity of validated experimental models. In contrast to current practice, a case is made for a unified definition of fatigue to facilitate its management in health and disease. Based on the classic two-domain concept of Mosso, fatigue is defined as a disabling symptom in which physical and cognitive function is limited by interactions between performance fatigability and perceived fatigability. As a symptom, fatigue can only be measured by self-report, quantified as either a trait characteristic or a state variable. One consequence of such a definition is that the word fatigue should not be preceded by an adjective (e.g., central, mental, muscle, peripheral, and supraspinal) to suggest the locus of the changes responsible for an observed level of fatigue. Rather, mechanistic studies should be performed with validated experimental models to identify the changes responsible for the reported fatigue. As indicated by three examples (walking endurance in old adults, time trials by endurance athletes, and fatigue in persons with multiple sclerosis) discussed in the review, however, it has proven challenging to develop valid experimental models of fatigue. The proposed framework provides a foundation to address the many gaps in knowledge of how laboratory measures of fatigue and fatigability impact real-world performance. PMID:27015386

Myoelectrical Manifestation of Fatigue Less Prominent in Patients with Cancer Related Fatigue

PubMed Central

Kisiel-Sajewicz, Katarzyna; Siemionow, Vlodek; Seyidova-Khoshknabi, Dilara; Davis, Mellar P.; Wyant, Alexandria; Ranganathan, Vinoth K.; Walsh, Declan; Yan, Jin H.; Hou, Juliet; Yue, Guang H.

2013-01-01

Purpose A lack of fatigue-related muscle contractile property changes at time of perceived physical exhaustion and greater central than peripheral fatigue detected by twitch interpolation technique have recently been reported in cancer survivors with fatigue symptoms. Based on these observations, it was hypothesized that compared to healthy people, myoelectrical manifestation of fatigue in the performing muscles would be less significant in these individuals while sustaining a prolonged motor task to self-perceived exhaustion (SPE) since their central fatigue was more prominent. The purpose of this study was to test this hypothesis by examining electromyographic (EMG) signal changes during fatiguing muscle performance. Methods Twelve individuals who had advanced solid cancer and cancer-related fatigue (CRF), and 12 age- and gender-matched healthy controls performed a sustained elbow flexion at 30% maximal voluntary contraction till SPE. Amplitude and mean power frequency (MPF) of EMG signals of the biceps brachii, brachioradialis, and triceps brachii muscles were evaluated when the individuals experienced minimal, moderate, and severe fatigue. Results CRF patients perceived physical “exhaustion” significantly sooner than the controls. The myoelectrical manifestation of muscular fatigue assessed by EMG amplitude and MPF was less significant in CRF than controls. The lower MPF even at minimal fatigue stage in CRF may indicate pathophysiologic condition of the muscle. Conclusions CRF patients experience less myoelectrical manifestation of muscle fatigue than healthy individuals near the time of SPE. The data suggest that central nervous system fatigue plays a more important role in limiting endurance-type of motor performance in patients with CRF. PMID:24391800

Advanced Environmental Barrier Coating Development for SiC/SiC Ceramic Matrix Composites: NASA's Perspectives

NASA Technical Reports Server (NTRS)

Zhu, Dongming

2016-01-01

This presentation reviews NASA environmental barrier coating (EBC) system development programs and the coating materials evolutions for protecting the SiC/SiC Ceramic Matrix Composites in order to meet the next generation engine performance requirements. The presentation focuses on several generations of NASA EBC systems, EBC-CMC component system technologies for SiC/SiC ceramic matrix composite combustors and turbine airfoils, highlighting the temperature capability and durability improvements in simulated engine high heat flux, high pressure, high velocity, and with mechanical creep and fatigue loading conditions. The current EBC development emphasis is placed on advanced NASA 2700F candidate environmental barrier coating systems for SiC/SiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, erosion-impact resistance, and long-term fatigue-environment system durability performance are described. The research and development opportunities for advanced turbine airfoil environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling are discussed.

Primary Sjögren's syndrome in Moroccan patients: characteristics, fatigue and quality of life.

PubMed

Ibn Yacoub, Yousra; Rostom, Samira; Laatiris, Assia; Hajjaj-Hassouni, Najia

2012-09-01

Our aim was to evaluate fatigue and quality of life (QoL) in Moroccan patients with primary Sjögren's syndrome (PSS) and determine their correlates with disease-related parameters. Fifty-seven consecutive patients with PSS according to the American-European Consensus group (AEGG) criteria were included. Demographic, clinical, biological and immunological characteristics for all patients were collected. Xerostomia was demonstrated by histological grading of lower lip glandular biopsy. A Schirmer test was performed to measure lachrymal flow. Oral, ocular, skin, vaginal and tracheal dryness were evaluated by using a visual analogue scale (VAS). Fatigue was assessed by the Multidimensional assessment of fatigue (MAF) and the QoL by using the generic instrument: SF-36. 90% of our patients were women. The mean age of patients was 53.73 ± 7.69 years, and the mean disease duration was 5.38 ± 4.11 years. The mean oral dryness was 68.38 ± 20.29, and the mean ocular dryness was 51.91 ± 14.03. The mean total score of the MAF was 26.73 ± 8.33, and 87.5% of our patients experienced severe fatigue. Also, physical and mental domains of QoL were altered in a significant way, and the severity of fatigue had a negative impact on SF-36 scores. MAF and SF-36 scores were correlated with the delay of diagnosis, the intensity of xerostomia and the activity of joint involvement. A low socioeconomic and educational level had a negative impact on fatigue scores and QoL. Histological grading of lower lip glandular biopsy, immunological status and the severity of systemic involvement had no correlations with fatigue scores or the alteration of QoL. Patients receiving antidepressant have lesser fatigue and those receiving Methotrexate have better SF-36 scores. In our data, there was a high prevalence of fatigue in Moroccan patients with PSS associated with altered QoL. Severe fatigue and reduced QoL seem to be related to the severity of joint involvement, xerostomia and both educational and socioeconomic levels. Also, treatment with methotrexate and antidepressant seems to improve patients' living and QoL. An appropriate therapeutic intervention for depression and articular manifestations in PSS should be applied to improve patients' living.

Interferon-free regimens improve health-related quality of life and fatigue in HIV/HCV-coinfected patients with advanced liver disease

PubMed Central

Scheiner, Bernhard; Schwabl, Philipp; Steiner, Sebastian; Bucsics, Theresa; Chromy, David; Aichelburg, Maximilian C.; Grabmeier-Pfistershammer, Katharina; Trauner, Michael; Peck-Radosavljevic, Markus; Reiberger, Thomas; Mandorfer, Mattias

2016-01-01

Abstract Health-related quality of life (HRQoL) is impaired in HIV/HCV-coinfected patients (HIV/HCV) and further decreased by interferon (IFN)-based therapies. We aimed to investigate the impact of IFN- and ribavirin (RBV)-free therapies on HRQoL and fatigue. Thirty-three HIV/HCV-coinfected patients who underwent HCV therapy with sofosbuvir in combination with daclatasvir or ledipasvir were retrospectively studied and compared to 17 patients who received boceprevir (BOC)/PEGIFN/RBV. HRQoL (mental [MCS] and physical [PCS] component score) and fatigue were assessed using the SF-36 (Short Form 36 Health Survey) and the FSS (Fatigue Severity Scale), respectively. HRQoL/fatigue was evaluated at baseline (BL), midway, and 12 weeks after the end of treatment (FU). At BL, both domains of HRQoL as well as the severity of fatigue were significantly impaired in HIV/HCV, when compared to a healthy population. Already during treatment, IFN/RBV-free therapy improved physical health (PCS: 41.4 ± 9.7 vs. 47.0 ± 11.2; P < 0.01) and reduced fatigue (37.8 ± 14.0 vs. 31.9 ± 15.2; P = 0.01), whereas we observed a substantial worsening of both factors in patients treated with BOC/PEGIFN/RBV. Since these improvements were maintained, patients treated with IFN/RBV-free therapy reported an improvement in physical health (PCS: 41.4 ± 9.7 vs. 45.8 ± 12.7; P < 0.01) and fatigue (37.8 ± 14.0 vs. 30.9 ± 14.8; P = 0.04) at FU. While AIDS-patients had a higher severity of fatigue at BL and showed a reduction of fatigue (42.5 ± 14.0 vs. 31.6 ± 15.7; P = 0.01), mental health only improved in patients without AIDS (MCS: 35.7 ± 5.3 vs.40.7 ± 6.4; P = 0.04). HIV/HCV with severe fatigue at BL (>median BL-FSS) showed most pronounced improvements in severity of fatigue (49.7 ± 7.0 vs. 32.0 ± 16.7; P < 0.01). In contrast to IFN-based regimens, highly effective and well-tolerated IFN-/RBV-free regimens improve HRQoL (especially physical health) and fatigue already during treatment. All patients with HIV/HCV coinfection should be considered for HCV treatment; however, patients with severe fatigue should be prioritized. PMID:27399090

A comparison of cognitive performance decreases during acute, progressive fatigue arising from different concurrent stressors.

PubMed

Fogt, Donovan L; Kalns, John E; Michael, Darren J

2010-12-01

Fatigue is known to impair cognitive performance, but it remains unclear whether concurrent common stressors affect cognitive performance similarly. We used the Stroop Color-Word Conflict Test to assess cognitive performance over 24 hours for four groups: control, sleep-deprived (SD), SD + energy deficit, and SD + energy deficit + fluid restricted. Fatigue levels were quantified using the Profile of Mood States (POMS) survey. Linear mixed-effects (LME) models allowed for testing of group-specific differences in cognitive performance while accounting for subject-level variation. Starting fatigue levels were similar among all groups, while 24-hour fatigue levels differed significantly. For each cognitive performance test, results were modeled separately. The simplest LME model contained a significant fixed-effects term for slope and intercept. Moreover, the simplest LME model used a single slope coefficient to fit data from all four groups, suggesting that loss in cognitive performance over a 24-hour duty cycle with respect to fatigue level is similar regardless of the cause.

Improvement of Performance and Reduction of Fatigue With Low-Level Laser Therapy in Competitive Cyclists.

PubMed

Lanferdini, Fábio J; Bini, Rodrigo R; Baroni, Bruno M; Klein, Kelli D; Carpes, Felipe P; Vaz, Marco A

2018-01-01

Evidence indicates that low-level laser therapy (LLLT) minimizes fatigue effects on muscle performance. However, the ideal LLLT dosage to improve athletes'performance during sports activities such as cycling is still unclear. Therefore, the goal of this study was to investigate the effects of different LLLT dosages on cyclists'performance in time-to-exhaustion tests. In addition, the effects of LLLT on the frequency content of the EMG signals to assess fatigue mechanisms were examined. Twenty male competitive cyclists participated in a crossover, randomized, double-blind, placebo-controlled trial. They performed an incremental cycling test to exhaustion (on day 1) followed by 4 time-to-exhaustion tests (on days 2-5) at their individual maximal power output. Before each time-to-exhaustion test, different dosages of LLLT (135, 270, and 405 J/thigh, respectively) or placebo were applied at the quadriceps muscle bilaterally. Power output and muscle activation from both lower limbs were recorded throughout the tests. Increased performance in time-to-exhaustion tests was observed with the LLLT-135 J (∼22 s; P < .01), LLLT-270 J (∼13 s; P = .03), and LLLT-405 J (∼13 s; P = .02) compared to placebo (149 ± 23 s). Although LLLT-270 J and LLLT-405 J did not show significant differences in muscle activation compared with placebo, LLLT-135 J led to an increased high-frequency content compared with placebo in both limbs at the end of the exhaustion test (P ≤ .03). In conclusion, LLLT increased time to exhaustion in competitive cyclists, suggesting this intervention as a possible nonpharmacological ergogenic agent in cycling. Among the different dosages, LLLT-135 J seems to promote the best effects.

The effects of individualized actigraph feedback on fatigue management in railroad engineers

DOT National Transportation Integrated Search

2003-01-01

A total of twenty-one participants completed the three-month study designed to assess the functionality of improving individual sleep habits with Actigraph Performance Feedback. There were eleven participants in the feedback group and ten participant...

Effects of an individual 12-week community-located "start-to-run" program on physical capacity, walking, fatigue, cognitive function, brain volumes, and structures in persons with multiple sclerosis.

PubMed

Feys, Peter; Moumdjian, Lousin; Van Halewyck, Florian; Wens, Inez; Eijnde, Bert O; Van Wijmeersch, Bart; Popescu, Veronica; Van Asch, Paul

2017-11-01

Exercise therapy studies in persons with multiple sclerosis (pwMS) primarily focused on motor outcomes in mid disease stage, while cognitive function and neural correlates were only limitedly addressed. This pragmatic randomized controlled study investigated the effects of a remotely supervised community-located "start-to-run" program on physical and cognitive function, fatigue, quality of life, brain volume, and connectivity. In all, 42 pwMS were randomized to either experimental (EXP) or waiting list control (WLC) group. The EXP group received individualized training instructions during 12 weeks (3×/week), to be performed in their community aiming to participate in a running event. Measures were physical (VO 2max , sit-to-stand test, Six-Minute Walk Test (6MWT), Multiple Sclerosis Walking Scale-12 (MSWS-12)) and cognitive function (Rao's Brief Repeatable Battery (BRB), Paced Auditory Serial Attention Test (PASAT)), fatigue (Fatigue Scale for Motor and Cognitive Function (FSMC)), quality of life (Multiple Sclerosis Impact Scale-29 (MSIS-29)), and imaging. Brain volumes and diffusion tensor imaging (DTI) were quantified using FSL-SIENA/FIRST and FSL-TBSS. In all, 35 pwMS completed the trial. Interaction effects in favor of the EXP group were found for VO 2max , sit-to-stand test, MSWS-12, Spatial Recall Test, FSMC, MSIS-29, and pallidum volume. VO 2max improved by 1.5 mL/kg/min, MSWS-12 by 4, FSMC by 11, and MSIS-29 by 14 points. The Spatial Recall Test improved by more than 10%. Community-located run training improved aerobic capacity, functional mobility, visuospatial memory, fatigue, and quality of life and pallidum volume in pwMS.

L-carnitine supplementation in patients with HIV/AIDS and fatigue: a double-blind, placebo-controlled pilot study.

PubMed

Cruciani, Ricardo A; Revuelta, Manuel; Dvorkin, Ella; Homel, Peter; Lesage, Pauline; Esteban-Cruciani, Nora

2015-01-01

The purpose of this study was to determine the effect of L-carnitine supplementation on fatigue in patients with terminal human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS). In this randomized, double-blind, placebo-controlled, parallel-group study, patients who had end-stage HIV/AIDS with carnitine deficiency and fatigue received 3 g of oral L-carnitine or placebo for 2 weeks, followed by a 2-week, open-label phase with the same amount of L-carnitine for all patients. The primary outcome was the degree of fatigue according to the Brief Fatigue Inventory. Secondary outcomes included serum carnitine and lactate levels, physical, emotional, social, and functional well-being, performance status, mood, and CD4 count. Eighteen patients in the treatment arm and 17 in the placebo arm completed the trial. At the end of the double-blind phase, total and free carnitine levels in the treatment arm rose from 28±9 to 48±17 nM/L (P<0.001) and from 24±8 to 40±13 nM/L (P<0.001) respectively, with no changes in the placebo arm. The primary outcome, ie, fatigue measured at the end of the blinded phase, did not improve. Secondary outcomes of function, quality of life, and mood did not show improvement either. The secondary outcome of serum lactate decreased from baseline in the treatment group (1.45±0.76 to 1.28±0.52 mmol/L) and increased in the placebo group (1.38±0.62 to 1.84±0.74 mmol/L; P<0.005). Our study suggests that 3 g of oral L-carnitine supplementation for 2 weeks in terminally ill HIV/AIDS patients does not improve fatigue. This study might help to determine the dose and duration of treatment used in future clinical trials, as higher doses and/or longer periods of supplementation might be needed in order to detect an improvement. The reduction in serum lactate levels suggests a potential role for L-carnitine supplementation in patients undergoing certain types of antiretroviral therapy. This study contributes evidence-based data to the field of alternative and complementary medicine, a multibillion dollar industry in which controlled studies are not the norm.

L-carnitine supplementation in patients with HIV/AIDS and fatigue: a double-blind, placebo-controlled pilot study

PubMed Central

Cruciani, Ricardo A; Revuelta, Manuel; Dvorkin, Ella; Homel, Peter; Lesage, Pauline; Esteban-Cruciani, Nora

2015-01-01

Background The purpose of this study was to determine the effect of L-carnitine supplementation on fatigue in patients with terminal human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS). Methods In this randomized, double-blind, placebo-controlled, parallel-group study, patients who had end-stage HIV/AIDS with carnitine deficiency and fatigue received 3 g of oral L-carnitine or placebo for 2 weeks, followed by a 2-week, open-label phase with the same amount of L-carnitine for all patients. The primary outcome was the degree of fatigue according to the Brief Fatigue Inventory. Secondary outcomes included serum carnitine and lactate levels, physical, emotional, social, and functional well-being, performance status, mood, and CD4 count. Results Eighteen patients in the treatment arm and 17 in the placebo arm completed the trial. At the end of the double-blind phase, total and free carnitine levels in the treatment arm rose from 28±9 to 48±17 nM/L (P<0.001) and from 24±8 to 40±13 nM/L (P<0.001) respectively, with no changes in the placebo arm. The primary outcome, ie, fatigue measured at the end of the blinded phase, did not improve. Secondary outcomes of function, quality of life, and mood did not show improvement either. The secondary outcome of serum lactate decreased from baseline in the treatment group (1.45±0.76 to 1.28±0.52 mmol/L) and increased in the placebo group (1.38±0.62 to 1.84±0.74 mmol/L; P<0.005). Conclusion Our study suggests that 3 g of oral L-carnitine supplementation for 2 weeks in terminally ill HIV/AIDS patients does not improve fatigue. This study might help to determine the dose and duration of treatment used in future clinical trials, as higher doses and/or longer periods of supplementation might be needed in order to detect an improvement. The reduction in serum lactate levels suggests a potential role for L-carnitine supplementation in patients undergoing certain types of antiretroviral therapy. This study contributes evidence-based data to the field of alternative and complementary medicine, a multibillion dollar industry in which controlled studies are not the norm. PMID:25733927

Sleep-deprivation effect on human performance: a meta-analysis approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Candice D. Griffith; Candice D. Griffith; Sankaran Mahadevan

Human fatigue is hard to define since there is no direct measure of fatigue, much like stress. Instead fatigue must be inferred from measures that are affected by fatigue. One such measurable output affected by fatigue is reaction time. In this study the relationship of reaction time to sleep deprivation is studied. These variables were selected because reaction time and hours of sleep deprivation are straightforward characteristics of fatigue to begin the investigation of fatigue effects on performance. Meta-analysis, a widely used procedure in medical and psychological studies, is applied to the variety of fatigue literature collected from various fieldsmore » in this study. Meta-analysis establishes a procedure for coding and analyzing information from various studies to compute an effect size. In this research the effect size reported is the difference between standardized means, and is found to be -0.6341, implying a strong relationship between sleep deprivation and performance degradation.« less

Production of Near-Mirror Surface Quality by Precision Grinding

NASA Technical Reports Server (NTRS)

Dimofte, Florin; Krantz, Timothy

2003-01-01

Mechanical components such as gears and bearings operate with the working surfaces in intimate contact with a mating part. The performance of such components will be influenced by the quality of the working surface. In general, a smoother surface will perform better than a rougher surface since the lubrication conditions are improved. For example, surfaces with a special near-mirror quality finish of low roughness performed better than ground surfaces when tested using a block-on-ring arrangement. Bearings with near-mirror quality have been tested and analyzed; lower running torques were measured and improved fatigue life was anticipated. Experiments have been done to evaluate the performance of gears with improved, low roughness surface finishing. The measured performance improvements include an increased scuffing (scoring) load capacity by a factor of 1.6, a 30-percent reduction of gear tooth running friction, and longer fatigue lives by a factor of about four. One can also anticipate that near-mirror quality surface finishing could improve the performance of other mechanical components such as mechanical seals and heavily loaded journal bearings. Given these demonstrated benefits, capable and economical methods for the production of mechanical components with near-mirror quality surfaces are desired. One could propose the production of near-mirror quality surfaces by several methods such as abrasive polishing, chemical assisted polishing, or grinding. Production of the surfaces by grinding offers the possibility to control the macro-geometry (form), waviness, and surface texture with one process. The present study was carried out to investigate the possibility of producing near-mirror quality surfaces by grinding. The present study makes use of a specially designed grinding machine spindle to improve the surface quality relative to the quality produced when using a spindle of conventional design.

Fatigue in rheumatoid arthritis; a persistent problem: a large longitudinal study

PubMed Central

van Steenbergen, Hanna W; Tsonaka, Roula; Huizinga, Tom W J; Boonen, Annelies; van der Helm-van Mil, Annette H M

2015-01-01

Objective Fatigue is prevalent and disabling in rheumatoid arthritis (RA). Surprisingly, the long-term course of fatigue is studied seldom and it is unclear to what extent it is influenced by inflammation. This study aimed to determine the course of fatigue during 8 years follow-up, its association with the severity of inflammation and the effect of improved treatment strategies. Methods 626 patients with RA included in the Leiden Early Arthritis Clinic cohort were studied during 8 years. Fatigue severity, measured on a 0–100 mm scale, and other clinical variables were assessed yearly. Patients included in 1993–1995, 1996–1998 and 1999–2007 were treated with delayed treatment with disease-modifying antirheumatic drugs (DMARDs), early treatment with mild DMARDs and early treatment with methotrexate respectively. After multiple imputation, the serial measurements were analysed using linear quantile mixed models. Results Median fatigue severity at baseline was 45 mm and remained, despite treatment, rather stable thereafter. Female gender (effect size=4.4 mm), younger age (0.2 mm less fatigue/year), higher swollen and tender joint counts (0.3 mm and 1.0 mm more fatigue/swollen or tender joint) and C reactive protein-levels (0.1 mm more fatigue per mg/L) were independently and significantly (p<0.05) associated with fatigue severity over 8 years. Although improved treatment strategies associated with less severe radiographic progression, there was no effect on fatigue severity (p=0.96). Conclusions This largest longitudinal study on fatigue so far demonstrated that the association between inflammation and fatigue is statistically significant but effect sizes are small, suggesting that non-inflammatory pathways mediate fatigue as well. Improved treatment strategies did not result in less severe fatigue. Therefore, fatigue in RA remains an ‘unmet need’. PMID:26509063

Understanding postoperative fatigue.

PubMed

Rose, E A; King, T C

1978-07-01

Performance characteristics of the central nervous, cardiovascular, respiratory and muscular systems in man postoperatively have received little investigative attention, despite the well known syndrome of postoperative fatigue. The impairmen in perception and psychomotor skills that has been shown to result from caloric restriction, bedrest, sedation and sleep deprivation suggests that a similar deficit may occur after surgical procedures. After a simple elective surgical procedure, maximal oxygen uptake decreases and the adaptability of heart rate to submaximal workloads is impaired. Similar deleterious effects on cardiorespiratory performance have been documented with starvation and bedrest; an understanding of cardiorespiratory performance postoperatively awaits further investigation. Maximal muscular force of contraction is also impaired by caloric restriction and bedrest, suggesting that similar effects may be seen in the postoperative state, although this has not been studied. A better understanding of the syndrome of postoperative fatigue could be achieved by a descriptive analysis of physiologic performance postoperatively. Such descriptive data could form the basis for objective evaluation of therapeutic measures intended to improve performance, such as nutritional supplementation and pharmacologic intervention. The observation that exercise with the patient in the supine position may decrease the impairment in maximal aerobic power otherwise expected in immobilized patients suggests that controlled exercise therapy may be of value in reducing physiologic impairment postoperatively.

First Annual Report: NASA-ONERA Collaboration on Human Factors in Aviation Accidents and Incidents

NASA Technical Reports Server (NTRS)

Srivastava, Ashok; Fabiani, Patrick

2012-01-01

This is the first annual report jointly prepared by NASA and ONERA on the work performed under the agreement to collaborate on a study of the human factors entailed in aviation accidents and incidents particularly focused on consequences of decreases in human performance associated with fatigue. The objective of this Agreement is to generate reliable, automated procedures that improve understanding of the levels and characteristics of flight-crew fatigue factors whose confluence will likely result in unacceptable crew performance. This study entails the analyses of numerical and textual data collected during operational flights. NASA and ONERA are collaborating on the development and assessment of automated capabilities for extracting operationally significant information from very large, diverse (textual and numerical) databases much larger than can be handled practically by human experts. This report presents the approach that is currently expected to be used in processing and analyzing the data for identifying decrements in aircraft performance and examining their relationships to decrements in crewmember performance due to fatigue. The decisions on the approach were based on samples of both the numerical and textual data that will be collected during the four studies planned under the Human Factors Monitoring Program (HFMP). Results of preliminary analyses of these sample data are presented in this report.

Integrating Oil Debris and Vibration Measurements for Intelligent Machine Health Monitoring. Degree awarded by Toledo Univ., May 2002

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.

2003-01-01

A diagnostic tool for detecting damage to gears was developed. Two different measurement technologies, oil debris analysis and vibration were integrated into a health monitoring system for detecting surface fatigue pitting damage on gears. This integrated system showed improved detection and decision-making capabilities as compared to using individual measurement technologies. This diagnostic tool was developed and evaluated experimentally by collecting vibration and oil debris data from fatigue tests performed in the NASA Glenn Spur Gear Fatigue Rig. An oil debris sensor and the two vibration algorithms were adapted as the diagnostic tools. An inductance type oil debris sensor was selected for the oil analysis measurement technology. Gear damage data for this type of sensor was limited to data collected in the NASA Glenn test rigs. For this reason, this analysis included development of a parameter for detecting gear pitting damage using this type of sensor. The vibration data was used to calculate two previously available gear vibration diagnostic algorithms. The two vibration algorithms were selected based on their maturity and published success in detecting damage to gears. Oil debris and vibration features were then developed using fuzzy logic analysis techniques, then input into a multi sensor data fusion process. Results show combining the vibration and oil debris measurement technologies improves the detection of pitting damage on spur gears. As a result of this research, this new diagnostic tool has significantly improved detection of gear damage in the NASA Glenn Spur Gear Fatigue Rigs. This research also resulted in several other findings that will improve the development of future health monitoring systems. Oil debris analysis was found to be more reliable than vibration analysis for detecting pitting fatigue failure of gears and is capable of indicating damage progression. Also, some vibration algorithms are as sensitive to operational effects as they are to damage. Another finding was that clear threshold limits must be established for diagnostic tools. Based on additional experimental data obtained from the NASA Glenn Spiral Bevel Gear Fatigue Rig, the methodology developed in this study can be successfully implemented on other geared systems.

Fatigue reduction diet in breast cancer survivors: a pilot randomized clinical trial.

PubMed

Zick, Suzanna Maria; Colacino, Justin; Cornellier, Maria; Khabir, Tohfa; Surnow, Katie; Djuric, Zora

2017-01-01

Fatigue is a prevalent and burdensome effect of breast cancer. Fatigue has been linked to chronic inflammation, and diets high in antioxidant nutrients have been associated with lesser prevalence and severity of fatigue. Studies are needed, however, to test if antioxidant-rich diets could improve fatigue. Pilot, randomized, trial conducted between January 2014 and April 2015, to investigate if a 3-month diet rich in fruit, vegetables, whole grains, and omega-3 fatty acid-rich foods, named the fatigue reduction diet (FRD), improved fatigue and sleep compared to an attention control, named the general health curriculum (GHC). 30 stage 0 to III breast cancer survivors, who had completed cancer treatments, were randomized: 15 receiving the FRD and 15 the GHC. Primary outcome was change in fatigue, as measured by the brief fatigue Inventory, from baseline to 3 months analyzed using linear mixed models. Secondary analyses were changes in sleep quality, serum carotenoids, and fatty acids. From baseline to 3-month fatigue improved by 44 ± 39% in FRD compared to 8 ± 34% in GHC (p = 0.01); sleep quality improved by 2.5 ± 3.3 points in FRD, and diminished by 0.9 ± 2.3 in GHC (p = 0.03); serum total carotenoids (p < 0.01), β-cryptoxanthin (p = 0.02), lutein (p = 0.05), zeaxanthin (p = 0.01), lycopene (p = 0.05), omega-3 fatty acids (p < 0.01), and ratio of omega-3:omega-6 fatty acids (p = 0.02) were significantly increased, and percent saturated fatty acids were decreased (p = 0.04) in FRD; γ-tocopherol was significantly increased in GHC (p = 0.03), and there was a significant visit by group difference for α-carotene between the study groups (p = 0.05). The FRD intervention improved fatigue and sleep in breast cancer survivors compared to the GHC. FRD diet could provide a non-toxic treatment strategy for persistent fatigue.

Work-family conflict and prolonged fatigue among Japanese married male physicians.

PubMed

Ohta, Hiroshi; Wada, Koji; Kawashima, Masatoshi; Arimatsu, Mayuri; Higashi, Toshiaki; Yoshikawa, Toru; Aizawa, Yoshiharu

2011-12-01

Fatigue experienced by physicians may not only endanger their own health but may also affect the safety of patients. Such fatigue may be associated with the work environment and personal factors such as work-family conflict (WFC). This study aimed to determine the association between WFC and prolonged fatigue among Japanese married male physicians. Physicians who graduated from a Japanese medical school answered a mailed anonymous self-report questionnaire. For assessment of WFC and prolonged fatigue, the Japanese versions of the WFC scale and the Checklist of Individual Strength questionnaire (CIS) were used. Prolonged fatigue was defined as the upper quartile of total CIS scores. The WFC scale comprises six dimensions. Total scores were divided into tertiles: low, intermediate, and high levels of WFC. A multiple logistic regression analysis was performed to examine the association between WFC and prolonged fatigue. A total of 540 male physicians answered the questionnaire, and the data of 444 married male physicians were analyzed. The data were then adjusted for age and work condition factors. Prolonged fatigue was significantly associated with high strain-based work interference with family (WIF; corrected odds ratio, 5.56; 95% confidence interval, 2.55-12.1), intermediate strain-based WIF (2.53, 1.25-5.10), high time-based family interference with work (FIW; 1.92, 1.08-3.40), and there was a weak association with high strain-based FIW (1.93, 0.98-3.83). Employers should take measures to improve working conditions in hospitals, and give physicians the opportunity to learn how to cope with WFC. These measures could ultimately help prevent prolonged fatigue.

Compressive Strength of Notched Poly(Phenylene Sulfide) Aerospace Composite: Influence of Fatigue and Environment

NASA Astrophysics Data System (ADS)

Niitsu, G. T.; Lopes, C. M. A.

2013-08-01

The purpose of this work is to evaluate the influences of fatigue and environmental conditions (-55 °C, 23 °C, and 82 °C/Wet) on the ultimate compression strength of notched carbon-fiber-reinforced poly(phenylene sulfide) composites by performing open-hole compression (OHC) tests. Analysis of the fatigue effect showed that at temperatures of -55 and 23 °C, the ultimate OHC strengths were higher for fatigued than for not-fatigued specimens; this could be attributed to fiber splitting and delamination during fatigue cycling, which reduces the stress concentration at the hole edge, thus increasing the composite strength. This effect of increasing strength for fatigued specimens was not observed under the 82 °C/Wet conditions, since the test temperature near the matrix glass transition temperature ( T g) together with moisture content resulted in matrix softening, suggesting a reduction in fiber splitting during cycling; similar OHC strengths were verified for fatigued and not-fatigued specimens tested at 82 °C/Wet. Analysis of the temperature effect showed that the ultimate OHC strengths decreased with increasing temperature. A high temperature together with moisture content (82 °C/Wet condition) reduced the composite compressive strengths, since a temperature close to the matrix T g resulted in matrix softening, which reduced the lateral support provided by the resin to the 0° fibers, leading to fiber instability failure at reduced applied loads. On the other hand, a low temperature (-55 °C) improved the compressive strength because of possible fiber-matrix interfacial strengthening, increasing the fiber contribution to compressive strength.

Night shift fatigue among anaesthesia trainees at a major metropolitan teaching hospital.

PubMed

Lancman, B M

2016-05-01

Night shifts expose anaesthesia trainees to the risk of fatigue and, potentially, fatigue-related performance impairment. This study examined the workload, fatigue and coping strategies of anaesthesia trainees during night shifts. A blinded survey-based study was undertaken at a major single centre metropolitan teaching hospital in Australia. All ten anaesthesia trainees who worked night shifts participated. The survey collected data on duration of night shifts, workload, and sleep patterns. Fatigue was assessed using the Karolinska Sleepiness Scale (KSS). There were 93 night shifts generating data out of a potential 165. Trainees tended to sleep an increasing amount before their shift as the nights progressed from 1 to 5. Night 1 was identified as an 'at risk' night due to the amount of time spent awake before arriving at work (32% awake for U+003E8 hours); on all other nights trainees were most likely to have slept 6-8 hours. The KSS demonstrated an increase in sleepiness of 3 to 4 points on the scale from commencement to conclusion of a night shift. The Night 1 conclusion sleepiness was markedly worse than any other night with 42% falling into an 'at-risk' category. The findings demonstrate fatigue and inadequate sleep in anaesthesia trainees during night shifts in a major metropolitan teaching hospital. The data obtained may help administrators prepare safer rosters, and junior staff develop improved strategies to reduce the likelihood of fatigue.

Strength and endurance training reduces the loss of eccentric hamstring torque observed after soccer specific fatigue.

PubMed

Matthews, Martyn J; Heron, Kate; Todd, Stefanie; Tomlinson, Andrew; Jones, Paul; Delextrat, Anne; Cohen, Daniel D

2017-05-01

To investigate the effect of two hamstring training protocols on eccentric peak torque before and after soccer specific fatigue. Twenty-two university male soccer players. Isokinetic strength tests were performed at 60°/s pre and post fatigue, before and after 2 different training interventions. A 45-min soccer specific fatigue modified BEAST protocol (M-BEAST) was used to induce fatigue. Players were randomly assigned to a 4 week hamstrings conditioning intervention with either a maximum strength (STR) or a muscle endurance (END) emphasis. The following parameters were evaluated: Eccentric peak torque (EccPT), angle of peak torque (APT), and angle specific torques at knee joint angles of 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° and 90°. There was a significant effect of the M-BEAST on the Eccentric torque angle profile before training as well as significant improvements in post-fatigue torque angle profile following the effects of both strength and muscle endurance interventions. Forty-five minutes of simulated soccer activity leads to reduced eccentric hamstring torque at longer muscle lengths. Short-term conditioning programs (4-weeks) with either a maximum strength or a muscular endurance emphasis can equally reduce fatigue induced loss of strength over this time period. Copyright © 2017 Elsevier Ltd. All rights reserved.

Quantifying the history dependency of muscle recovery from a fatiguing intermittent task.

PubMed

Rashedi, Ehsan; Nussbaum, Maury A

2017-01-25

Muscle fatigue and recovery are complex processes influencing muscle force generation capacity. While fatigue reduces this capacity, recovery acts to restore the unfatigued muscle state. Many factors can potentially affect muscle recovery, and among these may be a task dependency of recovery following an exercise. However, little has been reported regarding the history dependency of recovery after fatiguing contractions. We examined the dependency of muscle recovery subsequent to four different histories of fatiguing muscle contractions, imposed using two cycle times (30 and 60s) during low to moderate levels (15% and 25% of maximum voluntary contraction (MVC)) of intermittent static exertions involving index finger abduction. MVC and low-frequency electrical stimulation (LFES) measures (i.e., magnitude, rise and relaxation rates) of muscle capacity were used, all of which indicated a dependency of muscle recovery on the muscle capacity state existing immediately after fatiguing exercise. This dependency did not appear to be modified by either the cycle time or exertion level leading to that state. These results imply that the post-exercise rate of recovery is primarily influenced by the immediate post-exercise muscle contractile status (estimated by MVC and LFES measures). Such results may help improve existing models of muscle recovery, facilitating more accurate predictions of localized muscle fatigue development and thereby helping to enhance muscle performance and reduce the risk of injury. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fatigue Performance of Advanced High-Strength Steels (AHSS) GMAW Joints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Zhili; Sang, Yan; Jiang, Cindy

2009-01-01

The fatigue performance of gas metal arc welding (GMAW) joints of advanced high strength steels (AHSS) are compared and analyzed. The steel studied included a number of different grades of AHSS and baseline mild steels: DP600, DP780, DP980, M130, M220, solution annealed boron steel, fully hardened boron steels, HSLA690 and DR210 (a mild steel). Fatigue testing was conducted under a number of nominal stress ranges to obtain the S/N curves of the weld joints. A two-phase analytical model is developed to predict the fatigue performance of AHSS welds. It was found that there are appreciable differences in the fatigue S/Nmore » curves among different AHSS joints made using the same welding practices, suggesting that the local microstructure in the weld toe and root region plays non-negligible role in the fatigue performance of AHSS welds. Changes in weld parameters can influence the joint characteristics which in turn influence fatigue life of the weld joints, particularly of those of higher strength AHSS. The analytical model is capable of reasonably predicting the fatigue performance of welds made with various steel grades in this study.« less

Feasibility and Preliminary Efficacy of a 10-Week Resistance and Aerobic Exercise Intervention During Neoadjuvant Chemoradiation Treatment in Rectal Cancer Patients.

PubMed

Singh, Favil; Galvão, Daniel A; Newton, Robert U; Spry, Nigel A; Baker, Michael K; Taaffe, Dennis R

2018-06-01

Neoadjuvant chemoradiation treatment (CRT) in rectal cancer patients is associated with a reduction in physical capacity, lean mass and increased fatigue. As a countermeasure to these treatment-related adverse effects, we examined the feasibility and preliminary efficacy of a 10-week exercise program during CRT. Ten rectal cancer patients (7 men, aged 27-70 years, body mass index = 26.4 ± 3.8 kg/m 2 ) receiving CRT undertook supervised resistance and aerobic exercise twice weekly. Assessments were undertaken pre- and post-intervention for upper and lower body muscle strength by 1-RM, muscle endurance, physical performance tests, body composition by dual X-ray absorptiometry, quality of life, and fatigue. There was a significant loss in appendicular skeletal muscle (-1.1 kg, P = .012), and fat mass (-0.8 kg, P = .029) following CRT. Despite the loss in skeletal muscle, leg press ( P = .030) and leg extension ( P = .046) strength improved by 27.2% and 22.7%, respectively, and leg press endurance by 76.7% ( P = .007). Changes in strength were accompanied by improved performance ( P < .05) in 6-m fast walking speed (6.9%) and dynamic balance as determined by the 6-m backwards walk (15.5%). There was minimal change in quality of life and fatigue, and no adverse events related to training. Exercise during neoadjuvant CRT appears to be feasible and well tolerated in rectal cancer patients and may enhance physical function while minimizing adverse changes in body composition and cancer-related fatigue. These initial findings need to be confirmed in randomized controlled trials.

Does Dysphoria Lead to Divergent Mental Fatigue Effects on a Cognitive Task?

PubMed

Hopstaken, Jesper F; Wanmaker, Sabine; van der Linden, Dimitri; Bakker, Arnold B

2015-01-01

Tiredness, low energy, and listlessness are common symptoms to be associated with depression. The question remains to what extent these symptoms influence the effects of fatigue on sustained performance tasks, such as impaired task engagement and performance. Based on earlier findings, it was hypothesized that dysphoric (i.e., mildly depressed) individuals, compared to healthy controls, would display earlier fatigue onset and more severe fatigue effects on task engagement and performance during a cognitive task. Sixty-one dysphoric and twenty-one non-dysphoric control participants were compared during one hour of continuous performance on a 2-back task. During the task subjective fatigue, subjective engagement, objective task performance, baseline pupil diameter and stimulus-evoked pupil dilation were measured. While we found that the dysphoric group reported relatively higher subjective fatigue than the healthy control group at the start of the experiment, we did not find any other divergent fatigue effects during the experimental task. One explanation for the absence of divergent effect is that dysphoria may not have such a profound impact on available cognitive resources, like attention, as initially thought. Based on the results of the present study, we conclude that dysphoria is not necessarily an increased risk factor for impaired sustained performance on cognitive tasks that may induce mental fatigue.

Exploring the Relationship of Task Performance and Physical and Cognitive Fatigue During a Daylong Light Precision Task.

PubMed

Yung, Marcus; Manji, Rahim; Wells, Richard P

2017-11-01

Our aim was to explore the relationship between fatigue and operation system performance during a simulated light precision task over an 8-hr period using a battery of physical (central and peripheral) and cognitive measures. Fatigue may play an important role in the relationship between poor ergonomics and deficits in quality and productivity. However, well-controlled laboratory studies in this area have several limitations, including the lack of work relevance of fatigue exposures and lack of both physical and cognitive measures. There remains a need to understand the relationship between physical and cognitive fatigue and task performance at exposure levels relevant to realistic production or light precision work. Errors and fatigue measures were tracked over the course of a micropipetting task. Fatigue responses from 10 measures and errors in pipetting technique, precision, and targeting were submitted to principal component analysis to descriptively analyze features and patterns. Fatigue responses and error rates contributed to three principal components (PCs), accounting for 50.9% of total variance. Fatigue responses grouped within the three PCs reflected central and peripheral upper extremity fatigue, postural sway, and changes in oculomotor behavior. In an 8-hr light precision task, error rates shared similar patterns to both physical and cognitive fatigue responses, and/or increases in arousal level. The findings provide insight toward the relationship between fatigue and operation system performance (e.g., errors). This study contributes to a body of literature documenting task errors and fatigue, reflecting physical (both central and peripheral) and cognitive processes.

Randomized pilot trial of yoga versus strengthening exercises in breast cancer survivors with cancer-related fatigue.

PubMed

Stan, Daniela L; Croghan, Katrina A; Croghan, Ivana T; Jenkins, Sarah M; Sutherland, Stephanie J; Cheville, Andrea L; Pruthi, Sandhya

2016-09-01

Fatigue is one of the most common and bothersome refractory symptoms experienced by cancer survivors. Mindful exercise interventions such as yoga improve cancer-related fatigue; however, studies of yoga have included heterogeneous survivorship populations, and the effect of yoga on fatigued survivors remains unclear. We randomly assigned 34 early-stage breast cancer survivors with cancer-related fatigue (≥4 on a Likert scale from 1-10) within 1 year from diagnosis to a 12-week intervention of home-based yoga versus strengthening exercises, both presented on a DVD. The primary endpoints were feasibility and changes in fatigue, as measured by the Multidimensional Fatigue Symptom Inventory-Short Form (MFSI-SF). Secondary endpoint was quality of life, assessed by the Functional Assessment of Cancer Therapies-Breast (FACT-B). We invited 401 women to participate in the study; 78 responded, and we enrolled 34. Both groups had significant within-group improvement in multiple domains of the fatigue and quality of life scores from baseline to post-intervention, and these benefits were maintained at 3 months post-intervention. However, there was no significant difference between groups in fatigue or quality of life at any assessment time. Similarly, there was no difference between groups in adherence to the exercise intervention. Both DVD-based yoga and strengthening exercises designed for cancer survivors may be good options to address fatigue in breast cancer survivors. Both have reasonable uptake, are convenient and reproducible, and may be helpful in decreasing fatigue and improving quality of life in the first year post-diagnosis in breast cancer patients with cancer-related fatigue.

Study of the Impact of Educational Behavioral Interventions on Fatigue in Mothers in the Postpartum Period in the Groups of Face-to-Face and Electronic Training

PubMed Central

Gholami, Zahra; Mohammadirizi, Soheila; Bahadoran, Parvin

2017-01-01

Background: Maternal fatigue in the postpartum period include factors that affect the quality of life and health of both the mother and newborn. This study aimed to investigate two educational approaches regarding mother's fatigue in the postpartum period. Materials and Methods: This experimental study was performed among 110 pregnant mothers during their postpartum care using random sampling. The participants were divided in three groups, namely, face-to-face, e-learning, and control groups. Interventions included individual meetings between the researcher and mothers in the face-to-face group and giving educational compact disc to the e-learning department to improve maternal fatigue. Personal information and fertility data was obtained (before training); the maternal fatigue questionnaire Fatigue Severity Scale (FSS) was completed before and after any type of (face-to-face, e-learning, and control) education. Obtained data were analyzed using one-way analysis of variance (ANOVA) and repeated-measures ANOVA. Results: Results showed that both face-to-face and e-learning methods had similar maternal fatigue scores. The average change on the maternal fatigue score in the second treatment was (p = 0.02) and the third treatment was (p < 0.001)among three groups that was indicative of significant statistical differences. Similarly, there was no statistically significant difference in the average maternal fatigue score between the two groups before the intervention and in the second and third groups after the intervention. Therefore, over time, the training was unaffected. Conclusions: The findings of this study indicate that both face-to-face and e-learning methods are effective to reduce maternal postpartum fatigue. PMID:29184586

A Transcriptional Signature of Fatigue Derived from Patients with Primary Sjögren's Syndrome.

PubMed

James, Katherine; Al-Ali, Shereen; Tarn, Jessica; Cockell, Simon J; Gillespie, Colin S; Hindmarsh, Victoria; Locke, James; Mitchell, Sheryl; Lendrem, Dennis; Bowman, Simon; Price, Elizabeth; Pease, Colin T; Emery, Paul; Lanyon, Peter; Hunter, John A; Gupta, Monica; Bombardieri, Michele; Sutcliffe, Nurhan; Pitzalis, Costantino; McLaren, John; Cooper, Annie; Regan, Marian; Giles, Ian; Isenberg, David; Saravanan, Vadivelu; Coady, David; Dasgupta, Bhaskar; McHugh, Neil; Young-Min, Steven; Moots, Robert; Gendi, Nagui; Akil, Mohammed; Griffiths, Bridget; Wipat, Anil; Newton, Julia; Jones, David E; Isaacs, John; Hallinan, Jennifer; Ng, Wan-Fai

2015-01-01

Fatigue is a debilitating condition with a significant impact on patients' quality of life. Fatigue is frequently reported by patients suffering from primary Sjögren's Syndrome (pSS), a chronic autoimmune condition characterised by dryness of the eyes and the mouth. However, although fatigue is common in pSS, it does not manifest in all sufferers, providing an excellent model with which to explore the potential underpinning biological mechanisms. Whole blood samples from 133 fully-phenotyped pSS patients stratified for the presence of fatigue, collected by the UK primary Sjögren's Syndrome Registry, were used for whole genome microarray. The resulting data were analysed both on a gene by gene basis and using pre-defined groups of genes. Finally, gene set enrichment analysis (GSEA) was used as a feature selection technique for input into a support vector machine (SVM) classifier. Classification was assessed using area under curve (AUC) of receiver operator characteristic and standard error of Wilcoxon statistic, SE(W). Although no genes were individually found to be associated with fatigue, 19 metabolic pathways were enriched in the high fatigue patient group using GSEA. Analysis revealed that these enrichments arose from the presence of a subset of 55 genes. A radial kernel SVM classifier with this subset of genes as input displayed significantly improved performance over classifiers using all pathway genes as input. The classifiers had AUCs of 0.866 (SE(W) 0.002) and 0.525 (SE(W) 0.006), respectively. Systematic analysis of gene expression data from pSS patients discordant for fatigue identified 55 genes which are predictive of fatigue level using SVM classification. This list represents the first step in understanding the underlying pathophysiological mechanisms of fatigue in patients with pSS.

Sarcolipin overexpression improves muscle energetics and reduces fatigue

PubMed Central

Sopariwala, Danesh H.; Pant, Meghna; Shaikh, Sana A.; Goonasekera, Sanjeewa A.; Molkentin, Jeffery D.; Weisleder, Noah; Ma, Jianjie; Pan, Zui

2015-01-01

Sarcolipin (SLN) is a regulator of sarcoendoplasmic reticulum calcium ATPase in skeletal muscle. Recent studies using SLN-null mice have identified SLN as a key player in muscle thermogenesis and metabolism. In this study, we exploited a SLN overexpression (SlnOE) mouse model to determine whether increased SLN level affected muscle contractile properties, exercise capacity/fatigue, and metabolic rate in whole animals and isolated muscle. We found that SlnOE mice are more resistant to fatigue and can run significantly longer distances than wild-type (WT). Studies with isolated extensor digitorum longus (EDL) muscles showed that SlnOE EDL produced higher twitch force than WT. The force-frequency curves were not different between WT and SlnOE EDLs, but at lower frequencies the pyruvate-induced potentiation of force was significantly higher in SlnOE EDL. SLN overexpression did not alter the twitch and force-frequency curve in isolated soleus muscle. However, during a 10-min fatigue protocol, both EDL and soleus from SlnOE mice fatigued significantly less than WT muscles. Interestingly, SlnOE muscles showed higher carnitine palmitoyl transferase-1 protein expression, which could enhance fatty acid metabolism. In addition, lactate dehydrogenase expression was higher in SlnOE EDL, suggesting increased glycolytic capacity. We also found an increase in store-operated calcium entry (SOCE) in isolated flexor digitorum brevis fibers of SlnOE compared with WT mice. These data allow us to conclude that increased SLN expression improves skeletal muscle performance during prolonged muscle activity by increasing SOCE and muscle energetics. PMID:25701006

Stress ratio effects in fatigue of lost foam cast aluminum alloy 356

NASA Astrophysics Data System (ADS)

Palmer, David E.

Lost foam casting is a highly versatile metalcasting process that offers significant benefits in terms of design flexibility, energy consumption, and environmental impact. In the present work, the fatigue behavior of lost foam cast aluminum alloy 356, in conditions T6 and T7, was investigated, under both zero and non-zero mean stress conditions, with either as-cast or machined surface finish. Scanning electron microscopy was used to identify and measure the defect from which fatigue fracture initiated. Based on the results, the applicability of nine different fatigue mean stress equations was compared. The widely-used Goodman equation was found to be highly non-conservative, while the Stulen, Topper-Sandor, and Walker equations performed reasonably well. Each of these three equations includes a material-dependent term for stress ratio sensitivity. The stress ratio sensitivity was found to be affected by heat treatment, with the T6 condition having greater sensitivity than the T7 condition. The surface condition (as-cast vs. machined) did not significantly affect the stress ratio sensitivity. The fatigue life of as-cast specimens was found to be approximately 60--70% lower than that of machined specimens at the same equivalent stress. This reduction could not be attributed to pore size alone, and is suspected to be due to the greater concentration of pyrolysis products at the as-cast surface. Directions for future work, including improved testing methods and some possible methods of improving the properties of lost foam castings, are discussed.

Saccadic eye movement metrics reflect surgical residents' fatigue.

PubMed

Di Stasi, Leandro L; McCamy, Michael B; Macknik, Stephen L; Mankin, James A; Hooft, Nicole; Catena, Andrés; Martinez-Conde, Susana

2014-04-01

Little is known about the effects of surgical residents' fatigue on patient safety. We monitored surgical residents' fatigue levels during their call day using (1) eye movement metrics, (2) objective measures of laparoscopic surgical performance, and (3) subjective reports based on standardized questionnaires. Prior attempts to investigate the effects of fatigue on surgical performance have suffered from methodological limitations, including inconsistent definitions and lack of objective measures of fatigue, and nonstandardized measures of surgical performance. Recent research has shown that fatigue can affect the characteristics of saccadic (fast ballistic) eye movements in nonsurgical scenarios. Here we asked whether fatigue induced by time-on-duty (~24 hours) might affect saccadic metrics in surgical residents. Because saccadic velocity is not under voluntary control, a fatigue index based on saccadic velocity has the potential to provide an accurate and unbiased measure of the resident's fatigue level. We measured the eye movements of members of the general surgery resident team at St. Joseph's Hospital and Medical Center (Phoenix, AZ) (6 males and 6 females), using a head-mounted video eye tracker (similar configuration to a surgical headlight), during the performance of 3 tasks: 2 simulated laparoscopic surgery tasks (peg transfer and precision cutting) and a guided saccade task, before and after their call day. Residents rated their perceived fatigue level every 3 hours throughout their 24-hour shift, using a standardized scale. Time-on-duty decreased saccadic velocity and increased subjective fatigue but did not affect laparoscopic performance. These results support the hypothesis that saccadic indices reflect graded changes in fatigue. They also indicate that fatigue due to prolonged time-on-duty does not result necessarily in medical error, highlighting the complicated relationship among continuity of care, patient safety, and fatigued providers. Our data show, for the first time, that saccadic velocity is a reliable indicator of the subjective fatigue of health care professionals during prolonged time-on-duty. These findings have potential impacts for the development of neuroergonomic tools to detect fatigue among health professionals and in the specifications of future guidelines regarding residents' duty hours.

Role of beta-alanine supplementation on muscle carnosine and exercise performance.

PubMed

Artioli, Guilherme Giannini; Gualano, Bruno; Smith, Abbie; Stout, Jeffrey; Lancha, Antonio Herbert

2010-06-01

In this narrative review, we present and discuss the current knowledge available on carnosine and beta-alanine metabolism as well as the effects of beta-alanine supplementation on exercise performance. Intramuscular acidosis has been attributed to be one of the main causes of fatigue during intense exercise. Carnosine has been shown to play a significant role in muscle pH regulation. Carnosine is synthesized in skeletal muscle from the amino acids l-histidine and beta-alanine. The rate-limiting factor of carnosine synthesis is beta-alanine availability. Supplementation with beta-alanine has been shown to increase muscle carnosine content and therefore total muscle buffer capacity, with the potential to elicit improvements in physical performance during high-intensity exercise. Studies on beta-alanine supplementation and exercise performance have demonstrated improvements in performance during multiple bouts of high-intensity exercise and in single bouts of exercise lasting more than 60 s. Similarly, beta-alanine supplementation has been shown to delay the onset of neuromuscular fatigue. Although beta-alanine does not improve maximal strength or VO2max, some aspects of endurance performance, such as anaerobic threshold and time to exhaustion, can be enhanced. Symptoms of paresthesia may be observed if a single dose higher than 800 mg is ingested. The symptoms, however, are transient and related to the increase in plasma concentration. They can be prevented by using controlled release capsules and smaller dosing strategies. No important side effect was related to the use of this amino acid so far. In conclusion, beta-alanine supplementation seems to be a safe nutritional strategy capable of improving high-intensity anaerobic performance.

Mental Fatigue Impairs Intermittent Running Performance.

PubMed

Smith, Mitchell R; Marcora, Samuele M; Coutts, Aaron J

2015-08-01

The purpose of the study was to investigate the effects of mental fatigue on intermittent running performance. Ten male intermittent team sports players performed two identical self-paced, intermittent running protocols. The two trials were separated by 7 d and preceded, in a randomized-counterbalanced order, by 90 min of either emotionally neutral documentaries (control) or the AX-continuous performance test (AX-CPT; mental fatigue). Subjective ratings of fatigue and vigor were measured before and after these treatments, and motivation was recorded before the intermittent running protocol. Velocity, heart rate, oxygen consumption, blood glucose and lactate concentrations, and ratings of perceived exertion (RPE) were measured throughout the 45-min intermittent running protocol. Session RPE was recorded 30 min after the intermittent running protocol. Subjective ratings of fatigue were higher after the AX-CPT (P = 0.005). This mental fatigue significantly reduced velocity at low intensities (1.28 ± 0.18 m·s vs 1.31 ± 0.17 m·s; P = 0.037), whereas high-intensity running and peak velocities were not significantly affected. Running velocity at all intensities significantly declined over time in both conditions (P < 0.001). Oxygen consumption was significantly lower in the mental fatigue condition (P = 0.007). Other physiological variables, vigor and motivation, were not significantly affected. Ratings of perceived exertion during the intermittent running protocol were not significantly different between conditions despite lower overall velocity in the mental fatigue condition. Session RPE was significantly higher in the mental fatigue condition (P = 0.013). Mental fatigue impairs intermittent running performance. This negative effect of mental fatigue seems to be mediated by higher perception of effort.

Cyclic fatigue resistance of newly manufactured rotary nickel titanium instruments used in different rotational directions.

PubMed

Gambarini, Gianlucca; Gergi, Richard; Grande, Nicola Maria; Osta, Nada; Plotino, Gianluca; Testarelli, Luca

2013-12-01

The aim of this study was to investigate whether cyclic fatigue resistance is increased for nickel titanium instruments manufactured with improved heating processes in clockwise or counterclockwise continuous rotation. The instruments compared were produced either using the R-phase heat treatment (K3XF; SybronEndo, Orange, CA, USA) or the M-wire alloy (ProFile Vortex; DENTSPLY Tulsa Dental Specialties, Tulsa, OK, USA). Tests were performed with a specific cyclic fatigue device that evaluated cycles to failure of rotary instruments in curved artificial canals. Results indicated no significant difference in resistance to cyclic fatigue when rotary nickel titanium instruments are used in clockwise or counterclockwise continuous rotation. In both directions of rotation, size 04-25 K3XF showed a significant increase (P < 0.05) in the mean number of cycles to failure when compared with size 04-25 ProFile Vortex. © 2012 The Authors. Australian Endodontic Journal © 2012 Australian Society of Endodontology.

Oxidation, Creep And Fatigue Properties of Bare and Coated 31V alloy

DOE PAGES

Dryepondt, Sebastien N.; Jones, Samuel J.; Zhang, Ying; ...

2014-12-06

Increasing the efficiency of natural gas reciprocating engines will require materials with better mechanical and corrosion resistance at high temperatures. One solution to increase the lifetime of exhaust valves is to apply an aluminide coating to prevent corrosion assisted fatigue cracking, but the impact of the coating on the valve material mechanical properties needs to be assessed. Creep and high cycle fatigue (HCF) testing were conducted at 816°C on bare and slurry or pack-coated 31V alloy. After annealing according to the 31V standard heat treatment, the coated and bare creep specimens exhibited very similar creep rupture lives. The HCF behaviormore » of the pack-coated alloy was close to the behavior of the bar alloy, but fatigue lifetimes of slurry-coated 31V specimens had higher variability. Aluminide coatings have the potential to improve the valve performance at high temperature, but the coating deposition process needs to be tailored for the substrate standard heat treatment.« less

An Herbal Drug, Gongjin-dan, Ameliorates Acute Fatigue Caused by Short-Term Sleep-Deprivation: A Randomized, Double-Blinded, Placebo-Controlled, Crossover Clinical Trial.

PubMed

Son, Mi Ju; Im, Hwi-Jin; Ku, Boncho; Lee, Jun-Hwan; Jung, So Young; Kim, Young-Eun; Lee, Sung Bae; Kim, Jun Young; Son, Chang-Gue

2018-01-01

Introduction: Gongjin-dan (GJD) is an herbal drug commonly used in Korea and China to combat fatigue, but there are only few clinical studies on its effectiveness and experimental studies on its mechanism of action, and no randomized controlled trial of GJD on the efficacy and mechanism of action has been reported. Here, we performed an exploratory study to evaluate both questions regarding GJD use in humans. Methods: A randomized, double-blinded, placebo-controlled, crossover clinical trial was conducted in the Republic of Korea. Healthy male participants were recruited and randomly allocated to groups receiving GJD-placebo or placebo-GJD in sequence. Fatigue was artificially induced by sleep deprivation for 2 nights. The primary outcome was a change in serum cortisol level; levels of biomarkers for stress hormones as well as oxidative stress and immunologic factors were also assessed, and questionnaires on fatigue and sleep quality were conducted. Results: Twelve and 11 participants were assigned to the GJD-placebo and placebo-GJD groups, respectively. Of all 23 participants, depending on crossover design, we analyzed a total of 20 participants for GJD, and 21 for placebo. An increase in serum cortisol appeared to be attenuated by GJD administration ( p = 0.25), but the effect was not statistically significant; a similar pattern was observed in salivary cortisol levels ( p = 0.14). Overall, GJD showed a tendency to reduce fatigue according to the Brief Fatigue Inventory (BFI, p = 0.07) and the Fatigue Severity Scale (FSS, p = 0.13) questionnaires. BFI and FSS scores in the first stage (before the crossover), however, were significantly improved (BFI, p = 0.02; FSS, p = 0.05) after GJD treatment (relative to placebo). GJD also seemed to improve sleep quality as assessed by the Leeds Sleep Evaluation Questionnaire ( p = 0.06), with a significant improvement specifically in the condition "Getting To Sleep" ( p = 0.02). Five participants experienced minor adverse events, but no adverse events were specific to the GJD administration period. Conclusions: This trial produced the first clinical evidence that GJD might have anti-fatigue properties, especially under sleep deprivation; however, the investigation of cortisol-mediated mechanisms requires further larger-scale studies in the future. World Health Organization International Clinical Trials Registry Platform KCT0001681 (http://apps.who.int/trialsearch/Trial2.aspx?TrialID=KCT0001681).

Evidence-based efficacy of adaptogens in fatigue, and molecular mechanisms related to their stress-protective activity.

PubMed

Panossian, Alexander; Wikman, Georg

2009-09-01

The aim of this review article is to assess the level of scientific evidence presented by clinical trials of adaptogens in fatigue, and to provide a rationale at the molecular level for verified effects. Strong scientific evidence is available for Rhodiola rosea SHR-5 extract, which improved attention, cognitive function and mental performance in fatigue and in chronic fatigue syndrome. Good scientific evidence has been documented in trails in which Schisandra chinensis and Eleutherococcus senticosus increased endurance and mental performance in patients with mild fatigue and weakness. Based on their efficacy in clinical studies, adaptogens can be defined as a pharmacological group of herbal preparations that increase tolerance to mental exhaustion and enhance attention and mental endurance in situations of decreased performance. The beneficial stress-protective effect of adaptogens is related to regulation of homeostasis via several mechanisms of action associated with the hypothalamic-pituitary-adrenal axis and the control of key mediators of stress response such as molecular chaperons (e.g. Hsp70), stress-activated c-Jun N-terminal protein kinase (JNK1), Forkhead Box O transcription factor DAF-16, cortisol and nitric oxide (NO). The key point of action of phytoadaptogens appears to be their up-regulating and stress-mimetic effects on the "stress-sensor" protein Hsp70, which plays an important role in cell survival and apoptosis. Hsp70 inhibits the expression of NO synthase II gene and interacts with glucocorticoid receptors directly and via the JNK pathway, thus affecting the levels of circulating cortisol and NO. Prevention of stress-induced increase in NO, and the associated decrease in ATP production, results in increased performance and endurance. Adaptogen-induced up-regulation of Hsp70 triggers stress-induced JNK-1 and DAF-16-mediated pathways regulating the resistance to stress and resulting in enhanced mental and physical performance and, possibly, increased longevity.

Alertness Management In Flight Operations: A NASA Education and Training Module

NASA Technical Reports Server (NTRS)

Rosekind, Mark R.; Lebacqz, Victor J.; Gander, Philippa H.; Co, Elizabeth L.; Weldon, Keri J.; Smith, Roy M.; Miller, Donna L.; Gregory, Kevin B.; Statler, Irving C. (Technical Monitor)

1994-01-01

Since 1980, the NASA Ames Fatigue Countermeasures Program has been conducting research on sleep, circadian rhythms, and fatigue in a variety of flight operations 1. An original goal of the program was to return the scientific and operational knowledge to the aviation industry. To meet this goal, the NASA Ames Fatigue Countermeasures Program has created an Education and Training Module entitled, "Strategies for Alertness Management in Flight Operations." The Module was designed to meet three objectives: 1) explain the current state of knowledge about the physiological mechanisms underlying fatigue, 2) demonstrate how this knowledge can be applied to improve flight crew sleep, performance, and alertness, and 3) offer countermeasure recommendations. The Module is composed of two components: 1) a 60-minute live presentation provided by a knowledgeable individual and 2) a NASA/FAA Technical Memorandum (TM) that contains the presentation materials and appendices with complementary information. The TM is provided to all individuals attending the live presentation. The Module content is divided into three parts: 1) basic information on sleep, sleepiness, circadian rhythms, fatigue, and how flight operations affect these physiological factors, 2) common misconceptions about sleep, sleepiness, and fatigue, and 3) alertness management strategies. The Module is intended for pilots, management personnel, schedulers, flight attendants, and the many other individuals involved in the aviation system.

Monitoring Fatigue Status with HRV Measures in Elite Athletes: An Avenue Beyond RMSSD?

PubMed

Schmitt, Laurent; Regnard, Jacques; Millet, Grégoire P

2015-01-01

Among the tools proposed to assess the athlete's "fatigue," the analysis of heart rate variability (HRV) provides an indirect evaluation of the settings of autonomic control of heart activity. HRV analysis is performed through assessment of time-domain indices, the square root of the mean of the sum of the squares of differences between adjacent normal R-R intervals (RMSSD) measured during short (5 min) recordings in supine position upon awakening in the morning and particularly the logarithm of RMSSD (LnRMSSD) has been proposed as the most useful resting HRV indicator. However, if RMSSD can help the practitioner to identify a global "fatigue" level, it does not allow discriminating different types of fatigue. Recent results using spectral HRV analysis highlighted firstly that HRV profiles assessed in supine and standing positions are independent and complementary; and secondly that using these postural profiles allows the clustering of distinct sub-categories of "fatigue." Since, cardiovascular control settings are different in standing and lying posture, using the HRV figures of both postures to cluster fatigue state embeds information on the dynamics of control responses. Such, HRV spectral analysis appears more sensitive and enlightening than time-domain HRV indices. The wealthier information provided by this spectral analysis should improve the monitoring of the adaptive training-recovery process in athletes.

Work-related limitations and return-to-work experiences in prolonged fatigue: workers' perspectives before and after vocational treatment.

PubMed

Joosen, Margot C W; Frings-Dresen, Monique H W; Sluiter, Judith K

2011-01-01

To gain insight into fatigued workers' perspectives regarding work experience before and after receiving vocational rehabilitation (VR) treatments. A qualitative survey was conducted using semi-structured interviews with 21 fatigued workers who attended an outpatient multi-component VR treatment. Six months after treatment, work-related limitations and employed VR strategies at work before treatment were explored. Next, VR treatment experiences regarding return-to-work (RTW) were explored. Two researchers performed partially independent, qualitative analyses that revealed topics, discussed by the project team, and organised into domains, categories and sub-categories. Work-related limitations were: symptoms of prolonged fatigue, personal limitations (e.g. lack of self-reflection on individual capacity and limitations), interpersonal factors, activities and conditions at work and life/work imbalance. Before the treatment, VR strategies such as work adaptations, well-intentioned advice and support, and/or referral to psychological or physical care were employed. VR treatment experiences on RTW were: personal challenges (e.g. gained awareness and coping skills), improved activities during work, work adaptations and unresolved problems (e.g. remaining fatigue symptoms and sickness absence). New information about work experiences before and after multi-component VR treatments in workers with prolonged fatigue may help employers, occupational physicians and other caregivers to develop VR strategies that better meet individuals' needs.

Research on the Relationship between Reaction Ability and Mental State for Online Assessment of Driving Fatigue.

PubMed

Guo, Mengzhu; Li, Shiwu; Wang, Linhong; Chai, Meng; Chen, Facheng; Wei, Yunong

2016-11-24

Background: Driving fatigue affects the reaction ability of a driver. The aim of this research is to analyze the relationship between driving fatigue, physiological signals and driver's reaction time. Methods: Twenty subjects were tested during driving. Data pertaining to reaction time and physiological signals including electroencephalograph (EEG) were collected from twenty simulation experiments. Grey correlation analysis was used to select the input variable of the classification model. A support vector machine was used to divide the mental state into three levels. The penalty factor for the model was optimized using a genetic algorithm. Results: The results show that α/β has the greatest correlation to reaction time. The classification results show an accuracy of 86%, a sensitivity of 87.5% and a specificity of 85.53%. The average increase of reaction time is 16.72% from alert state to fatigued state. Females have a faster decrease in reaction ability than males as driving fatigue accumulates. Elderly drivers have longer reaction times than the young. Conclusions: A grey correlation analysis can be used to improve the classification accuracy of the support vector machine (SVM) model. This paper provides basic research that online detection of fatigue can be performed using only a simple device, which is more comfortable for users.

Research on the Relationship between Reaction Ability and Mental State for Online Assessment of Driving Fatigue

PubMed Central

Guo, Mengzhu; Li, Shiwu; Wang, Linhong; Chai, Meng; Chen, Facheng; Wei, Yunong

2016-01-01

Background: Driving fatigue affects the reaction ability of a driver. The aim of this research is to analyze the relationship between driving fatigue, physiological signals and driver’s reaction time. Methods: Twenty subjects were tested during driving. Data pertaining to reaction time and physiological signals including electroencephalograph (EEG) were collected from twenty simulation experiments. Grey correlation analysis was used to select the input variable of the classification model. A support vector machine was used to divide the mental state into three levels. The penalty factor for the model was optimized using a genetic algorithm. Results: The results show that α/β has the greatest correlation to reaction time. The classification results show an accuracy of 86%, a sensitivity of 87.5% and a specificity of 85.53%. The average increase of reaction time is 16.72% from alert state to fatigued state. Females have a faster decrease in reaction ability than males as driving fatigue accumulates. Elderly drivers have longer reaction times than the young. Conclusions: A grey correlation analysis can be used to improve the classification accuracy of the support vector machine (SVM) model. This paper provides basic research that online detection of fatigue can be performed using only a simple device, which is more comfortable for users. PMID:27886139

Program for establishing long-time flight service performance of composite materials in the center wing structure of C-130 aircraft. Phase 1: Advanced development

NASA Technical Reports Server (NTRS)

Harvill, W. E.; Kays, A. O.; Young, E. C.; Mcgee, W. M.

1972-01-01

Areas where selective reinforcement of conventional metallic structure can improve static strength/fatigue endurance at lower weight than would be possible if metal reinforcement were used are discussed. These advantages are now being demonstrated by design, fabrication, and tests of three boron-epoxy reinforced C-130E center wing boxes. This structural component was previously redesigned using an aluminum build-up to meet increased severity of fatigue loadings. Direct comparisons of relative structural weights, manufacturing costs, and producibility can therefore be obtained, and the long-time flight service performance of the composite reinforced structure can be evaluated against the wide background of metal reinforced structure.

A New Perspective on Fatigue Performance of Advanced High- Strength Steels (AHSS) GMAW Joints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Zhili; Chiang, Dr. John; Kuo, Dr. Min

2008-01-01

Weld fatigue performance is a critical aspect for application of advanced high-strength steels (AHSS) in automotive body structures. A comparative study has been conducted to evaluate the fatigue life of AHSS welds. The material studied included seven AHSS of various strength levels - DP 600, DP 780, DP 980, M130, M220, solution annealed boron and fully hardened boron steels. Two conventional steels, HSLA 590 and DR 210, were also included for baseline comparison. Lap fillet welds were made on 2-mm nominal thick sheets by the gas metal arc welding process (GMAW). Fatigue test was conducted under a number of stressmore » levels to obtain the S/N curves of the weld joints. It was found that, unlike in the static and impact loading conditions, the fatigue performance of AHSS is not influenced by the HAZ softening in AHSS. There are appreciable differences in the fatigue lives among different AHSS. Changes in weld parameters can influence the fatigue life of the weld joints, particularly of these of higher strength AHSS. A model is developed to predict the fatigue performance of AHSS welds. The validity of the model is benchmarked with the experimental results. This model is capable to capture the effects of weld geometry and weld microstructure and strength on the fatigue performance experimentally observed. The theoretical basis and application of the newly developed fatigue modeling methodology will be discussed.« less

Mental Fatigue and Physical and Cognitive Performance During a 2-Bout Exercise Test.

PubMed

Vrijkotte, Susan; Meeusen, Romain; Vandervaeren, Cloe; Buyse, Luk; Cutsem, Jeroen van; Pattyn, Nathalie; Roelands, Bart

2018-04-01

The 2-bout exercise protocol has been developed to diagnose nonfunctional overreaching and the "overtraining syndrome." It consists of 2 maximal exercise bouts separated by 4 hours. Mental fatigue negatively influences performance, but the effects of its occurrence during the 2-bout exercise protocol have never been investigated. The aim of this study was to examine whether mental fatigue (induced during the rest period) influences physical and cognitive performance during/after the second exercise bout of the 2-bout exercise protocol. Nine healthy, well-trained male cyclists participated in a single-blind, randomized, placebo-controlled crossover study. The intervention consisted of either 1.5-hour rest (control) or performing a computer-based Stroop task to induce mental fatigue. Cognitive (Eriksen Flanker task), physiological (lactate, maximum heart rate, and maximum wattage), and subjective data (mental fatigue-visual analog scale, Profile of Mood States, and rating of perceived exertion) were gathered. Ratings of fatigue, tension, and mental fatigue were affected in the mental fatigue condition (P < .05). Neither physiological nor cognitive differences were found between conditions. Ratings of mental fatigue were already affected after the first maximum exercise test (P < .05). Neither physical nor cognitive performance was affected by mental fatigue, but subjective ratings did reveal significant differences. It is recommended to exclude mentally challenging tasks during the 2-bout exercise protocol rest period to ascertain unaffected subjective test results. This study should be repeated in athletes diagnosed with nonfunctional overreaching/overtraining syndrome.

Effects of fatigue and surface instability on neuromuscular performance during jumping.

PubMed

Lesinski, M; Prieske, O; Demps, M; Granacher, U

2016-10-01

It has previously been shown that fatigue and unstable surfaces affect jump performance. However, the combination thereof is unresolved. Thus, the purpose of this study was to examine the effects of fatigue and surface instability on jump performance and leg muscle activity. Twenty elite volleyball players (18 ± 2 years) performed repetitive vertical double-leg box jumps until failure. Before and after a fatigue protocol, jump performance (i.e., jump height) and electromyographic activity of selected lower limb muscles were recorded during drop jumps (DJs) and countermovement jumps (CMJs) on a force plate on stable and unstable surfaces (i.e., balance pad on top of force plate). Jump performance (3-7%; P < 0.05; 1.14 ≤ d ≤ 2.82), and muscle activity (2-27%; P < 0.05; 0.59 ≤ d ≤ 3.13) were lower following fatigue during DJs and CMJs, and on unstable compared with stable surfaces during DJs only (jump performance: 8%; P < 0.01; d = 1.90; muscle activity: 9-25%; P < 0.05; 1.08 ≤ d ≤ 2.54). No statistically significant interactions of fatigue by surface condition were observed. Our findings revealed that fatigue impairs neuromuscular performance during DJs and CMJs in elite volleyball players, whereas surface instability affects neuromuscular DJ performance only. Absent fatigue × surface interactions indicate that fatigue-induced changes in jump performance are similar on stable and unstable surfaces in jump-trained athletes. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Improvements of mechanical fatigue reliability of Cu interconnects on flexible substrates through MoTi alloy under-layer

NASA Astrophysics Data System (ADS)

Lee, Young-Joo; Shin, Hae-A.-Seul; Nam, Dae-Hyun; Yeon, Han-Wool; Nam, Boae; Woo, Kyoohee; Joo, Young-Chang

2015-01-01

The mechanical fatigue of Cu films and lines on flexible substrates was investigated, and an improvement in the structures through the use of a MoTi alloy under-layer was proposed. Fatigue reliability was decreased by 3-fold in lines compared with films in the tensile condition and by 6-fold in the compressive condition. Crack formation was observed to be more detrimental for lines than for films. With a MoTi under-layer, the fatigue limit was increased by 2 times that of a structure without MoTi in the tensile condition and by 15 times in the compressive bending condition. The suppression of delamination through the use of a MoTi under-layer improved the fatigue reliability under compressive bending.

An experimental study on fatigue performance of cryogenic metallic materials for IMO type B tank

NASA Astrophysics Data System (ADS)

Lee, Jin-Sung; You, Won-Hyo; Yoo, Chang-Hyuk; Kim, Kyung-Su; Kim, Yooil

2013-12-01

Three materials SUS304, 9% Ni steel and Al 5083-O alloy, which are considered possible candidate for International Maritime Organization (IMO) type B Cargo Containment System, were studied. Monotonic tensile, fatigue, fatigue crack growth rate and Crack Tip Opening Displacement tests were carried out at room, intermediate low (-100 °C) and cryogenic (-163 °C) temperatures. The initial yield and tensile strengths of all materials tended to increase with decreasing temperature, whereas the change in elastic modulus was not as remarkable. The largest and smallest improvement ratio of the initial yield strengths due to a temperature reduction were observed in the SUS304 and Al 5083- O alloy, respectively. The fatigue strengths of the three materials increased with decreasing temperature. The largest increase in fatigue strength was observed in the Al 5083-O alloy, whereas the 9% Ni steel sample showed the smallest increase. In the fatigue crack growth rate test, SUS304 and Al 5083-O alloy showed a decrease in the crack propagation rate, due to decrease in temperature, but no visible improvement in da/dN was observed in the case of 9% Ni steel. In the Crack Tip Opening Displacement (CTOD) test, CTOD values were converted to critical crack length for the comparison with different thickness specimens. The critical crack length tended to decrease in the case of SUS304 and increase for the Al 5083-O alloy with decreasing temperature. In case of 9% Ni steel, change of critical crack length was not observed due to temperature decrease. In addition, the changing material properties according to the temperature of the LNG tank were analyzed according to the international code for the construction and equipment of ships carrying liquefied gases in bulk (IGC code) and the rules of classifications.

Sex Comparison of Knee Extensor Size, Strength and Fatigue Adaptation to Sprint Interval Training.

PubMed

Bagley, Liam; Al-Shanti, Nasser; Bradburn, Steven; Baig, Osamah; Slevin, Mark; McPhee, Jamie S

2018-03-12

Regular sprint interval training (SIT) improves whole-body aerobic capacity and muscle oxidative potential, but very little is known about knee extensor anabolic or fatigue resistance adaptations, or whether effects are similar for males and females. The purpose of this study was to compare sex-related differences in knee extensor size, torque-velocity relationship and fatigability adaptations to 12 weeks SIT. Sixteen males and fifteen females (mean (SEM) age: 41 (±2.5) yrs) completed measurements of total body composition assessed by DXA, quadriceps muscle cross-sectional area (CSAQ) assessed by MRI, the knee extensor torque-velocity relationship (covering 0 - 240°·sec) and fatigue resistance, which was measured as the decline in torque from the first to the last of 60 repeated concentric knee extensions performed at 180°·sec. SIT consisted of 4 x 20 second sprints on a cycle ergometer set at an initial power output of 175% of power at VO2max, three times per week for 12 weeks. CSAQ increased by 5% (p=0.023) and fatigue resistance improved 4.8% (p=0.048), with no sex differences in these adaptations (sex comparisons: p=0.140 and p=0.282, respectively). Knee extensor isometric and concentric torque was unaffected by SIT in both males and females (p>0.05 for all velocities). 12 weeks SIT, totalling 4 minutes very intense cycling per week, significantly increased fatigue resistance and CSAQ similarly in males and females, but did not significantly increase torque in males or females. These results suggest that SIT is a time-effective training modality for males and females to increase leg muscle size and fatigue resistance.

Effect of aerobic interval training on serum IL-10, TNFα, and adipokines levels in women with multiple sclerosis: possible relations with fatigue and quality of life.

PubMed

Mokhtarzade, Motahare; Ranjbar, Rouholah; Majdinasab, Nastaran; Patel, Darpan; Molanouri Shamsi, Mehdieh

2017-08-01

Multiple sclerosis is associated with immune system dysfunction and chronic inflammation; however, possible relations between immunologic and metabolic factors and some psychological indexes such as fatigue and quality of life, especially in relation to exercise training, have not yet been investigated. The present study was designed to investigate the effect of aerobic interval training on interleukin-10/tumor necrosis factor ratio and adipokine (leptin and adiponectin) concentrations in women with multiple sclerosis. Furthermore, the relationship between these factors with fatigue and quality of life were assessed. Forty women with multiple sclerosis (Expanded Disability Status Scale ≤3) were randomized into either a non-exercising control or training group. The training group performed 8-weeks of upper and lower limb aerobic interval training. Serum concentrations of tumor necrosis factorα, interleukin-10, leptin, and adiponectin were measured before and after the 8-week intervention. Moreover, antropometric measures and measures for fatigue and quality of life were determined at the onset of and after exercise training. The results revealed that leptin and tumor necrosis factorα levels significantly decreased subsequent to the aerobic interval training. Although blood adiponectin levels considerably increased in the training group, interleukin-10 and interleukin-10/tumor necrosis factorα ratio underwent no substantial change after the exercise training. In addition, the aerobic interval training was associated with improvement in fatigue, quality of life, and maximal oxygen consumption. Our findings suggested that aerobic interval training can be an effective strategy for managing the immune system at least by its significant impact on inflammatory cytokines and adipokines levels in women with multiple sclerosis. Additionally, this positive impact improved fatigue and adipose tissue indicators.

Fatigue life improvements of the AISI 304 stainless steel ground surfaces by wire brushing

NASA Astrophysics Data System (ADS)

Ben Fredj, Nabil; Ben Nasr, Mohamed; Ben Rhouma, Amir; Sidhom, Habib; Braham, Chedly

2004-10-01

The surface and subsurface integrity of metallic ground components is usually characterized by an induced tensile residual stress, which has a detrimental effect on the fatigue life of these components. In particular, it tends to accelerate the initiation and growth of the fatigue cracks. In this investigation, to deliberately generate compressive residual stresses into the ground surfaces of the AISI 304 stainless steel (SS), wire brushing was applied. It was found that under the experimental conditions selected in this investigation, while the surface roughness was slightly improved by the brushing process, the surface residual stress shifted from a tensile stress (σ‖=+450 MPa) to a compressive stress (σ‖=-435 MPa). On the other hand, the work-hardened deformation layer was almost two times deeper after wire brushing. Concerning the fatigue life, an improvement of 26% in terms of endurance limit at 2×106 cycles was realized. Scanning electron microscope (SEM) observations of the fatigue fracture location and size were carried out to explain the fatigue life improvement. It was found that the enhancement of the fatigue strength could be correlated with the distribution and location of the fatigue fracture nucleation sites. Concerning the ground surfaces, it was seen that the fatigue cracks initiated at the bottom of the grinding grooves and were particularly long (150-200 µm). However, the fatigue cracks at the brushed surfaces were shorter (20-40 µm) and appeared to initiate sideways to the plowed material caused by the wire brushing. The results of the wire-brushed surface characterization have shown that significant advantages can be realized regarding surface integrity by the application of this low-cost process compared to shot peening.

Phase III, Randomized, Double-Blind, Placebo-Controlled Study of Long-Acting Methylphenidate for Cancer-Related Fatigue: North Central Cancer Treatment Group NCCTG-N05C7 Trial

PubMed Central

Moraska, Amanda R.; Sood, Amit; Dakhil, Shaker R.; Sloan, Jeff A.; Barton, Debra; Atherton, Pamela J.; Suh, Jason J.; Griffin, Patricia C.; Johnson, David B.; Ali, Aneela; Silberstein, Peter T.; Duane, Steven F.; Loprinzi, Charles L.

2010-01-01

Purpose Fatigue is one of the most common symptoms experienced by patients with cancer. This trial was developed to evaluate the efficacy of long-acting methylphenidate for improving cancer-related fatigue and to assess its toxicities. Patients and Methods Adults with cancer were randomly assigned in a double-blinded manner to receive methylphenidate (target dose, 54 mg/d) or placebo for 4 weeks. The Brief Fatigue Inventory was the primary outcome measure, while secondary outcome measures included a Symptom Experience Diary (SED), the Short Form-36 (SF-36) Vitality Subscale, a linear analog self-assessment, the Pittsburgh Sleep Quality Index, and the Subject Global Impression of Change. Results In total, 148 patients were enrolled. Using an area under the serum concentration-time curve analysis, there was no evidence that methylphenidate, as compared with placebo, improved the primary end point of cancer-related fatigue in this patient population (P = .35). Comparisons of secondary end points, including clinically significant changes in quality-of-life variables and cancer-related fatigue change from baseline, were similarly negative. However, a subset analysis suggested that patients with more severe fatigue and/or with more advanced disease did have some fatigue improvement with methylphenidate (eg, in patients with stage III or IV disease, the mean improvement in usual fatigue was 19.7 with methylphenidate v 2.1 with placebo; P = .02). There was a significant difference in self-reported toxicities (SED), with increased levels of nervousness and appetite loss in the methylphenidate arm. Conclusion This clinical trial was unable to support the primary prestudy hypothesis that the chosen long-acting methylphenidate product would decrease cancer-related fatigue. PMID:20625123

Cognitive Fatigue Influences Time-On-Task during Bodyweight Resistance Training Exercise

PubMed Central

Head, James R.; Tenan, Matthew S.; Tweedell, Andrew J.; Price, Thomas F.; LaFiandra, Michael E.; Helton, William S.

2016-01-01

Prior investigations have shown measurable performance impairments on continuous physical performance tasks when preceded by a cognitively fatiguing task. However, the effect of cognitive fatigue on bodyweight resistance training exercise task performance is unknown. In the current investigation 18 amateur athletes completed a full body exercise task preceded by either a cognitive fatiguing or control intervention. In a randomized repeated measure design, each participant completed the same exercise task preceded by a 52 min cognitively fatiguing intervention (vigilance) or control intervention (video). Data collection sessions were separated by 1 week. Participants rated the fatigue intervention with a significantly higher workload compared to the control intervention (p < 0.001). Additionally, participants self-reported significantly greater energetic arousal for cognitively fatiguing task (p = 0.02). Cognitive fatigue did not significantly impact number of repetitions completed during the exercise task (p = 0.77); however, when cognitively fatigued, participants had decreased percent time-on-task (57%) relative to the no fatigue condition (60%; p = 0.04). RPE significantly changed over time (p < 0.001), but failed to show significant differences between the cognitive fatigue intervention and control intervention (p > 0.05). There was no statistical difference for heart rate or metabolic expenditure as a function of fatigue intervention during exercise. Cognitively fatigued athletes have decreased time-on-task in bodyweight resistance training exercise tasks. PMID:27635122

Exceptional high fatigue strength in Cu-15at.%Al alloy with moderate grain size

PubMed Central

Liu, Rui; Tian, Yanzhong; Zhang, Zhenjun; An, Xianghai; Zhang, Peng; Zhang, Zhefeng

2016-01-01

It is commonly proposed that the fatigue strength can be enhanced by increasing the tensile strength, but this conclusion needs to be reconsidered according to our study. Here a recrystallized α-Cu-15at.%Al alloy with moderate grain size of 0.62 μm was fabricated by cold rolling and annealing, and this alloy achieved exceptional high fatigue strength of 280 MPa at 107 cycles. This value is much higher than the fatigue strength of 200 MPa for the nano-crystalline counterpart (0.04 μm in grain size) despite its higher tensile strength. The remarkable improvement of fatigue strength should be mainly attributed to the microstructure optimization, which helps achieve the reduction of initial damage and the dispersion of accumulated damage. A new strategy of “damage reduction” was then proposed for fatigue strength improvement, to supplement the former strengthening principle. The methods and strategies summarized in this work offer a general pathway for further improvement of fatigue strength, in order to ensure the long-term safety of structural materials. PMID:27264347

A Self-Adaptive Dynamic Recognition Model for Fatigue Driving Based on Multi-Source Information and Two Levels of Fusion

PubMed Central

Sun, Wei; Zhang, Xiaorui; Peeta, Srinivas; He, Xiaozheng; Li, Yongfu; Zhu, Senlai

2015-01-01

To improve the effectiveness and robustness of fatigue driving recognition, a self-adaptive dynamic recognition model is proposed that incorporates information from multiple sources and involves two sequential levels of fusion, constructed at the feature level and the decision level. Compared with existing models, the proposed model introduces a dynamic basic probability assignment (BPA) to the decision-level fusion such that the weight of each feature source can change dynamically with the real-time fatigue feature measurements. Further, the proposed model can combine the fatigue state at the previous time step in the decision-level fusion to improve the robustness of the fatigue driving recognition. An improved correction strategy of the BPA is also proposed to accommodate the decision conflict caused by external disturbances. Results from field experiments demonstrate that the effectiveness and robustness of the proposed model are better than those of models based on a single fatigue feature and/or single-source information fusion, especially when the most effective fatigue features are used in the proposed model. PMID:26393615

Mental Fatigue and Spatial References Impair Soccer Players' Physical and Tactical Performances

PubMed Central

Coutinho, Diogo; Gonçalves, Bruno; Travassos, Bruno; Wong, Del P.; Coutts, Aaron J.; Sampaio, Jaime E

2017-01-01

This study examined the effects of mental fatigue and additional corridor and pitch sector lines on players' physical and tactical performances during soccer small-sided games. Twelve youth players performed four Gk+6vs6+Gk small-sided games. Prior to the game, one team performed a motor coordination task to induce mental fatigue, while the other one performed a control task. A repeated measures design allowed to compare players' performances across four conditions: (a) with mental fatigue against opponents without mental fatigue in a normal pitch (MEN), (b) with mental fatigue on a pitch with additional reference lines (#MEN); (c) without mental fatigue against mentally fatigued opponents on a normal pitch (CTR); and (d) without mental fatigue on a pitch with reference lines (#CTR). Player's physical performance was assessed by the distance covered per minute and the number of accelerations and decelerations (0.5–3.0 m/s2; > −3.0 m/s2). Positional data was used to determine individual (spatial exploration index, time synchronized in longitudinal and lateral directions) and team-related variables (length, width, speed of dispersion and contraction). Unclear effects were found for the physical activity measures in most of the conditions. There was a small decrease in time spent laterally synchronized and a moderate decrease in the contraction speed when MEN compared to the CTR. Also, there was a small decrease in the time spent longitudinally synchronized during the #MEN condition compared to MEN. The results showed that mental fatigue affects the ability to use environmental information and players' positioning, while the additional reference lines may have enhanced the use of less relevant information to guide their actions during the #MEN condition. Overall, coaches could manipulate the mental fatigue and reference lines to induce variability and adaptation in young soccer players' behavior. PMID:28983273

Fatigue and fatigability in neurologic illnesses

PubMed Central

Krupp, Lauren B.; Enoka, Roger M.

2013-01-01

Fatigue is commonly reported in many neurologic illnesses, including multiple sclerosis, Parkinson disease, myasthenia gravis, traumatic brain injury, and stroke. Fatigue contributes substantially to decrements in quality of life and disability in these illnesses. Despite the clear impact of fatigue as a disabling symptom, our understanding of fatigue pathophysiology is limited and current treatment options rarely lead to meaningful improvements in fatigue. Progress continues to be hampered by issues related to terminology and assessment. In this article, we propose a unified taxonomy and a novel assessment approach to addressing distinct aspects of fatigue and fatigability in clinical and research settings. This taxonomy is based on our current knowledge of the pathophysiology and phenomenology of fatigue and fatigability. Application of our approach indicates that the assessment and reporting of fatigue can be clarified and improved by utilizing this taxonomy and creating measures to address distinct aspects of fatigue and fatigability. We review the strengths and weaknesses of several common measures of fatigue and suggest, based on our model, that many research questions may be better addressed by using multiple measures. We also provide examples of how to apply and validate the taxonomy and suggest directions for future research. PMID:23339207

Strain energy release rate as a function of temperature and preloading history utilizing the edge delamination fatique test method

NASA Technical Reports Server (NTRS)

Zimmerman, Richard S.; Adams, Donald F.

1989-01-01

Static laminate and tension-tension fatigue tests of IM7/8551-7 composite materials was performed. The Edge Delamination Test (EDT) was utilized to evaluate the temperature and preloading history effect on the critical strain energy release rate. Static and fatigue testing was performed at room temperature and 180 F (82 C). Three preloading schemes were used to precondition fatigue test specimens prior to performing the normal tension-tension fatigue EDT testing. Computer software was written to perform all fatigue testing while monitoring the dynamic modulus to detect the onset of delamination and record the test information for later retrieval and reduction.

Treatment of HIV-related fatigue with armodafinil: a placebo-controlled randomized trial.

PubMed

Rabkin, Judith G; McElhiney, Martin C; Rabkin, Richard

2011-01-01

To evaluate the efficacy and safety of armodafinil in the treatment of fatigue in HIV+ patients, and to assess its effect on depressive symptoms and behavior once fatigue remitted. HIV+ patients with clinically significant fatigue were treated in a placebo-controlled randomized double-blind trial for 4 weeks. Armodafinil responders and placebo non-responders or relapsers were treated openly for a total of 16 weeks with armodafinil. The primary outcome measure for fatigue and depression was the Clinical Global Impressions-Improvement Scale, supplemented by the Fatigue Severity Scale, the Hamilton Depression Rating Scale, and the Beck Depression Inventory. Safety was assessed with assays of CD4 cell count and HIV RNA viral load and the SAFTEE side effects rating scale. Maximum trial dose of armodafinil was 250 mg/d. Seventy patients were enrolled. Attrition was 9%. In intention-to-treat analyses, fatigue response rate to armodafinil was 75% and to placebo, 26%. Armodafinil did not reduce depressive symptoms in the absence of improved energy, but of those patients with an Axis I depressive disorder at study entry whose energy improved, 82% experienced improved mood as well. Markers of immunologic suppression did not change during treatment. At 6 months, those still taking armodafinil had more energy and fewer depressive symptoms than those who were no longer taking it. As we found in our RCT of modafinil, armodafinil appears effective and well tolerated in treating fatigue in HIV+ patients. Side effects were minimal and most patients reported substantially improved energy and mood. Copyright © 2011 The Academy of Psychosomatic Medicine. Published by Elsevier Inc. All rights reserved.

Treatment of HIV-Related Fatigue with Armodafinil: A Placebo-controlled Randomized Trial

PubMed Central

Rabkin, Judith G.; McElhiney, Martin C.; Rabkin, Richard

2011-01-01

Objective To evaluate the efficacy and safety of armodafinil in the treatment of fatigue in HIV+ patients, and to assess effect on depressive symptoms and behavior once fatigue remitted. Method HIV+ patients with clinically significant fatigue were treated in a placebo controlled randomized double-blind trial for 4 weeks. Armodafinil responders and placebo non-responders or relapsers were treated openly for a total of 16 weeks of armodafinil. The primary outcome measure for fatigue and depression was the Clinical Global Impressions-Improvement Scale, supplemented by the Fatigue Severity Scale, Hamilton Depression Rating Scale and Beck Depression Inventory. Safety was assessed with assays of CD4 cell count and HIV RNA viral load and the SAFTEE side effects rating scale. Maximum trial dose of armodafinil was 250 mg/day. Results 70 patients were enrolled. Attrition was 9%. In Intention-to-treat analyses, fatigue response rate to armodafinil was 75% and to placebo, 26%. Armodafinil did not reduce depressive symptoms in the absence of improved energy, but of those patients with an Axis I depressive disorder at study entry whose energy improved, 82% experienced improved mood as well. Markers of immunologic suppression did not change during treatment. At 6 months, those still taking armodafinil had more energy and fewer depressive symptoms than those who were no longer taking it. Conclusions As we found in our RCT of modafinil, armodafinil appears effective and well tolerated in treating fatigue in HIV+ patients. Side effects were minimal and most patients reported substantially improved energy and mood. PMID:21777715

Study and treatment of post Lyme disease (STOP-LD): a randomized double masked clinical trial.

PubMed

Krupp, L B; Hyman, L G; Grimson, R; Coyle, P K; Melville, P; Ahnn, S; Dattwyler, R; Chandler, B

2003-06-24

To determine whether post Lyme syndrome (PLS) is antibiotic responsive. The authors conducted a single-center randomized double-masked placebo-controlled trial on 55 patients with Lyme disease with persistent severe fatigue at least 6 or more months after antibiotic therapy. Patients were randomly assigned to receive 28 days of IV ceftriaxone or placebo. The primary clinical outcomes were improvement in fatigue, defined by a change of 0.7 points or more on an 11-item fatigue questionnaire, and improvement in cognitive function (mental speed), defined by a change of 25% or more on a test of reaction time. The primary laboratory outcome was an experimental measure of CSF infection, outer surface protein A (OspA). Outcome data were collected at the 6-month visit. Patients assigned to ceftriaxone showed improvement in disabling fatigue compared to the placebo group (rate ratio, 3.5; 95% CI, 1.50 to 8.03; p = 0.001). No beneficial treatment effect was observed for cognitive function or the laboratory measure of persistent infection. Four patients, three of whom were on placebo, had adverse events associated with treatment, which required hospitalization. Ceftriaxone therapy in patients with PLS with severe fatigue was associated with an improvement in fatigue but not with cognitive function or an experimental laboratory measure of infection in this study. Because fatigue (a nonspecific symptom) was the only outcome that improved and because treatment was associated with adverse events, this study does not support the use of additional antibiotic therapy with parenteral ceftriaxone in post-treatment, persistently fatigued patients with PLS.

Effects of a Training Program Involving Body Cooling on Physical and Cognitive Capacities and Quality of Life in Multiple Sclerosis Patients: A Pilot Study.

PubMed

Gonzales, Benoit; Chopard, Gilles; Charry, Benjamin; Berger, Eric; Tripard, Julien; Magnin, Eloi; Groslambert, Alain

2017-01-01

Two methods using exercise and body cooling could influence the well-being of patients with multiple sclerosis (PwMS). The aim of this study was to determine whether wearing a cooling vest during a physical training program could increase the cognitive and physical capacities and quality of life in PwMS. Eighteen PwMS (49.6 ± 8 years; Expanded Disability Status Score 5.0 ± 1.0) were randomly assigned to a cooling or control group. PwMS underwent a 7-week physical training program. In the cooling group, PwMS wore a cooling vest during each training session, whereas in the control group, PwMS wore a cotton T-shirt. Before and after the training program, both groups completed the Isaacs Set Test (IST), Trail Making Test A-B (TMT A-B), SEP-59, Multidimensional Fatigue Inventory and performed a 6-minute walk test (6MWT). The cooling group showed significantly (p < 0.05) improved performance for IST, TMT A and 6MWT. Their emotional well-being and cognitive functions investigated in SEP-59 were significantly (p < 0.05) improved, and general and physical fatigue significantly (p < 0.05) decreased. This physical training program combined with a cooling strategy could have a significant positive influence on both cognitive and physical performances, perceived fatigue and emotional well-being in heat-sensitive PwMS. © 2017 S. Karger AG, Basel.

Resistance Training for Muscle Weakness in Multiple Sclerosis: Direct Versus Contralateral Approach in Individuals With Ankle Dorsiflexors' Disparity in Strength.

PubMed

Manca, Andrea; Cabboi, Maria Paola; Dragone, Daniele; Ginatempo, Francesca; Ortu, Enzo; De Natale, Edoardo Rosario; Mercante, Beniamina; Mureddu, Giovanni; Bua, Guido; Deriu, Franca

2017-07-01

To compare effects of contralateral strength training (CST) and direct strength training of the more affected ankle dorsiflexors on muscle performance and clinical functional outcomes in people with multiple sclerosis (MS) exhibiting interlimb strength asymmetry. Randomized controlled trial. University hospital. Individuals with relapsing-remitting MS (N=30) and mild-to-moderate disability (Expanded Disability Status Scale score ≤6) presenting with ankle dorsiflexors' strength disparity. Participants were randomly assigned to a CST (n=15) or direct strength training (n=15) group performing 6 weeks of maximal intensity strength training of the less or more affected dorsiflexors, respectively. Maximal strength, endurance to fatigue, and mobility outcomes were assessed before, at the intervention end, and at 12-week follow-up. Strength and fatigue parameters were measured after 3 weeks of training (midintervention). In the more affected limb of both groups, pre- to postintervention significant increases in maximal strength (P≤.006) and fatigue endurance (P≤.04) were detected along with consistent retention of these improvements at follow-up (P≤.04). At midintervention, the direct strength training group showed significant improvements (P≤.002), with no further increase at postintervention, despite training continuation. Conversely, the CST group showed nonsignificant strength gains, increasing to significance at postintervention (P≤.003). In both groups, significant pre- to postintervention improvements in mobility outcomes (P≤.03), not retained at follow-up, were observed. After 6 weeks of training, CST proved as effective as direct strength training in enhancing performance of the more affected limb with a different time course, which may have practical implications in management of severely weakened limbs where direct strength training is not initially possible. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Scapular-Muscle Performance: Two Training Programs in Adolescent Swimmers

PubMed Central

Van de Velde, Annemie; De Mey, Kristof; Maenhout, Annelies; Calders, Patrick; Cools, Ann M.

2011-01-01

Abstract Context: Swimming requires well-balanced scapular-muscle performance. An additional strength-training program for the shoulders is pursued by swimmers, but whether these muscle-training programs need to be generic or specific for endurance or strength is unknown. Objective: To evaluate isokinetic scapular-muscle performance in a population of adolescent swimmers and to compare the results of training programs designed for strength or muscle endurance. Design: Controlled laboratory study. Setting: University human research laboratory. Patients or Other Participants: Eighteen adolescent swimmers. Intervention(s): Each participant pursued a 12-week scapular-training program designed to improve either muscle strength or muscle endurance. Main Outcome Measure(s): Bilateral peak force, fatigue index, and protraction/retraction strength ratios before and after the scapular-training program. Results: Scapular protraction/retraction ratios were slightly higher than 1 (dominant side  =  1.08, nondominant side  =  1.25, P  =  .006). Side-to-side differences in retraction strength were apparent both before and after the training program (P  =  .03 and P  = .05, respectively). After the training program, maximal protraction (P < .05) and retraction (P < .01) strength improved on the nondominant side. Peak force and fatigue index were not different between the training groups. The fatigue indexes for protraction on both sides (P < .05) and retraction on the nondominant side (P  =  .009) were higher after the training program. Conclusions: We describe the scapular-muscle characteristics of a group of adolescent swimmers. Both muscle-strength and muscle-endurance programs improved absolute muscle strength. Neither of the strength programs had a positive effect on scapular-muscle endurance. Our results may be valuable for coaches and physiotherapists when they are designing exercise programs for swimmers. PMID:21391801

Physical function improvements and relief from fatigue and pain are associated with increased productivity at work and at home in rheumatoid arthritis patients treated with certolizumab pegol

PubMed Central

Taylor, Peter; Strand, Vibeke; Purcaru, Oana; Coteur, Geoffroy; Mease, Philip

2010-01-01

Objectives. To evaluate the association between improvements in physical function, fatigue and pain and improvements in productivity at work and at home in patients treated with certolizumab pegol (CZP) in combination with MTX. Methods. Physical function, fatigue and pain were assessed in two CZP clinical trials (Rheumatoid Arthritis PreventIon of structural Damage 1 and 2) using the HAQ-Disability Index (HAQ-DI), Fatigue Assessment Scale (FAS) and Patient Assessment of Pain, with minimal clinically important differences (MCIDs) defined as ≥0.22, ≥1 and ≥10 points, respectively. Work and home productivity were evaluated using the RA-specific Work Productivity Survey (WPS-RA). The odds of achieving an HAQ-DI, FAS or pain ‘response’ at Week 12, defined as improvements ≥MCID, were compared between CZP and control groups. Improvements in productivity at Week 12 were compared between CZP-treated HAQ-DI, FAS or pain responders and non-responders. Results. The odds of achieving improvements ≥MCID were five times higher for pain, and two to three times higher for physical function and fatigue, in patients receiving CZP vs control. Per month, responders reported significantly greater improvements in productivity at work and reduced interference of RA with their work productivity than non-responders. Responders also reported significantly greater improvements in productivity at home and participation in family, social and leisure activities. Conclusions. This study demonstrated a clear association between patient-reported improvements in physical function, fatigue and pain, and improvements in productivity both at work and home. PMID:20547658

The Boeing 747 fatigue integrity program

NASA Technical Reports Server (NTRS)

Spencer, M. M.

1972-01-01

The fatigue integrity program which was established to insure economic operations and to provide foundation data for inspection and maintenance is discussed. Significant features of the 747 fatigue integrity program are: (1) fatigue analyses which are continually updated to reflect design changes, fatigue test results, and static and flight load survey measurements; (2) material selection and detail design by using initial fatigue analyses, service experience, and testing; and (3) fatigue testing to check detail design quality and to verify the analyses, culminated by the test of a structurally complete airframe. Fatigue stress analyses were performed with the aid of experimental as well as analytical procedures. Extensive application was made of the stress severity factor, developed at Boeing, for evaluating peak stresses in complex joints. A frame of reference was established by families of structural fatigue performance curves (S-N curves) encompassing the range of materials and fatigue qualities anticipated for the 747 airplane design.

Effect of fatigue and gender on kinematics and ground reaction forces variables in recreational runners

PubMed Central

Durá-Gil, Juan V.; Palomares, Nicolás; Medina, Enrique; Llana-Belloch, Salvador

2018-01-01

The presence of fatigue has been shown to modify running biomechanics. Overall in terms of gender, women are at lower risk than men for sustaining running-related injuries, although it depends on the factors taken into account. One possible reason for these differences in the injury rate and location might be the dissimilar running patterns between men and women. The purpose of this study was to determine the effect of fatigue and gender on the kinematic and ground reaction forces (GRF) parameters in recreational runners. Fifty-seven participants (28 males and 29 females) had kinematic and GRF variables measured while running at speed of 3.3 m s−1 before and after a fatigue test protocol. The fatigue protocol included (1) a running Course-Navette test, (2) running up and down a flight of stairs for 5 min, and (3) performance of alternating jumps on a step (five sets of 1 minute each with 30 resting seconds between the sets). Fatigue decreased dorsiflexion (14.24 ± 4.98° in pre-fatigue and 12.65 ± 6.21° in fatigue condition, p < 0.05) at foot strike phase in females, and plantar flexion (−19.23 ± 4.12° in pre-fatigue and −18.26 ± 5.31° in fatigue condition, p < 0.05) at toe-off phase in males. These changes led to a decreased loading rate (88.14 ± 25.82 BW/s in pre-fatigue and 83.97 ± 18.83 BW/s in fatigue condition, p < 0.05) and the impact peak in females (1.95 ± 0.31 BW in pre-fatigue and 1.90 ± 0.31 BW in fatigue condition, p < 0.05), and higher peak propulsive forces in males (−0.26 ± 0.04 BW in pre-fatigue and −0.27 ± 0.05 BW in fatigue condition, p < 0.05) in the fatigue condition. It seems that better responses to impact under a fatigue condition are observed among women. Further studies should confirm whether these changes represent a strategy to optimize shock attenuation, prevent running injuries and improve running economy. PMID:29576960

Effect of fatigue and gender on kinematics and ground reaction forces variables in recreational runners.

PubMed

Bazuelo-Ruiz, Bruno; Durá-Gil, Juan V; Palomares, Nicolás; Medina, Enrique; Llana-Belloch, Salvador

2018-01-01

The presence of fatigue has been shown to modify running biomechanics. Overall in terms of gender, women are at lower risk than men for sustaining running-related injuries, although it depends on the factors taken into account. One possible reason for these differences in the injury rate and location might be the dissimilar running patterns between men and women. The purpose of this study was to determine the effect of fatigue and gender on the kinematic and ground reaction forces (GRF) parameters in recreational runners. Fifty-seven participants (28 males and 29 females) had kinematic and GRF variables measured while running at speed of 3.3 m s -1 before and after a fatigue test protocol. The fatigue protocol included (1) a running Course-Navette test, (2) running up and down a flight of stairs for 5 min, and (3) performance of alternating jumps on a step (five sets of 1 minute each with 30 resting seconds between the sets). Fatigue decreased dorsiflexion (14.24 ± 4.98° in pre-fatigue and 12.65 ± 6.21° in fatigue condition, p  < 0.05) at foot strike phase in females, and plantar flexion (-19.23 ± 4.12° in pre-fatigue and -18.26 ± 5.31° in fatigue condition, p  < 0.05) at toe-off phase in males. These changes led to a decreased loading rate (88.14 ± 25.82 BW/s in pre-fatigue and 83.97 ± 18.83 BW/s in fatigue condition, p  < 0.05) and the impact peak in females (1.95 ± 0.31 BW in pre-fatigue and 1.90 ± 0.31 BW in fatigue condition, p  < 0.05), and higher peak propulsive forces in males (-0.26 ± 0.04 BW in pre-fatigue and -0.27 ± 0.05 BW in fatigue condition, p  < 0.05) in the fatigue condition. It seems that better responses to impact under a fatigue condition are observed among women. Further studies should confirm whether these changes represent a strategy to optimize shock attenuation, prevent running injuries and improve running economy.

Effects of Stretch Shortening Cycle Exercise Fatigue on Stress Fracture Injury Risk during Landing

ERIC Educational Resources Information Center

James, C. Roger; Dufek, Janet S.; Bates, Barry T.

2006-01-01

The purpose of this study was to examine changes in landing performance during fatigue that could result in increased stress fracture injury risk. Five participants performed nonfatigued and fatigued drop landings (0.60 m), while ground reaction force (GRF), electromyographic (EMG) activity, and kinematics were recorded. Fatigue was defined as a…

Exhausting the Fatigue University: In Search of a Biopolitics of Research

ERIC Educational Resources Information Center

D'Hoest, Florelle; Lewis, Tyson E.

2015-01-01

Today it would seem that being fatigued is a fairly common physical and psychological effect of educational systems based on an increasing demand for high-yield performance quotas. In higher education, "publish or perish" is a kind of imperative to perform, perform better, and perform optimally leading to an overall economy of fatigue.…

Chronicity and remission of fatigue in patients with established HIV infection.

PubMed

Pence, Brian Wells; Barroso, Julie; Harmon, James L; Leserman, Jane; Salahuddin, Naima; Hammill, Bradley G

2009-04-01

Fatigue is one of the most common and debilitating complaints of HIV-positive individuals, potentially leading to important functional limitations. We recruited 128 HIV-positive individuals (fatigued and nonfatigued) between March 2005 and May 2006; 66% were male, 66% were African American, 45% had greater than a high school education, 67% were unemployed, and ages ranged from 26-66 (median, 44). Every 3 months for 15 months, participants completed a 56-item self-report fatigue scale developed and validated by the authors. Participants were classified as fatigued or not fatigued at each assessment and received scores for fatigue intensity and impact of fatigue on functioning. We used linear mixed-effects models to assess longitudinal variation in fatigue scores and generalized estimating equations for binary outcomes to model predictors of fatigue remission among those fatigued at baseline. At baseline, 88% of the sample was fatigued. Fatigue measures were highly correlated across time points (rho 0.63-0.85 [intensity], 0.63-0.80 [functioning]) and showed no evidence of overall improvement, deterioration, or convergence over time. Predictors of lower fatigue scores included higher income, employment, longer time since HIV diagnosis, and antiretroviral therapy use. Those employed at baseline were likely to show improvements in fatigue while those unemployed were not. Of those fatigued at baseline, 11% experienced remission during follow-up; remission was associated with Caucasian race and employment. In summary, fatigue intensity and related functional limitations were persistent, stable, and unlikely to remit over 15 months of follow-up in this sample of patients with established HIV infection.

An exploration of the relationship between fatigue and physical functioning in patients with end stage renal disease receiving haemodialysis.

PubMed

O'Sullivan, Dawn; McCarthy, Geraldine

2007-11-01

To measure fatigue and physical functioning in patients with end stage renal disease (ESRD) receiving haemodialysis and to investigate the relationships between fatigue and physical functioning. Fatigue and reduced physical functioning are among the most bothersome symptoms experienced by individuals receiving haemodialysis for ESRD. Research has shown that increasing activity levels has resulted in decreased fatigue levels and improved physical functioning in individuals with cancer. Establishing whether or not a relationship exists between both concepts in haemodialysis patients is a preliminary step in identifying potential fatigue reducing strategies necessary for improved wellbeing. A quantitative exploratory correlational design was used with 46 individuals completing the Multi-dimensional Fatigue Inventory, the Medical Outcomes Study Short-Form 36-item questionnaire and a Demographic Questionnaire. Results indicated fatigue was prevalent with highest scores achieved for physical fatigue; reduced activity and general fatigue. Substantial limitations in physical functioning were found. A significant moderate negative relationship between general fatigue and physical functioning indicated that, as physical functioning levels increased, fatigue levels decreased. A significant difference was also found between general fatigue scores for males and females. Significant relationships were found between overall physical functioning, older age and employment status. The research indicates the prevalence of fatigue and limitations in physical functioning in individuals with ESRD. However, as physical functioning increased fatigue decreased; a finding relevant to clinical nursing. Understanding the levels of fatigue and the value of exercise is of relevance to clinical practice thus assessment of fatigue and physical functioning ability in the clinical setting is necessary.

Effect of Caffeine on Golf Performance and Fatigue during a Competitive Tournament.

PubMed

Mumford, Petey W; Tribby, Aaron C; Poole, Christopher N; Dalbo, Vincent J; Scanlan, Aaron T; Moon, Jordan R; Roberts, Michael D; Young, Kaelin C

2016-01-01

This study aimed to determine the effect of a caffeine-containing supplement on golf-specific performance and fatigue during a 36-hole competitive golf tournament. Twelve male golfers (34.8 ± 13.9 yr, 175.9 ± 9.3 cm, 81.23 ± 13.14 kg) with a United States Golf Association handicap of 3-10 participated in a double-blind, placebo-controlled, crossover design in which they played an 18-hole round of golf on two consecutive days (36-hole tournament) and were randomly assigned to consume a caffeine-containing supplement (CAF) or placebo (PLA). CAF/PLA was consumed before and after nine holes during each 18-hole round. Total score, drive distance, fairways and greens in regulation, first putt distance, HR, breathing rate, peak trunk acceleration, and trunk posture while putting were recorded. Self-perceived ratings of energy, fatigue, alertness and concentration were also recorded. Total score (76.9 ± 8.1 vs 79.4 ± 9.1, P = 0.039), greens in regulation (8.6 ± 3.3 vs 6.9 ± 4.6, P = 0.035), and drive distance (239.9 ± 33.8 vs 233.2 ± 32.4, P = 0.047) were statistically better during the CAF condition compared with those during PLA. Statistically significant main effects for condition (P < 0.05) and time (P < 0.001) occurred for perceived feelings of energy and fatigue. Compared with PLA, CAF reported more energy (P = 0.025) and less fatigue (P = 0.05) over the competitive round of golf. There were no substantial differences in HR or breathing rates, peak trunk acceleration, or putting posture between conditions or over the round (P > 0.05). A moderate dose (1.9 ± 0.3 mg · kg(-1)) of caffeine consumed before and during a round of golf improves golf-specific measures of performance and reduces fatigue in skilled golfers.

Interactive processes link the multiple symptoms of fatigue in sport competition.

PubMed

Knicker, Axel J; Renshaw, Ian; Oldham, Anthony R H; Cairns, Simeon P

2011-04-01

Muscle physiologists often describe fatigue simply as a decline of muscle force and infer this causes an athlete to slow down. In contrast, exercise scientists describe fatigue during sport competition more holistically as an exercise-induced impairment of performance. The aim of this review is to reconcile the different views by evaluating the many performance symptoms/measures and mechanisms of fatigue. We describe how fatigue is assessed with muscle, exercise or competition performance measures. Muscle performance (single muscle test measures) declines due to peripheral fatigue (reduced muscle cell force) and/or central fatigue (reduced motor drive from the CNS). Peak muscle force seldom falls by >30% during sport but is often exacerbated during electrical stimulation and laboratory exercise tasks. Exercise performance (whole-body exercise test measures) reveals impaired physical/technical abilities and subjective fatigue sensations. Exercise intensity is initially sustained by recruitment of new motor units and help from synergistic muscles before it declines. Technique/motor skill execution deviates as exercise proceeds to maintain outcomes before they deteriorate, e.g. reduced accuracy or velocity. The sensation of fatigue incorporates an elevated rating of perceived exertion (RPE) during submaximal tasks, due to a combination of peripheral and higher CNS inputs. Competition performance (sport symptoms) is affected more by decision-making and psychological aspects, since there are opponents and a greater importance on the result. Laboratory based decision making is generally faster or unimpaired. Motivation, self-efficacy and anxiety can change during exercise to modify RPE and, hence, alter physical performance. Symptoms of fatigue during racing, team-game or racquet sports are largely anecdotal, but sometimes assessed with time-motion analysis. Fatigue during brief all-out racing is described biomechanically as a decline of peak velocity, along with altered kinematic components. Longer sport events involve pacing strategies, central and peripheral fatigue contributions and elevated RPE. During match play, the work rate can decline late in a match (or tournament) and/or transiently after intense exercise bursts. Repeated sprint ability, agility and leg strength become slightly impaired. Technique outcomes, such as velocity and accuracy for throwing, passing, hitting and kicking, can deteriorate. Physical and subjective changes are both less severe in real rather than simulated sport activities. Little objective evidence exists to support exercise-induced mental lapses during sport. A model depicting mind-body interactions during sport competition shows that the RPE centre-motor cortex-working muscle sequence drives overall performance levels and, hence, fatigue symptoms. The sporting outputs from this sequence can be modulated by interactions with muscle afferent and circulatory feedback, psychological and decision-making inputs. Importantly, compensatory processes exist at many levels to protect against performance decrements. Small changes of putative fatigue factors can also be protective. We show that individual fatigue factors including diminished carbohydrate availability, elevated serotonin, hypoxia, acidosis, hyperkalaemia, hyperthermia, dehydration and reactive oxygen species, each contribute to several fatigue symptoms. Thus, multiple symptoms of fatigue can occur simultaneously and the underlying mechanisms overlap and interact. Based on this understanding, we reinforce the proposal that fatigue is best described globally as an exercise-induced decline of performance as this is inclusive of all viewpoints. © 2011 Adis Data Information BV. All rights reserved.

The Impact of Moderate and High Intensity Total Body Fatigue on Passing Accuracy in Expert and Novice Basketball Players

PubMed Central

Lyons, Mark; Al-Nakeeb, Yahya; Nevill, Alan

2006-01-01

Despite the acknowledged importance of fatigue on performance in sport, ecologically sound studies investigating fatigue and its effects on sport-specific skills are surprisingly rare. The aim of this study was to investigate the effect of moderate and high intensity total body fatigue on passing accuracy in expert and novice basketball players. Ten novice basketball players (age: 23.30 ± 1.05 yrs) and ten expert basketball players (age: 22.50 ± 0.41 yrs) volunteered to participate in the study. Both groups performed the modified AAHPERD Basketball Passing Test under three different testing conditions: rest, moderate intensity and high intensity total body fatigue. Fatigue intensity was established using a percentage of the maximal number of squat thrusts performed by the participant in one minute. ANOVA with repeated measures revealed a significant (F 2,36 = 5.252, p = 0.01) level of fatigue by level of skill interaction. On examination of the mean scores it is clear that following high intensity total body fatigue there is a significant detriment in the passing performance of both novice and expert basketball players when compared to their resting scores. Fundamentally however, the detrimental impact of fatigue on passing performance is not as steep in the expert players compared to the novice players. The results suggest that expert or skilled players are better able to cope with both moderate and high intensity fatigue conditions and maintain a higher level of performance when compared to novice players. The findings of this research therefore, suggest the need for trainers and conditioning coaches in basketball to include moderate, but particularly high intensity exercise into their skills sessions. This specific training may enable players at all levels of the game to better cope with the demands of the game on court and maintain a higher standard of play. Key Points Aim: to investigate the effect of moderate and high intensity total body fatigue on basketball-passing accuracy in expert and novice basketball players. Fatigue intensity was set as a percentage of the maximal number of squat thrusts performed by the participant in one minute. ANOVA with repeated measures revealed a significant level of fatigue by level of skill interaction. Despite a significant detriment in passing-performance in both novice and expert players following high intensity total body fatigue, this detriment was not as steep in the expert players when compared to the novice players PMID:24259994

The Evolution of Plate and Extruded Products with High Strength and Fracture Toughness

NASA Astrophysics Data System (ADS)

Denzer, D. K.; Rioja, R. J.; Bray, G. H.; Venema, G. B.; Colvin, E. L.

From the first use of 2017-T74 on the Junkers F13, improvements have been made to plate and extruded products for applications requiring the highest attainable strength and adequate fracture toughness. One such application is the upper wing of large aircraft. The progression of these product improvements achieved through the development of alloys that include 7075-(T6 & T76), 7150-(T6 & T77) and 7055-(T77 & T79) and most recently 7255-(T77 & T79) is reviewed. The most current advancements include aluminum-copper-lithium, alloy 2055 plate and extruded products that can attain strength equivalent to that of 7055-T77 with higher modulus, similar fracture toughness and improved fatigue, fatigue crack growth and corrosion performance. The achievement of these properties is explained in terms of the several alloy design principles. The highly desired and balanced characteristics make these products ideal for upper wing applications.

Measuring neurophysiological signals in aircraft pilots and car drivers for the assessment of mental workload, fatigue and drowsiness.

PubMed

Borghini, Gianluca; Astolfi, Laura; Vecchiato, Giovanni; Mattia, Donatella; Babiloni, Fabio

2014-07-01

This paper reviews published papers related to neurophysiological measurements (electroencephalography: EEG, electrooculography EOG; heart rate: HR) in pilots/drivers during their driving tasks. The aim is to summarise the main neurophysiological findings related to the measurements of pilot/driver's brain activity during drive performance and how particular aspects of this brain activity could be connected with the important concepts of "mental workload", "mental fatigue" or "situational awareness". Review of the literature suggests that exists a coherent sequence of changes for EEG, EOG and HR variables during the transition from normal drive, high mental workload and eventually mental fatigue and drowsiness. In particular, increased EEG power in theta band and a decrease in alpha band occurred in high mental workload. Successively, increased EEG power in theta as well as delta and alpha bands characterise the transition between mental workload and mental fatigue. Drowsiness is also characterised by increased blink rate and decreased HR values. The detection of such mental states is actually performed "offline" with accuracy around 90% but not online. A discussion on the possible future applications of findings provided by these neurophysiological measurements in order to improve the safety of the vehicles will be also presented. Copyright © 2012 Elsevier Ltd. All rights reserved.

Pumpkin (Cucurbita moschata) fruit extract improves physical fatigue and exercise performance in mice.

PubMed

Wang, Shih-Yi; Huang, Wen-Ching; Liu, Chieh-Chung; Wang, Ming-Fu; Ho, Chin-Shan; Huang, Wen-Pei; Hou, Chia-Chung; Chuang, Hsiao-Li; Huang, Chi-Chang

2012-10-09

Pumpkin (Cucurbita moschata) is a popular and nutritious vegetable consumed worldwide. The overall purpose of this study was to evaluate the effects of C. moschata fruit extract (CME) on anti-fatigue and ergogenic functions following physiological challenges. Male ICR mice from four groups designated vehicle, CME-50, CME-100 and CME-250, respectively (n = 8 per group in each test) were orally administered CME for 14 days at 0, 50, 100 and 250 mg/kg/day. The anti-fatigue activity and exercise performance were evaluated using exhaustive swimming time, forelimb grip strength, as well as levels of plasma lactate, ammonia, glucose, and creatine kinase after an acute swimming exercise. The resting muscular and hepatic glycogen was also analyzed after 14-day supplementation with CME. Trend analysis revealed that CME treatments increased grip strength. CME dose-dependently increased 5% body weight loaded swimming time, blood glucose, and muscular and hepatic glycogen levels. CME dose-dependently decreased plasma lactate and ammonia levels and creatine kinase activity after a 15-min swimming test. The mechanism was relevant to the increase in energy storage (as glycogen) and release (as blood glucose), and the decrease of plasma levels of lactate, ammonia, and creatine kinase. Therefore, CME may be potential for the pharmacological effect of anti-fatigue.

Rutting and Fatigue Cracking Resistance of Waste Cooking Oil Modified Trinidad Asphaltic Materials.

PubMed

Maharaj, Rean; Ramjattan-Harry, Vitra; Mohamed, Nazim

2015-01-01

The influence of waste cooking oil (WCO) on the performance characteristics of asphaltic materials indigenous to Trinidad, namely, Trinidad Lake Asphalt (TLA), Trinidad Petroleum Bitumen (TPB), and TLA : TPB (50 : 50) blend, was investigated to deduce the applicability of the WCO as a performance enhancer for the base asphalt. The rheological properties of complex modulus (G (∗) ) and phase angle (δ) were measured for modified base asphalt blends containing up to 10% WCO. The results of rheology studies demonstrated that the incremental addition of WCO to the three parent binders resulted in incremental decreases in the rutting resistance (decrease in G (∗) /sinδ values) and increases in the fatigue cracking resistance (decrease in G (∗) sinδ value). The fatigue cracking resistance and rutting resistance for the TLA : TPB (50 : 50) blends were between those of the blends containing pure TLA and TPB. As operating temperature increased, an increase in the resistance to fatigue cracking and a decrease in the rutting resistance were observed for all of the WCO modified asphaltic blends. This study demonstrated the capability to create customized asphalt-WCO blends to suit special applications and highlights the potential for WCO to be used as an environmentally attractive option for improving the use of Trinidad asphaltic materials.

Rutting and Fatigue Cracking Resistance of Waste Cooking Oil Modified Trinidad Asphaltic Materials

PubMed Central

Maharaj, Rean; Ramjattan-Harry, Vitra; Mohamed, Nazim

2015-01-01

The influence of waste cooking oil (WCO) on the performance characteristics of asphaltic materials indigenous to Trinidad, namely, Trinidad Lake Asphalt (TLA), Trinidad Petroleum Bitumen (TPB), and TLA : TPB (50 : 50) blend, was investigated to deduce the applicability of the WCO as a performance enhancer for the base asphalt. The rheological properties of complex modulus (G ∗) and phase angle (δ) were measured for modified base asphalt blends containing up to 10% WCO. The results of rheology studies demonstrated that the incremental addition of WCO to the three parent binders resulted in incremental decreases in the rutting resistance (decrease in G ∗/sinδ values) and increases in the fatigue cracking resistance (decrease in G ∗sinδ value). The fatigue cracking resistance and rutting resistance for the TLA : TPB (50 : 50) blends were between those of the blends containing pure TLA and TPB. As operating temperature increased, an increase in the resistance to fatigue cracking and a decrease in the rutting resistance were observed for all of the WCO modified asphaltic blends. This study demonstrated the capability to create customized asphalt-WCO blends to suit special applications and highlights the potential for WCO to be used as an environmentally attractive option for improving the use of Trinidad asphaltic materials. PMID:26336652

Fatigue-Induced Changes in Movement Pattern and Muscle Activity During Ballet Releve on Demi-Pointe.

PubMed

Lin, Cheng-Feng; Lee, Wan-Chin; Chen, Yi-An; Hsue, Bih-Jen

2016-08-01

Fatigue in ballet dancers may lead to injury, particularly in the lower extremities. However, few studies have investigated the effects of fatigue on ballet dancers' performance and movement patterns. Thus, the current study examines the effect of fatigue on the balance, movement pattern, and muscle activities of the lower extremities in ballet dancers. Twenty healthy, female ballet dancers performed releve on demi-pointe before and after fatigue. The trajectory of the whole body movement and the muscle activities of the major lower extremity muscles were recorded continuously during task performance. The results show that fatigue increases the medial-lateral center of mass (COM) displacement and hip and trunk motion, but decreases the COM velocity and ankle motion. Moreover, fatigue reduces the activities of the hamstrings and tibialis anterior, but increases that of the soleus. Finally, greater proximal hip and trunk motions are applied to compensate for the effects of fatigue, leading to a greater COM movement. Overall, the present findings show that fatigue results in impaired movement control and may therefore increase the risk of dance injury.

Effect of unilateral knee extensor fatigue on force and balance of the contralateral limb.

PubMed

Arora, Shruti; Budden, Shawn; Byrne, Jeannette M; Behm, David G

2015-10-01

Fatigue in one limb can decrease force production in the homologous muscle as well as other muscles of the non-fatigued limb affecting balance. The objective of the study was to examine the effect of unilateral knee extensor fatigue on the non-fatigued limb's standing balance, muscle force and activation. Sixteen healthy male subjects performed pre-fatigue balance trials, warm-up exercises, maximum voluntary isometric contractions, a knee extensors fatigue protocol, and post-fatigue balance trials. The fatigue protocol consisted of sets of 15 consecutive isometric contractions of 16 s each with 4 s recovery between repetitions, which were performed at 30% peak force for the dominant knee extensor muscles. Additional sets of contractions continued until a 50% decrease in MVIC knee extensor force was observed. Pre- and post-fatigue balance assessment consisted of transition from double to single leg standing and also single leg standing trials, which were performed bilaterally and in randomized order. The peak force and F100 were significantly decreased by 44.8% (ES = 2.54) and 39.9% (ES = 0.59), respectively, for the fatigued limb post-fatigue. There were no significant changes in the non-fatigued limb's muscle force, activation, muscle onset timing or postural stability parameters. While the lack of change in non-fatigued limb force production is in agreement with some of the previous literature in this area, the lack of effect on postural measures directly contradicts earlier work. It is hypothesized that discrepancies in the duration and the intensity of the fatigue protocol may have accounted for this discrepancy.

Patient-controlled methylphenidate for cancer fatigue: a double-blind, randomized, placebo-controlled trial.

PubMed

Bruera, Eduardo; Valero, Vicente; Driver, Larry; Shen, Loren; Willey, Jie; Zhang, Tao; Palmer, J Lynn

2006-05-01

To evaluate the effectiveness of patient-controlled methylphenidate as compared with placebo in cancer patients with fatigue, as measured by the Functional Assessment for Chronic Illness Therapy-Fatigue (FACIT-F). Patients with a fatigue score of at least 4 on a scale of 0 to 10 (0 = no fatigue, 10 = worst possible fatigue) and hemoglobin level of at least 10 g/dL were included. Patients were randomly assigned to receive 5 mg methylphenidate or placebo every 2 hours as needed (maximum of four capsules a day), for 7 days. Patients completed a daily diary including study drug record and fatigue intensity. A research nurse telephoned patients daily to assess toxicity and fatigue level. All patients were offered open-label methylphenidate for 4 weeks. FACIT-F and the Edmonton Symptom Assessment System (ESAS) were assessed at baseline, and days 8, 15, and 36. The FACIT-F fatigue subscore on day 8 was considered the primary end point. Of 112 patients randomly assigned, 52 patients in the methylphenidate and 53 in the placebo group were assessable for analysis. Fatigue intensity improved significantly on day 8 in both the methylphenidate and placebo groups. However, there was no significant difference in fatigue improvement by FACIT-F (P = .31) or ESAS (P = .14) between groups. In open-label phase, fatigue intensity maintained low as compared with baseline. No significant toxicities were observed. Both methylphenidate and placebo resulted in significant symptom improvement. Methylphenidate was not significantly superior to placebo after 1 week of treatment. Longer study duration is justified. The role of daily telephone calls from a research nurse should be explored as a palliative care intervention.

Monitoring driver fatigue using a single-channel electroencephalographic device: A validation study by gaze-based, driving performance, and subjective data.

PubMed

Morales, José M; Díaz-Piedra, Carolina; Rieiro, Héctor; Roca-González, Joaquín; Romero, Samuel; Catena, Andrés; Fuentes, Luis J; Di Stasi, Leandro L

2017-12-01

Driver fatigue can impair performance as much as alcohol does. It is the most important road safety concern, causing thousands of accidents and fatalities every year. Thanks to technological developments, wearable, single-channel EEG devices are now getting considerable attention as fatigue monitors, as they could help drivers to assess their own levels of fatigue and, therefore, prevent the deterioration of performance. However, the few studies that have used single-channel EEG devices to investigate the physiological effects of driver fatigue have had inconsistent results, and the question of whether we can monitor driver fatigue reliably with these EEG devices remains open. Here, we assessed the validity of a single-channel EEG device (TGAM-based chip) to monitor changes in mental state (from alertness to fatigue). Fifteen drivers performed a 2-h simulated driving task while we recorded, simultaneously, their prefrontal brain activity and saccadic velocity. We used saccadic velocity as the reference index of fatigue. We also collected subjective ratings of alertness and fatigue, as well as driving performance. We found that the power spectra of the delta EEG band showed an inverted U-shaped quadratic trend (EEG power spectra increased for the first hour and half, and decreased during the last thirty minutes), while the power spectra of the beta band linearly increased as the driving session progressed. Coherently, saccadic velocity linearly decreased and speeding time increased, suggesting a clear effect of fatigue. Subjective data corroborated these conclusions. Overall, our results suggest that the TGAM-based chip EEG device is able to detect changes in mental state while performing a complex and dynamic everyday task as driving. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mental fatigue detection based on the functional near infrared spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, Zhen; Xu, Fenggang; Yang, Hanjun; Jiang, Jin; Cao, Yong; Jiao, Xuejun

2017-02-01

Mental fatigue can be induced by long time mental work, mental fatigue caused worse performance and accidents. As a non-invasive technique, functional near-infrared spectroscopy (fNIRS) can measure blood oxygen activity in the cerebral cortex which reflect the cognitive function of brain indirectly. Aiming at investigating whether fNIRS can measure the mental fatigue and study the spatial pattern of hemodynamic response for mental fatigue, we used three sessions of verbal 2-back working memory task for a total of 120 minutes to induce mental fatigue, 15 healthy subjects were recruited and 30 channels including prefrontal cortex (PFC) and motor cortex (MC) were measured by fNIRS. The mean oxyhemoglobin feature for 20s was extracted as well as subjective fatigue level and performance. The results showed significant increase of subjected fatigue level as well as significant decrease performance from session one to three task. With the increased level of fatigue, oxyhemoglobin in PFC increase significantly and the spatial pattern of hemodynamic response in the all 30 channels varied with task duration as well. These findings indicated the potential of fNIRS measured hemodynamic as a mental fatigue indicator.

Effects of fatigue on driving performance under different roadway geometries: a simulator study.

PubMed

Du, Hongji; Zhao, Xiaohua; Zhang, Xingjian; Zhang, Yunlong; Rong, Jian

2015-01-01

This article examines the effects of fatigue on driving performance under different roadway geometries using a driving simulator. Twenty-four participants each completed a driving scenario twice: while alert and while experiencing fatigue. The driving scenario was composed of straight road segments and curves; there were 6 curves with 3 radius values (i.e., 200, 500, and 800 m) and 2 turning directions (i.e., left and right). Analysis was conducted on driving performance measures such as longitudinal speed, steering wheel movements, and lateral position. RESULTS confirmed that decremental changes in driving performance due to fatigue varied among road conditions. On straight segments, drivers' abilities to steer and maintain lane position were impaired, whereas on curves we found decremental changes in the quality of longitudinal speed as well as steering control and keeping the vehicle in the lane. Moreover, the effects of fatigue on driving performance were relative to the radius and direction of the curve. Fatigue impaired drivers' abilities to control the steering wheel, and the impairment proved more obvious on curves. The degree varied significantly as the curve radius changed. Drivers tended to drive closer to the right side due to fatigue, and the impairment in maintaining lane position became more obvious as the right-turn curve radius decreased. Driver fatigue has detrimental effects on driving performance, and the effects differ under different roadway geometries.

Effects of human fatigue on speech signals

NASA Astrophysics Data System (ADS)

Stamoulis, Catherine

2004-05-01

Cognitive performance may be significantly affected by fatigue. In the case of critical personnel, such as pilots, monitoring human fatigue is essential to ensure safety and success of a given operation. One of the modalities that may be used for this purpose is speech, which is sensitive to respiratory changes and increased muscle tension of vocal cords, induced by fatigue. Age, gender, vocal tract length, physical and emotional state may significantly alter speech intensity, duration, rhythm, and spectral characteristics. In addition to changes in speech rhythm, fatigue may also affect the quality of speech, such as articulation. In a noisy environment, detecting fatigue-related changes in speech signals, particularly subtle changes at the onset of fatigue, may be difficult. Therefore, in a performance-monitoring system, speech parameters which are significantly affected by fatigue need to be identified and extracted from input signals. For this purpose, a series of experiments was performed under slowly varying cognitive load conditions and at different times of the day. The results of the data analysis are presented here.

Experimental Investigation of Principal Residual Stress and Fatigue Performance for Turned Nickel-Based Superalloy Inconel 718.

PubMed

Hua, Yang; Liu, Zhanqiang

2018-05-24

Residual stresses of turned Inconel 718 surface along its axial and circumferential directions affect the fatigue performance of machined components. However, it has not been clear that the axial and circumferential directions are the principle residual stress direction. The direction of the maximum principal residual stress is crucial for the machined component service life. The present work aims to focuses on determining the direction and magnitude of principal residual stress and investigating its influence on fatigue performance of turned Inconel 718. The turning experimental results show that the principal residual stress magnitude is much higher than surface residual stress. In addition, both the principal residual stress and surface residual stress increase significantly as the feed rate increases. The fatigue test results show that the direction of the maximum principal residual stress increased by 7.4%, while the fatigue life decreased by 39.4%. The maximum principal residual stress magnitude diminished by 17.9%, whereas the fatigue life increased by 83.6%. The maximum principal residual stress has a preponderant influence on fatigue performance as compared to the surface residual stress. The maximum principal residual stress can be considered as a prime indicator for evaluation of the residual stress influence on fatigue performance of turned Inconel 718.

Comparison of the effect of selected muscle groups fatigue on postural control during bipedal stance in healthy young women.

PubMed

Shirazi, Zahra Rojhani; Jahromi, Fatemeh Nikhalat

2013-09-01

The maintenance of balance is an essential requirement for the performance of daily tasks and sporting activities and muscular fatigue is a factor to impair postural control, so this study was done to compare the effect of selected muscle groups fatigue on postural control during bipedal stance in healthy subjects. Fifteen healthy female students (24.3 ± 2.6 years) completed three testing session with a break period of at least 2 days. During each session, postural control was assessed during two 30-s trials of bipedal stance with eyes close before and after the fatigue protocol. Fatigue protocols were performed by 60% of their unfatigued Maximum Voluntary Contraction of unilateral ankle plantar flexors, bilateral lumbar extensors and bilateral neck extensors. One of the three fatigue protocols was performed on each session. The result showed that fatigue had a significant effect on COP velocity and it increase COP velocity but there was not found any difference in postural sway between muscle groups. Localized muscle fatigue caused deficits in postural control regardless of the location of fatigue. Authors suggest the possibility of the contributions of central mechanisms to postural deficits due to fatigue and it seems that difference was not between muscle groups due to central fatigue.

Thermal behavior of crumb-rubber modified asphalt concrete mixtures

NASA Astrophysics Data System (ADS)

Epps, Amy Louise

Thermal cracking is one of the primary forms of distress in asphalt concrete pavements, resulting from either a single drop in temperature to an extreme low or from multiple temperature cycles above the fracture temperature of the asphalt-aggregate mixture. The first mode described is low temperature cracking; the second is thermal fatigue. The addition of crumb-rubber, manufactured from scrap tires, to the binder in asphalt concrete pavements has been suggested to minimize both types of thermal cracking. Four experiments were designed and completed to evaluate the thermal behavior of crumb-rubber modified (CRM) asphalt-aggregate mixtures. Modified and unmodified mixture response to thermal stresses was measured in four laboratory tests. The Thermal Stress Restrained Specimen Test (TSRST) and the Indirect Tensile Test (IDT) were used to compare mixture resistance to low temperature cracking. Modified mixtures showed improved performance, and cooling rate did not affect mixture resistance according to the statistical analysis. Therefore results from tests with faster rates can predict performance under slower field rates. In comparison, predicted fracture temperatures and stresses (IDT) were generally higher than measured values (TSRST). In addition, predicted fracture temperatures from binder test results demonstrated that binder testing alone is not sufficient to evaluate CRM mixtures. Thermal fatigue was explored in the third experiment using conventional load-induced fatigue tests with conditions selected to simulate daily temperature fluctuations. Test results indicated that thermal fatigue may contribute to transverse cracking in asphalt pavements. Both unmodified and modified mixtures had a finite capacity to withstand daily temperature fluctuations coupled with cold temperatures. Modified mixtures again exhibited improved performance. The fourth experiment examined fracture properties of modified and unmodified mixtures using a common fracture toughness test. Results showed no effect from modification, but the small experiment size may have masked this effect. Reliability concepts were introduced to include risk and uncertainty in a comparison of mixture response measured in the laboratory and estimated environmental conditions. This comparison provided evidence that CRM mixtures exhibit improved resistance to both types of thermal cracking at high levels of reliability. In conclusion, a mix design and analysis framework for evaluating thermal behavior was recommended.

Behaviour of several fatigue prone bridge details

NASA Astrophysics Data System (ADS)

Kubiš, Petr; Ryjáček, Pavel

2017-09-01

Three fatigue welded bridge joints analysed in this work are the alternative details of the bottom flange connection. This construction detail is mainly used for the erection connection for steel and composite bridges. If applied in the place, where live load is significant, the fatigue becomes the main design criterion. The detail category is thus very important factor. The aim of this paper is to analyse the possibilities of the improving the behaviour of this detail, by various methods. First solution is to modify the shape of the cope hole to the elliptic shape. Second option is to use the “Olemutz” fully welded detail. This detail is often used in bridge designing despite there is no exact information about the fatigue category, and doubts of the performance exists. “Olemutz” is a long web plate slit that is filled by the double bevel weld after the execution of the bottom flange weld. The last detail is the elliptic cope hole filled by the plate-cap welded into an empty hole. The geometry is the same, as in the first case. The conclusion of the numerical analysis and the pilot fatigue experiments is discussed with several practical recommendations for designing.

Prescribed Travel Schedules for Fatigue Management

NASA Technical Reports Server (NTRS)

Whitmire, Alexandra; Johnston, Smith; Lockley, Steven

2011-01-01

The NASA Fatigue Management Team is developing recommendations for managing fatigue during travel and for shift work operations, as Clinical Practice Guidelines for the Management of Circadian Desynchrony in ISS Operations. The Guidelines provide the International Space Station (ISS ) flight surgeons and other operational clinicians with evidence-based recommendations for mitigating fatigue and other factors related to sleep loss and circadian desynchronization. As much international travel is involved both before and after flight, the guidelines provide recommendations for: pre-flight training, in-flight operations, and post-flight rehabilitation. The objective of is to standardize the process by which care is provided to crewmembers, ground controllers, and other support personnel such as trainers, when overseas travel or schedule shifting is required. Proper scheduling of countermeasures - light, darkness, melatonin, diet, exercise, and medications - is the cornerstone for facilitating circadian adaptation, improving sleep, enhancing alertness, and optimizing performance. The Guidelines provide, among other things, prescribed travel schedules that outline the specific implementation of these mitigation strategies. Each travel schedule offers evidence based protocols for properly using the NASA identified countermeasures for fatigue. This presentation will describe the travel implementation schedules and how these can be used to alleviate the effects of jet lag and/or schedule shifts.

Fatigue and muscle-tendon stiffness after stretch-shortening cycle and isometric exercise.

PubMed

Toumi, Hechmi; Poumarat, Georges; Best, Thomas M; Martin, Alain; Fairclough, John; Benjamin, Mike

2006-10-01

The purpose of the present study was to compare vertical jump performance after 2 different fatigue protocols. In the first protocol, subjects performed consecutive sets of 10 repetitions of stretch-shortening cycle (SSC) contractions. In the second protocol, successive sets of 10 repetitions of isometric contractions were performed for 10 s with the knee at 90 degrees of flexion. The exercises were stopped when the subjects failed to reach 50% of their maximum voluntary isometric contractions. Maximal isometric force and maximal concentric power were assessed by performing supine leg presses, squat jumps, and drop jumps. Surface EMG was used to determine changes in muscle activation before and after fatigue. In both groups, the fatigue exercises reduced voluntary isometric force, maximal concentric power, and drop jump performance. Kinematic data showed a decrease in knee muscle-tendon stiffness accompanied by a lengthened ground contact time. EMG analysis showed that the squat and drop jumps were performed similarly before and after the fatigue exercise for both groups. Although it was expected that the stiffness would decrease more after SSC than after isometric fatigue (as a result of a greater alteration of the reflex sensitivity SSC), our results showed that both protocols had a similar effect on knee muscle stiffness during jumping exercises. Both fatigue protocols induced muscle fatigue, and the decrease in jump performance was linked to a decrease in the strength and stiffness of the knee extensor muscles.

Performance Evaluation and Improving Mechanisms of Diatomite-Modified Asphalt Mixture

PubMed Central

Yang, Chao; Xie, Jun; Zhou, Xiaojun; Liu, Quantao; Pang, Ling

2018-01-01

Diatomite is an inorganic natural resource in large reserve. This study consists of two phases to evaluate the effects of diatomite on asphalt mixtures. In the first phase, we characterized the diatomite in terms of mineralogical properties, chemical compositions, particle size distribution, mesoporous distribution, morphology, and IR spectra. In the second phase, road performances, referring to the permanent deformation, crack, fatigue, and moisture resistance, of asphalt mixtures with diatomite were investigated. The characterization of diatomite exhibits that it is a porous material with high SiO2 content and large specific surface area. It contributes to asphalt absorption and therefore leads to bonding enhancement between asphalt and aggregate. However, physical absorption instead of chemical reaction occurs according to the results of FTIR. The resistance of asphalt mixtures with diatomite to permanent deformation and moisture are superior to those of the control mixtures. But, the addition of diatomite does not help to improve the crack and fatigue resistance of asphalt mixture. PMID:29702579

Performance Evaluation and Improving Mechanisms of Diatomite-Modified Asphalt Mixture.

PubMed

Yang, Chao; Xie, Jun; Zhou, Xiaojun; Liu, Quantao; Pang, Ling

2018-04-27

Diatomite is an inorganic natural resource in large reserve. This study consists of two phases to evaluate the effects of diatomite on asphalt mixtures. In the first phase, we characterized the diatomite in terms of mineralogical properties, chemical compositions, particle size distribution, mesoporous distribution, morphology, and IR spectra. In the second phase, road performances, referring to the permanent deformation, crack, fatigue, and moisture resistance, of asphalt mixtures with diatomite were investigated. The characterization of diatomite exhibits that it is a porous material with high SiO₂ content and large specific surface area. It contributes to asphalt absorption and therefore leads to bonding enhancement between asphalt and aggregate. However, physical absorption instead of chemical reaction occurs according to the results of FTIR. The resistance of asphalt mixtures with diatomite to permanent deformation and moisture are superior to those of the control mixtures. But, the addition of diatomite does not help to improve the crack and fatigue resistance of asphalt mixture.

Monitoring and Managing Fatigue in Basketball

PubMed Central

Edwards, Toby; Spiteri, Tania; Piggott, Benjamin; Bonhotal, Joshua; Joyce, Christopher

2018-01-01

The sport of basketball exposes athletes to frequent high intensity movements including sprinting, jumping, accelerations, decelerations and changes of direction during training and competition which can lead to acute and accumulated chronic fatigue. Fatigue may affect the ability of the athlete to perform over the course of a lengthy season. The ability of practitioners to quantify the workload and subsequent fatigue in basketball athletes in order to monitor and manage fatigue levels may be beneficial in maintaining high levels of performance and preventing unfavorable physical and physiological training adaptations. There is currently limited research quantifying training or competition workload outside of time motion analysis in basketball. In addition, systematic research investigating methods to monitor and manage athlete fatigue in basketball throughout a season is scarce. To effectively optimize and maintain peak training and playing performance throughout a basketball season, potential workload and fatigue monitoring strategies need to be discussed. PMID:29910323

Clinically distinct trajectories of fatigue and their longitudinal relationship with the disturbance of personal goals following a cancer diagnosis.

PubMed

Müller, Fabiola; Tuinman, Marrit A; Janse, Moniek; Almansa, Josué; Sprangers, Mirjam A G; Smink, Ans; Ranchor, Adelita V; Fleer, Joke; Hagedoorn, Mariët

2017-09-01

Most studies on fatigue in patients with cancer aggregate its prevalence and severity on a group level, ignoring the possibility that subgroups of patients may differ widely in their development of fatigue. This study aimed to identify subgroups of patients with clinically distinct trajectories of fatigue from diagnosis to 18 months post-diagnosis. As fatigue might trigger goal disturbance, the study also identified trajectories of concrete and abstract goal disturbance and longitudinally examined their co-occurrence with fatigue. Prospective design with quantitative and qualitative method of data collection. Patients with colorectal cancer (n = 183) reported on their levels of fatigue and goal disturbance shortly after diagnosis (T 1 ) and at 7 months (T 2 ) and 18 months (T 3 ) post-diagnosis. Growth mixture model analyses were performed to identify trajectories of fatigue and goal disturbance. Guidelines for the clinical relevance of fatigue were applied. Four clinically distinct trajectories of fatigue were identified as follows: (1) persistent severe fatigue (25.4%), (2) moderate fatigue (56.1%), (3) no fatigue (13.8%), and (4) rapidly improving fatigue (4.7%). The majority of patients with cancer reported high disturbance of their concrete goals, while high disturbance of abstract goals was less evident. Fatigue and concrete goal disturbance co-occurred longitudinally. The fatigue and goal disturbance experienced from diagnosis to 18 months post-diagnosis differ considerably for subgroups of patients with cancer. Fatigue and concrete goal disturbance are persistent burdens in the majority of patients. Investigating symptom burden beyond average trends can guide clinicians to identify patients most in need for treatment. Targeting goal disturbance might benefit the psychological well-being in patients suffering from persistent symptoms. Statement of contribution What is already known on this subject? Fatigue is a common and distressing symptom at all stages of the cancer experience. Earlier studies suggest that many patients recover from fatigue after treatment completion. Patients with cancer experience disturbance in their personal goals, which is related to poor psychological well-being. What does this study add? Developments of fatigue and goal disturbance differ between subgroups of patients with cancer but co-occur within these subgroups. About 30% of the patients experience severe fatigue after diagnosis, of which only few patients recover within 18 months post-diagnosis. Targeting goal disturbance might benefit patients with severe and ongoing symptoms. © 2017 The British Psychological Society.

Effects of a resistance training program on balance and fatigue perception in patients with Parkinson's disease: A randomized controlled trial.

PubMed

Ortiz-Rubio, Araceli; Cabrera-Martos, Irene; Torres-Sánchez, Irene; Casilda-López, Jesús; López-López, Laura; Valenza, Marie Carmen

2017-11-22

Fatigue and balance impairment leads to a loss of independence and are important to adequately manage. The objective of this study was to examine the effects of a resistance training program on dynamic balance and fatigue in patients with Parkinson's disease (PD). Randomized controlled trial. Forty-six patients with PD were randomly allocated to an intervention group receiving a 8-week resistance training program focused on lower limbs or to a control group. Balance was assessed using the Mini-BESTest and fatigue was assessed by the Piper Fatigue Scale. Patients in the intervention group improved significantly (p<0.05) on dynamic balance (reactive postural control and total values) and perceived fatigue. An 8-week resistance training program was found to be effective at improving dynamic balance and fatigue in patients with PD. Copyright © 2017 Elsevier España, S.L.U. All rights reserved.

Analysis of cancer-related fatigue based on smart bracelet devices.

PubMed

Shen, Hong; Hou, Honglun; Tian, Wei; Wu, MingHui; Chen, Tianzhou; Zhong, Xian

2016-01-01

Fatigue is the most common symptom associated with cancer and its treatment, and profoundly affects all aspects of quality of life for cancer patients. It is very important to measure and manage cancer-related fatigue. Usually, the cancer-related fatigue scores, which estimate the degree of fatigue, are self-reported by cancer patients using standardized assessment tools. But most of the classical methods used for measurement of fatigue are subjective and inconvenient. In this study, we try to establish a new method to assess cancer-related fatigue objectively and accurately by using smart bracelet. All patients with metastatic pancreatic cancer wore smart bracelet for recording the physical activity including step count and sleep time before and after chemotherapy. Meantime, their psychological state was assessed by completing questionnaire tables as cancer-related fatigue scores. Step count record by smart bracelet reflecting the physical performance dramatically decreased in the initial days of chemotherapy and recovered in the next few days. Statistical analysis showed a strong and significant correlation between self-reported cancer-related fatigue and physical performance (P= 0.000, r=-0.929). Sleep time was also significantly correlated with fatigue (P= 0.000, r= 0.723). Multiple regression analysis showed that physical performance and sleep time are significant predictors of fatigue. Measuring activity using smart bracelets may be an appropriate method for quantitative and objective measurement of cancer-related fatigue by using smart bracelet devices.

Fracture resistance of dental nickel-titanium rotary instruments with novel surface treatment: Thin film metallic glass coating.

PubMed

Chi, Chih-Wen; Deng, Yu-Lun; Lee, Jyh-Wei; Lin, Chun-Pin

2017-05-01

Dental nickel-titanium (NiTi) rotary instruments are widely used in endodontic therapy because they are efficient with a higher success rate. However, an unpredictable fracture of instruments may happen due to the surface characteristics of imperfection (or irregularity). This study assessed whether a novel surface treatment could increase fatigue fracture resistance of dental NiTi rotary instruments. A 200- or 500-nm thick Ti-zirconium-boron (Ti-Zr-B) thin film metallic glass was deposited on ProTaper Universal F2 files using a physical vapor deposition process. The characteristics of coating were analyzed by scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry. In cyclic fatigue tests, the files were performed in a simulated root canal (radius=5 mm, angulation=60°) under a rotating speed of 300rpm. The fatigue fractured cross sections of the files were analyzed with their fractographic performances through scanning electron microscopy images. The amorphous structure of the Ti-Zr-B coating was confirmed by transmission electron microscopy and X-ray diffractometry. The surface of treated files presented smooth morphologies without grinding irregularity. For the 200- and 500-nm surface treatment groups, the coated files exhibited higher resistance of cyclic fatigue than untreated files. In fractographic analysis, treated files showed significantly larger crack-initiation zone; however, no significant differences in the areas of fatigue propagation and catastrophic fracture were found compared to untreated files. The novel surface treatment of Ti-Zr-B thin film metallic glass on dental NiTi rotary files can effectively improve the fatigue fracture resistance by offering a smooth coated surface with amorphous microstructure. Copyright © 2016. Published by Elsevier B.V.

Monitoring Training Load and Fatigue in Rugby Sevens Players

PubMed Central

Elloumi, Mohamed; Makni, Emna; Moalla, Wassim; Bouaziz, Taieb; Tabka, Zouhair; Lac, Gérard; Chamari, Karim

2012-01-01

Purpose Trainers and physical fitness coaches’ need a useful tool to assess training loads to avoid overtraining. However, perceived scales or questionnaires were required. Therefore, the purpose of this study was to assess whether a short 8-item questionnaire of fatigue could be a useful tool for monitoring changes in perceived training load and strain among elite rugby Sevens (7s) players during preparation for a major competition. Methods Sixteen elite rugby 7s players completed an 8-week training program composed of 6-week intense training (IT) and 2-week reduced training (RT). They were tested before (T0), after the IT (T1) and after the RT (T2). The quantification of the perceived training load and strain were performed by the session-RPE (rating of perceived exertion) method and concomitantly the 8-item questionnaire of fatigue was administered. Results Training load (TL) and strain (TS) and total score of fatigue (TSF from the 8-item questionnaire) increased during IT and decreased during RT. Simultaneously, physical performances decreased during IT and were improved after LT. The changes in TL, TS and TSF correlated significantly over the training period (r=0.63-0.83). Conclusions These findings suggest that the short questionnaire of fatigue could be a practical and a sensitive tool for monitoring changes in training load and strain in team-sport athletes. Accordingly, the simultaneous use of the short questionnaire of fatigue along with the session-RPE method for perceived changes in training load and strain during training could provide additional information on the athletes’ status, allowing coaches to prevent eventual states of overreaching or overtraining. PMID:23012637

A new method for overhead drilling.

PubMed

Rempel, David; Star, Demetra; Barr, Alan; Gibbons, Billy; Janowitz, Ira

2009-12-01

In the construction sector, overhead drilling into concrete or metal ceilings is a strenuous task associated with shoulder, neck and back musculoskeletal disorders due to the large applied forces and awkward arm postures. Two intervention devices, an inverted drill press and a foot lever design, were developed then compared to the usual method by construction workers performing their normal overhead drilling activities (n = 14). While the intervention devices were rated as less fatiguing than the usual method, their ratings on usability measures were worse than the usual method. The study demonstrates that the intervention devices can reduce fatigue; however, additional modifications are necessary in order to improve usability and productivity. Devices designed to improve workplace safety may need to undergo several rounds of field testing and modification prior to implementation.

Risk reclassification analysis investigating the added value of fatigue to sickness absence predictions.

PubMed

Roelen, Corné A M; Bültmann, Ute; Groothoff, Johan W; Twisk, Jos W R; Heymans, Martijn W

2015-11-01

Prognostic models including age, self-rated health and prior sickness absence (SA) have been found to predict high (≥ 30) SA days and high (≥ 3) SA episodes during 1-year follow-up. More predictors of high SA are needed to improve these SA prognostic models. The purpose of this study was to investigate fatigue as new predictor in SA prognostic models by using risk reclassification methods and measures. This was a prospective cohort study with 1-year follow-up of 1,137 office workers. Fatigue was measured at baseline with the 20-item checklist individual strength and added to the existing SA prognostic models. SA days and episodes during 1-year follow-up were retrieved from an occupational health service register. The added value of fatigue was investigated with Net Reclassification Index (NRI) and integrated discrimination improvement (IDI) measures. In total, 579 (51 %) office workers had complete data for analysis. Fatigue was prospectively associated with both high SA days and episodes. The NRI revealed that adding fatigue to the SA days model correctly reclassified workers with high SA days, but incorrectly reclassified workers without high SA days. The IDI indicated no improvement in risk discrimination by the SA days model. Both NRI and IDI showed that the prognostic model predicting high SA episodes did not improve when fatigue was added as predictor variable. In the present study, fatigue increased false-positive rates which may reduce the cost-effectiveness of interventions for preventing SA.

A glucose-caffeine 'energy drink' ameliorates subjective and performance deficits during prolonged cognitive demand.

PubMed

Kennedy, David O; Scholey, Andrew B

2004-06-01

Effects of a combination of caffeine and glucose were assessed in two double-blind, placebo-controlled, cross-over studies during extended performance of cognitively demanding tasks. In the first study, 30 participants received two drinks containing carbohydrate and caffeine (68 g/38 mg; 68 g/46 mg, respectively) and a placebo drink, in counter-balanced order, on separate days. In the second study 26 participants received a drink containing 60 g of carbohydrate and 33 mg of caffeine and a placebo drink. In both studies, participants completed a 10-min battery of tasks comprising 2-min versions of Serial 3s and Serial 7s subtraction tasks and a 5-min version of the Rapid Visual Information Processing task (RVIP), plus a rating of 'mental fatigue', once before the drink and six times in succession commencing 10 min after its consumption. In comparison to placebo, all three active drinks improved the accuracy of RVIP performance and both the drink with the higher level of caffeine in first study and the active drink in the second study resulted in lower ratings of mental fatigue. These results indicate that a combination of caffeine and glucose can ameliorate deficits in cognitive performance and subjective fatigue during extended periods of cognitive demand.

A Multiscale Virtual Fabrication and Lattice Modeling Approach for the Fatigue Performance Prediction of Asphalt Concrete

NASA Astrophysics Data System (ADS)

Dehghan Banadaki, Arash

Predicting the ultimate performance of asphalt concrete under realistic loading conditions is the main key to developing better-performing materials, designing long-lasting pavements, and performing reliable lifecycle analysis for pavements. The fatigue performance of asphalt concrete depends on the mechanical properties of the constituent materials, namely asphalt binder and aggregate. This dependent link between performance and mechanical properties is extremely complex, and experimental techniques often are used to try to characterize the performance of hot mix asphalt. However, given the seemingly uncountable number of mixture designs and loading conditions, it is simply not economical to try to understand and characterize the material behavior solely by experimentation. It is well known that analytical and computational modeling methods can be combined with experimental techniques to reduce the costs associated with understanding and characterizing the mechanical behavior of the constituent materials. This study aims to develop a multiscale micromechanical lattice-based model to predict cracking in asphalt concrete using component material properties. The proposed algorithm, while capturing different phenomena for different scales, also minimizes the need for laboratory experiments. The developed methodology builds on a previously developed lattice model and the viscoelastic continuum damage model to link the component material properties to the mixture fatigue performance. The resulting lattice model is applied to predict the dynamic modulus mastercurves for different scales. A framework for capturing the so-called structuralization effects is introduced that significantly improves the accuracy of the modulus prediction. Furthermore, air voids are added to the model to help capture this important micromechanical feature that affects the fatigue performance of asphalt concrete as well as the modulus value. The effects of rate dependency are captured by implementing the viscoelastic fracture criterion. In the end, an efficient cyclic loading framework is developed to evaluate the damage accumulation in the material that is caused by long-sustained cyclic loads.

Effectiveness of online and face-to-face fatigue self-management programmes for adults with neurological conditions.

PubMed

Ghahari, Setareh; Packer, Tanya

2012-01-01

To evaluate effectiveness of a face-to-face and an online fatigue self-management programme and to compare these to two control groups (information-only and no-intervention) in a sample of adults (n = 115) with neurological conditions reporting extreme fatigue. Non-equivalent pre-test post-test control group design using the Fatigue Impact Scale, Personal Wellbeing Index and Activity Card Sort as primary outcome measures. Participants in the two intervention groups and the information-only group showed clinically significant improvements in fatigue over time (p < 0.05). When compared to the no-intervention group, face-to-face participants showed significantly greater improvement in overall and cognitive fatigue, while participants in the online group showed significant improvement in self-efficacy and stress. Participation in either the online or face-to-face programme appears to result in improved self-management, however, with different potency depending on outcomes. The improvement in the online information only group further complicates the understanding of the results. With few other comparisons of online and face-to-face self-management protocols available, further research is needed to understand differential impacts which may be related to the delivery format, the rural versus urban split of participants or other unknown factors.

Occupational fatigue and other health and safety issues for young Australian workers: an exploratory mixed methods study.

PubMed

Paterson, Jessica Louise; Clarkson, Larissa; Rainbird, Sophia; Etherton, Hayley; Blewett, Verna

2015-01-01

Youth are vulnerable to sleep loss and fatigue due to biological, social and psychological factors. However, there are few studies addressing the risk that sleep loss and fatigue pose for youth in the workplace. The aim of this study was to explore work health and safety (WHS) issues for young workers and develop strategies and solutions for improved WHS outcomes, with a focus on issues related to fatigue, using a mixed-method, multi-stage approach. Participants either completed a survey (n=212) or took part in focus groups (n=115) addressing WHS for young workers, or attended a Future Inquiry Workshop (n=29) where strategies for improving youth WHS were developed. Fatigue was identified as a significant problem by the majority of young workers and was associated with unpredictable working time arrangements, precarious employment, high workload, working overtime and limited ability to self-advocate. Participants identified six key areas for action to improve WHS outcomes for young workers; 1) develop expertise, 2) give young workers a voice, 3) improve education and training, 4) build stakeholder engagement, 5) increase employer awareness of WHS responsibilities and, 6) improve processes for employers to manage and monitor WHS outcomes. The application of these directives to fatigue is discussed.

Occupational fatigue and other health and safety issues for young Australian workers: an exploratory mixed methods study

PubMed Central

PATERSON, Jessica Louise; CLARKSON, Larissa; RAINBIRD, Sophia; ETHERTON, Hayley; BLEWETT, Verna

2015-01-01

Youth are vulnerable to sleep loss and fatigue due to biological, social and psychological factors. However, there are few studies addressing the risk that sleep loss and fatigue pose for youth in the workplace. The aim of this study was to explore work health and safety (WHS) issues for young workers and develop strategies and solutions for improved WHS outcomes, with a focus on issues related to fatigue, using a mixed-method, multi-stage approach. Participants either completed a survey (n=212) or took part in focus groups (n=115) addressing WHS for young workers, or attended a Future Inquiry Workshop (n=29) where strategies for improving youth WHS were developed. Fatigue was identified as a significant problem by the majority of young workers and was associated with unpredictable working time arrangements, precarious employment, high workload, working overtime and limited ability to self-advocate. Participants identified six key areas for action to improve WHS outcomes for young workers; 1) develop expertise, 2) give young workers a voice, 3) improve education and training, 4) build stakeholder engagement, 5) increase employer awareness of WHS responsibilities and, 6) improve processes for employers to manage and monitor WHS outcomes. The application of these directives to fatigue is discussed. PMID:25752253

Fatigue Lives Of Laser-Cut Metals

NASA Technical Reports Server (NTRS)

Martin, Michael R.

1988-01-01

Fatigue lives made to approach those attainable by traditional grinding methods. Fatigue-test specimens prepared from four metallic alloys, and material removed from specimens by manual grinding, by Nd:glass laser, and by Nd:YAG laser. Results of fatigue tests of all specimens indicated reduction of fatigue strengths of laser-fired specimens. Laser machining holds promise for improved balancing of components of gas turbines.

The Mediating Role of Exercise on Relationships Between Fatigue, Sleep Quality, and Quality of Life for Adolescents With Cancer.

PubMed

Wu, Wei-Wen; Jou, Shiann-Tarng; Liang, Shu-Yuan; Tsai, Shao-Yu

2018-02-27

Fatigue and poor sleep are two of the most common and most distressing symptoms for adolescents with cancer. These 2 symptoms concurrently heighten distress, further decreasing quality of life (QoL). The aims of this study were to describe the degree of exercise involvement, fatigue, sleep quality, and QoL among adolescents with cancer and to determine whether exercise mediates the relationships between (a) fatigue and QoL and (b) sleep quality and QoL. A cross-sectional study of 100 participants was conducted. Multiple regression was performed to examine the mediation relationship. Participants in the off-treatment group had a significantly higher degree of exercise involvement, as well as less fatigue, greater sleep quality, and less QoL distress. Exercise partially mediated the adverse effect of fatigue on QoL for adolescents undergoing cancer treatment, accounting for 49.80% of the total variation; exercise partially mediated the adverse effect of poor sleep on QoL for adolescents both in treatment and in survivorship, accounting for 42.06% and 28.71% of the total variations, respectively. Exercise partially mediated the relationship between fatigue and QoL for adolescents in cancer treatment and partially mediated the relationship between sleep quality and QoL both for those in cancer treatment and for those in survivorship. Developing tailored exercise programs based on both treatment status and the degree of fatigue and sleep quality is important. In-service education that enhances nurses' awareness of the importance of exercise in improving adolescents' QoL is recommended.

Effect of higher frequency on the classification of steady-state visual evoked potentials

NASA Astrophysics Data System (ADS)

Won, Dong-Ok; Hwang, Han-Jeong; Dähne, Sven; Müller, Klaus-Robert; Lee, Seong-Whan

2016-02-01

Objective. Most existing brain-computer interface (BCI) designs based on steady-state visual evoked potentials (SSVEPs) primarily use low frequency visual stimuli (e.g., <20 Hz) to elicit relatively high SSVEP amplitudes. While low frequency stimuli could evoke photosensitivity-based epileptic seizures, high frequency stimuli generally show less visual fatigue and no stimulus-related seizures. The fundamental objective of this study was to investigate the effect of stimulation frequency and duty-cycle on the usability of an SSVEP-based BCI system. Approach. We developed an SSVEP-based BCI speller using multiple LEDs flickering with low frequencies (6-14.9 Hz) with a duty-cycle of 50%, or higher frequencies (26-34.7 Hz) with duty-cycles of 50%, 60%, and 70%. The four different experimental conditions were tested with 26 subjects in order to investigate the impact of stimulation frequency and duty-cycle on performance and visual fatigue, and evaluated with a questionnaire survey. Resting state alpha powers were utilized to interpret our results from the neurophysiological point of view. Main results. The stimulation method employing higher frequencies not only showed less visual fatigue, but it also showed higher and more stable classification performance compared to that employing relatively lower frequencies. Different duty-cycles in the higher frequency stimulation conditions did not significantly affect visual fatigue, but a duty-cycle of 50% was a better choice with respect to performance. The performance of the higher frequency stimulation method was also less susceptible to resting state alpha powers, while that of the lower frequency stimulation method was negatively correlated with alpha powers. Significance. These results suggest that the use of higher frequency visual stimuli is more beneficial for performance improvement and stability as time passes when developing practical SSVEP-based BCI applications.

Effect of higher frequency on the classification of steady-state visual evoked potentials.

PubMed

Won, Dong-Ok; Hwang, Han-Jeong; Dähne, Sven; Müller, Klaus-Robert; Lee, Seong-Whan

2016-02-01

Most existing brain-computer interface (BCI) designs based on steady-state visual evoked potentials (SSVEPs) primarily use low frequency visual stimuli (e.g., <20 Hz) to elicit relatively high SSVEP amplitudes. While low frequency stimuli could evoke photosensitivity-based epileptic seizures, high frequency stimuli generally show less visual fatigue and no stimulus-related seizures. The fundamental objective of this study was to investigate the effect of stimulation frequency and duty-cycle on the usability of an SSVEP-based BCI system. We developed an SSVEP-based BCI speller using multiple LEDs flickering with low frequencies (6-14.9 Hz) with a duty-cycle of 50%, or higher frequencies (26-34.7 Hz) with duty-cycles of 50%, 60%, and 70%. The four different experimental conditions were tested with 26 subjects in order to investigate the impact of stimulation frequency and duty-cycle on performance and visual fatigue, and evaluated with a questionnaire survey. Resting state alpha powers were utilized to interpret our results from the neurophysiological point of view. The stimulation method employing higher frequencies not only showed less visual fatigue, but it also showed higher and more stable classification performance compared to that employing relatively lower frequencies. Different duty-cycles in the higher frequency stimulation conditions did not significantly affect visual fatigue, but a duty-cycle of 50% was a better choice with respect to performance. The performance of the higher frequency stimulation method was also less susceptible to resting state alpha powers, while that of the lower frequency stimulation method was negatively correlated with alpha powers. These results suggest that the use of higher frequency visual stimuli is more beneficial for performance improvement and stability as time passes when developing practical SSVEP-based BCI applications.

Improvements in exercise performance with high-intensity interval training coincide with an increase in skeletal muscle mitochondrial content and function.

PubMed

Jacobs, Robert Acton; Flück, Daniela; Bonne, Thomas Christian; Bürgi, Simon; Christensen, Peter Møller; Toigo, Marco; Lundby, Carsten

2013-09-01

Six sessions of high-intensity interval training (HIT) are sufficient to improve exercise capacity. The mechanisms explaining such improvements are unclear. Accordingly, the aim of this study was to perform a comprehensive evaluation of physiologically relevant adaptations occurring after six sessions of HIT to determine the mechanisms explaining improvements in exercise performance. Sixteen untrained (43 ± 6 ml·kg(-1)·min(-1)) subjects completed six sessions of repeated (8-12) 60 s intervals of high-intensity cycling (100% peak power output elicited during incremental maximal exercise test) intermixed with 75 s of recovery cycling at a low intensity (30 W) over a 2-wk period. Potential training-induced alterations in skeletal muscle respiratory capacity, mitochondrial content, skeletal muscle oxygenation, cardiac capacity, blood volumes, and peripheral fatigue resistance were all assessed prior to and again following training. Maximal measures of oxygen uptake (Vo2peak; ∼8%; P = 0.026) and cycling time to complete a set amount of work (∼5%; P = 0.008) improved. Skeletal muscle respiratory capacities increased, most likely as a result of an expansion of skeletal muscle mitochondria (∼20%, P = 0.026), as assessed by cytochrome c oxidase activity. Skeletal muscle deoxygenation also increased while maximal cardiac output, total hemoglobin, plasma volume, total blood volume, and relative measures of peripheral fatigue resistance were all unaltered with training. These results suggest that increases in mitochondrial content following six HIT sessions may facilitate improvements in respiratory capacity and oxygen extraction, and ultimately are responsible for the improvements in maximal whole body exercise capacity and endurance performance in previously untrained individuals.

Fatigue and associated performance decrements in air transport operations

NASA Technical Reports Server (NTRS)

Lyman, E. G.; Orlady, H. W.

1981-01-01

A study of safety reports was conducted to examine the hypothesis that fatigue and associated performance decrements occur in air transport operations, and that these are associated with some combination of factors: circadian desynchronosis, duty time; pre-duty activity; sleep; work scheduling; workload; and environmental deprivation. The findings are based on a selected sample of reported incidents in which the reporter associated fatigue with the occurrence. In comparing the fatigue reports with a control set, significant performance decrements were found to exist related to time-of-day, awareness and attention to duty, less significantly, final phases of flights. The majority of the fatigue incidents involved such unsafe events as altitude deviations, takeoffs and landing without clearance, and the like. Considerations of duty and sleep are the major factors in the reported fatigue conditions.

Improving fatigue and depression in individuals with multiple sclerosis using telephone-administered physical activity counseling.

PubMed

Turner, Aaron P; Hartoonian, Narineh; Sloan, Alicia P; Benich, Marisa; Kivlahan, Daniel R; Hughes, Christina; Hughes, Abbey J; Haselkorn, Jodie K

2016-04-01

To evaluate the impact of a physical activity intervention consisting of telephone counseling with home-based monitoring to improve fatigue and depression in individuals with multiple sclerosis (MS). Single-blind randomized controlled trial. Sixty-four individuals with MS received either telephone counseling (N = 31), or self-directed physical activity education (N = 33). The education condition (EC) consisted of advice to increase physical activity and a DVD with examples of in-home exercises for multiple physical ability levels. The telephone counseling condition (TC) included EC as well as mailed graphic feedback, 6 telephone counseling sessions using principles of motivational interviewing, and telehealth home monitoring to track progress on physical activity goals. Booster sessions were provided when participants indicated they did not meet their goals. Assessment was conducted at baseline, 3-month, and 6-month follow-up. TC participants reported significantly reduced fatigue (d = -.70), reduced depression (d = -.72) and increased physical activity (d = .92) relative to EC participants. Of individuals receiving TC, 33.3% experienced clinically significant improvement in fatigue (vs. 18.2% in EC) and 53.3% experienced clinically significant improvement in depression (vs. 9.1% in EC). Improvements in physical activity mediated improvements in fatigue with a similar trend for depression. TC was highly feasible (participants completed 99.5% of schedule telephone sessions) and well tolerated (100% rated it highly successful). Telephone-based counseling with home monitoring is a promising modality to improve physical activity and treat fatigue and depression. (c) 2016 APA, all rights reserved).

The effectiveness of empirical anti-parasitic treatment in returning travellers with persistent abdominal symptoms.

PubMed

Nissan, Batel; Lachish, Tamar; Schwartz, Eli

2018-01-01

Persistent abdominal symptoms (PAS) are common among returning-travellers. In the absence of sensitive tests to identify intestinal parasites, gastrointestinal (GI) symptoms often remain a diagnostic challenge. In this study we examined the effectiveness of empirical anti-parasitic treatment in returning-travellers with PAS despite no positive stool-test. A retrospective study among returning travellers who approached the clinic between the years 2014 and 2016 with GI complaints without a positive stool-test. The empirical treatment included broad-spectrum anti-parasitic agents-oral Tinidazole and Albendazole. A follow-up questionnaire was performed at least 6 months post-treatment. A total of 102 patients responded the questionnaire-50% women; average age 31.14 (±12.20) years. The average duration of complaints before treatment was 16.52 (±30.06) months. Common GI symptoms included abdominal pain (83.3%) and diarrhoea (78.4%); 67.6% of the patients complained of extreme fatigue. Overall, 69% of the patients reported an improvement in GI symptoms, 37% of them reported full recovery within a few weeks post-treatment. Furthermore, there was an improvement in the energy level and general well-being in 68% and 70% of the patients, respectively. Only 33% of the patients reported minor side effects related to the treatment. The improvement in GI symptoms, energy level and general well-being shortly after anti-parasitic treatment justifies this empirical approach in returning-travellers with PAS despite negative stool-tests. The association between fatigue and PAS post-travel and the improvement in both as a response to treatment defines fatigue as part of a new syndrome-'Post-travel fatigue and abdominal symptoms'. © International Society of Travel Medicine, 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

Fatigue behavior of ULTIMETRTM alloy: Experiment and theoretical modeling

NASA Astrophysics Data System (ADS)

Jiang, Liang

ULTIMETRTM alloy is a commercial Co-26Cr-9Ni (weight percent) superalloy, which possesses excellent resistance to both wear and corrosion. In order to extend the structural applications of this alloy and improve the fundamental understanding of the fatigue damage mechanisms, stress- and strain-controlled fatigue tests were performed at various temperatures and in different environments. The stress- and strain-life data were developed for the structural design and engineering applications of this material. Fractographic studies characterized the crack-initiation and propagation behavior of the alloy. Microstructure evolution during fatigue was revealed by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Specifically, it was found that the metastable face-centered-cubic structure of this alloy in the as-received condition could be transformed into a hexagonal-close-packed structure either under the action of plastic deformation at room temperature, or due to the aging and cyclic deformation at intermediate temperatures. This interesting observation constructed a sound basis for the alloy development. The dominant mechanisms, which control the fatigue behavior of ULTIMET alloy, were characterized. High-speed, high-resolution infrared (IR) thermography, as a non-contact, full-field, and nondestructive technique, was used to characterize the damage during fatigue. The temperature variations during each fatigue cycle, which were due to the thermal-elastic-plastic effect, were observed and related to stress-strain analyses. The temperature evolution during fatigue manifested the cumulative fatigue damage process. A constitutive model was developed to predict thermal and mechanical responses of ULTIMET alloy subjected to cyclic deformation. The predicted cyclic stress-strain responses and temperature variations were found to be in good agreement with the experimental results. In addition, a fatigue life prediction model was developed based on the strain-energy consideration, and the measured temperature could be utilized as an index for fatigue-life prediction.

Life prediction technologies for aeronautical propulsion systems

NASA Technical Reports Server (NTRS)

Mcgaw, Michael A.

1990-01-01

Fatigue and fracture problems continue to occur in aeronautical gas turbine engines. Components whose useful life is limited by these failure modes include turbine hot-section blades, vanes, and disks. Safety considerations dictate that catastrophic failures be avoided, while economic considerations dictate that catastrophic failures be avoided, while economic considerations dictate that noncatastrophic failures occur as infrequently as possible. Therefore, the decision in design is making the tradeoff between engine performance and durability. LeRC has contributed to the aeropropulsion industry in the area of life prediction technology for over 30 years, developing creep and fatigue life prediction methodologies for hot-section materials. At the present time, emphasis is being placed on the development of methods capable of handling both thermal and mechanical fatigue under severe environments. Recent accomplishments include the development of more accurate creep-fatigue life prediction methods such as the total strain version of LeRC's strain-range partitioning (SRP) and the HOST-developed cyclic damage accumulation (CDA) model. Other examples include the development of a more accurate cumulative fatigue damage rule - the double damage curve approach (DDCA), which provides greatly improved accuracy in comparison with usual cumulative fatigue design rules. Other accomplishments in the area of high-temperature fatigue crack growth may also be mentioned. Finally, we are looking to the future and are beginning to do research on the advanced methods which will be required for development of advanced materials and propulsion systems over the next 10-20 years.

Effects of consumption of sucromalt, a slowly digestible carbohydrate, on mental and physical energy questionnaire responses.

PubMed

Dammann, Kristen W; Bell, Margie; Kanter, Mitch; Berger, Alvin

2013-03-01

To evaluate whether consumption of the low-glycemic index (GI) carbohydrate sucromalt improves healthy adults' perceptions of mental and physical energy and fatigue compared to dextrose (glucose), a high GI control. In this double-blind, randomized, cross-over study, subjects (n = 44 healthy adults) consumed a standardized dinner, and following an overnight fast, ingested 75 g of either sucromalt or glucose in solution at 7:30 AM the next day. Subjects completed validated questionnaires that assessed mental and physical energy, and fatigue, hunger, and sleepiness at baseline and hourly until 12:30 PM for a total of five post-consumption time points. Within-subject differences adjusted for baseline for individual questions and composite scores (Mental Energy State, Mental Fatigue State, Physical Energy State, and Physical Fatigue State) were analyzed using repeated measures analysis of variance. Mental Energy State, Physical Energy State, and Physical Fatigue State results favored sucromalt compared to glucose, with significant differences emerging particularly after 4-5 hours (P < 0.050). A trend toward a delay in Mental Fatigue State was also observed with sucromalt compared to glucose (P < 0.100). Minimal differences in ratings of hunger and sleepiness were observed between the beverages. Sucromalt may help attenuate the perceived decline in mental and physical energy and rise in mental and physical fatigue that can occur 4-5 hours after ingestion of a high GI beverage. Trials examining effects of sucromalt on cognitive and physical performance are of future interest.

Efficacy of Ginseng Supplements on Fatigue and Physical Performance: a Meta-analysis

PubMed Central

2016-01-01

We conducted a meta-analysis to investigate the efficacy of ginseng supplements on fatigue reduction and physical performance enhancement as reported by randomized controlled trials (RCTs). RCTs that investigated the efficacy of ginseng supplements on fatigue reduction and physical performance enhancement compared with placebos were included. The main outcome measures were fatigue reduction and physical performance enhancement. Out of 155 articles meeting initial criteria, 12 RCTs involving 630 participants (311 participants in the intervention group and 319 participants in the placebo group) were included in the final analysis. In the fixed-effect meta-analysis of four RCTs, there was a statistically significant efficacy of ginseng supplements on fatigue reduction (standardized mean difference, SMD = 0.34; 95% confidence interval [CI] = 0.16 to 0.52). However, ginseng supplements were not associated with physical performance enhancement in the fixed-effect meta-analysis of eight RCTs (SMD = −0.01; 95% CI = −0.29 to 0.27). We found that there was insufficient clinical evidence to support the use of ginseng supplements on reducing fatigue and enhancing physical performance because only few RCTs with a small sample size have been published so far. Further lager RCTs are required to confirm the efficacy of ginseng supplements on fatigue reduction. PMID:27822924

Computational inverse methods of heat source in fatigue damage problems

NASA Astrophysics Data System (ADS)

Chen, Aizhou; Li, Yuan; Yan, Bo

2018-04-01

Fatigue dissipation energy is the research focus in field of fatigue damage at present. It is a new idea to solve the problem of calculating fatigue dissipation energy by introducing inverse method of heat source into parameter identification of fatigue dissipation energy model. This paper introduces the research advances on computational inverse method of heat source and regularization technique to solve inverse problem, as well as the existing heat source solution method in fatigue process, prospects inverse method of heat source applying in fatigue damage field, lays the foundation for further improving the effectiveness of fatigue dissipation energy rapid prediction.

Effects of bionic units on the fatigue wear of gray cast iron surface with different shapes and distributions

NASA Astrophysics Data System (ADS)

Chen, Zhi-kai; Lu, Shu-chao; Song, Xi-bin; Zhang, Haifeng; Yang, Wan-shi; Zhou, Hong

2015-03-01

To improve the fatigue wear resistance of gray cast iron (GCI), GCI samples were modified by a laser to imitate the unique structure of some soil animals alternating between soft and hard phases; the hard phase resists the deformation and the soft phase releases the deformation. Using the self-controlled fatigue wear test method, the fatigue wear behaviors of treated and untreated samples were investigated and compared experimentally. The results show that the bionic non-smooth surface obtains a beneficial effect on improving the fatigue wear resistance of a sample, and the fatigue wear resistance of the bionic sample assembled with reticulate units (60°+0°), whose mass loss was reduced by 62%, was superior to the others. Meanwhile, a finite element (FE) was used to simulate the compression and the distributions of strain and stress on the non-smooth surface was inferred. From these results, we understood that the functions of the bionic unit such as reducing strain and stress, and also obstructing the closure and propagation of cracks were the main reasons for improving the fatigue wear property of GCI.

Parametric analysis of electromechanical and fatigue performance of total knee replacement bearing with embedded piezoelectric transducers.

PubMed

Safaei, Mohsen; Meneghini, R Michael; Anton, Steven R

2017-09-01

Total knee arthroplasty (TKA) is a common procedure in the United States; it has been estimated that about 4 million people are currently living with primary knee replacement in this country. Despite huge improvements in material properties, implant design, and surgical techniques, some implants fail a few years after surgery. A lack of information about in vivo kinetics of the knee prevents the establishment of a correlated intra- and postoperative loading pattern in knee implants. In this study, a conceptual design of an ultra high molecular weight (UHMW) knee bearing with embedded piezoelectric transducers is proposed, which is able to measure the reaction forces from knee motion as well as harvest energy to power embedded electronics. A simplified geometry consisting of a disk of UHMW with a single embedded piezoelectric ceramic is used in this work to study the general parametric trends of an instrumented knee bearing. A combined finite element and electromechanical modeling framework is employed to investigate the fatigue behavior of the instrumented bearing and the electromechanical performance of the embedded piezoelectric. The model is validated through experimental testing and utilized for further parametric studies. Parametric studies consist of the investigation of the effects of several dimensional and piezoelectric material parameters on the durability of the bearing and electrical output of the transducers. Among all the parameters, it is shown that adding large fillet radii results in noticeable improvement in the fatigue life of the bearing. Additionally, the design is highly sensitive to the depth of piezoelectric pocket. Finally, using PZT-5H piezoceramics, higher voltage and slightly enhanced fatigue life is achieved.

Parametric analysis of electromechanical and fatigue performance of total knee replacement bearing with embedded piezoelectric transducers

NASA Astrophysics Data System (ADS)

Safaei, Mohsen; Meneghini, R. Michael; Anton, Steven R.

2017-09-01

Total knee arthroplasty is a common procedure in the United States; it has been estimated that about 4 million people are currently living with primary knee replacement in this country. Despite huge improvements in material properties, implant design, and surgical techniques, some implants fail a few years after surgery. A lack of information about in vivo kinetics of the knee prevents the establishment of a correlated intra- and postoperative loading pattern in knee implants. In this study, a conceptual design of an ultra high molecular weight (UHMW) knee bearing with embedded piezoelectric transducers is proposed, which is able to measure the reaction forces from knee motion as well as harvest energy to power embedded electronics. A simplified geometry consisting of a disk of UHMW with a single embedded piezoelectric ceramic is used in this work to study the general parametric trends of an instrumented knee bearing. A combined finite element and electromechanical modeling framework is employed to investigate the fatigue behavior of the instrumented bearing and the electromechanical performance of the embedded piezoelectric. The model is validated through experimental testing and utilized for further parametric studies. Parametric studies consist of the investigation of the effects of several dimensional and piezoelectric material parameters on the durability of the bearing and electrical output of the transducers. Among all the parameters, it is shown that adding large fillet radii results in noticeable improvement in the fatigue life of the bearing. Additionally, the design is highly sensitive to the depth of piezoelectric pocket. Finally, using PZT-5H piezoceramics, higher voltage and slightly enhanced fatigue life is achieved.

The Influence of Roughness on Gear Surface Fatigue

NASA Technical Reports Server (NTRS)

Krantz, Timothy

2005-01-01

Gear working surfaces are subjected to repeated rolling and sliding contacts, and often designs require loads sufficient to cause eventual fatigue of the surface. This research provides experimental data and analytical tools to further the understanding of the causal relationship of gear surface roughness to surface fatigue. The research included evaluations and developments of statistical tools for gear fatigue data, experimental evaluation of the surface fatigue lives of superfinished gears with a near-mirror quality, and evaluations of the experiments by analytical methods and surface inspections. Alternative statistical methods were evaluated using Monte Carlo studies leading to a final recommendation to describe gear fatigue data using a Weibull distribution, maximum likelihood estimates of shape and scale parameters, and a presumed zero-valued location parameter. A new method was developed for comparing two datasets by extending the current methods of likelihood-ratio based statistics. The surface fatigue lives of superfinished gears were evaluated by carefully controlled experiments, and it is shown conclusively that superfinishing of gears can provide for significantly greater lives relative to ground gears. The measured life improvement was approximately a factor of five. To assist with application of this finding to products, the experimental condition was evaluated. The fatigue life results were expressed in terms of specific film thickness and shown to be consistent with bearing data. Elastohydrodynamic and stress analyses were completed to relate the stress condition to fatigue. Smooth-surface models do not adequately explain the improved fatigue lives. Based on analyses using a rough surface model, it is concluded that the improved fatigue lives of superfinished gears is due to a reduced rate of near-surface micropitting fatigue processes, not due to any reduced rate of spalling (sub-surface) fatigue processes. To complete the evaluations, surface inspection were completed. The surface topographies of the ground gears changed substantially due to running, but the topographies of the superfinished gears were essentially unchanged with running.

Qigong/Tai Chi Easy for fatigue in breast cancer survivors: Rationale and design of a randomized clinical trial.

PubMed

Larkey, Linda; Huberty, Jennifer; Pedersen, Maja; Weihs, Karen

2016-09-01

Breast cancer survivors (BCSs) often report fatigue that persists for years following treatment. Despite a growing body of evidence for meditative movement practices to improve symptoms among BCSs, few studies have explored using Qigong/Tai Chi to reduce fatigue. Additionally, few have examined the biological mechanisms through which fatigue may be reduced using Qigong/Tai Chi. We will recruit 250 fatigued, post-menopausal women diagnosed with breast cancer (stage 0-III), between 6months and 5years past primary treatment and randomize to a standardized Qigong/Tai Chi Easy (QG/TCE) intervention, a "sham" Qigong group (movements without a focus on the breath and meditative state) (SQG), or an educational support (ES) group. The primary outcome (fatigue), secondary outcomes (anxiety, depression, sleep quality, cognitive function, physical activity), and a biomarker of HPA axis dysregulation (diurnal cortisol) will be assessed at baseline, post-intervention and 6months postintervention, and biomarkers of inflammation (IL1ra, IL6, TNFα and INFᵧ) at pre/post-intervention. We hypothesize that QG/TCE will reduce fatigue (and improve other symptoms associated with fatigue) in BCSs experiencing persistent cancer-related fatigue more than SQG and ES. Biomarkers will be examined for relationships to changes in fatigue. Findings from this study may reveal the effects of the unique mind-body aspects of QG/TCE on fatigue in BCSs with a complex design that separates the effects of low-intensity physical activity (SQG) and social support/attention (ES) from the primary intervention. Further, results will likely contribute greater understanding of the biological mechanisms of these practices related to improved symptoms among BCSs. Copyright © 2016 Elsevier Inc. All rights reserved.

Modeling Operator Performance in Low Task Load Supervisory Domains

DTIC Science & Technology

2011-06-01

PDF Probability Distribution Function SAFE System for Aircrew Fatigue Evaluation SAFTE Sleep , Activity, Fatigue, and Task Effectiveness SCT...attentional capacity due to high mental workload. In low task load settings, fatigue is mainly caused by lack of sleep and boredom experienced by...performance decrements. Also, psychological fatigue is strongly correlated with lack of sleep . Not surprisingly, operators of the morning shift reported the

Structural Damage Identification in Stiffened Plate Fatigue Specimens Using Piezoelectric Active Sensing

DTIC Science & Technology

2011-09-01

isolated AO mode first arrival, recorded at PZT 2, is shown at 3 different fatigue levels. Figure 5. The area under the PSD curve, calculated twice...Structural Damage Identification in Stiffened Plate Fatigue Specimens Using Piezoelectric Active Sensing B. L. GRISSO, G. PARK, L. W. SALVINO...with several challenges including limited performance knowledge of the materials, aluminum sensitization, structural fatigue performance, and

Donepezil for cancer fatigue: a double-blind, randomized, placebo-controlled trial.

PubMed

Bruera, Eduardo; El Osta, Badi; Valero, Vicente; Driver, Larry C; Pei, Be-Lian; Shen, Loren; Poulter, Valerie A; Palmer, J Lynn

2007-08-10

To evaluate the effectiveness of donepezil compared with placebo in cancer patients with fatigue as measured by the Functional Assessment for Chronic Illness Therapy-Fatigue (FACIT-F). Patients with fatigue score >or= 4 on a scale of 0 to 10 (0 = no fatigue, 10 = worst possible fatigue) for more than 1 week were included. Patients were randomly assigned to receive donepezil 5 mg or placebo orally every morning for 7 days. A research nurse contacted the patients by telephone daily to assess toxicity and fatigue level. All patients were offered open-label donepezil during the second week. FACIT-F and/or the Edmonton Symptom Assessment System (ESAS) were assessed at baseline, and days 8, 11, and 15. The FACIT-F fatigue subscale score on day 8 was considered the primary end point. Of 142 patients randomly assigned to treatment, 47 patients in the donepezil group and 56 in the placebo group were assessable for final analysis. Fatigue intensity improved significantly on day 8 in both donepezil and placebo groups. However, there was no significant difference in fatigue improvement by FACIT-F (P = .57) or ESAS (P = .18) between groups. In the open-label phase, fatigue intensity continued to be low as compared with baseline. No significant toxicities were observed. Donepezil was not significantly superior to placebo in the treatment of cancer-related fatigue.

Effects of a Short Physical Exercise Intervention on Patients with Multiple Sclerosis (MS).

PubMed

Kerling, Arno; Keweloh, Karin; Tegtbur, Uwe; Kück, Momme; Grams, Lena; Horstmann, Hauke; Windhagen, Anja

2015-07-10

The aim of this prospective randomized controlled trial was to investigate if a short-term endurance or combined endurance/resistance exercise program was sufficient to improve aerobic capacity and maximum force in adult patients (18-65 years) with multiple sclerosis (MS). All patients performed a three-month exercise program consisting of two training sessions per week, lasting 40 min each, with moderate intensity. All patients had a maximum value of 6 (low to moderate disability) on the Expanded Disability Status Scale (EDSS). One group (combined workout group (CWG); 15 females, 4 males) completed a combined endurance/resistance workout (20 min on a bicycle ergometer, followed by 20 min of resistance training), while the other group (endurance workout group (EWG); 13 females, 5 males) completed a 40 min endurance training program. Aerobic capacity was assessed as peak oxygen uptake, ventilatory anaerobic threshold, and workload expressed as Watts. Maximum force of knee and shoulder extensors and flexors was measured using isokinetic testing. Quality of life was assessed with the SF-36 questionnaire, and fatigue was measured using the Modified Fatigue Impact Scale. Both training groups increased in aerobic capacity and maximum force. EWG, as well as CWG, showed improvement in several subscales of the SF-36 questionnaire and decrease of their fatigue. A short exercise intervention increased both aerobic capacity and maximum force independent of whether endurance or combined endurance/resistance workouts were performed.

Prior Heat Stress Effects Fatigue Recovery of the Elbow Flexor Muscles

PubMed Central

Iguchi, Masaki; Shields, Richard K.

2011-01-01

Introduction Long-lasting alterations in hormones, neurotransmitters and stress proteins after hyperthermia may be responsible for the impairment in motor performance during muscle fatigue. Methods Subjects (n = 25) performed a maximal intermittent fatigue task of elbow flexion after sitting in either 73 or 26 deg C to examine the effects of prior heat stress on fatigue mechanisms. Results The heat stress increased the tympanic and rectal temperatures by 2.3 and 0.82 deg C, respectively, but there was full recovery prior to the fatigue task. While prior heat stress had no effects on fatigue-related changes in volitional torque, EMG activity, torque relaxation rate, MEP size and SP duration, prior heat stress acutely increased the pre-fatigue relaxation rate and chronically prevented long-duration fatigue (p < 0.05). Discussion These findings indicate that prior passive heat stress alone does not alter voluntary activation during fatigue, but prior heat stress and exercise produce longer-term protection against long-duration fatigue. PMID:21674526

Study on functional relationships between ergonomics indexes of manual performance

NASA Astrophysics Data System (ADS)

Hu, Hui-Min; Ding, Li; Chen, Shou-Ping; Yang, Chun-Xin; Yuan, Xiu-Gan

This paper investigates functional relationships between some of the key ergonomics indexes in manual performance, and attempts to condense the ergonomics appraisal indexes system and thus evaluate hand performance wearing EVA (extravehicular activity) glove, design and improve EVA glove's performance. Four types of ergonomics indexes were studied, i.e., dexterity, tactile sensibility (TS), strength and fatigue. Two test items of insert sticks into a holes-board (ISIHB) and nuts-bolts assembly task (NBAT) were used to measure dexterity, while shape discrimination (SD) was employed for TS, and grip force (GF) for strength and fatigue. The variables measured in this investigation included accomplishing time (AT) of ISIHB and NBAT, correct rate (CR) of SD, maximal grip force (MGF), instant grip force (IGF) and endurance time of grip force (ETGF). Experiments were conducted on 31 undergraduates (eight female and 23 male) with two experiment conditions of bare-hand group and gloved hand group. Results demonstrated that dexterity and TS performance of gloved hand group declined significantly compared with those of bare-hand group (p<0.001). There were not significant differences in strength and fatigue between two conditions (p>0.05). Four effective functional relationships were developed between four pairs of ergonomics indexes in bare-hand group. In gloved hand group, in addition to above-mentioned four pairs of relationships, another formula was found, which was y^=0.02061+0.01233x ( p<0.01, dexterity and TS).

Effects of a supportive educational nursing care programme on fatigue and quality of life in patients with heart failure: a randomised controlled trial.

PubMed

Wang, Tzu-Chieh; Huang, Jin-Long; Ho, Wen-Chao; Chiou, Ai-Fu

2016-04-01

Fatigue is a common symptom in patients with heart failure that is easy to ignore. In addition, fatigue may affect patients' physical function and psychosocial conditions that can impair their quality of life. An effective nursing care programme is required to alleviate patients' fatigue and improve their quality of life. To investigate the effects of a supportive educational nursing care programme on fatigue and quality of life in patients with heart failure. A randomised controlled trial design was used. Ninety-two patients with heart failure were randomly assigned to an intervention group (n=47) or a control group (n=45). The patients in the intervention group participated in 12 weeks of a supportive educational nursing care programme including fatigue assessment, education, coaching self-care and evaluation. The intervention was conducted by a cardiac nurse during four face-to-face interviews and three follow-up telephone interviews. Fatigue and quality of life were assessed at the baseline and 4 weeks, 8 weeks and 12 weeks after enrollment in both groups. The participants in the intervention group exhibited a significant decrease in the level of fatigue after 12 weeks, whereas those in the control group exhibited no significant changes. Compared with the control group, the intervention group exhibited a significantly greater decrease in the level of fatigue and significantly greater improvement in quality of life after 12 weeks of intervention. The supportive educational nursing care programme was recommended to alleviate fatigue and improve quality of life in patients with heart failure. © The European Society of Cardiology 2015.

Accelerated fatigue durability of a high performance composite

NASA Technical Reports Server (NTRS)

Rotem, A.

1982-01-01

The fatigue behavior of multidirectional graphite-epoxy laminates was analyzed theoretically and experimentally in an effort to establish an accelerated testing methodology. Analysis of the failure mechanism in fatigue of the laminates led to the determination of the failure mode governing fracture. The nonlinear, cyclic-dependent shear modulus was used to calculate the changing stress field in the laminate during the fatigue loading. Fatigue tests were performed at three different temperatures: 25 C, 74 C, and 114 C. The prediction of the S-N curves was made based on the artificial static strength artificial static strength at a reference temperature and the fatigue functions associated with them. The prediction of an S-N curve at other temperatures was performed using shifting factors determined for the specific failure mode. For multidirectional laminates, different S-N curves at different temperatures could be predicted using these shifting factors. Different S-N curves at different temperatures occur only when the fatigue failure mode is matrix dominated. It was found that whenever the fatigue failure mode is fiber dominated, temperature, over the range investigated, had no influence on the fatigue life. These results permit the prediction of long-time, low temperature fatigue behavior from data obtained in short time, high temperature testing, for laminates governed by a matrix failure mode.

Royal Sun Culinary-Medicinal Mushroom, Agaricus brasiliensis (Agaricomycetes), Supplement in Training Capacity Improvement Parameters.

PubMed

Silva, Flávio F; de Oliveira, Guilherme A C; Costa, Hugo C Martins; Regis, Wiliam C B

2017-01-01

People seek a greater quality of life and healthy aging that culminates in improved self-esteem and vitality in the performance of daily activities; this is generating a growing number of people enrolled in gyms in search of quick results. However, this training can result in physical and metabolic damage. During physical exercise, under conditions of oxidative stress, changes take place that lead to the onset of fatigue. The Agaricus brasiliensis mushroom is native to Brazil and has therapeutic potential, with widely studied antioxidant and immunomodulatory capabilities. However, little is known about its potential benefits regarding muscular strength. Therefore, this study evaluated the possible effects of supplementation with this mushroom with respect to strength performance before and after a resistance training session. A blinded randomized trial was performed with male volunteers (n = 5) randomly divided into 2 groups (placebo and treatment with A. brasiliensis). Perceptions of muscle soreness and performance were assessed before and after high-intensity resistance training sessions. The study was executed over a 24-day period. Promising results were found related to intrasession rapid strength, most likely a result of antioxidant action and redox balance. The bioactive compounds in A. brasiliensis revealed the potential to improve conditions of muscle fatigue without altering other parameters. Thus, this mushroom has become a target of great expectations in the fields of fitness and athletics.

The perceptual features of vocal fatigue as self-reported by a group of actors and singers.

PubMed

Kitch, J A; Oates, J

1994-09-01

Performers (10 actors/10 singers) rated via a self-report questionnaire the severity of their voice-related changes when vocally fatigued. Similar frequency patterns and perceptual features of vocal fatigue were found across subjects. Actors rated "power" aspects (e.g., voice projection) and singers rated vocal dynamic aspects (e.g., pitch range) of their voices as most affected when vocally fatigued. Vocal fatigue was evidenced by changes in kinesthetic/proprioceptive sensations and vocal dynamics. The causes and context of vocal fatigue were vocal misuse, being "run down," high performance demands, and using high pitch/volume levels. Further research is needed to delineate the perceptual features of "normal" levels of vocal fatigue and its possible causes.

Performance of Diffusion Aluminide Coatings Applied on Alloy CF8C-Plus at 800oC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Deepak; Dryepondt, Sebastien N; Zhang, Ying

2012-01-01

High performance cast stainless steel, CF8C-Plus, is a low cost alloy with prospective applications ranging from covers and casings of small and medium size gas turbines to turbocharger housing and manifolds in internal combustion engines. Diffusion aluminide coatings were applied on this alloy as a potential strategy for improved oxidation resistance, particularly in wet air and steam. In this paper the performance of the aluminide coatings evaluated by cyclic oxidation experiments in air containing 10 vol.% H2O at 800 C and conventional tension-compression low-cycle-fatigue tests in air at 800 C with a strain range of 0.5% is presented. The resultsmore » show that specimens coated by a chemical vapor deposition process provide better oxidation resistance than those coated by an Al-slurry coating process. The application of a coating by pack cementation reduced the fatigue life by 15%.« less

Improved Functional Properties and Efficiencies of Nitinol Wires Under High-Performance Shape Memory Effect (HP-SME)

NASA Astrophysics Data System (ADS)

Casati, R.; Saghafi, F.; Biffi, C. A.; Vedani, M.; Tuissi, A.

2017-10-01

Martensitic Ti-rich NiTi intermetallics are broadly used in various cyclic applications as actuators, which exploit the shape memory effect (SME). Recently, a new approach for exploiting austenitic Ni-rich NiTi shape memory alloys as actuators was proposed and named high-performance shape memory effect (HP-SME). HP-SME is based on thermal recovery of de-twinned martensite produced by mechanical loading of the parent phase. The aim of the manuscript consists in evaluating and comparing the fatigue and actuation properties of austenitic HP-SME wires and conventional martensitic SME wires. The effect of the thermomechanical cycling on the actuation response and the changes in the electrical resistivity of both shape memory materials were studied by performing the actuation tests at different stages of the fatigue life. Finally, the changes in the transition temperatures before and after cycling were also investigated by differential calorimetric tests.

The effects of fatigue on robotic surgical skill training in Urology residents.

PubMed

Mark, James R; Kelly, Douglas C; Trabulsi, Edouard J; Shenot, Patrick J; Lallas, Costas D

2014-09-01

This study reports on the effect of fatigue on Urology residents using the daVinci surgical skills simulator (dVSS). Seven Urology residents performed a series of selected exercises on the dVSS while pre-call and post-call. Prior to dVSS performance a survey of subjective fatigue was taken and residents were tested with the Epworth Sleepiness Scale (ESS). Using the metrics available in the dVSS software, the performance of each resident was evaluated. The Urology residents slept an average of 4.07 h (range 2.5-6 h) while on call compared to an average of 5.43 h while not on call (range 3-7 h, p = 0.08). Post-call residents were significantly more likely to be identified as fatigued by the Epworth Sleepiness Score than pre-call residents (p = 0.01). Significant differences were observed in fatigued residents performing the exercises, Tubes and Match Board 2 (p = 0.05, 0.02). Additionally, there were significant differences in the total number of critical errors during the training session (9.29 vs. 3.14, p = 0.04). Fatigue in post-call Urology residents leads to poorer performance on the dVSS simulator. The dVSS may become a useful instrument in the education of fatigued residents and a tool to identify fatigue in trainees.

Research on the Fatigue Flexural Performance of RC Beams Attacked by Salt Spray

NASA Astrophysics Data System (ADS)

Mao, Jiang-hong; Xu, Fang-yuan; Jin, Wei-liang; Zhang, Jun; Wu, Xi-xi; Chen, Cai-sheng

2018-04-01

The fatigue flexural performance of RC beams attacked by salt spray was studied. A testing method involving electro osmosis, electrical accelerated corrosion and salt spray was proposed. This corrosion process method effectively simulates real-world salt spray and fatigue loading exerted by RC components on sea bridges. Four RC beams that have different stress amplitudes were tested. It is found that deterioration by corrosion and fatigue loading reduces the fatigue life of the RC and decreases the ability of deformation. The fatigue life and deflection ability could be reduced by increasing the stress amplitude and the corrosion duration time. The test result demonstrates that this experimental method can couple corrosion deterioration and fatigue loading reasonably. This procedure may be applied to evaluate the fatigue life and concrete durability of RC components located in a natural salt spray environment.

Does aerobic training alleviate fatigue and improve societal participation in patients with multiple sclerosis? A randomized controlled trial.

PubMed

Heine, Martin; Verschuren, Olaf; Hoogervorst, Erwin Lj; van Munster, Erik; Hacking, Hub Ga; Visser-Meily, Anne; Twisk, Jos Wr; Beckerman, Heleen; de Groot, Vincent; Kwakkel, Gert

2017-10-01

Evidence supporting the effectiveness of aerobic training, specific for fatigue, in severely fatigued patients with multiple sclerosis (MS) is lacking. To estimate the effectiveness of aerobic training on MS-related fatigue and societal participation in ambulant patients with severe MS-related fatigue. Patients ( N = 90) with severe MS-related fatigue were allocated to 16-week aerobic training or control intervention. Primary outcomes were perceived fatigue (Checklist Individual Strength (CIS20r) fatigue subscale) and societal participation. An improvement of ⩾8 points on the CIS20r fatigue subscale was considered clinically relevant. Outcomes were assessed by a blinded observer at baseline, 2, 4, 6 and 12 months. Of the 89 patients that started treatment (median Expanded Disability Status Scale (interquartile range), 3.0 (2.0-3.6); mean CIS20r fatigue subscale (standard deviation (SD)), 42.6 (8.0)), 43 received aerobic training and 46 received the control intervention. A significant post-intervention between-group mean difference (MD) on the CIS20r fatigue subscale of 4.708 (95% confidence interval (CI) = 1.003-8.412; p  = 0.014) points was found in favour of aerobic training that, however, was not sustained during follow-up. No effect was found on societal participation. Aerobic training in MS patients with severe fatigue does not lead to a clinically meaningful reduction in fatigue or societal participation when compared to a low-intensity control intervention.

Finite Element Creep-Fatigue Analysis of a Welded Furnace Roll for Identifying Failure Root Cause

NASA Astrophysics Data System (ADS)

Yang, Y. P.; Mohr, W. C.

2015-11-01

Creep-fatigue induced failures are often observed in engineering components operating under high temperature and cyclic loading. Understanding the creep-fatigue damage process and identifying failure root cause are very important for preventing such failures and improving the lifetime of engineering components. Finite element analyses including a heat transfer analysis and a creep-fatigue analysis were conducted to model the cyclic thermal and mechanical process of a furnace roll in a continuous hot-dip coating line. Typically, the roll has a short life, <1 year, which has been a problem for a long time. The failure occurred in the weld joining an end bell to a roll shell and resulted in the complete 360° separation of the end bell from the roll shell. The heat transfer analysis was conducted to predict the temperature history of the roll by modeling heat convection from hot air inside the furnace. The creep-fatigue analysis was performed by inputting the predicted temperature history and applying mechanical loads. The analysis results showed that the failure was resulted from a creep-fatigue mechanism rather than a creep mechanism. The difference of material properties between the filler metal and the base metal is the root cause for the roll failure, which induces higher creep strain and stress in the interface between the weld and the HAZ.

Fatigue Characteristics of 3D Printed Acrylonitrile Butadiene Styrene (ABS)

NASA Astrophysics Data System (ADS)

Padzi, M. M.; Bazin, M. M.; Muhamad, W. M. W.

2017-11-01

Recently, the use of 3D printer technology has become significant to industries, especially when involving the new product development. 3D printing is a technology, which produces the 3D product or prototype using a layer-by-layer technique. However, there becomes less research on the mechanical performance of the 3D printed component. In the present work, fatigue characteristics of 3D printed specimen have been studied. Acrylonitrile butadiene styrene (ABS) has been chosen as a material research due to its wide applications. Two types of specimen used, which is the 3D printing and moulding specimens. Fused deposition modelling (FDM) technique was used to produce the specimens. The dog bone shape part was produced based on ASTM D638 standard and the tensile test has been carried out to get the mechanical properties. Fatigue test was carried out at 40%, 60% and 80% of the tensile strength. The moulded part shows higher fatigue cycles compared to 3D printed part for all loading percentages. Fatigue lives for 40%, 60% and 80%, were 911, 2645 and 26948 cycles, respectively. The results indicated that 3D printed part has a lower fatigue life, which may not suitable for industrial applications. However, the 3D printed part could be improved by using various parameters and may be introduced in low strength application.

A Repeated Power Training Enhances Fatigue Resistance While Reducing Intraset Fluctuations.

PubMed

Gonzalo-Skok, Oliver; Tous-Fajardo, Julio; Moras, Gerard; Arjol-Serrano, José Luis; Mendez-Villanueva, Alberto

2018-04-04

Oliver, GS, Julio, TF, Moras, G, José Luis, AS, and Alberto, MV. A repeated power training enhances fatigue resistance while reducing intraset fluctuations. J Strength Cond Res XX(X): 000-000, 2018-The present study analyzed the effects of adding an upper-body repeated power ability (RPA) training to habitual strength training sessions. Twenty young elite male basketball players were randomly allocated into a control group (CON, n = 10) or repeated power group (RPG, n = 10) and evaluated by 1 repetition maximum (1RM), incremental load, and RPA tests in the bench press exercise before and after a 7-week period and a 4-week cessation period. Repeated power group performed 1-3 blocks of 5 sets of 5 repetitions using the load that maximized power output with 30 seconds and 3 minute of passive recovery between sets and blocks, respectively. Between-group analysis showed substantial greater improvements in RPG compared with CON in: best set (APB), last set (APL), mean power over 5 sets (APM), percentage of decrement, fluctuation decrease during APL and RPA index (APLpost/APBpre) during the RPA test (effect size [ES] = 0.64-1.86), and 1RM (ES = 0.48) and average power at 80% of 1RM (ES = 1.11) in the incremental load test. The improvements of APB and APM were almost perfectly correlated. In conclusion, RPA training represents an effective method to mainly improve fatigue resistance together with the novel finding of a better consistency in performance (measured as reduced intraset power fluctuations) at the end of a dynamic repeated effort.

Study on Fatigue Performance of Composite Bolted Joints with Bolt-Hole Delamination

NASA Astrophysics Data System (ADS)

Liu, M. J.; Yu, S.; Zhao, Q. Y.

2018-03-01

Fatigue performance of composite structure with imperfections is a challenging subject at present. Based on cohesive zone method and multi-continuum theory, delamination evolution response and fatigue life prediction of a 3D composite single-lap joint with a bolt-hole have been investigated through computer codes Abaqus and Fe-safe. Results from the comparison of a perfect composite bolted joint with another defect one indicates that a relatively small delamination damage around the bolt hole brings about significant degradation of local material performance. More notably, fatigue life of stress concentration region of composite bolted joints is highly sensitive to external loads, as an increase of 67% cyclic load amplitude leads to an decrease of 99.5% local fatigue life in this study. However, the numerical strategy for solving composite fatigue problems is meaningful to engineering works.

Laparoscopic skills suffer on the first shift of sequential night shifts: program directors beware and residents prepare.

PubMed

Leff, Daniel R; Aggarwal, Rajesh; Rana, Mariam; Nakhjavani, Batool; Purkayastha, Sanjay; Khullar, Vik; Darzi, Ara W

2008-03-01

Research evaluating fatigue-induced skills decline has focused on acute sleep deprivation rather than the effects of circadian desynchronization associated with multiple shifts. As a result, the number of consecutive night shifts that residents can safely be on duty without detrimental effects to their technical skills remains unknown. A prospective observational cohort study was conducted to assess the impact of 7 successive night shifts on the technical surgical performance of junior residents. The interventional strategy included training 21 residents from surgery and allied disciplines on a virtual reality surgical simulator, towards the achievement of preset benchmark scores, followed by 294 technical skills assessments conducted over 1764 manpower night shift hours. Primary outcomes comprised serial technical skills assessments on 2 tasks of a virtual reality surgical simulator. Secondary outcomes included assessments of introspective fatigue, duration of sleep, and prospective recordings of activity (number of "calls" received, steps walked, and patients evaluated). Maximal deterioration in performance was observed following the first night shift. Residents took significantly longer to complete the first (P = 0.002) and second tasks (P = 0.005) compared with baseline. They also committed significantly greater numbers of errors (P = 0.025) on the first task assessed. Improved performance was observed across subsequent shifts towards baseline levels. Newly acquired technical surgical skills deteriorate maximally after the first night shift, emphasizing the importance of adequate preparation for night rotas. Performance improvements across successive shifts may be due to ongoing learning or adaptation to chronic fatigue. Further research should focus on assessments of both technical procedural skills and cognitive abilities to determine the rotas that best minimize errors and maximize patient safety.

PlenadrEMA: effect of dual-release versus conventional hydrocortisone on fatigue, measured by ecological momentary assessments: a study protocol for an open-label switch pilot study.

PubMed

Boesen, Victor Brun; Christoffersen, Thea; Watt, Torquil; Borresen, Stina Willemoes; Klose, Marianne; Feldt-Rasmussen, Ulla

2018-01-23

Patients with adrenal insufficiency have impaired health-related quality of life (QoL). The dual-release hydrocortisone preparation, Plenadren, has been developed to mimic the physiological cortisol release more closely than conventional hydrocortisone treatment. Plenadren has been shown to improve QoL, in particular fatigue, in patients with primary adrenal insufficiency. However, the effect has not been investigated in patients with secondary adrenal insufficiency; furthermore, no study has taken the diurnal variation of fatigue into account. To assess diurnal variations, it is necessary to use repeated daily measurements, such as ecological momentary assessments (EMAs). This study aims to evaluate EMAs of fatigue as outcome in future large-scale randomised clinical trials. The PlenadrEMA trial is an investigator-initiated open-label switch pilot trial of the effect of Plenadren versus conventional hydrocortisone on fatigue in patients with secondary adrenal insufficiency. The trial will include 30 participants. After 5 weeks on their usual hydrocortisone treatment, patients will be shifted to Plenadren for 16 weeks. Fatigue will be assessed using momentary versions of the Multidimensional Fatigue Inventory (MFI-20). Items will be administered to participants via a smartphone application four times daily during 20 days. Assessments will be performed before treatment shift and repeated after 12.5 weeks on Plenadren. The study will identify the best suited outcome for future randomised clinical trials, and in addition, estimate the variability and difference in fatigue between the two treatments to perform power calculations. The trial will be conducted in accordance with the Declaration of Helsinki and has been approved by the Regional Scientific Ethical Committee in Copenhagen (ID: H-1-2014-073). All patients will receive written and verbal information about the trial and will give informed consent before enrolment. Findings will be published in peer-reviewed journals and presented at international conferences. EudraCT201400203932. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Effects of knee and ankle muscle fatigue on postural control in the unipedal stance.

PubMed

Bizid, Riadh; Margnes, Eric; François, Yrieix; Jully, Jean Louis; Gonzalez, Gerard; Dupui, Philippe; Paillard, Thierry

2009-06-01

The aim of this study was to compare the effects of acute muscle fatigue of the ankle and knee musculature on postural control by immediate measures after performing fatiguing tasks (POST condition). One group of subjects (n = 8) performed a fatiguing task by voluntary contractions of the triceps surae (group TRI) and the other (n = 9) performed a fatiguing task by voluntary contractions of the quadriceps femoris (group QUA). Each muscle group was exercised until the loss of maximal voluntary contraction torque reached 50% (isokinetic dynamometer). Posture was assessed by measuring the centre of foot pressure (COP) with a force platform during a test of unipedal quiet standing posture with eyes closed. Initially (in PRE condition), the mean COP velocity was not significantly different between group TRI and group QUA. In POST condition, the mean COP velocity increased more in group QUA than in group TRI. The postural control was more impaired by knee muscle fatigue than by ankle muscle fatigue.

The Effect of Fatigue-Induced Changes in Eggbeater-Kick Kinematics on Performance and Risk of Injury.

PubMed

Oliveira, Nuno; Saunders, David H; Sanders, Ross H

2016-01-01

To investigate the effects of fatigue on the vertical force and kinematics of the lower limbs during maximal water polo eggbeater kicking. Twelve male water polo players maintained as high a position as possible while performing the eggbeater kick with the upper limbs raised out of the water until they were unable to keep the top of the sternum (manubrium) above water. Data comprising 27 complete eggbeater-kick cycles were extracted corresponding to 9 cycles of the initial nonfatigued (0%), 50% time point (50%), and final fatigued (100%) periods of the trial. Vertical force, foot speed, and hip-, knee-, and ankle-joint angles were calculated. Mean vertical force (0%, 212.2 N; 50%, 184.5 N; 100%, 164.3 N) progressively decreased with time. Speed of the feet (0.4 m/s), hip abduction (2.9°), and flexion (3.6°) decreased with fatigue, while hip internal rotation (3.6°) and ankle inversion (4°) increased with fatigue. Average angular velocity decreased for all joint motions. Eggbeater-kick performance decreases with fatigue. Inability to maintain foot speeds and hip and ankle actions with progressing fatigue diminishes the ability of the player to produce vertical force during the cycle. Increased internal rotation of the hip when fatigued and the large eversion/abduction of the ankle during the cycle may be predisposing factors for the prevalence of patellofemoral pain syndrome observed among eggbeater-kick performers. Appropriate training interventions that can limit the effects of fatigue on performance and injury risk should be considered.

Improved High-Cycle Fatigue (HCF) Life Prediction

DTIC Science & Technology

2001-01-01

fatigue in 2024 - T351 aluminum alloy ’, Wear 221, 24-36. Appendix 6C CHARACTERIZATION OF FRETTING FATIGUE INITIATED CRACKS P.J. Golden A.F...0.8. To evaluate the effects of surface residual stresses on notch fatigue life , shot peened specimens were tested at R = -1.0 and 0.1. Data in...Behavior - Response • The undamaged fatigue test program demonstrates the sensitivity of surface effects (for different

Evaluating the Training Effects of Two Swallowing Rehabilitation Therapies Using Surface Electromyography--Chin Tuck Against Resistance (CTAR) Exercise and the Shaker Exercise.

PubMed

Sze, Wei Ping; Yoon, Wai Lam; Escoffier, Nicolas; Rickard Liow, Susan J

2016-04-01

In this study, the efficacy of two dysphagia interventions, the Chin Tuck against Resistance (CTAR) and Shaker exercises, were evaluated based on two principles in exercise science-muscle-specificity and training intensity. Both exercises were developed to strengthen the suprahyoid muscles, whose contractions facilitate the opening of the upper esophageal sphincter, thereby improving bolus transfer. Thirty-nine healthy adults performed two trials of both exercises in counter-balanced order. Surface electromyography (sEMG) recordings were simultaneously collected from suprahyoid muscle group and sternocleidomastoid muscle during the exercises. Converging results using sEMG amplitude analyses suggested that the CTAR was more specific in targeting the suprahyoid muscles than the Shaker exercise. Fatigue analyses on sEMG signals further indicated that the suprahyoid muscle group were equally or significantly fatigued (depending on metric), when participants carried out CTAR compared to the Shaker exercise. Importantly, unlike during Shaker exercise, the sternocleidomastoid muscles were significantly less activated and fatigued during CTAR. Lowering the chin against resistance is therefore sufficiently specific and intense to fatigue the suprahyoid muscles.

[Effects of self-foot reflexology on stress, fatigue, skin temperature and immune response in female undergraduate students].

PubMed

Lee, Young-Mee

2011-02-01

The purpose of this study was to evaluate the effects of self-foot reflexology on stress (perceived stress, urine cortisol level, and serum cortisol level), fatigue, skin temperature and immune response in female undergraduate students. The research design was a nonequivalent control group pretest-post test design. Participants were 60 university students: 30 in the experiment group and 30 in the control group. The period of this study was from April to June 2010. The program was performed for 1 hr a session, three times a week for 6 weeks. The data were analyzed using the SPSS/WIN 17.0 program. The results showed that self-foot reflexology was effective in reducing perceived stress and fatigue, and raised skin temperature in female undergraduate students. But cortisol levels and immune response were not statistically significant different. The results of this study indicate that self-foot reflexology is an effective nursing intervention in reducing perceived stress and fatigue and, in improving skin temperature. Therefore, it is recommended that this be used in clinical practice as an effective nursing intervention for in female undergraduate students.

Is Listening in Noise Worth It? The Neurobiology of Speech Recognition in Challenging Listening Conditions.

PubMed

Eckert, Mark A; Teubner-Rhodes, Susan; Vaden, Kenneth I

2016-01-01

This review examines findings from functional neuroimaging studies of speech recognition in noise to provide a neural systems level explanation for the effort and fatigue that can be experienced during speech recognition in challenging listening conditions. Neuroimaging studies of speech recognition consistently demonstrate that challenging listening conditions engage neural systems that are used to monitor and optimize performance across a wide range of tasks. These systems appear to improve speech recognition in younger and older adults, but sustained engagement of these systems also appears to produce an experience of effort and fatigue that may affect the value of communication. When considered in the broader context of the neuroimaging and decision making literature, the speech recognition findings from functional imaging studies indicate that the expected value, or expected level of speech recognition given the difficulty of listening conditions, should be considered when measuring effort and fatigue. The authors propose that the behavioral economics or neuroeconomics of listening can provide a conceptual and experimental framework for understanding effort and fatigue that may have clinical significance.

Is Listening in Noise Worth It? The Neurobiology of Speech Recognition in Challenging Listening Conditions

PubMed Central

Eckert, Mark A.; Teubner-Rhodes, Susan; Vaden, Kenneth I.

2016-01-01

This review examines findings from functional neuroimaging studies of speech recognition in noise to provide a neural systems level explanation for the effort and fatigue that can be experienced during speech recognition in challenging listening conditions. Neuroimaging studies of speech recognition consistently demonstrate that challenging listening conditions engage neural systems that are used to monitor and optimize performance across a wide range of tasks. These systems appear to improve speech recognition in younger and older adults, but sustained engagement of these systems also appears to produce an experience of effort and fatigue that may affect the value of communication. When considered in the broader context of the neuroimaging and decision making literature, the speech recognition findings from functional imaging studies indicate that the expected value, or expected level of speech recognition given the difficulty of listening conditions, should be considered when measuring effort and fatigue. We propose that the behavioral economics and/or neuroeconomics of listening can provide a conceptual and experimental framework for understanding effort and fatigue that may have clinical significance. PMID:27355759

Current challenges and concepts of the thermomechanical treatment of nickel-titanium instruments.

PubMed

Shen, Ya; Zhou, Hui-min; Zheng, Yu-feng; Peng, Bin; Haapasalo, Markus

2013-02-01

The performance and mechanical properties of nickel-titanium (NiTi) instruments are influenced by factors such as cross-section, flute design, raw material, and manufacturing processes. Many improvements have been proposed by manufacturers during the past decade to provide clinicians with safer and more efficient instruments. The mechanical performance of NiTi alloys is sensitive to their microstructure and associated thermomechanical treatment history. Heat treatment or thermal processing is one of the most fundamental approaches toward adjusting the transition temperature in NiTi alloy, which affects the fatigue resistance of NiTi endodontic files. The newly developed NiTi instruments made from controlled memory wire, M-Wire (Dentsply Tulsa Dental Specialties, Tulsa, OK), or R-phase wire represent the next generation of NiTi alloys with improved flexibility and fatigue resistance. The advantages of NiTi files for canal cleaning and shaping are decreased canal transportation and ledging, a reduced risk of file fracture, and faster and more efficient instrumentation. The clinician must understand the nature of different NiTi raw materials and their impact on instrument performance because many new instruments are introduced on a regular basis. This review summarizes the metallurgical properties of next-generation NiTi instruments, the impact of thermomechanical treatment on instrument flexibility, and the resistance to cyclic fatigue and torsion. The aim of this review was to provide clinicians with the knowledge necessary for evidence-based practices, maximizing the benefits from the selection and application of NiTi rotary instruments for root canal treatment. Copyright © 2013 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

A busy day has minimal effect on factors associated with falls in older people: An ecological randomised crossover trial.

PubMed

Sturnieks, Daina L; Yak, Sin Lin; Ratanapongleka, Mayna; Lord, Stephen R; Menant, Jasmine C

2018-06-01

Fatigue is a common complaint in older people. Laboratory-induced muscle fatigue has been found to affect physical functions in older populations but these protocols are rigorous and are unlikely to accurately reflect daily activities. This study used an ecological approach to determine the effects of a busy day on self-reported fatigue and fall-related measures of physical and cognitive function in older people. Fifty community-dwelling adult volunteers, aged 60-88 (mean 73) years participated in this randomised crossover trial. Participants undertook assessments of balance, strength, gait, mobility, cognitive function and self-reported fatigue, before and after a planned rest day and a planned busy day (randomly allocated) at least one week apart. Participants wore an activity monitor on both the rest and busy days. On average, participants undertook twice as many steps and 2.5 times more minutes of activity on the busy, compared with the rest day. Participants had a significant increase in self-reported fatigue on the afternoon of the busy day and no change on the rest day. Repeated measures ANOVAs found no significant day (rest/busy) × time (am/pm) interaction effects, except for the timed up and go test of mobility, resulting from relatively improved mobility performance over the rest day, compared with the busy day. This study showed few effects of a busy day on physical and cognitive performance tests associated with falls in older people. Copyright © 2018 Elsevier Inc. All rights reserved.

Corrosion fatigue crack propagation in metals

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.

1990-01-01

This review assesses fracture mechanics data and mechanistic models for corrosion fatigue crack propagation in structural alloys exposed to ambient temperature gases and electrolytes. Extensive stress intensity-crack growth rate data exist for ferrous, aluminum and nickel based alloys in a variety of environments. Interactive variables (viz., stress intensity range, mean stress, alloy composition and microstructure, loading frequency, temperature, gas pressure and electrode potential) strongly affect crack growth kinetics and complicate fatigue control. Mechanistic models to predict crack growth rates were formulated by coupling crack tip mechanics with occluded crack chemistry, and from both the hydrogen embrittlement and anodic dissolution/film rupture perspectives. Research is required to better define: (1) environmental effects near threshold and on crack closure; (2) damage tolerant life prediction codes and the validity of similitude; (3) the behavior of microcrack; (4) probes and improved models of crack tip damage; and (5) the cracking performance of advanced alloys and composites.

Analysis of the binder yield energy test as an indicator of fatigue behaviour of asphalt mixes

NASA Astrophysics Data System (ADS)

O'Connell, Johan; Mturi, Georges A. J.; Komba, Julius; Du Plessis, Louw

2017-09-01

Empirical binder testing has increasingly failed to predict pavement performance in South Africa, with fatigue cracking being one of the major forms of premature pavement distress. In response, it has become a national aspiration to incorporate a performance related fatigue test into the binder specifications for South Africa. The Binder Yield Energy Test (BYET) was the first in a series of tests analysed for its potential to predict the fatigue performance of the binder. The test is performed with the dynamic shear rheometer, giving two key parameters, namely, yield energy and shear strain at maximum shear stress (γτmax). The objective of the investigation was to perform a rudimentary evaluation of the BYET; followed by a more in-depth investigation should the initial BYET results prove promising. The paper discusses the results generated from the BYET under eight different conditions, using six different binders. The results are then correlated with four point bending beam fatigue test results obtained from asphalt mix samples that were manufactured from the same binders. Final results indicate that the BYET is not ideal as an indicator of fatigue performance.

Approach to the Underperforming Athlete.

PubMed

Solomon, Mary L; Weiss Kelly, Amanda K

2016-03-01

Children and adolescents who participate in intense sports training may face physical and psychologic stresses. The pediatric health care provider can play an important role in monitoring an athlete's preparation by obtaining a proper sports history, assessing sleep hygiene, discussing nutrition and hydration guidelines, and evaluating physiologic causes of fatigue. Educating parents and athletes on the potential risks of high-intensity training, inadequate rest and sleep, and a poor diet may improve the athlete's performance and prevent symptoms of overtraining syndrome. Infectious mononucleosis must also be considered a cause of fatigue among adolescents. The signs and symptoms of overtraining and burnout are discussed in this article. Copyright 2016, SLACK Incorporated.

A Transcriptional Signature of Fatigue Derived from Patients with Primary Sjögren’s Syndrome

PubMed Central

James, Katherine; Al-Ali, Shereen; Tarn, Jessica; Cockell, Simon J.; Gillespie, Colin S.; Hindmarsh, Victoria; Locke, James; Mitchell, Sheryl; Lendrem, Dennis; Bowman, Simon; Price, Elizabeth; Pease, Colin T.; Emery, Paul; Lanyon, Peter; Hunter, John A.; Gupta, Monica; Bombardieri, Michele; Sutcliffe, Nurhan; Pitzalis, Costantino; McLaren, John; Cooper, Annie; Regan, Marian; Giles, Ian; Isenberg, David; Saravanan, Vadivelu; Coady, David; Dasgupta, Bhaskar; McHugh, Neil; Young-Min, Steven; Moots, Robert; Gendi, Nagui; Akil, Mohammed; Griffiths, Bridget; Wipat, Anil; Newton, Julia; Jones, David E.; Isaacs, John; Hallinan, Jennifer; Ng, Wan-Fai

2015-01-01

Background Fatigue is a debilitating condition with a significant impact on patients’ quality of life. Fatigue is frequently reported by patients suffering from primary Sjögren’s Syndrome (pSS), a chronic autoimmune condition characterised by dryness of the eyes and the mouth. However, although fatigue is common in pSS, it does not manifest in all sufferers, providing an excellent model with which to explore the potential underpinning biological mechanisms. Methods Whole blood samples from 133 fully-phenotyped pSS patients stratified for the presence of fatigue, collected by the UK primary Sjögren’s Syndrome Registry, were used for whole genome microarray. The resulting data were analysed both on a gene by gene basis and using pre-defined groups of genes. Finally, gene set enrichment analysis (GSEA) was used as a feature selection technique for input into a support vector machine (SVM) classifier. Classification was assessed using area under curve (AUC) of receiver operator characteristic and standard error of Wilcoxon statistic, SE(W). Results Although no genes were individually found to be associated with fatigue, 19 metabolic pathways were enriched in the high fatigue patient group using GSEA. Analysis revealed that these enrichments arose from the presence of a subset of 55 genes. A radial kernel SVM classifier with this subset of genes as input displayed significantly improved performance over classifiers using all pathway genes as input. The classifiers had AUCs of 0.866 (SE(W) 0.002) and 0.525 (SE(W) 0.006), respectively. Conclusions Systematic analysis of gene expression data from pSS patients discordant for fatigue identified 55 genes which are predictive of fatigue level using SVM classification. This list represents the first step in understanding the underlying pathophysiological mechanisms of fatigue in patients with pSS. PMID:26694930

A statistical model for predicting muscle performance

NASA Astrophysics Data System (ADS)

Byerly, Diane Leslie De Caix

The objective of these studies was to develop a capability for predicting muscle performance and fatigue to be utilized for both space- and ground-based applications. To develop this predictive model, healthy test subjects performed a defined, repetitive dynamic exercise to failure using a Lordex spinal machine. Throughout the exercise, surface electromyography (SEMG) data were collected from the erector spinae using a Mega Electronics ME3000 muscle tester and surface electrodes placed on both sides of the back muscle. These data were analyzed using a 5th order Autoregressive (AR) model and statistical regression analysis. It was determined that an AR derived parameter, the mean average magnitude of AR poles, significantly correlated with the maximum number of repetitions (designated Rmax) that a test subject was able to perform. Using the mean average magnitude of AR poles, a test subject's performance to failure could be predicted as early as the sixth repetition of the exercise. This predictive model has the potential to provide a basis for improving post-space flight recovery, monitoring muscle atrophy in astronauts and assessing the effectiveness of countermeasures, monitoring astronaut performance and fatigue during Extravehicular Activity (EVA) operations, providing pre-flight assessment of the ability of an EVA crewmember to perform a given task, improving the design of training protocols and simulations for strenuous International Space Station assembly EVA, and enabling EVA work task sequences to be planned enhancing astronaut performance and safety. Potential ground-based, medical applications of the predictive model include monitoring muscle deterioration and performance resulting from illness, establishing safety guidelines in the industry for repetitive tasks, monitoring the stages of rehabilitation for muscle-related injuries sustained in sports and accidents, and enhancing athletic performance through improved training protocols while reducing injury.

Correlation between Driver Subjective Fatigue and Bus Lateral Position in a Driving Simulator.

PubMed

Gharagozlou, Faramarz; Mazloumi, Adel; Saraji, Gebraeil Nasl; Nahvi, Ali; Ashouri, Mohammadreza; Mozaffari, Hamed

2015-08-01

Driver fatigue as a leading cause of death in the transportation industry can impair the driving performance in long-distance driving task. Studies on the links of driver subjective fatigue and the bus lateral position are still an exploratory issue that requires further investigation. This study aimed to determine the correlation between the driver subjective fatigue and the bus lateral position in a driving simulator. This descriptive-analytical research was conducted on 30 professional male bus drivers participated in a two-hour driving session. The driver subjective fatigue was assessed by the Fatigue Visual Analogue Scale (F-VAS) at 10-min intervals. Simultaneously, the performance measures of lane drifting as the mean and standard deviation of the bus lateral position (SDLP) were calculated during the simulated driving task. Descriptive statistics and the Spearman correlation coefficient were used to describe and analyze the data. Fatigue levels had an increasing trend as the time-on-task of driving increased. Time-on-task of driving had the greatest effect on the fatigue self-evaluation (r = 0.605, p < 0.0001). The results showed a significant correlation between fatigue self-evaluation and bus lateral position (r = 0.567, p < 0.0001). As the time of driving increased, driving performance was affected adversely, as shown by the increase in the SDLP. Even so, the effect of individual differences on driving performance should not be overlooked. This work concludes that predicting the state of a driver fatigue based on the group mean data has some complications for any application.

Correlation between Driver Subjective Fatigue and Bus Lateral Position in a Driving Simulator

PubMed Central

Gharagozlou, Faramarz; Mazloumi, Adel; Saraji, Gebraeil Nasl; Nahvi, Ali; Ashouri, Mohammadreza; Mozaffari, Hamed

2015-01-01

Background: Driver fatigue as a leading cause of death in the transportation industry can impair the driving performance in long-distance driving task. Studies on the links of driver subjective fatigue and the bus lateral position are still an exploratory issue that requires further investigation. This study aimed to determine the correlation between the driver subjective fatigue and the bus lateral position in a driving simulator. Methods: This descriptive-analytical research was conducted on 30 professional male bus drivers participated in a two-hour driving session. The driver subjective fatigue was assessed by the Fatigue Visual Analogue Scale (F-VAS) at 10-min intervals. Simultaneously, the performance measures of lane drifting as the mean and standard deviation of the bus lateral position (SDLP) were calculated during the simulated driving task. Descriptive statistics and the Spearman correlation coefficient were used to describe and analyze the data. Results: Fatigue levels had an increasing trend as the time-on-task of driving increased. Time-on-task of driving had the greatest effect on the fatigue self-evaluation (r = 0.605, p < 0.0001). The results showed a significant correlation between fatigue self-evaluation and bus lateral position (r = 0.567, p < 0.0001). Conclusion: As the time of driving increased, driving performance was affected adversely, as shown by the increase in the SDLP. Even so, the effect of individual differences on driving performance should not be overlooked. This work concludes that predicting the state of a driver fatigue based on the group mean data has some complications for any application. PMID:26396734

The mediating role of emotional symptomatology between anticipatory fatigue and the perception of fatigue.

PubMed

Rodríguez Testal, Juan F; Fuentes Márquez, Sandra; Senín Calderón, Cristina; Carrasco, Miguel A

2016-05-01

Clinical research stresses the importance of cognitive variables for predisposition, onset, and especially, perpetuation of perceived fatigue. The aim was to analyze the mediating effects of emotional symptomatology (somatic, depressive and anxiety) between anticipatory fatigue and perception of physical and cognitive fatigue. The sample was composed of 317 participants (29% from a clinical population) aged 18 to 76. Anticipatory fatigue and perception of fatigue were measured by fatigue scales. Emotional symptoms were assessed by the General Health Questionnaire, GHQ-28.  Results : Depressive symptomatology mediated the relationship between anticipatory fatigue and cognitive fatigue in both groups, and also somatic symptoms/somatization in patients. The indirect effect of physical fatigue was observed only in the clinical group, with depressive symptoms partially mediating the anticipatory fatigue and cognitive fatigue relationship. Anticipatory fatigue has a partial indirect effect on total physical fatigue, and full indirect effect on cognitive fatigue, mediated by depressive and somatic symptoms. Anticipatory fatigue is a relevant cognitive factor in the design of psychological intervention for improvement of cognitive and physical fatigue.

Is there a cognitive signature for MS-related fatigue?

PubMed

Hanken, Katrin; Eling, Paul; Hildebrandt, Helmut

2015-04-01

The compensatory approach of fatigue argues that it is a state caused by task load. The neuropsychiatric approach argues that fatigue is a trait (like depression), unrelated to environmental challenges. We propose that fatigue is an internal state that can be measured behaviorally only by applying specific cognitive tasks. PubMed was searched for articles concerning the relation between fatigue and cognitive performance or brain atrophy or functional MRI, distinguishing between the following cognitive domains: learning/memory, cognitive speed/selective attention, language, visuospatial processing, working memory, alerting/vigilance. Only tasks assessing alerting/vigilance are strongly related to fatigue. Areas with brain atrophy in fatigue patients overlap with brain regions activated in healthy controls performing alerting/vigilance tasks. Fatigue is not a compensatory state, nor a psychogenic trait. It is a feeling with behavioral effects that seems to be caused by brain atrophy or a neurochemical dysfunction of the alerting/vigilance system. © The Author(s), 2014.

Effects of Total SAT® Test Time on Performance and Fatigue. Research Notes. RN-37

ERIC Educational Resources Information Center

Ackerman, Phillip L.; Kanfer, Ruth; Wolman, Stacey D.

2005-01-01

The current study was designed to examine performance effects and fatigue effects associated with different total SAT testing times. In addition, the researchers examined personality, motivation, and other determinants of individual differences in examinee fatigue before, during, and after testing.

Isothermal and thermal-mechanical fatigue of VVER-440 reactor pressure vessel steels

NASA Astrophysics Data System (ADS)

Fekete, Balazs; Trampus, Peter

2015-09-01

The fatigue life of the structural materials 15Ch2MFA (CrMoV-alloyed ferritic steel) and 08Ch18N10T (CrNi-alloyed austenitic steel) of VVER-440 reactor pressure vessel under completely reserved total strain controlled low cycle fatigue tests were investigated. An advanced test facility was developed for GLEEBLE-3800 physical simulator which was able to perform thermomechanical fatigue experiments under in-service conditions of VVER nuclear reactors. The low cycle fatigue results were evaluated with the plastic strain based Coffin-Manson law, and plastic strain energy based model as well. It was shown that both methods are able to predict the fatigue life of reactor pressure vessel steels accurately. Interrupted fatigue tests were also carried out to investigate the kinetic of the fatigue evolution of the materials. On these samples microstructural evaluation by TEM was performed. The investigated low cycle fatigue behavior can provide reference for remaining life assessment and lifetime extension analysis.

Mental Fatigue: Impairment of Technical Performance in Small-Sided Soccer Games.

PubMed

Badin, Oliver O; Smith, Mitchell R; Conte, Daniele; Coutts, Aaron J

2016-11-01

To assess the effects of mental fatigue on physical and technical performance in small-sided soccer games. Twenty soccer players (age 17.8 ± 1.0 y, height 179 ± 5 cm, body mass 72.4 ± 6.8 kg, playing experience 8.3 ± 1.4 y) from an Australian National Premier League soccer club volunteered to participate in this randomized crossover investigation. Participants played 15-min 5-vs-5 small-sided games (SSGs) without goalkeepers on 2 occasions separated by 1 wk. Before the SSG, 1 team watched a 30-min emotionally neutral documentary (control), while the other performed 30 min of a computer-based Stroop task (mental fatigue). Subjective ratings of mental and physical fatigue were recorded before and after treatment and after the SSG. Motivation was assessed before treatment and SSG; mental effort was assessed after treatment and SSG. Player activity profiles and heart rate (HR) were measured throughout the SSG, whereas ratings of perceived exertion (RPEs) were recorded before the SSG and immediately after each half. Video recordings of the SSG allowed for notational analysis of technical variables. Subjective ratings of mental fatigue and effort were higher after the Stroop task, whereas motivation for the upcoming SSG was similar between conditions. HR during the SSG was possibly higher in the control condition, whereas RPE was likely higher in the mental-fatigue condition. Mental fatigue had an unclear effect on most physical-performance variables but impaired most technical-performance variables. Mental fatigue impairs technical but not physical performance in small-sided soccer games.

Prospective evaluation of a 12-week walking exercise program and its effect on fatigue in prostate cancer patients undergoing radical external beam radiotherapy.

PubMed

Truong, Pauline T; Gaul, Catherine A; McDonald, Rachel E; Petersen, Ross B; Jones, Stuart O; Alexander, Abraham S; Lim, Jan T W; Ludgate, Charles

2011-08-01

To evaluate tolerability and compliance to a walking exercise program and its effect on fatigue during and after radical external beam radiation therapy (EBRT) for prostate cancer. A total of 50 subjects with prostate cancer undergoing EBRT over 6 to 8 weeks were prospectively accrued to an exercise intervention group, matched for age and clinical characteristics to 30 subjects in a historical control group who underwent EBRT with no specific exercise intervention. Starting 1 week before EBRT, exercise participants performed moderate-intensity walking targeting 60% to 70% age-predicted maximum heart rate, at least 20 min/d, 3 d/wk over 12 weeks. The Brief Fatigue Inventory was administered at baseline, mid-EBRT (week 3-4), end-EBRT (week 6-8), and 6 months post-EBRT. Of 50, 42 (84%) of exercise participants completed the walking program. There were no cardiovascular complications, musculoskeletal injuries, or other adverse events. A total of 89% subjects reported "Good-Excellent" satisfaction during and up to 6 months post-EBRT. Fatigue in control subjects escalated from baseline to end-EBRT, remaining high at 6 months post-EBRT (P[r] = 0.03). In contrast, mean total fatigue scores in exercise subjects were stable from baseline up to 6 months post-EBRT (P = 0.52). Trends for higher fatigue interference with quality of life were observed in the control group as compared with the exercise group. Moderate-intensity walking exercise during radical EBRT is safe and feasible. The high convenience and satisfaction ratings, in conjunction with the observed fatigue trends, indicate that this activity has the potential to attenuate fatigue and improve quality of life for patients with localized prostate cancer undergoing curative therapy.

The effect of six weeks endurance training on dynamic muscular control of the knee following fatiguing exercise.

PubMed

Hassanlouei, H; Falla, D; Arendt-Nielsen, L; Kersting, U G

2014-10-01

The aim of the study was to examine whether six weeks of endurance training minimizes the effects of fatigue on postural control during dynamic postural perturbations. Eighteen healthy volunteers were assigned to either a 6-week progressive endurance training program on a cycle ergometer or a control group. At week 0 and 7, dynamic exercise was performed on an ergometer until exhaustion and immediately after, the anterior-posterior centre of pressure (COP) sway was analyzed during full body perturbations. Maximal voluntary contractions (MVC) of the knee flexors and extensors, muscle fiber conduction velocity (MFCV) of the vastus lateralis and medialis during sustained isometric knee extension contractions, and power output were measured. Following the training protocol, maximum knee extensor and flexor force and power output increased significantly for the training group with no changes observed for the control group. Moreover, the reduction of MFCV due to fatigue changed for the training group only (from 8.6% to 3.4%). At baseline, the fatiguing exercise induced an increase in the centre of pressure sway during the perturbations in both groups (>10%). The fatiguing protocol also impaired postural control in the control group when measured at week 7. However, for the training group, sway was not altered after the fatiguing exercise when assessed at week 7. In summary, six weeks of endurance training delayed the onset of muscle fatigue and improved the ability to control balance in response to postural perturbations in the presence of muscle fatigue. Results implicate that endurance training should be included in any injury prevention program. Copyright © 2014 Elsevier Ltd. All rights reserved.

How shift scheduling practices contribute to fatigue amongst freight rail operating employees: Findings from Canadian accident investigations.

PubMed

Rudin-Brown, Christina M; Harris, Sarah; Rosberg, Ari

2018-02-01

Canada's freight rail system moves 70% of the country's surface goods and almost half of all exports (RAC, 2016). These include dangerous goods. Anonymous survey of freight rail operating employees conducted by the Teamsters Canada Rail Conference (TCRC, 2014) revealed that many do not report getting enough sleep because of their work schedules, and that fatigue may be affecting their performance at work. Besides general impairments in attention and cognitive functioning, fatigue in railway operating employees slows reaction time to safety alarms and impairs conformance to train operating requirements. Shift scheduling practices can contribute to sleep-related fatigue by restricting sleep opportunities, requiring extended periods of wakefulness and by disrupting daily (circadian) rhythms. The primary goal of accident investigation is to identify causal and contributing factors so that similar occurrences can be prevented. A database search of Transportation Safety Board (TSB) rail investigation reports published in the 21-year period from 1995 to 2015 identified 18 that cited sleep-related fatigue of freight rail operating employees as a causal, contributing, or risk finding. This number represents about 20% of TSB rail investigations from the same period in which a human factors aspect of freight train activities was a primary cause. Exploration of accident themes suggests that management of fatigue and shift scheduling in the freight rail industry is a complex issue that is often not conducive to employee circadian rhythms and sleep requirements. It also suggests that current shift scheduling and fatigue management practices may be insufficient to mitigate the associated safety risk. Railway fatigue management systems that are based on the principles of modern sleep science are needed to improve scheduling practices and mitigate the ongoing safety risk. Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.

Using aggregated single patient (N-of-1) trials to determine the effectiveness of psychostimulants to reduce fatigue in advanced cancer patients: a rationale and protocol.

PubMed

Senior, Hugh Ej; Mitchell, Geoffrey K; Nikles, Jane; Carmont, Sue-Ann; Schluter, Philip J; Currow, David C; Vora, Rohan; Yelland, Michael J; Agar, Meera; Good, Phillip D; Hardy, Janet R

2013-04-23

It is estimated that 29% of deaths in Australia are caused by malignant disease each year and can be expected to increase with population ageing. In advanced cancer, the prevalence of fatigue is high at 70-90%, and can be related to the disease and/or the treatment. The negative impact of fatigue on function (physical, mental, social and spiritual) and quality of life is substantial for many palliative patients as well as their families/carers. This paper describes the design of single patient trials (n-of-1 s or SPTs) of a psychostimulant, methylphenidate hydrochloride (MPH) (5 mg bd), compared to placebo as a treatment for fatigue, with a population estimate of the benefit by the aggregation of multiple SPTs. Forty patients who have advanced cancer will be enrolled through specialist palliative care services in Australia. Patients will complete up to 3 cycles of treatment. Each cycle is 6 days long and has 3 days treatment and 3 days placebo. The order of treatment and placebo is randomly allocated for each cycle. The primary outcome is a reduction in fatigue severity as measured by the Functional Assessment of Cancer Therapy-fatigue subscale (FACIT-F). Secondary outcomes include adverse events, quality of life, additional fatigue assessments, depression and Australian Karnovsky Performance Scale. This study will provide high-level evidence using a novel methodological approach about the effectiveness of psychostimulants for cancer-related fatigue. If effective, the findings will guide clinical practice in reducing this prevalent condition to improve function and quality of life. Australian New Zealand Clinical Trials Registry ACTRN12609000794202.

Machining of Aircraft Titanium with Abrasive-Waterjets for Fatigue Critical Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, H. T.; Hovanski, Yuri; Dahl, Michael E.

2010-10-04

Laboratory tests were conducted to determine the fatigue performance of AWJ-machined aircraft titanium. Dog-bone specimens machined with AWJs were prepared and tested with and without sanding and dry-grit blasting with Al2O3 as secondary processes. The secondary processes were applied to remove the visual appearance of AWJ-generated striations and to clean up the garnet embedment. The fatigue performance of AWJ-machined specimens was compared with baseline specimens machined with CNC milling. Fatigue test results not only confirmed the findings of the aluminum dog-bone specimens but also further enhance the fatigue performance. In addition, titanium is known to be notoriously difficult to cutmore » with contact tools while AWJs cut it 34% faster than stainless steel. AWJ cutting and dry-grit blasting are shown to be a preferred combination for processing aircraft titanium that is fatigue critical.« less

Power spectral density analysis of the electromyogram from a work task performed in a full pressure suit. Ph.D. Thesis - Houston Univ.; [for determining muscular fatigue

NASA Technical Reports Server (NTRS)

Lafevers, E. V.

1974-01-01

Surface electromyograms (EMG) taken from three upper torso muscles during a push-pull task were analyzed by a power spectral density technique to determine the utility of the spectral analysis for identifying changes in the EMG caused by muscular fatigue. The results confirmed the value of the frequency analysis for identifying fatigue producing muscular performance. Data revealed reliable differences between muscles in fatigue induced responses to various locations in the reach envelope at which the subjects were required to perform the push-pull exercise, and the differential sensitivity of individual muscles to the various reach positions; i.e., certain reach positions imposed more fatigue related shifts in EMG power than did others. It was found that a pressurized space suit changed the pattern of normal shirtsleeve muscle fatigue responses in all three of the muscles.

The NASA Ames Fatigue Countermeasures Program: The Next Generation

NASA Technical Reports Server (NTRS)

Rosekind, Mark R.; Neri, David F.; Miller, Donna L.; Gregory, Kevin B.; Webbon, Lissa L.; Oyung, Ray L.

1997-01-01

Twenty-four hour, global aviation operations pose unique challenges to humans. Physiological requirements related to sleep, the internal circadian clock, and human fatigue are critical factors that are known to affect safety, performance, and productivity. Understanding the human operators' physiological capabilities, and limitations, will be important to address these issues as global demand for aviation activities continues to increase. In 1980, in response to a Congressional request, the National Aeronautics and Space Administration (NASA) Ames Research Center initiated a Fatigue/Jet Lag Program to examine the role of fatigue in flight operations. Originally established by Dr. John K. Lauber and Dr. Charles E. Billings, the Program was designed to address three objectives: (1) determine the extent of fatigue, sleep loss, and circadian disruption in flight operations; (2) determine how fatigue affected flight crew performance; and (3) develop strategies to maximize performance and alertness during flight operations.

Physical fatigue increases neural activation during eyes-closed state: a magnetoencephalography study.

PubMed

Tanaka, Masaaki; Ishii, Akira; Watanabe, Yasuyoshi

2015-11-05

Fatigue, defined as difficulty initiating or sustaining voluntary activities, can be classified as physical or mental. In this study, we use magnetoencephalography (MEG) to quantify the effect of physical fatigue on neural activity under the condition of simulated physical load. Thirteen healthy right-handed male volunteers participated in this study. The experiment consisted of one fatigue-inducing physical task session performed between two MEG sessions. During the 10-min physical task session, participants performed maximum-effort handgrips with the left hand lasting 1 s every 4 s; during MEG sessions, 3-min recordings were made during the eyes-closed state. MEG data were analyzed using narrow-band adaptive spatial filtering methods. Alpha-frequency band (8-13 Hz) power in the left postcentral gyrus, precentral gyrus, and middle frontal gyrus (Brodmann's areas 1, 2, 3, 4, 6, and 46) were decreased after performing the physical fatigue-inducing task. These results show that performing the physical fatigue-inducing task caused activation of the left sensorimotor and prefrontal areas, manifested as decreased alpha-frequency band power in these brain areas. Our results increase understanding of the neural mechanisms of physical fatigue.

The fatigue behavior of an amorphous brittle composite material

NASA Astrophysics Data System (ADS)

Kumar, Brijesh

The use of poly methyl methacrylate (PMMA) based bone cement as a grouting agent for the in-vivo fixation of orthopaedic implants has been in practice for nearly fifty years. Fatigue failure of the bone cement has been identified as the primary cause of cement failure. Implant loosening due to the failure of the cement is one of the major reasons necessitating revision surgery. The need for a more fatigue resistant bone cement is well documented in the literature. One method of producing a more fatigue resistant bone cement is to reinforce it with short fibers. The fundamental purpose of this work was to investigate the possible improvement of the fatigue characteristics of bone cement provided by the following two types of fiber reinforcements: short flexible Polyethylene Terephalate (PET) fibers and stiff milled carbon fibers. It has been shown that the reinforcement of the bone cement with fibers provides substantial improvement of the fracture toughness of the bone cement. In this investigation the impact of fiber reinforcement on the fatigue properties of the bone cement was studied. The effects of the fiber reinforcement on the fatigue life of bone cement has been determined experimentally. Since fatigue characteristics are known to have considerable scatter, a methodology was developed to analyze the experimental data in a statistically rigorous manner. The effect of the fiber reinforcement on bone cement was also analyzed using a theoretical approach and by conducting extensive Scanning Electron Microscopy (SEM) of the fractured surfaces. The results of this study indicate that fiber reinforcement improves the fatigue life of bone cement at a very high level of reliability. This could potentially lead to a more fatigue tolerant bone cement, which would delay the need for revision surgery due to implant loosening.

Thermal fatigue behavior of H-13 die steel for aluminum die casting with various ion sputtered coatings

NASA Technical Reports Server (NTRS)

Nieh, C. Y.; Wallace, J. F.

1981-01-01

Sputtered coatings of Mo, W, Pt, Ag, Au, Co, Cr, Ni, Ag + Cu, Mo + Pt, Si3N4, A1N, Cr3C2, Ta5Si3, and ZrO2 were applied to a 2-inch-square, 7-inch-long thermal fatigue test specimen which was then internally water cooled and alternately immersed in molten aluminum and cooled in air. After 15,000 cycles the thermal fatigue cracks at the specimen corners were measured. Results indicate that a significant improvement in thermal fatigue resistance was obtained with platinum, molybdenum, and tungsten coatings. Metallographic examination indicates that the improvement in thermal fatigue resistance resulted from protection of the surface of the die steel from oxidation. The high yield strength and ductility of molybdenum and tungsten contributed to the better thermal fatigue resistance.

Effects of service condition on rolling contact fatigue failure mechanism and lifetime of thermal spray coatings—A review

NASA Astrophysics Data System (ADS)

Cui, Huawei; Cui, Xiufang; Wang, Haidou; Xing, Zhiguo; Jin, Guo

2015-01-01

The service condition determines the Rolling Contact Fatigue(RCF) failure mechanism and lifetime under ascertain material structure integrity parameter of thermal spray coating. The available literature on the RCF testing of thermal spray coatings under various condition services is considerable; it is generally difficult to synthesize all of the result to obtain a comprehensive understanding of the parameters which has a great effect on a thermal spray coating's resistance of RCF. The effects of service conditions(lubrication states, contact stresses, revolve speed, and slip ratio) on the changing of thermal spray coatings' contact fatigue lifetime is introduced systematically. The effects of different service condition on RCF failure mechanism of thermal spray coating from the change of material structure integrity are also summarized. Moreover, In order to enhance the RCF performance, the parameter optimal design formula of service condition and material structure integrity is proposed based on the effect of service condition on thermal spray coatings' contact fatigue lifetime and RCF failure mechanism. The shortage of available literature and the forecast focus in future researches are discussed based on available research. The explicit result of RCF lifetime law and parameter optimal design formula in term of lubrication states, contact stresses, revolve speed, and slip ratio, is significant to improve the RCF performance on the engineering application.

Analysis and modification of a single-mesh gear fatigue rig for use in diagnostic studies

NASA Technical Reports Server (NTRS)

Zakrajsek, James J.; Townsend, Dennis P.; Oswald, Fred B.; Decker, Harry J.

1992-01-01

A single-mesh gear fatigue rig was analyzed and modified for use in gear mesh diagnostic research. The fatigue rig allowed unwanted vibration to mask the test-gear vibration signal, making it difficult to perform diagnostic studies. Several possible sources and factors contributing to the unwanted components of the vibration signal were investigated. Sensor mounting location was found to have a major effect on the content of the vibration signal. In the presence of unwanted vibration sources, modal amplification made unwanted components strong. A sensor location was found that provided a flatter frequency response. This resulted in a more useful vibration signal. A major network was performed on the fatigue rig to reduce the influence of the most probable sources of the noise in the vibration signal. The slave gears were machined to reduce weight and increase tooth loading. The housing and the shafts were modified to reduce imbalance, looseness, and misalignment in the rotating components. These changes resulted in an improved vibration signal, with the test-gear mesh frequency now the dominant component in the signal. Also, with the unwanted sources eliminated, the sensor mounting location giving the most robust representation of the test-gear meshing energy was found to be at a point close to the test gears in the load zone of the bearings.

The neural effects of positively and negatively re-experiencing mental fatigue sensation: a magnetoencephalography study.

PubMed

Ishii, Akira; Ishizuka, Takuya; Muta, Yuki; Tanaka, Masaaki; Yamano, Emi; Watanabe, Yasuyoshi

2018-06-01

Fatigue sensation is an essential biological alarm that urges us to take rest to avoid disrupting homeostasis and thus plays an important role in maintaining well-being. However, there are situations in which the anticipation of unpleasant fatigue sensation undesirably reduces motivation for activity. The aim of this study was to examine whether thinking positively about the fatigue sensation would increase motivation to accomplish the workload. Fourteen healthy male volunteers participated in this study and performed a two-back test for 30 min to induce mental fatigue sensation. After their subjective level of fatigue had recovered to the baseline level, they re-experienced the fatigue sensation experienced in the two-back test positively, negatively, and without any modification (i.e., re-experienced the fatigue sensation as it was). The level of motivation to perform another two-back test they felt during the re-experiencing was assessed. The neural activity related to the re-experiencing was recorded using magnetoencephalography. The level of the motivation to perform another two-back test was increased by positively re-experiencing the fatigue sensation. The increase in delta band power in Brodmann area 7 was positively associated with the increase in motivation. These results show that positive thinking about fatigue sensation can enhance motivation and suggest that this enhanced motivation may have some effects on visual attention system.

The effect of mental fatigue on sustained attention: an fNIRS study

NASA Astrophysics Data System (ADS)

Zhang, Zhen; Yang, Hanjun; Cao, Yong; Xu, Fenggang; Jiang, Jin; Jiao, Xuejun

2017-01-01

Sustained attention is the ability to keep focused and vigilance for long time in external stimulation, which was crucial in safe-critical human-machine system. While the ability of sustained attention will decline because of mental fatigue, even lead to serious accidents in fatigue state. Therefore, it is of great significance to explore the impact of fatigue on sustained attention. Functional Near-Infrared Spectroscopy (fNIRS) can measure cerebral hemoglobin in order to reflect cognitive function indirectly. In previous related fatigue studies, monotonous and long-time CPT (continuous performance test task) was often used to explore the performance change and brain activity, but the effect of time on task (TOT) was always involved. In this study, in order to avoid the TOT effect, the sustained attention task and fatigue task were separated. It was adopted in the study that the modified continuous performance test (CPT) was chosen as the sustained attention task and verbal 2-back task as the fatigue induced task. The fNIRS signals were extracted from 10 channels in the prefrontal cortex (PFC) from 20 healthy subjects. Studies found that cerebral lateralization increased significantly from alert to fatigue state in sustained attention task. Besides, Average oxyhemoglobin (HBO) of PFC increased significantly from alert to fatigue task, and the spatial pattern of activity of oxyhemoglobin also changed, which c be sensitive features to fatigue detection.

The hybrid assisted limb (HAL) for Care Support, a motion assisting robot providing exoskeletal lumbar support, can potentially reduce lumbar load in repetitive snow-shoveling movements.

PubMed

Miura, Kousei; Kadone, Hideki; Koda, Masao; Abe, Tetsuya; Endo, Hirooki; Murakami, Hideki; Doita, Minoru; Kumagai, Hiroshi; Nagashima, Katsuya; Fujii, Kengo; Noguchi, Hiroshi; Funayama, Toru; Kawamoto, Hiroaki; Sankai, Yoshiyuki; Yamazaki, Masashi

2018-03-01

An excessive lumbar load with snow-shoveling is a serious problem in snowfall areas. Various exoskeletal robots have been developed to reduce lumbar load in lifting work. However, few studies have reported the attempt of snow-shoveling work using exoskeletal robots. The purpose of the present study was to test the hypothesis that the HAL for Care Support robot would reduce lumbar load in repetitive snow-shoveling movements. Nine healthy male volunteers performed repetitive snow-shoveling movements outdoors in a snowfall area for as long as possible until they were fatigued. The snow-shoveling trial was performed under two conditions: with and without HAL for Care Support. Outcome measures were defined as the lumbar load assessed by the VAS of lumbar fatigue after the snow-shoveling trial and the snow-shoveling performance, including the number of scoops, and snow shoveling time and distance. The mean of VAS of lumbar fatigue, the number of scoops, and snow-shoveling time and distance without HAL for Care Support were 75.4 mm, 50.3, 145 s, and 9.6 m, while with HAL for Care Support were 39.8 mm, 144, 366 s, and 35.4 m. The reduction of lumbar fatigue and improvement of snow-shoveling performance using HAL for Care Support were statistically significant. There was no adverse event during snow-shoveling with HAL for Care Support. In conclusion, the HAL for Care Support can reduce lumbar load in repetitive snow-shoveling movements. Copyright © 2017 Elsevier Ltd. All rights reserved.

Randomized controlled pilot trial of mindfulness-based stress reduction for breast and colorectal cancer survivors: effects on cancer-related cognitive impairment.

PubMed

Johns, Shelley A; Von Ah, Diane; Brown, Linda F; Beck-Coon, Kathleen; Talib, Tasneem L; Alyea, Jennifer M; Monahan, Patrick O; Tong, Yan; Wilhelm, Laura; Giesler, R Brian

2016-06-01

Cancer-related cognitive impairment (CRCI) is a common, fatigue-related symptom that disrupts cancer survivors' quality of life. Few interventions for CRCI exist. As part of a randomized pilot study targeting cancer-related fatigue, the effects of mindfulness-based stress reduction (MBSR) on survivors' cognitive outcomes were investigated. Breast and colorectal cancer survivors (n = 71) with moderate-to-severe fatigue were randomized to MBSR (n = 35) or a fatigue education and support (ES; n = 36) condition. The Attentional Function Index (AFI) and the Stroop test were used to assess survivors' cognitive function at baseline (T1), after the 8-week intervention period (T2), and 6 months later (T3) using intent-to-treat analysis. Mediation analyses were performed to explore mechanisms of intervention effects on cognitive functioning. MBSR participants reported significantly greater improvement on the AFI total score compared to ES participants at T2 (d = 0.83, p = 0.001) and T3 (d = 0.55, p = 0.021). MBSR also significantly outperformed ES on most AFI subscales, although both groups improved over time. MBSR produced greater Stroop accuracy rates relative to ES at T2 (r = 0.340, p = 0.005) and T3 (r = 0.280, p = 0.030), with improved accuracy over time only for the MBSR group. There were no significant differences in Stroop reaction time between groups. Improvements in mindfulness mediated the effect of group (e.g., MBSR vs. ES) on AFI total score at T2 and T3. Additional randomized trials with more comprehensive cognitive measures are warranted to definitively assess the efficacy of MBSR for CRCI. This pilot study has important implications for all cancer survivors as it is the first published trial to show that MBSR offers robust and durable improvements in CRCI.

Experimental and modeling results of creep fatigue life of Inconel 617 and Haynes 230 at 850 C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xiang; Sokolov, Mikhail A; Sham, Sam

Creep fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure formore » both materials decreased under creep fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep fatigue life. The linear damage summation could predict the creep fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep fatigue life prediction results for both materials.« less

Experimental and modeling results of creep-fatigue life of Inconel 617 and Haynes 230 at 850 °C

NASA Astrophysics Data System (ADS)

Chen, Xiang; Sokolov, Mikhail A.; Sham, Sam; Erdman, Donald L., III; Busby, Jeremy T.; Mo, Kun; Stubbins, James F.

2013-01-01

Creep-fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 °C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep-fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep-fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep-fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep-fatigue life. The linear damage summation could predict the creep-fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep-fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep-fatigue life prediction results for both materials.

Hydraulic Fatigue-Testing Machine

NASA Technical Reports Server (NTRS)

Hodo, James D.; Moore, Dennis R.; Morris, Thomas F.; Tiller, Newton G.

1987-01-01

Fatigue-testing machine applies fluctuating tension to number of specimens at same time. When sample breaks, machine continues to test remaining specimens. Series of tensile tests needed to determine fatigue properties of materials performed more rapidly than in conventional fatigue-testing machine.

Does aerobic training alleviate fatigue and improve societal participation in patients with multiple sclerosis? A randomized controlled trial

PubMed Central

Heine, Martin; Verschuren, Olaf; Hoogervorst, Erwin LJ; van Munster, Erik; Hacking, Hub GA; Visser-Meily, Anne; Twisk, Jos WR; Beckerman, Heleen; de Groot, Vincent; Kwakkel, Gert

2017-01-01

Background: Evidence supporting the effectiveness of aerobic training, specific for fatigue, in severely fatigued patients with multiple sclerosis (MS) is lacking. Objective: To estimate the effectiveness of aerobic training on MS-related fatigue and societal participation in ambulant patients with severe MS-related fatigue. Methods: Patients (N = 90) with severe MS-related fatigue were allocated to 16-week aerobic training or control intervention. Primary outcomes were perceived fatigue (Checklist Individual Strength (CIS20r) fatigue subscale) and societal participation. An improvement of ⩾8 points on the CIS20r fatigue subscale was considered clinically relevant. Outcomes were assessed by a blinded observer at baseline, 2, 4, 6 and 12 months. Results: Of the 89 patients that started treatment (median Expanded Disability Status Scale (interquartile range), 3.0 (2.0–3.6); mean CIS20r fatigue subscale (standard deviation (SD)), 42.6 (8.0)), 43 received aerobic training and 46 received the control intervention. A significant post-intervention between-group mean difference (MD) on the CIS20r fatigue subscale of 4.708 (95% confidence interval (CI) = 1.003–8.412; p = 0.014) points was found in favour of aerobic training that, however, was not sustained during follow-up. No effect was found on societal participation. Conclusion: Aerobic training in MS patients with severe fatigue does not lead to a clinically meaningful reduction in fatigue or societal participation when compared to a low-intensity control intervention. PMID:28528566

Sleep Patterns and Fatigue in New Mothers and Fathers

PubMed Central

Gay, Caryl L.; Lee, Kathryn A.; Lee, Shih-Yu

2005-01-01

The purpose of this study was to describe the sleep patterns and fatigue of both mothers and fathers before and after childbirth. The authors used wrist actigraphy and questionnaires to estimate sleep and fatigue in 72 couples during their last month of pregnancy and 1st month postpartum. Both parents experienced more sleep disruption at night during the postpartum period as compared to the last month of pregnancy. Compared to fathers, with their stable 24-h sleep patterns over time, mothers had less sleep at night and more sleep during the day after the baby was born. Sleep patterns were also related to parents’work status and type of infant feeding. Both parents self-reported more sleep disturbance and fatigue during the 1st month postpartum than during pregnancy. Mothers reported more sleep disturbance than fathers, but there was no gender difference in ratings of fatigue. At both time points, fathers obtained less total sleep than mothers when sleep was objectively measured throughout the entire 24-h day. Further research is needed to determine the duration of sleep loss for both mothers and fathers, to evaluate the effect of disrupted sleep and sleep loss on psychosocial functioning and job performance, and to develop interventions for improving sleep patterns of new parents. PMID:15068660

Effect of initial contact surface condition on the friction and wear properties of bearing steel in cyclic reciprocating sliding contact

NASA Astrophysics Data System (ADS)

Tanaka, Y.; Endo, M.; Moriyama, S.

2017-05-01

Delamination failure is one of the most important engineering problems. This failure can frequently be detrimental to rolling contact machine elements such as bearings, gear wheels, etc. This phenomenon, called rolling contact fatigue, has a close relationship not only with opening-mode but also with shear-mode fatigue crack growth. The crack face interference is known to significantly affect the shear-mode fatigue crack propagation and its threshold behavior. Quantitative investigation on friction and wear at fatigue crack faces in the material is essentially impossible. Previously, thus, a novel ring-on-ring test by making use of fatigue testing machine was proposed to simulate a cyclic reciprocating sliding contact of crack surfaces. However, this test procedure had some problems. For instance, in order to achieve the uniform contact at the start of test, the rubbing of specimens must be conducted in advance. By this treatment, the specimen surfaces were already damaged before the test. In this study, an improvement of experimental method was made to perform the test using the damage-free specimens. The friction and wear properties for heat-treated high carbon-chromium bearing steel were investigated with this new method and the results were compared to the results obtained by using the initially damaged specimens.

Ion plated gold films: Properties, tribological behavior and performance

NASA Technical Reports Server (NTRS)

Spalvins, Talivaldis

1987-01-01

The glow discharge energizing favorably modifies and controls the coating/substrate adherence and the nucleation and growth sequence of ion plated gold films. As a result the adherence, coherence, internal stresses, and morphology of the films are significantly improved. Gold ion plated films because of their graded coating/substrate interface and fine uniform densely packed microstructure not only improve the tribological properties but also induce a surface strengthening effect which improves the mechanical properties such as yield, tensile, and fatigue strength. Consequently significant improvements in the tribological performance of ion plated gold films as compared to vapor deposited gold films are shown in terms of decreased friction/wear and prolonged endurance life.

Fatigue influences lower extremity angular velocities during a single-leg drop vertical jump.

PubMed

Tamura, Akihiro; Akasaka, Kiyokazu; Otsudo, Takahiro; Shiozawa, Junya; Toda, Yuka; Yamada, Kaori

2017-03-01

[Purpose] Fatigue alters lower extremity landing strategies and decreases the ability to attenuate impact during landing. The purpose of this study was to reveal the influence of fatigue on dynamic alignment and joint angular velocities in the lower extremities during a single leg landing. [Subjects and Methods] The 34 female college students were randomly assigned to either the fatigue or control group. The fatigue group performed single-leg drop vertical jumps before, and after, the fatigue protocol, which was performed using a bike ergometer. Lower extremity kinematic data were acquired using a three-dimensional motion analysis system. The ratio of each variable (%), for the pre-fatigue to post-fatigue protocols, were calculated to compare differences between each group. [Results] Peak hip and knee flexion angular velocities increased significantly in the fatigue group compared with the control group. Furthermore, hip flexion angular velocity increased significantly between each group at 40 milliseconds after initial ground contact. [Conclusion] Fatigue reduced the ability to attenuate impact by increasing angular velocities in the direction of hip and knee flexion during landings. These findings indicate a requirement to evaluate movement quality over time by measuring hip and knee flexion angular velocities in landings during fatigue conditions.

Development of Custom 465® Corrosion-Resisting Steel for Landing Gear Applications

NASA Astrophysics Data System (ADS)

Daymond, Benjamin T.; Binot, Nicolas; Schmidt, Michael L.; Preston, Steve; Collins, Richard; Shepherd, Alan

2016-04-01

Existing high-strength low-alloy steels have been in place on landing gear for many years owing to their superior strength and cost performance. However, there have been major advances in improving the strength of high-performance corrosion-resisting steels. These materials have superior environmental robustness and remove the need for harmful protective coatings such as chromates and cadmium now on the list for removal under REACH legislation. A UK government-funded collaborative project is underway targeting a refined specification Custom 465® precipitation hardened stainless steel to replace the current material on Airbus A320 family aircraft main landing gear, a main fitting component developed by Messier-Bugatti-Dowty. This is a collaborative project between Airbus, Messier-Bugatti-Dowty, and Carpenter Technology Corporation. An extensive series of coupon tests on four production Heats of the material have been conducted, to obtain a full range of mechanical, fatigue, and corrosion properties. Custom 465® is an excellent replacement to the current material, with comparable tensile strength and fracture toughness, better ductility, and very good general corrosion and stress corrosion cracking resistance. Fatigue performance is the only significant area of deficit with respect to incumbent materials, fatigue initiation being often related to carbo-titanium-nitride particles and cleavage zones.

Validation of a Smartphone-Based Approach to In Situ Cognitive Fatigue Assessment

PubMed Central

Linden, Mark

2017-01-01

Background Acquired Brain Injuries (ABIs) can result in multiple detrimental cognitive effects, such as reduced memory capability, concentration, and planning. These effects can lead to cognitive fatigue, which can exacerbate the symptoms of ABIs and hinder management and recovery. Assessing cognitive fatigue is difficult due to the largely subjective nature of the condition and existing assessment approaches. Traditional methods of assessment use self-assessment questionnaires delivered in a medical setting, but recent work has attempted to employ more objective cognitive tests as a way of evaluating cognitive fatigue. However, these tests are still predominantly delivered within a medical environment, limiting their utility and efficacy. Objective The aim of this research was to investigate how cognitive fatigue can be accurately assessed in situ, during the quotidian activities of life. It was hypothesized that this assessment could be achieved through the use of mobile assistive technology to assess working memory, sustained attention, information processing speed, reaction time, and cognitive throughput. Methods The study used a bespoke smartphone app to track daily cognitive performance, in order to assess potential levels of cognitive fatigue. Twenty-one participants with no prior reported brain injuries took place in a two-week study, resulting in 81 individual testing instances being collected. The smartphone app delivered three cognitive tests on a daily basis: (1) Spatial Span to measure visuospatial working memory; (2) Psychomotor Vigilance Task (PVT) to measure sustained attention, information processing speed, and reaction time; and (3) a Mental Arithmetic Test to measure cognitive throughput. A smartphone-optimized version of the Mental Fatigue Scale (MFS) self-assessment questionnaire was used as a baseline to assess the validity of the three cognitive tests, as the questionnaire has already been validated in multiple peer-reviewed studies. Results The most highly correlated results were from the PVT, which showed a positive correlation with those from the prevalidated MFS, measuring 0.342 (P<.008). Scores from the cognitive tests were entered into a regression model and showed that only reaction time in the PVT was a significant predictor of fatigue (P=.016, F=2.682, 95% CI 9.0-84.2). Higher scores on the MFS were related to increases in reaction time during our mobile variant of the PVT. Conclusions The results show that the PVT mobile cognitive test developed for this study could be used as a valid and reliable method for measuring cognitive fatigue in situ. This test would remove the subjectivity associated with established self-assessment approaches and the need for assessments to be performed in a medical setting. Based on our findings, future work could explore delivering a small set of tests with increased duration to further improve measurement reliability. Moreover, as the smartphone assessment tool can be used as part of everyday life, additional sources of data relating to physiological, psychological, and environmental context could be included within the analysis to improve the nature and precision of the assessment process. PMID:28818818

Men exhibit greater fatigue resistance than women in alternated bench press and leg press exercises.

PubMed

Monteiro, Estêvão R; Steele, James; Novaes, Jefferson S; Brown, Amanda F; Cavanaugh, Mark T; Vingren, Jakob L; Behm, David G

2017-11-17

The purpose of this study was to evaluate the influence of sex, exercise order, and rest interval on neuromuscular fatigue resistance for an alternated strength training sequence of bench press (BP) and leg press (LP) exercises. Twelve women and 16 men, both recreationally trained, performed four sessions in a random order: 1) BP followed by LP with three-minutes rest (BP+LP with rest), 2) LP followed by BP with three-minutes rest (LP+BP with rest), 3) BP followed by LP without rest interval (BP+LP no rest), and 4) LP followed by BP without rest interval (LP+BP no rest). Participants performed four sets with 100% of 10RM load to concentric failure with the goal of completing the maximum number of repetitions in both exercises. The fatigue index was analyzed from the first and last sets of each exercise bout. A main effect for sex showed that women exhibited 25.5% (p=0.001) and 24.5% (p=0.001) greater BP and LP fatigue than men respectively when performing 10RM. Men exhibited greater BP (p<0.0001; 34.1%) and LP (p<0.0001; 30.5%) fatigue resistance when a rest period was provided. Men did not show an exercise order effect for BP fatigue and exhibited greater (p=0.0003; 14.5%) LP fatigue resistance when BP was performed first. The present study demonstrated the greater fatigue resistance of men when performing 10RM BP and LP exercises. Since men tend to experience less fatigue with the second exercise in the exercise pairing, women's training programs should be adjusted to ensure they do not parallel men's resistance training programs.

Investigating the Effects of Exam Length on Performance and Cognitive Fatigue

PubMed Central

Jensen, Jamie L.; Berry, Dane A.; Kummer, Tyler A.

2013-01-01

This study examined the effects of exam length on student performance and cognitive fatigue in an undergraduate biology classroom. Exams tested higher order thinking skills. To test our hypothesis, we administered standard- and extended-length high-level exams to two populations of non-majors biology students. We gathered exam performance data between conditions as well as performance on the first and second half of exams within conditions. We showed that lengthier exams led to better performance on assessment items shared between conditions, possibly lending support to the spreading activation theory. It also led to greater performance on the final exam, lending support to the testing effect in creative problem solving. Lengthier exams did not result in lower performance due to fatiguing conditions, although students perceived subjective fatigue. Implications of these findings are discussed with respect to assessment practices. PMID:23950918

Cognitive remediation training improves performance in patients with chronic fatigue syndrome.

PubMed

McBride, Richard L; Horsfield, Sarah; Sandler, Carolina X; Cassar, Joanne; Casson, Sally; Cvejic, Erin; Vollmer-Conna, Uté; Lloyd, Andrew R

2017-11-01

Neurocognitive disturbance with subjectively-impaired concentration and memory is a common, disabling symptom reported by patients with chronic fatigue syndrome (CFS). We recently reported preliminary evidence for benefits of cognitive remediation as part of an integrated cognitive-behavioral therapy (CBT)/ graded exercise therapy (GET) program. Here, we describe a contemporaneous, case-control trial evaluating the effectiveness of an online cognitive remediation training program (cognitive exercise therapy; CET) in addition to CBT/GET (n=36), compared to CBT/GET alone (n=36). The study was conducted in an academic, tertiary referral outpatient setting over 12 weeks (11 visits) with structured, home-based activities between visits. Participants self-reported standardized measures of symptom severity and functional status before and after the intervention. Those in the CET arm also completed standardized neurocognitive assessment before, and following, treatment. The addition of formal CET led to significantly greater improvements in self-reported neurocognitive symptoms compared to CBT/GET alone. Subjective improvement was predicted by CET group and lower baseline mood disturbance. In the CET group, significant improvements in objectively-measured executive function, processing speed, and working memory were observed. These subjective and objective performance improvements suggest that a computerized, home-based cognitive training program may be an effective intervention for patients with CFS, warranting randomized controlled trials. Copyright © 2017 Elsevier B.V. All rights reserved.

Dietary antioxidants and exercise.

PubMed

Powers, Scott K; DeRuisseau, Keith C; Quindry, John; Hamilton, Karyn L

2004-01-01

Muscular exercise promotes the production of radicals and other reactive oxygen species in the working muscle. Growing evidence indicates that reactive oxygen species are responsible for exercise-induced protein oxidation and contribute to muscle fatigue. To protect against exercise-induced oxidative injury, muscle cells contain complex endogenous cellular defence mechanisms (enzymatic and non-enzymatic antioxidants) to eliminate reactive oxygen species. Furthermore, exogenous dietary antioxidants interact with endogenous antioxidants to form a cooperative network of cellular antioxidants. Knowledge that exercise-induced oxidant formation can contribute to muscle fatigue has resulted in numerous investigations examining the effects of antioxidant supplementation on human exercise performance. To date, there is limited evidence that dietary supplementation with antioxidants will improve human performance. Furthermore, it is currently unclear whether regular vigorous exercise increases the need for dietary intake of antioxidants. Clearly, additional research that analyses the antioxidant requirements of individual athletes is needed.

Caffeine Reduces Reaction Time and Improves Performance in Simulated-Contest of Taekwondo

PubMed Central

Santos, Victor G. F.; Santos, Vander R. F.; Felippe, Leandro J. C.; Almeida, Jose W.; Bertuzzi, Rômulo; Kiss, Maria A. P. D. M.; Lima-Silva, Adriano E.

2014-01-01

The aim of this study was to investigate the effects of caffeine on reaction time during a specific taekwondo task and athletic performance during a simulated taekwondo contest. Ten taekwondo athletes ingested either 5 mg·kg−1 body mass caffeine or placebo and performed two combats (spaced apart by 20 min). The reaction-time test (five kicks “Bandal Tchagui”) was performed immediately prior to the first combat and immediately after the first and second combats. Caffeine improved reaction time (from 0.42 ± 0.05 to 0.37 ± 0.07 s) only prior to the first combat (P = 0.004). During the first combat, break times during the first two rounds were shorter in caffeine ingestion, followed by higher plasma lactate concentrations compared with placebo (P = 0.029 and 0.014, respectively). During the second combat, skipping-time was reduced, and relative attack times and attack/skipping ratio was increased following ingestion of caffeine during the first two rounds (all P < 0.05). Caffeine resulted in no change in combat intensity parameters between the first and second combat (all P > 0.05), but combat intensity was decreased following placebo (all P < 0.05). In conclusion, caffeine reduced reaction time in non-fatigued conditions and delayed fatigue during successive taekwondo combats. PMID:24518826

Modafinil In Debilitating fatigue After Stroke (MIDAS): study protocol for a randomised, double-blinded, placebo-controlled, crossover trial.

PubMed

Lillicrap, Thomas; Krishnamurthy, Venkatesh; Attia, John; Nilsson, Michael; Levi, Christopher R; Parsons, Mark W; Bivard, Andrew

2016-08-17

Fatigue is a common symptom in stroke survivors for which there is currently no proven therapy. Modafinil is a wakefulness-promoting agent with established benefits in other disease models. We aim to test if modafinil will improve patient's self-reported fatigue scores when compared to placebo and if therapy results in increased quality of life. MIDAS is a phase II, single-centre, prospective, double-blinded, randomised, crossover trial of modafinil for the treatment of persistent fatigue in survivors of ischaemic stroke. The inclusion criteria will require an average score of 12 or more across all domains of the Multi-dimensional Fatigue Inventory (MFI-20) and the diagnosis of a stroke more than 6 months prior. Patients will be randomised 1:1 to receive either modafinil 200 mg daily or placebo for a period of 6 weeks, after which a crossover will occur where patients who are on modafinil will begin taking placebo and vice versa. The primary outcome will be improvement in fatigue as measured by the MFI-20. Secondary outcomes will include changes in the Fatigue Severity Scale, improved cognition measured using the Montreal Cognitive Assessment, improvement in mood as determined by the Depression, Anxiety and Stress Scale and improvement in each patient's stroke-specific quality of life score. All participants will also undergo magnetic resonance imaging (MRI) at baseline, crossover and study conclusion to measure cerebral blood flow on arterial spin labelling and brain activity on resting state functional MRI. This study will comply with the CONSORT guidelines. The projected sample size requirement is 36 participants in a crossover trial giving a power of 80 % and a type-1 error rate of 0.05. MIDAS seeks to enhance the quality of life in stroke survivors by assisting or resolving stroke-associated fatigue. ACTRN12615000350527 , registered on the 17 April 2015. Protocol version 3, approved 16 June 2015.

Beneficial effects of voluntary wheel running on the properties of dystrophic mouse muscle.

PubMed

Hayes, A; Williams, D A

1996-02-01

Effects of voluntary exercise on the isometric contractile, fatigue, and histochemical properties of hindlimb dystrophic (mdx and 129ReJ dy/dy) skeletal muscles were investigated. Mice were allowed free access to a voluntary running wheel at 4 wk of age for a duration of 16 (mdx) or 5 (dy/dy) wk. Running performance of mdx mice (approximately 4 km/day at 1.6 km/h) was inferior to normal mice (approximately 6.5 km/day at 2.1 km/h). However, exercise improved the force output (approximately 15%) and the fatigue resistance of both C57BL/10 and mdx soleus muscles. These changes coincided with increased proportions of smaller type I fibers and decreased proportions of larger type IIa fibers in the mdx soleus. The extensor digitorum longus of mdx, but not of normal, mice also exhibited improved resistance to fatigue and conversion towards oxidative fiber types. The dy/dy animals were capable of exercising, yet ran significantly less than normal animals (approximately 0.5 km/day). Despite this, running increased the force output of the plantaris muscle (approximately 50%). Taken together, the results showed that exercise can have beneficial effects on dystrophic skeletal muscles.

Armodafinil for fatigue associated with menopause: an open-label trial.

PubMed

Meyer, Fremonta; Freeman, Marlene P; Petrillo, Laura; Barsky, Maria; Galvan, Thania; Kim, Semmie; Cohen, Lee; Joffe, Hadine

2016-02-01

This study aims to obtain preliminary data on the efficacy of armodafinil for improving menopause-related fatigue and quality of life. Women (aged 40-65 y) experiencing menopause-related fatigue received open-label armodafinil therapy (up to 150 mg/d) for 4 weeks. Changes from baseline in Brief Fatigue Inventory score and Menopause-Specific Quality of Life (MENQOL) physical domain score were examined using the Wilcoxon signed rank test. Exploratory analyses examined the effects of armodafinil on hot flashes, overall quality of life, insomnia, depression, anxiety, and perceived cognitive performance. After open-label treatment, participants were randomized to double-blind continuation of armodafinil versus placebo for 2 weeks to examine whether treatment discontinuation would precipitate symptom recurrence. Of 29 eligible participants, 20 women (69.0%) completed the trial. During treatment with armodafinil (mean dose, 120 mg/d), median Brief Fatigue Inventory scores decreased by 57.7% from 5.2 (interquartile range [IQR], 4.6-6.2) to 2.2 (IQR, 1.1-4.4; P = 0.0002), and median MENQOL physical domain scores decreased by 51.3% from 3.9 (IQR, 2.3-4.8) to 1.9 (IQR, 1.3-2.7; P = 0.0001). Median hot flashes for 24 hours decreased by 48.3% from 2.9 (IQR, 1.1-4.6) to 1.5 (IQR, 0.4-2.4; P = 0.0005). Improvements in MENQOL total score (49%; P = 0.0001), cognitive function (59.2%; P = 0.0002), depressive symptoms (64.7%; P = 0.0006), insomnia (72.7%; P = 0.0012), and excessive sleepiness (57.1%; P = 0.0006) were noted. Randomized continuation (n = 10) or discontinuation (n = 10) did not indicate group differences. Armodafinil was well-tolerated; three women (12%) were withdrawn for adverse events. These preliminary results suggest a therapeutic effect of armodafinil on fatigue affecting quality of life during menopause, and a potential benefit for other menopause-related symptoms.

Effects of a dance-based aquatic exercise program in obese postmenopausal women with knee osteoarthritis: a randomized controlled trial.

PubMed

Casilda-López, Jesús; Valenza, Marie Carmen; Cabrera-Martos, Irene; Díaz-Pelegrina, Ana; Moreno-Ramírez, Maria Paz; Valenza-Demet, Gerald

2017-07-01

To evaluate the effects of a dance-based aquatic exercise program on functionality, cardiorespiratory capacity, postexercise heart rate, and fatigue in obese postmenopausal women with knee osteoarthritis. A randomized controlled trial was performed. In all, 34 obese women diagnosed with knee osteoarthritis participated. Women were randomly allocated to an experimental group (n = 17) or a control group (n = 17). Participants in the experimental group were included in an 8-week dance-based aquatic exercise program conducted in community swimming pools. Those in the control group underwent a global aquatic exercise program. The primary outcome measure was functionality assessed with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Secondary outcomes were cardiorespiratory capacity evaluated with the 6-minute walk test, and postexercise heart rate and fatigue assessed using a visual analog scale. Variables were measured at baseline, after the intervention, and at 3-month follow-up. A between-group analysis showed significant postintervention differences in functionality (aggregate postintervention WOMAC score of 37.30 ± 16.61 vs 41.83 ± 13.69; P = 0.048) in favor of the experimental group. In addition, significant between-group differences were found after the 8 weeks in cardiorespiratory capacity, postexercise heart rate, and fatigue. Follow-up continued to show significant differences between groups in function (aggregate WOMAC score of 38.60 ± 13.61 vs 42.60 ± 9.05; P = 0.038), postexercise heart rate, and fatigue. An 8-week dance-based exercise program significantly improved function and cardiorespiratory capacity, and decreased postexercise heart rate and fatigue. Most of these improvements were maintained at 3-month follow-up in obese postmenopausal women.

The effect of modafinil on fatigue, cognitive functioning, and mood in primary brain tumor patients: a multicenter randomized controlled trial

PubMed Central

Boele, Florien W.; Douw, Linda; de Groot, Marjolein; van Thuijl, Hinke F.; Cleijne, Wilmy; Heimans, Jan J.; Taphoorn, Martin J.B.; Reijneveld, Jaap C.; Klein, Martin

2013-01-01

Background Fatigue, cognitive deficits, and depression are frequently reported but often undertreated symptoms that can profoundly affect daily life in patients with primary brain tumors (PBTs). To evaluate the effects of the psychostimulant modafinil on fatigue, depression, health-related quality of life (HRQOL), and cognitive functioning in PBT patients, we performed a multicenter, double-blind placebo-controlled crossover trial. Methods Patients randomly received either 6 weeks of treatment with modafinil (up to 400 mg/day) or 6 weeks with placebo. After a 1-week washout period, the opposite treatment was provided. Assessments took place at baseline and immediately after the first and second condition. Patients completed self-report questionnaires on fatigue (Checklist Individual Strength [CIS]), depression (Center for Epidemiologic Studies Depression Scale [CES-D]), HRQOL (Short-Form Health Survey [SF-36]), and self-perceived cognitive functioning (Medical Outcomes Study [MOS]). They also underwent comprehensive neurocognitive testing. Results In total, 37 patients participated. Relative to baseline, patients reported lower fatigue severity (CIS) and better motivation (CIS) in both the modafinil (P = .010 and P = .021, respectively) and the placebo condition (P < .001 and P = .027, respectively). The same held for physical health (SF-36 Physical Component Summary score; P = .001 and P = .008, respectively), working memory (P = .040 and P = .043), and information processing capacity (P = .036 and P = .040). No improvement in depressive symptoms was found in either condition. Conclusions Modafinil did not exceed the effects of placebo with respect to symptom management. Patient accrual was slow, and relatively many patients dropped out during the trial, due mostly to side effects. Other, preferably nonpharmacologic intervention studies should be considered to improve symptom management of PBT patients. PMID:23925452

An interventional approach for patient and nurse safety: a fatigue countermeasures feasibility study.

PubMed

Scott, Linda D; Hofmeister, Nancee; Rogness, Neal; Rogers, Ann E

2010-01-01

Studies indicate that extended shifts worked by hospital staff nurses are associated with higher risk of errors. Long work hours coupled with insufficient sleep and fatigue are even riskier. Although other industries have developed programs to reduce fatigue-related errors and injury, fatigue countermeasures program for nurses (FCMPN) are lacking. The objective of this study was to evaluate the feasibility of an FCMPN for improving sleep duration and quality while reducing daytime sleepiness and patient care errors. Selected sleep variables, errors and drowsy driving, were evaluated among hospital staff nurses (n = 47) before and after FCMPN implementation. A one-group pretest-posttest repeated-measures approach was used. Participants provided data 2 weeks before the FCMPN, 4 weeks after receiving the intervention, and again at 3 months after intervention. Most of the nurses experienced poor sleep quality, severe daytime sleepiness, and decreased alertness at work and while operating a motor vehicle. After the FCMPN, significant improvements were noted in sleep duration, sleep quality, alertness, and error prevention. Although significant improvements were not found in daytime sleepiness scores, severity of daytime sleepiness appeared to decrease. Despite improvements in fatigue management, nurses reported feelings of guilt when engaging in FCMPN activities, especially strategic naps and relieved breaks. Initial findings support the feasibility of using an FCMPN for mitigating fatigue, improving sleep, and reducing errors among hospital staff nurses. In future investigations, the acceptability, efficacy, and effectiveness of FCMPNs can be examined.

Assessment of gait parameters and fatigue in MS patients during inpatient rehabilitation: a pilot trial.

PubMed

Sacco, Rosaria; Bussman, Rita; Oesch, Peter; Kesselring, Jürg; Beer, Serafin

2011-05-01

Gait impairment and fatigue are common and disabling problems in multiple sclerosis (MS). Characterisation of abnormal gait in MS patients has been done mainly using observational studies and simple walking tests providing only limited quantitative and no qualitative data, or using intricate and time-consuming assessment procedures. In addition, the correlation of gait impairments with fatigue is largely unknown. The aim of this study was to characterise spatio-temporal gait parameters by a simple and easy-to-use gait analysis system (GAITRite®) in MS patients compared with healthy controls, and to analyse changes and correlation with fatigue during inpatient rehabilitation. Twenty-four MS patients (EDSS <6.5) admitted for inpatient rehabilitation and 19 healthy subjects were evaluated using the GAITRite® Functional Ambulation System. Between-group differences and changes of gait parameters during inpatient rehabilitation were analysed, and correlation with fatigue, using the Wurzburg Fatigue Inventory for Multiple Sclerosis (WEIMuS), was determined. Compared to healthy controls MS patients showed significant impairments in different spatio-temporal gait parameters, which showed a significant improvement during inpatient rehabilitation. Different gait parameters were correlated with fatigue physical score, and change of gait parameters was correlated with improvement of fatigue. Spatio-temporal gait analysis is helpful to assess specific walking impairments in MS patients and subtle changes during rehabilitation. Correlation with fatigue may indicate a possible negative impact of fatigue on rehabilitation outcome.

Improving Fatigue Strength of polymer concrete using nanomaterials.

DOT National Transportation Integrated Search

2016-11-30

Polymer concrete (PC) is that type of concrete where the cement binder is replaced with polymer. PC is often used to improve friction and protect structural substrates in reinforced concrete and orthotropic steel bridges. However, its low fatigue per...

Evaluation of multidimensional COPD-related subjective fatigue following a pulmonary rehabilitation programme.

PubMed

Lewko, Agnieszka; Bidgood, Penelope L; Jewell, Andy; Garrod, Rachel

2014-01-01

Subjective fatigue has been recognised as an important, multi-component symptom in COPD. Pulmonary Rehabilitation (PR) improves fatigue component of the Chronic Respiratory Questionnaire, a quality of life (QoL) measure. However, it is not clear if all fatigue dimensions are affected equally. This study aims to evaluate changes in subjective multidimensional fatigue among people with COPD who participated in PR. Thirty seven stable COPD patients were recruited; 23 patients (15 male) mean age 68.5 (range 49-86) yrs, mean (SD) %predicted FEV1 45.3 (19.8); completed 7 weeks of PR. Assessments (pre and post PR) consisted of the Multidimensional Fatigue Inventory (MFI-20), QoL (SGRQ), Anxiety and Depression (HADS), the London Chest Activity of Daily Living Scale (LCADL), muscle strength, incremental (ISWT) and endurance (ESWT) shuttle walk tests. The differences between pre and post PR fatigue were tested using Wilcoxon's test and relationships with other outcomes were examined using Spearman's correlation. There were statistically significant improvements in Reduced Activity (RA) (p = 0.01), General (GF) (p < 0.01) and Physical Fatigue (PF) (p = 0.03) components of MFI-20 after PR, but there were no differences in Motivation or Mental Fatigue (p > 0.05). There were significant improvements in ISWT (p < 0.05), ESWT (p < 0.01) and muscle strength (p = 0.03). Statistically significant correlations (p < 0.05) were found between changes in GF and in both ISWT (r = -0.43) and SGRQ impact (r = 0.46); and between RA and ESWT changes (r = -0.45). Some dimensions of fatigue in COPD are modifiable by a 7-week PR programme. Change in fatigue dimensions in COPD may be associated with a change in maximal or endurance walking distances or QoL. Copyright © 2013 Elsevier Ltd. All rights reserved.

Driver fatigue alarm based on eye detection and gaze estimation

NASA Astrophysics Data System (ADS)

Sun, Xinghua; Xu, Lu; Yang, Jingyu

2007-11-01

The driver assistant system has attracted much attention as an essential component of intelligent transportation systems. One task of driver assistant system is to prevent the drivers from fatigue. For the fatigue detection it is natural that the information about eyes should be utilized. The driver fatigue can be divided into two types, one is the sleep with eyes close and another is the sleep with eyes open. Considering that the fatigue detection is related with the prior knowledge and probabilistic statistics, the dynamic Bayesian network is used as the analysis tool to perform the reasoning of fatigue. Two kinds of experiments are performed to verify the system effectiveness, one is based on the video got from the laboratory and another is based on the video got from the real driving situation. Ten persons participate in the test and the experimental result is that, in the laboratory all the fatigue events can be detected, and in the practical vehicle the detection ratio is about 85%. Experiments show that in most of situations the proposed system works and the corresponding performance is satisfying.

The influence of stimulants, sedatives, and fatigue on tunnel vision: risk factors for driving and piloting.

PubMed

Mills, K C; Spruill, S E; Kanne, R W; Parkman, K M; Zhang, Y

2001-01-01

A computerized task was used in two studies to examine the influence of stimulants, sedatives, and fatigue on single-target and divided-attention responses in different parts of the visual field. The drug effects were evaluated over time with repeated behavioral and subjective measures against ascending and descending drug levels. In the first study, 18 fully rested participants received placebo, alprazolam (0.5 mg), and dextroamphetamine (10 mg). Alprazolam impairs performance, whereas dextroamphetamine induces enhancement and tunnel vision. Study 2 exposed 32 participants to fatigue and no fatigue with a repeated-measures crossover design. Four independent groups subsequently received placebo, dextroamphetamine (10 mg), caffeine (250 mg), or alcohol (.07%). Under fatigue, stimulants have no performance-enhancing effects, whereas impairment from alcohol is severe. Under no fatigue, alcohol has a modest effect, caffeine has no effect, and dextroamphetamine significantly enhances divided-attention performance coincident with tunnel vision. Participants rate all drug effects more stimulating and less sedating while fatigued. Implications for transportation safety are discussed. Actual or potential applications of this research include driver and pilot training.

Analysis of Railroad Car Truck and Wheel Fatigue : Part 1. Service Load Data and Procedures for the Development of Fatigue Performance Criteria.

DOT National Transportation Integrated Search

1975-05-01

The development of fatigue performance standards for freight car truck components and wheels requires a knowledge of the fluctuation service load environment, and a basis for stating the conservatism of the design with respect to the environment. On ...

A randomised control trial of walking to ameliorate brain injury fatigue: a NIDRR TBI model system centre-based study.

PubMed

Kolakowsky-Hayner, Stephanie A; Bellon, Kimberly; Toda, Ketra; Bushnik, Tamara; Wright, Jerry; Isaac, Linda; Englander, Jeffrey

2017-10-01

Fatigue is one of the most commonly reported sequelae after traumatic brain injury (TBI). This study evaluated the impact of a graduated physical activity programme on fatigue after TBI. Using a prospective randomised single-blind crossover design, 123 individuals with TBI, over the age of 18, were enrolled. Interventions included a home-based walking programme utilising a pedometer to track daily number of steps at increasing increments accompanied by tapered coaching calls over a 12-week period. Nutritional counselling with the same schedule of coaching calls served as the control condition. Main outcome measures included: the Global Fatigue Index (GFI), the Barrow Neurological Institute (BNI) Fatigue Scale Overall Severity Index Score, and the Multidimensional Fatigue Inventory (MFI). Step counts improved over time regardless of group assignment. The walking intervention led to a decrease in GFI, BNI Total, and MFI General scores. Participants reported less fatigue at the end of the active part of the intervention (24 weeks) and after a wash out period (36 weeks) as measured by the BNI Overall. The study suggests that walking can be used as an efficient and cost-effective tool to improve fatigue in persons who have sustained a TBI.

Mission-based Scenario Research: Experimental Design And Analysis

DTIC Science & Technology

2012-01-01

neurotechnologies called Brain-Computer Interaction Technologies. 15. SUBJECT TERMS neuroimaging, EEG, task loading, neurotechnologies , ground... neurotechnologies called Brain-Computer Interaction Technologies. INTRODUCTION Imagine a system that can identify operator fatigue during a long-term...BCIT), a class of neurotechnologies , that aim to improve task performance by incorporating measures of brain activity to optimize the interactions

[Effect of fatigue on the fitness to drive].

PubMed

Makowiec-Dabrowska, Teresa; Bortkiewicz, Alicja; Siedlecka, Jadwiga; Gadzicka, Elzbieta

2011-01-01

The 1995 U.S. Department of Transportation files contain a statement that driver fatigue has been a major problem among road vehicle professional drivers, while the consequences of participation in public road traffic of drivers affected by fatigue represent a serious threat to the public safety. Therefore, studies on the causes and consequences of fatigue in drivers are of significant practical value. The authors of this work discuss definitions of fatigue and fatigue classifications relative to the location of the functional changes (physical and mental fatigue, general and local - muscular, ocular, auditory) and relative to intensity (acute, sub-acute, chronic fatigue and weariness), and duration Particular attention has been paid to the factors contributing to fatigue in drivers. These may be classified into two groups: 1. sleep-related (SR), i.e. cumulative sleep deficit, long wake time, and time of the day; 2. task-related (TR), i.e. factors related with vehicle driving and working (driving) time. Studies on the effect of fatigue on driving performance (longer reaction time, poorer vigilance, slower information processing, impaired recent memory) have been analyzed. The major effect of driver fatigue is that he/she becomes gradually diverted from the road and road traffic, with the resultant poorer driving performance. Thus, the effects of fatigue in a driver are comparable to those after alcohol intake. This paper also discusses the methods used to counteract and prevent fatigue.

[Effects of physical exercise in a population with systemic lupus erythematosus: A systematic review].

PubMed

Ayán, C; de Pedro-Múñez, A; Martínez-Lemos, I

2018-04-01

This systematic review was aimed at analysing the existing scientific evidence regarding the effects of physical exercise on the symptomatology, disease activity, and fitness level in a population with systemic lupus erythematosus. Following the PRISMA checklist, a search was carried out on PubMed, PEDro, and Sportdiscus databases. The PEDro and MINORS checklists were used in order to identify the methodological quality of the studies selected. A total of 14 studies were found, of which 10 were randomised controlled trials, and 4 were comparative studies. The performance of physical exercise led to significant improvements in fitness and fatigue. No adverse effects were registered. None of the studies found reported positive effects on the disease activity. The obtained results imply that the performance of physical exercise is safe for people with systemic lupus erythematosus, although its benefits are reduced mainly to improvements in their fitness and perceived level of fatigue. Copyright © 2018 Sociedad Española de Médicos de Atención Primaria (SEMERGEN). Publicado por Elsevier España, S.L.U. All rights reserved.

Linking asphalt binder fatigue to asphalt mixture fatigue performance using viscoelastic continuum damage modeling

NASA Astrophysics Data System (ADS)

Safaei, Farinaz; Castorena, Cassie; Kim, Y. Richard

2016-08-01

Fatigue cracking is a major form of distress in asphalt pavements. Asphalt binder is the weakest asphalt concrete constituent and, thus, plays a critical role in determining the fatigue resistance of pavements. Therefore, the ability to characterize and model the inherent fatigue performance of an asphalt binder is a necessary first step to design mixtures and pavements that are not susceptible to premature fatigue failure. The simplified viscoelastic continuum damage (S-VECD) model has been used successfully by researchers to predict the damage evolution in asphalt mixtures for various traffic and climatic conditions using limited uniaxial test data. In this study, the S-VECD model, developed for asphalt mixtures, is adapted for asphalt binders tested under cyclic torsion in a dynamic shear rheometer. Derivation of the model framework is presented. The model is verified by producing damage characteristic curves that are both temperature- and loading history-independent based on time sweep tests, given that the effects of plasticity and adhesion loss on the material behavior are minimal. The applicability of the S-VECD model to the accelerated loading that is inherent of the linear amplitude sweep test is demonstrated, which reveals reasonable performance predictions, but with some loss in accuracy compared to time sweep tests due to the confounding effects of nonlinearity imposed by the high strain amplitudes included in the test. The asphalt binder S-VECD model is validated through comparisons to asphalt mixture S-VECD model results derived from cyclic direct tension tests and Accelerated Loading Facility performance tests. The results demonstrate good agreement between the asphalt binder and mixture test results and pavement performance, indicating that the developed model framework is able to capture the asphalt binder's contribution to mixture fatigue and pavement fatigue cracking performance.

Effects of local and widespread muscle fatigue on movement timing.

PubMed

Cowley, Jeffrey C; Dingwell, Jonathan B; Gates, Deanna H

2014-12-01

Repetitive movements can cause muscle fatigue, leading to motor reorganization, performance deficits, and/or possible injury. The effects of fatigue may depend on the type of fatigue task employed, however. The purpose of this study was to determine how local fatigue of a specific muscle group versus widespread fatigue of various muscle groups affected the control of movement timing. Twenty healthy subjects performed an upper extremity low-load work task similar to sawing for 5 continuous minutes both before and after completing a protocol that either fatigued all the muscles used in the task (widespread fatigue) or a protocol that selectively fatigued the primary muscles used to execute the pushing stroke of the sawing task (localized fatigue). Subjects were instructed to time their movements with a metronome. Timing error, movement distance, and speed were calculated for each movement. Data were then analyzed using a goal-equivalent manifold approach to quantify changes in goal-relevant and non-goal-relevant variability. We applied detrended fluctuation analysis to each time series to quantify changes in fluctuation dynamics that reflected changes in the control strategies used. After localized fatigue, subjects made shorter, slower movements and exerted greater control over non-goal-relevant variability. After widespread fatigue, subjects exerted less control over non-goal-relevant variability and did not change movement patterns. Thus, localized and widespread muscle fatigue affected movement differently. Local fatigue may reduce the available motor solutions and therefore cause greater movement reorganization than widespread muscle fatigue. Subjects altered their control strategies but continued to achieve the timing goal after both fatigue tasks.

Developing measures of fatigue using an alcohol comparison to validate the effects of fatigue on performance.

PubMed

Williamson, A M; Feyer, A M; Mattick, R P; Friswell, R; Finlay-Brown, S

2001-05-01

The effects of 28 h of sleep deprivation were compared with varying doses of alcohol up to 0.1% blood alcohol concentration (BAC) in the same subjects. The study was conducted in the laboratory. Twenty long-haul truck drivers and 19 people not employed as professional drivers acted as subjects. Tests were selected that were likely to be affected by fatigue, including simple reaction time, unstable tracking, dual task, Mackworth clock vigilance test, symbol digit coding, visual search, sequential spatial memory and logical reasoning. While performance effects were seen due to alcohol for all tests, sleep deprivation affected performance on most tests, but had no effect on performance on the visual search and logical reasoning tests. Some tests showed evidence of a circadian rhythm effect on performance, in particular, simple reaction time, dual task, Mackworth clock vigilance, and symbol digit coding, but only for response speed and not response accuracy. Drivers were slower but more accurate than controls on the symbol digit test, suggesting that they took a more conservative approach to performance of this test. This study demonstrated which tests are most sensitive to sleep deprivation and fatigue. The study therefore has established a set of tests that can be used in evaluations of fatigue and fatigue countermeasures.

Evaluation of a functional medicine approach to treating fatigue, stress, and digestive issues in women.

PubMed

Cutshall, Susanne M; Bergstrom, Larry R; Kalish, Daniel J

2016-05-01

Fatigue, stress, and digestive disorders are common among adults, especially women. We conducted a 28-week pilot study to assess the efficacy of a functional medicine approach to improving stress, energy, fatigue, digestive issues, and quality of life in middle-aged women. Findings showed significant improvements in many stress, fatigue, and quality-of-life measures. The treatment program increased mean salivary dehydroepiandrosterone levels and the cortisol-dehydroepiandrosterone ratio. Stool sample analyses suggested that these treatments reduced Helicobacter pylori infections. This study suggests that functional medicine may be an effective approach to managing stress and gastrointestinal symptoms. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impact of physical activity on fatigue and quality of life in people with advanced lung cancer: a randomized controlled trial.

PubMed

Dhillon, H M; Bell, M L; van der Ploeg, H P; Turner, J D; Kabourakis, M; Spencer, L; Lewis, C; Hui, R; Blinman, P; Clarke, S J; Boyer, M J; Vardy, J L

2017-08-01

Physical activity (PA) improves fatigue and quality of life (QOL) in cancer survivors. Our aim was to assess whether a 2-month PA intervention improves fatigue and QOL for people with advanced lung cancer. Participants with advanced lung cancer, Eastern Cooperative Oncology Group performance status (PS) ≤2, >6 months life expectancy, and ability to complete six-min walk test, were stratified (disease stage, PS 0-1 versus 2, centre) and randomized (1:1) in an open-label study to usual care (UC) (nutrition and PA education materials) or experimental intervention (EX): UC plus 2-month supervised weekly PA and behaviour change sessions. Assessments occurred at baseline, 2, 4, and 6 months. The primary endpoint was fatigue [Functional Assessment of Cancer Therapy-Fatigue (FACT-F) questionnaire] at 2 months. The study was designed to detect a difference in mean FACT-F subscale score of 6. Analysis was intention-to-treat using linear mixed models. We recruited 112 patients: 56 (50.4%) were randomized to EX, 55(49.5%) to UC; 1 ineligible. Male 55%; median age 64 years (34-80); 106 (96%) non-small cell lung cancer; 106 (95.5%) stage IV. At 2, 4 and 6 months, 90, 73 and 62 participants were assessed, respectively, with no difference in attrition between groups. There were no significant differences in fatigue between the groups at 2, 4 or 6 months: mean scores at 2 months EX 37.5, UC 36.4 (difference 1.2, 95% CI - 3.5, 5.8, P = 0.62). There were no significant differences in QOL, symptoms, physical or functional status, or survival. Adherence to the intervention was good but the intervention group did not increase their PA enough compared to the control group, and no difference was seen in fatigue or QOL. Australian New Zealand Clinical Trials Registry No. ACTRN12609000971235. © The Author 2017. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Low visual information-processing speed and attention are predictors of fatigue in elementary and junior high school students

PubMed Central

2011-01-01

Background Fatigue is a common complaint among elementary and junior high school students, and is known to be associated with reduced academic performance. Recently, we demonstrated that fatigue was correlated with decreased cognitive function in these students. However, no studies have identified cognitive predictors of fatigue. Therefore, we attempted to determine independent cognitive predictors of fatigue in these students. Methods We performed a prospective cohort study. One hundred and forty-two elementary and junior high school students without fatigue participated. They completed a variety of paper-and-pencil tests, including list learning and list recall tests, kana pick-out test, semantic fluency test, figure copying test, digit span forward test, and symbol digit modalities test. The participants also completed computerized cognitive tests (tasks A to E on the modified advanced trail making test). These cognitive tests were used to evaluate motor- and information-processing speed, immediate and delayed memory function, auditory and visual attention, divided and switching attention, retrieval of learned material, and spatial construction. One year after the tests, a questionnaire about fatigue (Japanese version of the Chalder Fatigue Scale) was administered to all the participants. Results After the follow-up period, we confirmed 40 cases of fatigue among 118 students. In multivariate logistic regression analyses adjusted for grades and gender, poorer performance on visual information-processing speed and attention tasks was associated with increased risk of fatigue. Conclusions Reduced visual information-processing speed and poor attention are independent predictors of fatigue in elementary and junior high school students. PMID:21672212

Muscle fatigue effects can be anticipated to reproduce a movement kinematics learned without fatigue.

PubMed

Monjo, Florian; Forestier, Nicolas

2016-12-17

Muscle fatigue modifies the gain between motor command magnitude and the mechanical muscular response. In other words, post-fatigue, central drives to the muscles must increase to maintain a particular submaximum mechanical output. In this study, we tested the hypothesis that this modified gain can be predicted by the central nervous system (CNS) during discrete ballistic movements. In two separate experiments, subjects were required to perform shoulder flexions in standing and sitting positions at submaximum target peak accelerations. They were assisted with visual feedback informing them on their performance after each trial. Shoulder flexions were performed before and after fatiguing protocols of the focal muscles. Acceleration signals, focal and postural muscle electromyograms (EMGs) were recorded. The results demonstrated that participants were able to reach with precision the target acceleration during the first movements post-fatigue at the cost of significant increase in focal motor command magnitude. Decreased variance of peak accelerations associated with increased focal command variability was observed post-fatigue. During the standing experiment, postural muscle EMGs revealed that anticipatory postural adjustments (APAs) scaled to focal movement acceleration post-fatigue. All these results support that fatigue effects are taken into account during movement planning. Indeed, given that no feedback could enable participants to adjust acceleration during movement, this capacity to anticipate fatigue effects is the exclusive result of feedforward processes. To account for this prediction capacity, we discuss the role of fatigue-related modifications in sensory inputs from the working muscles. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Low visual information-processing speed and attention are predictors of fatigue in elementary and junior high school students.

PubMed

Mizuno, Kei; Tanaka, Masaaki; Fukuda, Sanae; Yamano, Emi; Shigihara, Yoshihito; Imai-Matsumura, Kyoko; Watanabe, Yasuyoshi

2011-06-14

Fatigue is a common complaint among elementary and junior high school students, and is known to be associated with reduced academic performance. Recently, we demonstrated that fatigue was correlated with decreased cognitive function in these students. However, no studies have identified cognitive predictors of fatigue. Therefore, we attempted to determine independent cognitive predictors of fatigue in these students. We performed a prospective cohort study. One hundred and forty-two elementary and junior high school students without fatigue participated. They completed a variety of paper-and-pencil tests, including list learning and list recall tests, kana pick-out test, semantic fluency test, figure copying test, digit span forward test, and symbol digit modalities test. The participants also completed computerized cognitive tests (tasks A to E on the modified advanced trail making test). These cognitive tests were used to evaluate motor- and information-processing speed, immediate and delayed memory function, auditory and visual attention, divided and switching attention, retrieval of learned material, and spatial construction. One year after the tests, a questionnaire about fatigue (Japanese version of the Chalder Fatigue Scale) was administered to all the participants. After the follow-up period, we confirmed 40 cases of fatigue among 118 students. In multivariate logistic regression analyses adjusted for grades and gender, poorer performance on visual information-processing speed and attention tasks was associated with increased risk of fatigue. Reduced visual information-processing speed and poor attention are independent predictors of fatigue in elementary and junior high school students. © 2011 Mizuno et al; licensee BioMed Central Ltd.

Recent Niobium Developments for High Strength Steel Energy Applications

NASA Astrophysics Data System (ADS)

Jansto, Steven G.

Niobium-containing high strength steel materials have been developed for oil and gas pipelines, offshore platforms, nuclear plants, boilers and alternative energy applications. Recent research and the commercialization of alternative energy applications such as windtower structural supports and power transmission gear components provide enhanced performance. Through the application of these Nb-bearing steels in demanding energy-related applications, the designer and end user experience improved toughness at low temperature, excellent fatigue resistance and fracture toughness and excellent weldability. These enhancements provide structural engineers the opportunity to further improve the structural design and performance. For example, through the adoption of these Nb-containing structural materials, several design-manufacturing companies are initiating new windtower designs operating at higher energy efficiency, lower cost, and improved overall material design performance.