Fatigue and fatigability in neurologic illnesses: proposal for a unified taxonomy

Protocol for a phase II, monocentre, double-blind, placebo-controlled, cross-over trial to assess efficacy of pyridostigmine in patients with spinal muscular atrophy types 2-4 (SPACE trial)

INTRODUCTION

Hereditary proximal spinal muscular atrophy (SMA) is caused by homozygous loss of function of the survival motor neuron 1 gene. The main characteristic of SMA is degeneration of alpha motor neurons in the anterior horn of the spinal cord, but recent studies in animal models and patients have shown additional anatomical abnormalities and dysfunction of the neuromuscular junction (NMJ). NMJ dysfunction could contribute to symptoms of weakness and fatigability in patients with SMA. We hypothesise that pyridostigmine, an acetylcholinesterase inhibitor that improves neuromuscular transmission, could improve NMJ function and thereby muscle strength and fatigability in patients with SMA.

METHODS AND ANALYSIS

We designed a monocentre, placebo-controlled, double-blind cross-over trial with pyridostigmine and placebo to investigate the effect and efficacy of pyridostigmine on muscle strength and fatigability in patients with genetically confirmed SMA. We aim to include 45 patients with SMA types 2-4, aged 12 years and older in the Netherlands. Participants receive 8 weeks of treatment with pyridostigmine and 8 weeks of treatment with placebo in a random order separated by a washout period of 1 week. Treatment allocation is double blinded. Treatment dose will gradually be increased from 2 mg/kg/day to the maximum dose of 6 mg/kg/day in four daily doses, in the first week of each treatment period. The primary outcome measures are a change in the Motor Function Measure and repeated nine-hole peg test before and after treatment. Secondary outcome measures are changes in recently developed endurance tests, that is, the endurance shuttle nine-hole peg test, the endurance shuttle box and block test and the endurance shuttle walk test, muscle strength, level of daily functioning, quality of and activity in life, perceived fatigue and fatigability, presence of decrement on repetitive nerve stimulation and adverse events.

ETHICS AND DISSEMINATION

The protocol is approved by the local medical ethical review committee at the University Medical Center Utrecht and by the national Central Committee on Research Involving Human Subjects. Findings will be shared with the academic and medical community, funding and patient organisations in order to contribute to optimisation of medical care and quality of life for patients with SMA.

TRIAL REGISTRATION NUMBER

NCT02941328.

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

Background and purpose

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.

Methods

Patients with an aneurysmal SAH (aSAH) or angiographically negative SAH (anSAH) were assessed 3–10 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. Between‐group comparisons and binary logistic regression analysis were performed.

Results

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 χ² = 52.99, P < 0.001; Nagelkerke R² = 0.32).

Conclusions

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.

Tailored exercise interventions to reduce fatigue in cancer survivors: study protocol of a randomized controlled trial

Background

Cancer-related fatigue (CRF) is a common and distressing symptom of cancer and/or cancer treatment that persists for years after treatment completion in approximately one third of cancer survivors. Exercise is beneficial for the management of CRF, and general exercise guidelines for cancer survivors are available. There are multiple potential pathways by which exercise improves CRF, and cancer survivors with CRF are diverse with respect to cancer type, treatments and experienced side effects. While the general exercise guidelines are likely sufficient for most cancer survivors, tailoring of exercise interventions may be more effective in those with persistent fatigue. The primary aim of this research is to investigate the effect of a traditional vs. tailored exercise intervention on CRF severity in cancer survivors with persistent CRF.

Methods/design

Cancer survivors (≥ 3 months and ≤ 5 years since primary treatment) who score ≤ 34 on the Functional Assessment of Chronic Illness Therapy Fatigue Scale (FACIT-F) will be randomly allocated to one of two parallel treatment arms: traditional (active control) and tailored exercise. Participants in the traditional exercise group will engage in aerobic and resistance exercise that is consistent with exercise guidelines for cancer survivors. The tailored exercise group will be prescribed an intervention designed to address individual deficits identified at baseline, such as loss of muscular strength, cardiorespiratory deconditioning or sleep disturbance. Participants will be assessed before and after the intervention for CRF severity and other patient-reported outcomes, neuromuscular function and fatigue in response to whole-body exercise, sleep quantity and quality, physical activity levels, cardiorespiratory fitness and blood biomarkers.

Discussion

To our knowledge, this will be the first study to compare the effects of a traditional vs. tailored exercise intervention on CRF severity in cancer survivors with persistent CRF. Using physiological, behavioural and patient-reported outcomes, this study will add to the current knowledge about both the factors contributing to CRF, and the potential reduction in CRF severity with an exercise intervention.

Trial registration

The study is registered at ClinicalTrials.gov (NCT03049384), February, 2017.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4668-z) contains supplementary material, which is available to authorized users.

The neurobiology of interoception in health and disease

Interoception is the sensing of internal bodily sensations. Interoception is an umbrella term that encompasses (1) the afferent (body-to-brain) signaling through distinct neural and humoral (including immune and endocrine) channels; (2) the neural encoding, representation, and integration of this information concerning internal bodily state; (3) the influence of such information on other perceptions, cognitions, and behaviors; (4) and the psychological expression of these representations as consciously accessible physical sensations and feelings. Interoceptive mechanisms ensure physiological health through the cerebral coordination of homeostatic reflexes and allostatic responses that include motivational behaviors and associated affective and emotional feelings. Furthermore, the conscious, unitary sense of self in time and space may be grounded in the primacy and lifelong continuity of interoception. Body-to-brain interactions influence physical and mental well-being. Consequently, we show that systematic investigation of how individual differences, and within-individual changes, in interoceptive processing can contribute to the mechanistic understanding of physical and psychological disorders. We present a neurobiological overview of interoception and describe how interoceptive impairments at different levels relate to specific physical and mental health conditions, including sickness behaviors and fatigue, depression, eating disorders, autism, and anxiety. We frame these findings in an interoceptive predictive processing framework and highlight potential new avenues for treatments.

6-minute walk test as a measure of disease progression and fatigability in a cohort of individuals with RYR1-related myopathies

Background

RYR1-related Myopathies (RYR1-RM) comprise a group of rare neuromuscular diseases (NMDs) occurring in approximately 1/90000 people in the US pediatric population. RYR1-RM result from pathogenic mutations in the ryanodine receptor isoform-1 (RYR1) gene where consequent RyR1 protein calcium dysregulation leads to impaired excitation-contraction coupling, oxidative and nitrosative stress, and mitochondrial depletion. These physiological deficits perpetuate RyR1 dysfunction causing further muscle injury, muscle weakness, and muscle fatigue. Muscle weakness and fatigue are two primary complaints in patients with RYR1-RM and are major symptoms that limit the ability of individuals to perform activities of daily living. The six-minute walk test (6MWT) is an endurance test with high reliability and validity used to measure walking capacity, disease progression, and more recently, fatigability in NMDs with limited results in RYR1-RM. Therefore, the purpose of our study is to objectively assess disease progression and fatigability in RYR1-RM affected individuals using the 6MWT. We hypothesized that 6MWT distance and fatigability would not change significantly between 0 and 6-month visits in RYR1-RM patients, given the clinically reported stable or slowly progressive nature of the disease. We also hypothesized participants would show fatigability during the 6MWT, given muscle weakness and fatigue are the two primary complaints of affected individuals.

Results

As expected, paired t-test analyses revealed no significant difference between total distance traveled (p = .608) or percent change in speed (p = .141) at 0-months compared with the 6-month visit. Fatigability was observed given the decline in speed between the first and last minute of the 6MWT at the 6-month time point (p ≤ .0005,). Although this decline was not significant at baseline, a significant decline in speed from the 1st minute did occur at minutes 2, 3, and 4 during the baseline visit.

Conclusion

In this RYR1-RM cohort, the 6MWT showed disease stability over a 6-month period but revealed fatigability during the test. Given these results, the 6MWT may be a promising endpoint for evaluating fatigability and therapeutic efficacy in the 6-month treatment phase of our current n-acetylcysteine trial in this population. Improvement post intervention could be attributed to the intervention rather than variability in disease progression.

Trial Registration

Clinical Trials.gov, NCT02362425, Registered 13 February 2015-Prospectively registered.

Ankle Kinematics and Temporal Gait Characteristics over the Duration of a 6-Minute Walk Test in People with Multiple Sclerosis Who Experience Foot Drop

Foot drop is a common gait impairment in people with MS (pwMS) but in some foot drop may only occur after a period of prolonged walking and may be a sign of motor fatigability. The purpose of the study was to explore whether, for pwMS, an adapted six-minute walk test (6minWT) would result in an increase in foot drop as measured using electrogoniometry. Sagittal ankle kinematics were recorded for fifteen participants (10 females and 5 males, aged 37-64) with MS (EDSS 4-6) throughout the 6minWT. Ankle kinematics and temporal stride parameters were compared between the first and last 10 gait cycles of the 6minWT. Peak dorsiflexion in swing was significantly reduced at the end of the 6minWT compared to the start, with six of the fifteen participants having a decrease of two degrees or more. Statistically significant changes in temporal stride parameters suggested a decrease in walking speed. Our results suggest that with the protocol used in this study it is feasible to identify patients who experience increased foot drop as a result of a prolonged exercise task.

Increases in fatigue do not change spasticity scores in persons with multiple sclerosis

AIM

Fatigue is a common finding in multiple sclerosis (MS) which may result in worsening of gait, function and other MS symptoms, like spasticity. Although the worsening of spasticity with fatigue has been reported by persons with MS, the effect of fatigue on spasticity has not been measured.

PURPOSE

The purpose of this study was to compare lower extremity Modified Ashworth Scale (MAS) scores of persons with mild-to-moderate MS symptoms before and after fatigued and unfatigued conditions.

METHODS

Using a randomized crossover design, MS subjects underwent 6-min walk to induce fatigue and 6-min supine rests, with lower extremity spasticity measured before and after each condition. Friedman tests gave paired comparisons of MAS before and after each condition.

RESULTS

16 subjects with mild-to-moderate MS completed the study (mean age = 56; standard deviation = 11.7). Friedman tests showed a significant decrease in mean rank for overall average MAS for both lower extremities (p = 0.031) when comparing fatigued to unfatigued conditions. This appeared to be driven by the right lower extremity average MAS (p = 0.002) and, more specifically, in post hoc pre to post-test comparisons for right knee flexor (p = 0.002 fatigued; p = 0.059 unfatigued) and right knee extensor (p = 0.001 fatigued; p = 0.020 unfatigued) MAS mean rank differences. Fatigue did not result in increased spasticity.

CONCLUSION

Spasticity in these subjects with MS was not worsened by fatigue suggesting that worsening of gait with fatigue may be due to causes other than spasticity.

Handgrip fatiguing exercise can provide objective assessment of cancer-related fatigue: a pilot study

PURPOSE

As a subjective symptom, cancer-related fatigue is assessed via patient-reported outcomes. Due to the inherent bias of such evaluation, screening and treatment for cancer-related fatigue remains suboptimal. The purpose is to evaluate whether objective cancer patients' hand muscle mechanical parameters (maximal force, critical force, force variability) extracted from a fatiguing handgrip exercise may be correlated to the different dimensions (physical, emotional, and cognitive) of cancer-related fatigue.

METHODS

Fourteen women with advanced breast cancer, still under or having previously received chemotherapy within the preceding 3 months, and 11 healthy women participated to the present study. Cancer-related fatigue was first assessed through the EORTC QLQ-30 and its fatigue module. Fatigability was then measured during 60 maximal repeated handgrip contractions. The maximum force, critical force (asymptote of the force-time evolution), and force variability (root mean square of the successive differences) were extracted. Multiple regression models were performed to investigate the influence of the force parameters on cancer-related fatigue's dimensions.

RESULTS

The multiple linear regression analysis evidenced that physical fatigue was best explained by maximum force and critical force (r = 0.81; p = 0.029). The emotional fatigue was best explained by maximum force, critical force, and force variability (r = 0.83; p = 0.008). The cognitive fatigue was best explained by critical force and force variability (r = 0.62; p = 0.035).

CONCLUSION

The handgrip maximal force, critical force, and force variability may offer objective measures of the different dimensions of cancer-related fatigue and could provide a complementary approach to the patient reported outcomes.

Neural Indicators of Fatigue in Chronic Diseases: A Systematic Review of MRI Studies

While fatigue is prevalent in chronic diseases, the neural mechanisms underlying this symptom remain unknown. Magnetic resonance imaging (MRI) has the potential to enable us to characterize this symptom. The aim of this review was to gather and appraise the current literature on MRI studies of fatigue in chronic diseases. We systematically searched the following databases: MedLine, PsycInfo, Embase and Scopus (inception to April 2016). We selected studies according to a predefined inclusion and exclusion criteria. We assessed the quality of the studies and conducted descriptive statistical analyses. We identified 26 studies of varying design and quality. Structural and functional MRI, alongside diffusion tensor imaging (DTI) and functional connectivity (FC) studies, identified significant brain indicators of fatigue. The most common regions were the frontal lobe, parietal lobe, limbic system and basal ganglia. Longitudinal studies offered more precise and reliable analysis. Brain structures found to be related to fatigue were highly heterogeneous, not only between diseases, but also for different studies of the same disease. Given the different designs, methodologies and variable results, we conclude that there are currently no well-defined brain indicators of fatigue in chronic diseases.

Age modification of the relationship between C-reactive protein and fatigue: findings from Understanding Society (UKHLS)

BACKGROUND

Systemic inflammation may play a role in the development of idiopathic fatigue, that is, fatigue not explained by infections or diagnosed chronic illness, but this relationship has never been investigated in community studies including the entire adult age span. We examine the association of the inflammatory marker C-reactive protein (CRP) and fatigue assessed annually in a 3-year outcome period for UK adults aged 16-98.

METHODS

Multilevel models were used to track fatigue 7, 19, and 31 months after CRP measurement, in 10 606 UK individuals. Models accounted for baseline fatigue, demographics, health conditions diagnosed at baseline and during follow-up, adiposity, and psychological distress. Sensitivity analyses considered factors including smoking, sub-clinical disease (blood pressure, anaemia, glycated haemoglobin), medications, ethnicity, and alcohol consumption.

RESULTS

Fatigue and CRP increased with age, and women had higher values than men. CRP was associated with future self-reported fatigue, but only for the oldest participants. Thus, in those aged 61-98 years, high CRP (>3 mg/L) independently predicted greater fatigue 7, 19, and 31 months after CRP measurement [odds ratio for new-onset fatigue after 7 months: 1.88, 95% confidence interval (CI) 1.21-2.92; 19 months: 2.25, CI 1.46-3.49; 31 months: 1.65, CI 1.07-2.54]. No significant longitudinal associations were seen for younger participants.

CONCLUSIONS

Our findings support previously described CRP-fatigue associations in older individuals. However, there are clear age modifications in these associations, which may reflect a contribution of unmeasured sub-clinical disease of limited relevance to younger individuals. Further work is necessary to clarify intervening processes linking CRP and fatigue in older individuals.

Muscle-specific endurance of the trapezius muscles using electrical twitch mechanomyography

BACKGROUND

Symptoms of fatigue and pain are often reported for the trapezius muscle in the shoulder. The present study evaluated endurance in the trapezius muscles of healthy participants using electric twitch mechanomyography (ETM).

METHODS

Surface electrodes and a tri-axial accelerometer were placed over the left trapezius muscle. Muscles were stimulated for 3 min each at 2 Hz, 4 Hz and 6 Hz. Maintenance of acceleration during muscle twitches was used to calculate an endurance index (EI). Subjects (n = 9) were tested on two separate days to assess reproducibility of the trapezius EI measurements. The endurance measurements were made on the wrist flexor and vastus lateralis muscles for comparison. Near infrared spectroscopy was used to measure muscle oxygenation (HbO₂) during the stimulation protocol (n = 8).

RESULTS

Mean (SD) EI was 84.9% (8.7%), 63.3% (19.1%) and 41.7% (20.0%) for 2 Hz, 4 Hz and 6 Hz, respectively. The coefficients of variation were 7.4%, 11.3% and 24.0% for 2 Hz, 4 Hz and 6 Hz, respectively. EI values were significantly lower in the trapezius compared to arm and leg muscles (p < 0.05). HbO₂ values were unchanged from resting values with electrical stimulation.

CONCLUSIONS

The EI as measured by ETM may provide a reproducible method of evaluating function in trapezius muscles that is not influenced by oxygen saturation.

Fatigue in Parkinson's disease: Metric properties of the fatigue impact scale for daily use (D-FIS), and its impact on quality of life

OBJECTIVE

In Parkinson's disease patients, fatigue is a disabling non-motor symptom whose prevalence ranges from 28% to 58%. The Fatigue Impact Scale for Daily Use (D-FIS), one of the various scales for quantifying fatigue. The aim of our study was to analyze the metric properties of the D-FIS in PD subjects and assess the impact of fatigue on their quality of life.

PATIENTS AND METHODS

The cohort in this study was comprised of 211 consecutive patients with a PD diagnosis regularly followed up at the Movement Disorders Unit of the Neurology Department at Carlos Andrade Marín Hospital (HCAM) in Quito, Ecuador, according to the United Kingdom PD Society Brain Bank criteria. Data Quality, Acceptability, Reliability, Stability (test-retest), Validity and Multiple linear regression analysis were determined.

RESULTS

The final sample consisted of 138 men (65.4%) and 73 women. Forty-six percent of these (98 patients) were in stage II of H&Y. We obtained a Cronbach's α value of 0.912 and an ICC value of 0.79. D-FIS was strongly correlated with depression (Spearman rho [Srho] 0.60), anxiety (Srho 0.59), quality of life (Srho 0.67), and non-motor symptoms (Srho 0.66). The scale's discriminant validity, assessed among the different stages of H&Y by the Kruskal-Wallis test, showed major significance (X² = 23.183, p ≤ 0.001). In the Multiple linear regression study, the resulting model proves that fatigue has a determining effect on quality of life.

CONCLUSIONS

The D-FIS has good metric properties and demonstrates that fatigue significantly affects PD patients' quality of life and that its impact is independent from that of anxiety, depression, and sleep disorders.

Multidimensional fatigue in pulmonary hypertension: prevalence, severity and predictors

Pulmonary hypertension is a potentially fatal disease. Despite pharmacological advances in pulmonary hypertension, fatigue remains common in patients with pulmonary hypertension.

A convenience sample of 120 participants at an international patient conference completed the Multidimensional Fatigue Inventory (MFI)-20 scale. Data on New York Heart Association Functional Class, body mass index, oxygen use and medication type/use were also collected.

There was a high prevalence of “severe” to “very severe” fatigue for each dimension: General Fatigue (60%), Physical Fatigue (55.8%), Reduced Activity (41.7%), Reduced Motivation (32.5%) and Mental Fatigue (27.5%). The mean±sd overall MFI-20 score was 58±5.1. Dimensions with the highest averaged levels were General Fatigue (13.40±3.61), Physical Fatigue (13.23±3.67) and Reduced Activity (11.33±4.16). Body mass index correlated with higher fatigue scores. Phosphodiesterase inhibitor plus endothelin receptor antagonist combination negatively predicted General Fatigue, Physical Fatigue, Reduced Motivation and Reduced Activity. Triple therapy was a significant predictor of General Fatigue, Physical Fatigue and Reduced Activity. There were no significant predictors of Mental Fatigue.

Multidimensional fatigue is common and severe in patients with pulmonary hypertension. Phosphodiesterase inhibitor plus endothelin receptor antagonist combination resulted in lower scores in most fatigue dimensions. Comprehensive assessment of fatigue should be considered in the clinical care of patients with pulmonary hypertension and clinical research to develop formal interventions that target this disabling symptom.

Fatigue is common and severe in PH, and impacted by medications; targeted strategies to mitigate fatigue are neededhttp://ow.ly/EISN30i0WWU

Fatigue in Parkinson's disease: concepts and clinical approach

Parkinson's disease (PD) is a progressive neurological disorder characterized by a large number of motor and non-motor features. Fatigue is one of the most common and most disabling symptoms among patients with PD, and it has a significant impact on their quality of life. Although fatigue has been recognized for a long time, its pathophysiology remains poorly understood, and there is no evidence to support any therapeutic approach in PD patients. Expert consensus on case definition and diagnostic criteria for PD-related fatigue have been recently published, and although they still need to be adequately validated, they provide a great step forward in the study of fatigue. The goal of this article is to provide relevant information for the identification and management of patients with fatigue.

Predicting Fatigue 12 Months after Child Traumatic Brain Injury: Child Factors and Postinjury Symptoms

OBJECTIVES

Fatigue is a common and persisting symptom after childhood brain injury. This study examined whether child characteristics and symptomatology preinjury or 6 months postinjury (pain, sleep, and mood, inattention) predicted fatigue at 12months postinjury.

METHODS

Parents of 79 children (0-18 years) rated fatigue at 12 months after injury on a multidimensional scale (general, sleep/rest, and cognitive). Demographic and clinical data were collected at injury. Parents rated child sleep, pain, physical/motor function, mood, and inattention at injury (preinjury description), and 6 months postinjury. Children were divided into two traumatic brain injury severity groups: mild TBI (n=57) and moderate/severe TBI (n=27). Hierarchical regression models were used to examine (i) preinjury factors and (ii) symptoms 6 months postinjury predictive of fatigue (general, sleep/rest, and cognitive) at 12 months postinjury.

RESULTS

Sleep/rest fatigue was predicted by preinjury fatigue (7% of variance) and psychological symptoms preinjury (10% of variance). General fatigue was predicted by physical/motor symptoms (27%), sleep (10%) and mood symptoms (9%) 6 months postinjury. Sleep/rest fatigue was predicted by physical/motor symptoms (10%), sleep symptoms (13%) and mood symptoms (9%) 6 months postinjury. Cognitive fatigue was predicted by physical/motor symptoms (17%) 6 months postinjury.

CONCLUSIONS

Preinjury fatigue and psychological functioning identified those at greatest risk of fatigue 12 months post-TBI. Predictors of specific fatigue domains at 12 months differed across each of the domains, although consistently included physical/motor function as well as sleep and mood symptoms postinjury. (JINS, 2018, 24, 224-236).

Walking measures to evaluate assistive technology for foot drop in multiple sclerosis: A systematic review of psychometric properties

BACKGROUND

Foot drop in people with multiple sclerosis (pwMS) often managed with assistive technologies, such as functional electrical stimulation and ankle foot orthoses. No evidence synthesis exists for the psychometric properties of outcomes used to evaluate the efficacy of these interventions.

OBJECTIVE

This systematic review aimed to identify the outcome measures reported to assess the benefits of assistive technology for pwMS and then synthesize the psychometric evidence in pwMS for a subset of these measures.

METHODS

Two searches in eight databases were conducted up to May 2017. Methodological quality was rated using the COSMIN guidelines. Overall level of evidence was scored according to the Cochrane criteria.

RESULTS

The first search identified 27 measures, with the 10 m walk test, gait kinematics and Physiological Cost Index (PCI) most frequently used. The second search resulted in 41 studies evaluating 10 measures related to walking performance. Strong levels of evidence were found for the internal consistency and test-retest reliability of the Multiple Sclerosis Walking Scale-12 and for the construct validity for Timed 25 Foot Walk. No psychometric studies were identified for gait kinematics and PCI in pwMS. There was a lack of evidence for measurement error and responsiveness.

CONCLUSION

Although a strong level of evidence exists for some measures included in this review, there was an absence of psychometric studies on commonly used measures such as gait kinematics. Future psychometric studies should evaluate a wider range of walking related measures used to assess the efficacy of interventions to treat foot drop in pwMS.

Perceived fatigue and energy are independent unipolar states: Supporting evidence

Persistent fatigue is a common problem (∼20-45% of U.S. population), with higher prevalence and severity in people with medical conditions such as cancer, depression, fibromyalgia, heart failure, sleep apnea and multiple sclerosis. There are few FDA-approved treatments for fatigue and great disagreement on how to measure fatigue, with over 250 instruments used in research. Many instruments define fatigue as "a lack of energy", thus viewing energy and fatigue states as opposites on a single bipolar continuum. In this paper, we hypothesize that energy and fatigue are distinct perceptual states, should be measured using separate unipolar scales, have different mechanisms, and deficits should be treated using tailored therapies. Energy and fatigue independence has been found in both exploratory and confirmatory factor analysis studies. Experiments in various fields, including behavioral pharmacology and exercise science, often find changes in energy and not fatigue, or vice versa. If the hypothesis that energy and fatigue are independent is correct, there are likely different mechanisms that drive energy and fatigue changes. Energy could be increased by elevated dopamine and norepinephrine transmission and binding. Fatigue could be increased by elevated brain serotonin and inflammatory cytokines and reduced histamine binding. The hypothesis could be tested by an experiment that attempts to produce simultaneously high ratings of energy and fatigue (such as with two drugs using a randomized, double-blind, placebo-controlled design), which would offer strong evidence against the common viewpoint of a bipolar continuum. If the hypothesis is correct, prior literature using bipolar instruments will be limited, and research on the prevalence, mechanisms, and treatment of low energy and elevated fatigue as separate conditions will be needed. In the immediate future, measuring both energy and fatigue using unipolar measurement tools may improve our understanding of these states and improve therapeutic outcomes.

Exercise-induced fatigue in young people: advances and future perspectives

PURPOSE

In recent decades, the interest for exercise-induced fatigue in youth has substantially increased, and the effects of growth on the peripheral (muscular) and central (neural) mechanisms underpinning differences in neuromuscular fatigue between healthy children and adults have been described more extensively. The purpose of this review is to retrieve, report, and analyse the findings of studies comparing neuromuscular fatigue between children and adults. Objective measures of the evaluation of the physiological mechanisms are discussed.

METHOD

Major databases (PubMed, Ovid, Scopus and Web of Science) were systematically searched and limited to English language from inception to September 2017.

RESULT

Collectively, the analyzed studies indicate that children experience less muscular and potentially more neural fatigue than adults. However, there are still many unknown aspects of fatigue regarding neural (supraspinal and spinal) and peripheral mechanisms that should be more thoroughly examined in children.

CONCLUSION

Suitable methods, such as transcranial magnetic stimulation, transcranial electrical stimulation, functional magnetic resonance imaging, near-infrared spectroscopy, tendon vibration, H-reflex, and ultrasound are recommended in the research field of fatigue in youth. By designing studies that test the fatigue effects in movements that replicate daily activities, new knowledge will be acquired. The linkage and interaction between physiological, cognitive, and psychological aspects of human performance remain to be resolved in young people. This can only be successful if research is based on a foundation of basic research focused on the mechanisms of fatigue while measuring all three above aspects.

Exploring the Specific Needs of Persons with Multiple Sclerosis for mHealth Solutions for Physical Activity: Mixed-Methods Study

Background

Multiple sclerosis (MS) is one of the world’s most common neurologic disorders, with symptoms such as fatigue, cognitive problems, and issues with mobility. Evidence suggests that physical activity (PA) helps people with MS reduce fatigue and improve quality of life. The use of mobile technologies for health has grown in recent years with little involvement from relevant stakeholders. User-centered design (UCD) is a design philosophy with the goal of creating solutions specific to the needs and tasks of the intended users. UCD involves stakeholders early and often in the design process. In a preliminary study, we assessed the landscape of commercially available MS mobile health (mHealth) apps; to our knowledge, no study has explored what persons with MS and their formal care providers think of mHealth solutions for PA.

Objective

The aim of this study was to (1) explore MS-specific needs for MS mHealth solutions for PA, (2) detect perceived obstacles and facilitators for mHealth solutions from persons with MS and health care professionals, and (3) understand the motivational aspects behind adoption of mHealth solutions for MS.

Methods

A mixed-methods design study was conducted in Kliniken Valens, Switzerland, a clinic specializing in neurological rehabilitation. We explored persons with MS and health care professionals who work with them separately. The study had a qualitative part comprising focus groups and interviews, and a quantitative part with standardized tools such as satisfaction with life scale and electronic health (eHealth) literacy.

Results

A total of 12 persons with relapsing-remitting MS and 12 health care professionals from different backgrounds participated in the study. Participants were well-educated with an even distribution between genders. Themes identified during analysis were MS-related barriers and facilitators, mHealth design considerations, and general motivational aspects. The insights generated were used to create MS personas for design purposes. Desired mHealth features were as follows: (1) activity tracking, (2) incentives for completing tasks and objectives, (3) customizable goal setting, (4) optional sociability, and (5) game-like attitude among others. Potential barriers to mHealth apps adoption were as follows: (1) rough on-boarding experiences, (2) lack of clear use benefits, and (3) disruption of the health care provider-patient relationship. Potential facilitators were identified: (1) endorsements from experts, (2) playfulness, and (3) tailored to specific persons with MS needs. A total of 4 MS personas were developed to provide designers and computer scientists means to help in the creation of future mHealth solutions for MS.

Conclusions

mHealth solutions for increasing PA in persons with MS hold promise. Allowing for realistic goal setting and positive feedback, while minimizing usability burdens, seems to be critical for the adoption of such apps. Fatigue management is especially important in this population; more attention should be brought to this area.

Significance of fatigue in patients with migraine

Fatigue is often stated as a headache trigger or migraine-specific symptom. We investigated predictors of fatigue and its impact on quality of life (QOL) in patients with migraine. Patients with migraine were recruited from a headache clinic and completed psychosomatic instruments, including the 12-item Allodynia Symptom Checklist (ASC-12), the Migraine Disability Assessment Scale (MIDAS), the Patients Health Questionnaire-9 (PHQ-9), the Generalized Anxiety Disorder-7 (GAD-7), the Epworth Sleepiness Scale (ESS), the Insomnia Severity Index (ISI), the Fatigue Severity Scale (FSS), and Migraine-Specific Quality of Life Questionnaire (MSQ). Two hundreds twenty-six patients with migraine were eligible for the study. Pathologic fatigue was manifested in 133 patients (58.8%). The FSS score was significantly associated with age, age of onset, the Visual Analog Scale (VAS) depicting headache intensity, photophobia, phonophobia, and the scores of the ASC-12, the MIDAS, the ESS, the ISI, the PHQ-9 and the GAD-7. The strongest predictor for the FSS was the PHQ-9 (β = 0.432, p < .001), followed by age (β = -0.169, p = .002), the ISI (β = 0.151, p = .016), and the VAS (β = 0.139, p = .018). There was an inverse correlation between the FSS score and three dimensional scores of the MSQ (p < .001). Appropriate interventions for depression, insomnia, and headache intensity are likely to lessen fatigue and improve QOL.

Fatigue and Sleep in Multiple Sclerosis Patients: A Comparison of Self-Report and Performance-Based Measures

BACKGROUND

Multiple sclerosis (MS) patients suffer very often from MS fatigue and sleep problems. Despite the detrimental impact on the activities of daily living, a short and objective quantification of fatigue and sleep problems is currently lacking.

OBJECTIVE

The objective of the study was to systematically investigate tonic, intrinsic, and phasic alertness and the relationship of these performance-based measures with self-report measures of fatigue and quality of sleep.

METHODS

Thirty-three MS patients without (MS-) and 26 with selected comorbid disorders (MS+) and 43 healthy controls (HCs) performed the pupillographic sleepiness test (measuring tonic alertness) and the alertness subtest of the Test of Attentional Performance (measuring intrinsic and phasic alertness).

RESULTS

Self-reported and performance-based measures revealed poorer performance for both MS groups compared to HC. MS+ patients presented higher rates of MS fatigue, sleep problems and depressive symptoms but similar alertness scores compared to MS- patients. However, tonic alertness was only higher in MS- patients compared to HC. Intrinsic and phasic alertness correlated moderately with fatigue ratings.

CONCLUSION

In the diagnostic process of MS fatigue and quality of sleep comorbid disorders (depression, anemia, thyroid dysfunction) and performance-based measures such as alertness should be considered in daily clinical practice.

Understanding the interplay between mild traumatic brain injury and cognitive fatigue: models and treatments

Nearly 2 million traumatic brain injuries occur annually, most of which are mild (mTBI). One debilitating sequela of mTBI is cognitive fatigue: fatigue following cognitive work. Cognitive fatigue has proven difficult to quantify and study, but this is changing, allowing models to be proposed and tested. Here, we review evidence for four models of cognitive fatigue, and relate them to specific treatments following mTBI. The evidence supports two models: cognitive fatigue results from the increased work/effort required for the brain to process information after trauma-induced damage; and cognitive fatigue results from sleep disturbances. While there are no evidence-based treatments for fatigue after mTBI, some pharmacological and nonpharmacological treatments show promise for treating this debilitating problem. Future work may target the role of genetics, neuroinflammation and the microbiome and their role in complex cognitive responses such as fatigue.

Motor fatigability in persons with multiple sclerosis: Relation between different upper limb muscles, and with fatigue and the perceived use of the arm in daily life

BACKGROUND

Motor fatigability is increasingly acknowledged in persons with MS (pwMS). It is unknown whether fatigability is generalized across upper limb muscles and relates to fatigue and perceived difficulties in upper limb use.

METHODS

This observational case-controlled study included twenty PwMS (median EDSS = 3, range 1.5-6.5) and twenty healthy controls who performed 30″ sustained maximal muscle contractions for index finger abduction, hand grip, elbow flexion and shoulder abduction. A static fatigue index (SFI) was calculated to assess motor fatigability for each muscle group. PwMS completed the Fatigue Severity Scale (FSS) and Modified Fatigue Index Scale (MFIS), to quantify severity and perceived impact of fatigue and the Manual Ability Measure (MAM-36) reflecting perceived difficulty in using the upper limbs. Comparisons between groups and muscles was made by t-tests. Associations between outcomes were calculated with correlation coefficients.

RESULTS

Fatigue was highest in pwMS. PwMS showed preserved muscle strength and a greater motor fatigability in elbow flexors compared to healthy controls. SFI of elbow flexors and shoulder abductors were associated, and contributed to FSS and MFIS. SFI of elbow flexors and finger abductors predicted half of the variation in MAM-36.

CONCLUSION

Increased motor fatigability was only present in elbow flexors of PwMS, indicating that expression of motor fatigability is not generalized. Fatigability was associated with perceived fatigue (impact) and daily life upper limb use. Results are preliminary given the small sample size with predominantly persons with mild MS.

Evidence for unconscious regulation of performance in fatigue

Since fatigue is prevalent in modern societies, it is necessary to clarify the neural mechanisms of fatigue. The regulation of performance through fatigue sensation is one of the mechanisms that decreases performance in fatigue. However, it is unknown whether subjective feeling of fatigue is necessary for the regulation of performance. Here, we examined whether decreased performance occurs without increased fatigue sensation through the experiment which was designed to test if fatigue can be learned unconsciously. Healthy male volunteers performed a fatigue-inducing hand-grip task for 10 min while viewing a target image presented without awareness. On the next day, they viewed a control and the target images presented with awareness and the neural activity caused by viewing the images was measured using magnetoencephalography. Results showed the level of fatigue sensation was not altered but grip-strength was decreased by viewing the target image on the second day. The level of beta band power in Brodmann's area 31 was increased by viewing the target image and this increase was negatively associated with the decrease of grip-strength caused in the hand-grip task. These findings demonstrated that fatigue can be learned unconsciously and that there is a mechanism to decrease performance without fatigue sensation.

Neural correlates of effort-dependent and effort-independent cognitive fatigue components in patients with multiple sclerosis

Background:

Among patients with multiple sclerosis (MS), fatigue is the most commonly reported symptom. It can be subdivided into an effort-dependent (fatigability) and an effort-independent component (trait-fatigue).

Objective:

The objective was to disentangle activity changes associated with effort-independent “trait-fatigue” from those associated with effort-dependent fatigability in MS patients.

Methods:

This study employed behavioral measures and functional magnetic imaging to investigate neural changes in MS patients associated with fatigue. A total of 40 MS patients and 22 age-matched healthy controls performed in a fatigue-inducing N-back task. Effort-independent fatigue was assessed using the Fatigue Scale of Motor and Cognition (FSMC) questionnaire.

Results:

Effort-independent fatigue was observed to be reflected by activity increases in fronto-striatal-subcortical networks primarily involved in the maintenance of homeostatic processes and in motor and cognitive control. Effort-dependent fatigue (fatigability) leads to activity decreases in attention-related cortical and subcortical networks.

Conclusion:

These results indicate that effort-independent (fatigue) and effort-dependent fatigue (fatigability) in MS patients have functionally related but fundamentally different neural correlates. Fatigue in MS as a general phenomenon is reflected by complex interactions of activity increases in control networks (effort-independent component) and activity reductions in executive networks (effort-dependent component) of brain areas.

Development and Validity of the Rating-of-Fatigue Scale

OBJECTIVE

The purpose of these experiments was to develop a rating-of-fatigue (ROF) scale capable of tracking the intensity of perceived fatigue in a variety of contexts.

METHODS

Four experiments were carried out. The first provided the evidential basis for the construction of the ROF scale. The second tested the face validity of the ROF, and the third tested the convergent and divergent validity of the ROF scale during ramped cycling to exhaustion and 30 min of resting recovery. The final experiment tested the convergent validity of the ROF scale with time of day and physical activity (accelerometer counts) across a whole week.

RESULTS

Modal selections of descriptions and diagrams at different levels of exertion and recovery were found during Experiment 1 upon which the ROF scale was constructed and finalised. In Experiment 2, a high level of face validity was indicated, in that ROF was reported to represent fatigue rather than exertion. Descriptor and diagrammatic elements of ROF reportedly added to the coherence and ease of use of the scale. In Experiment 3, high convergence between ROF and various physiological measures were found during exercise and recovery (heart rate, blood lactate concentration, oxygen uptake, carbon dioxide production, respiratory exchange ratio and ventilation rate were all P < 0.001). During ramped cycling to exhaustion ROF and RPE did correspond (P < 0.0001) but not during recovery, demonstrating discriminant validity. Experiment 4 found ROF to correspond with waking time during each day (Mon-Sun all P < 0.0001) and with physical activity (accelerometer count) (Mon-Sun all P < 0.001).

CONCLUSIONS

The ROF scale has good face validity and high levels of convergent validity during ramped cycling to exhaustion, resting recovery and daily living activities. The ROF scale has both theoretical and applied potential in understanding changes in fatigue in a variety of contexts.

Motor, behavioural, and cognitive correlates of fatigue in early, de novo Parkinson disease patients

INTRODUCTION

Fatigue is one of the most common and disabling non-motor symptoms in Parkinson's disease (PD). The objective of this study was to determine prevalence and motor, behavioural, and cognitive correlates of distressing fatigue in early, de novo PD patients.

METHODS

Eighty-one consecutive de novo PD patients (64% men; mean age 65.73 ± 8.26 years) underwent a comprehensive examination, including Parkinson's disease Fatigue Scale (PFS), Epworth Sleepiness Scale (ESS), Parkinson's Disease Sleep Scale (PDSS), Beck Depression Inventory (BDI), Parkinson's Anxiety Scale (PAS), and Apathy Evaluation Scale (AES). Moreover, all patients underwent a detailed neuropsychological evaluation exploring attention and working memory, executive functions, memory, visuospatial abilities and language. Score of patients with or without distressing fatigue (defined as a PFS score ≥ 8) were compared by Student's t-test or Pearson's chi-square test. Logistic regression analyses were performed to search for motor and non-motor features independently associated with presence of distressing fatigue.

RESULTS

Twelve (15%) patients presented distressing fatigue. Logistic regression identified sleepiness (p = 0.04), "episodic anxiety" subscale of PAS (p = 0.005), and "cognitive apathy" subscale of AES (p = 0.017) as the main factors associated with distressing fatigue. No significant association was found between diagnosis of Mild Cognitive Impairment and distressing fatigue (p = 0.745).

CONCLUSION

In a sample of consecutive de novo PD patients, distressing fatigue is associated with episodic anxiety, cognitive apathy and sleepiness, but not with cognitive impairment. Our findings suggest possible shared pathogenic mechanisms underlying these non-motor symptoms and foster development of early combined therapeutic approaches.

Cortical Substrate of Supraspinal Fatigue following Exhaustive Aerobic Exercise Localizes to a Large Cluster in the Anterior Premotor Cortex

Strenuous exercise leads to a progressive reduction in the performance of voluntary physical exercise. This is due to a process described as fatigue and is defined as the failure to maintain the required or expected power output. While some of this is muscular in origin, there are data suggestive of how fatigue is modulated by cortical signals, leading to a concept of central fatigue. The previously reported fatigue-induced changes in cortical activity may have been due to blood oxygen-dependent (BOLD) signal drift and/or neural habituation alone. We implemented a functional magnetic resonance imaging paradigm to effectively isolate brain areas responsible for central (supraspinal) fatigue following exercise. Our data identify a large cluster that includes dominant the anterior ventral premotor cortex (aPMv), the insula and postcentral gyrus as critical nodes in the brain network where supraspinal fatigue might have their functional neural imprints. Findings here show that activity in the ipsilateral aPMv and the adjacent areas in the premotor cortex correlates with both localized fatigue (fatigue specific hand grip contraction), and generalized full body exhaustive fatigue. In addition, from a methodological standpoint, we have also shown that the effects of BOLD signal drift can be modeled and removed to arrive at specific brain activity patterns in our experiments. Once the loci of central fatigue are isolated in this way, treatments aimed at modulating activity in these premotor areas may reduce exercise-induced fatigue and perhaps also benefit various clinical conditions in which fatigue is a major symptom.

Fatigue and Cognitive Fatigability in Mild Traumatic Brain Injury are Correlated with Altered Neural Activity during Vigilance Test Performance

Introduction

Fatigue is the most frequently reported persistent symptom following a mild traumatic brain injury (mTBI), but the explanations for the persisting fatigue symptoms in mTBI remain controversial. In this study, we investigated the change of cerebral blood flow during the performance of a psychomotor vigilance task (PVT) by using pseudo-continuous arterial spin labeling (PCASL) MRI technique to better understand the relationship between fatigability and brain activity in mTBI.

Material and methods

Ten patients (mean age: 37.5 ± 11.2 years) with persistent complaints of fatigue after mTBI and 10 healthy controls (mean age 36.9 ± 11.0 years) were studied. Both groups completed a 20-min long PVT inside a clinical MRI scanner during simultaneous measurements of reaction time and regional cerebral blood flow (rCBF) with PCASL technique. Cognitive fatigability and neural activity during PVT were analyzed by dividing the performance and rCBF data into quintiles in addition to the assessment of self-rated fatigue before and after the PVT.

Results

The patients showed significant fatigability during the PVT while the controls had a stable performance. The variability in performance was also significantly higher among the patients, indicating monitoring difficulty. A three-way ANOVA, modeling of the rCBF data demonstrated that there was a significant interaction effect between the subject group and performance time during PVT in a mainly frontal/thalamic network, indicating that the pattern of rCBF change for the mTBI patients differed significantly from that of healthy controls. In the mTBI patients, fatigability at the end of the PVT was related to increased rCBF in the right middle frontal gyrus, while self-rated fatigue was related to increased rCBF in left medial frontal and anterior cingulate gyri and decreases of rCBF in a frontal/thalamic network during this period.

Discussion

This study demonstrates that PCASL is a useful technique to investigate neural correlates of fatigability and fatigue in mTBI patients. Patients suffering from fatigue after mTBI used different brain networks compared to healthy controls during a vigilance task and in mTBI, there was a distinction between rCBF changes related to fatigability vs. perceived fatigue. Whether networks for fatigability and self-rated fatigue are different, needs to be investigated in future studies.

Utilizing Physiological Principles of Motor Unit Recruitment to Reduce Fatigability of Electrically-Evoked Contractions: A Narrative Review

Neuromuscular electrical stimulation (NMES) is used to produce contractions to restore movement and reduce secondary complications for individuals experiencing motor impairment. NMES is conventionally delivered through a single pair of electrodes over a muscle belly or nerve trunk using short pulse durations and frequencies between 20 and 40Hz (conventional NMES). Unfortunately, the benefits and widespread use of conventional NMES are limited by contraction fatigability, which is in large part because of the nonphysiological way that contractions are generated. This review provides a summary of approaches designed to reduce fatigability during NMES, by using physiological principles that help minimize fatigability of voluntary contractions. First, relevant principles of the recruitment and discharge of motor units (MUs) inherent to voluntary contractions and conventional NMES are introduced, and the main mechanisms of fatigability for each contraction type are briefly discussed. A variety of NMES approaches are then described that were designed to reduce fatigability by generating contractions that more closely mimic voluntary contractions. These approaches include altering stimulation parameters, to recruit MUs in their physiological order, and stimulating through multiple electrodes, to reduce MU discharge rates. Although each approach has unique advantages and disadvantages, approaches that minimize MU discharge rates hold the most promise for imminent translation into rehabilitation practice. The way that NMES is currently delivered limits its utility as a rehabilitative tool. Reducing fatigability by delivering NMES in ways that better mimic voluntary contractions holds promise for optimizing the benefits and widespread use of NMES-based programs.

Noradrenaline Reuptake Inhibition Impairs Cortical Output and Limits Endurance Time

PURPOSE

To assess the neural mechanisms that limit endurance time, we compared a fatiguing task performed under the influence of reboxetine (REB), a noradrenaline reuptake inhibitor, and placebo (PLA).

METHODS

Nine male subjects (age = 24 ± 2 yr) participated in this study. The fatiguing task involved repeated 3-s submaximal isometric contractions of the knee extensors (∼33% maximal voluntary contraction) with a 2-s rest between each contraction and performed until task failure. Before, during, and after exercise, changes in voluntary activation, corticospinal (motor-evoked potential) and spinal excitability (Hoffman reflex), and muscle contractile properties were tested using electrical and transcranial magnetic stimulations. A psychomotor vigilance task assessed reaction time before and after exercise.

RESULTS

Compared with PLA, REB reduced the endurance time by 15.6% (P = 0.04). The maximal voluntary contraction torque decreased to a similar extent at task failure in both conditions (P < 0.01), whereas the rate of decline was greater in REB than that in PLA (P = 0.02). The level of voluntary activation tested by transcranial magnetic stimulation and electrical stimulation decreased (P < 0.01) by 10%-15% at the end of the task, but the mean rate of decline was greater in REB (P ≤ 0.03). Although motor-evoked potential did not change during fatigue, Hoffman reflex, and electrically evoked torque decreased similarly in the PLA and REB conditions (P ≤ 0.02). After exercise, reaction time increased by 3.5% (P = 0.02) in REB but did not change in the PLA condition.

CONCLUSION

These findings suggest that because of the noradrenaline reuptake inhibition, the output from the motor cortex is decreased at a greater rate than that in the PLA condition, contributing thereby to shorten endurance time.

Relationship between perceived fatigue and performance fatigability in people with multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Perceived fatigue (i.e., subjective perception of reduced capacity) is one of the most common and disabling symptoms for people with multiple sclerosis (MS). Perceived fatigue may also be related to performance fatigability (i.e., decline in physical performance over time), although study findings have been inconsistent.

OBJECTIVE

To locate all studies reporting the relationship between perceived fatigue and fatigability in people with MS, determine the population correlation, and examine moderating variables of the correlation size.

METHODS

In accordance with PRISMA guidelines, systematic searches were completed in Medline, PsychInfo, Google Scholar, and the Cochrane Library for peer-reviewed articles published between March 1983 and August 2016. Included articles measured perceived fatigue and performance fatigability in people with MS and provided a correlation between measures. Moderator variables expected to influence the relationship were also coded. Searches located 19 studies of 848 people with MS and a random-effects model was used to pool correlations.

RESULTS

The mean correlation between fatigue and fatigability was positive, "medium" in magnitude, and statistically significant, r=0.31 (95% CI=0.21, 0.42), p<0.001. Despite moderate between-study heterogeneity (I²=46%) no statistically significant moderators were found, perhaps due to the small number of studies per moderator category.

CONCLUSION

There is a significant relationship between perceived fatigue and fatigability in MS, such that people reporting elevated fatigue also are highly fatigable. The size of the relationship is not large enough to suggest fatigue and fatigability are the same construct, and both should continue to be assessed independently.

Relationship Between Fatigability and Perceived Fatigue Measured Using the Neurological Fatigue Index in People with Multiple Sclerosis

BACKGROUND

Understanding the relationship between perceived fatigue and performance fatigability could lead to more effective interventions to manage multiple sclerosis (MS)-related fatigue. However, the relationship between self-perceived fatigue measured using the Neurological Fatigue Index (NFI-MS) and performance fatigability in people with MS is unknown. We sought to explore the relationship between the NFI-MS and performance fatigability in people with MS.

METHODS

Fifty-two participants (mean ± SD age, 46.8 ± 10.1 years) completed the study. Three measures of performance fatigability were used: percent change in meters walked from first to last minute of the 6-Minute Walk Test, percent change in force exerted from first to last trial on a repetitive maximal hand grip test, and response speed variability on the Continuous Performance Test. Perceived physical and cognitive fatigue were measured using the NFI-MS. The state level of fatigue was examined immediately before and after performing the fatigability measures using a one-item visual analogue fatigue scale.

RESULTS

Of the three performance fatigability measures, only the attentional task (response speed variability) was significantly associated with NFI-MS physical (r = 0.326, P = .020) and cognitive (r = 0.276, P = .050) domain scores. Participants demonstrated significantly higher state levels of fatigue after performing all performance fatigability measures (P ≤ .001).

CONCLUSIONS

The NFI-MS and the performance fatigability measures used in this study are easy to administer. We encourage wider use of these measures in clinical and research settings for comprehensive assessment of MS-related fatigue.

Disease-Induced Skeletal Muscle Atrophy and Fatigue

Numerous health problems, including acute critical illness, cancer, diseases associated with chronic inflammation, and neurological disorders, often result in skeletal muscle weakness and fatigue. Disease-related muscle atrophy and fatigue is an important clinical problem because acquired skeletal muscle weakness can increase the duration of hospitalization, result in exercise limitation, and contribute to a poor quality of life. Importantly, skeletal muscle atrophy is also associated with increased morbidity and mortality of patients. Therefore, improving our understanding of the mechanism(s) responsible for skeletal muscle weakness and fatigue in patients is a required first step to develop clinical protocols to prevent these skeletal muscle problems. This review will highlight the consequences and potential mechanisms responsible for skeletal muscle atrophy and fatigue in patients experiencing acute critical illness, cancer, chronic inflammatory diseases, and neurological disorders.

Translating Fatigue to Human Performance

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.

Cognitive fatigue in individuals with traumatic brain injury is associated with caudate activation

We investigated differences in brain activation associated with cognitive fatigue between persons with traumatic brain injury (TBI) and healthy controls (HCs). Twenty-two participants with moderate-severe TBI and 20 HCs performed four blocks of a difficult working memory task and four blocks of a control task during fMRI imaging. Cognitive fatigue, assessed before and after each block, was used as a covariate to assess fatigue-related brain activation. The TBI group reported more fatigue than the HCs, though their performance was comparable. Regarding brain activation, the TBI group showed a Task X Fatigue interaction in the caudate tail resulting from a positive correlation between fatigue and brain activation for the difficult task and a negative relationship for the control task. The HC group showed the same Task X Fatigue interaction in the caudate head. Because we had prior hypotheses about the caudate, we performed a confirmatory analysis of a separate dataset in which the same subjects performed a processing speed task. A relationship between Fatigue and brain activation was evident in the caudate for this task as well. These results underscore the importance of the caudate nucleus in relation to cognitive fatigue.

Interactions of Subjective and Objective Measures of Fatigue Defined in the Context of Brain Control of Locomotion

Background

Fatigue adversely impacts quality of life in old age. The relationship between subjective and objective measurements of fatigue, however, is poorly understood. We examined whether subjective fatigue moderated the expression of objective fatigue during locomotion. Associations between objective and subjective measures of fatigue were predicted to manifest only under dual-task conditions that maximized cognitive demands.

Methods

Participants were 314 nondemented older adults (age = 76.8±6.7 years; % female = 56). Functional near-infrared spectroscopy was used to assess oxygenated hemoglobin (HbO2) levels during walking. A 4×14-foot Zeno electronic walkway was utilized to assess stride velocity (cm/s). Objective fatigue was operationalized as attenuation in HbO2 levels and decline in stride velocity (cm/s) during six continuous straight walks under single- (normal-walk) and dual-task (walk-while-talk) conditions. The Brief Fatigue Inventory assessed subjective fatigue.

Results

Worse subjective fatigue was associated with attenuated increase in HbO2 levels (estimate = 0.175; p < .05) but not with decline in stride velocity (estimate = 0.394; p > .05) from normal-walk to walk-while-talk conditions. Objective fatigue did not manifest and was not associated with subjective fatigue during the course of normal-walk. Worse subjective fatigue was associated with attenuated HbO2 levels in the fourth (estimate = -0.178; p < .05), fifth (estimate = -0.230; p < .01), and sixth (estimate = -0.231; p < .01) straight walks compared to the first during walk-while-talk.

Conclusion

Dual-task walking paradigms provide a unique environment to simultaneously assess different facets of fatigue. The prefrontal cortex subserves both subjective and objective measurements of fatigue as defined in the context of attention-demanding locomotion.

Integrated Imaginative Distention Therapy to Cope with Fatigue. DIMMI SI Study: The First Randomized Controlled Trial in Multiple Sclerosis

Introduction

Fatigue is a frequent, disabling, and difficult to treat symptom in neurological disease and in other stress-related conditions; Integrated Imaginative Distention (IID) is a therapy combining muscular and imaginative relaxation, feasible also in disabled subjects; the DIMMI SI trial was planned to evaluate IID efficacy on fatigue.

Methods

The design was a parallel, randomised 1:1 (intervention:waiting list), controlled, open-label trial. Participants were persons with multiple sclerosis (pwMS), persons with insomnia (pwINS), and health professionals (HP) as conditions related to fatigue and stress. The primary outcome was the post-intervention change of fatigue; secondary outcomes were changes in insomnia, stress, and quality of life (QoL). Eight IID weekly training group sessions were delivered by a skilled psychotherapist. The study lasted 12 months.

Results

One hundred and forty-four subjects were enrolled, 48 for each condition. The mean change in Modified Fatigue Impact Scale (MFIS) score among exposed was 7.7 [95% CI 1.1, 14.4] (P = 0.023) in pwMS; 7.1 [1.9, 12.3] (P = 0.007) among pwINS, and 11.3 [4.3, 18.2] among HP (P = 0.002). At the last follow-up, the benefit was confirmed on physical fatigue for pwMS, on total fatigue for pwINS and HP.

Conclusions

DIMMI SI is the first randomized controlled trial evaluating the efficacy of IID on fatigue. IID resulted a complementary intervention to reduce fatigue in stress-related conditions, in both health and disease status. NCT02290990ClinicalTrials.gov.

Electronic supplementary material

The online version of this article (doi:10.1007/s40120-017-0081-9) contains supplementary material, which is available to authorized users.

Patient-Reported Outcomes and Fatigue in Patients with Chronic Hepatitis C Infection

Fatigue is a common symptom. Diagnosis is difficult. Fatigue is often a complex symptom. In the recent years, fatigue has gained considerable amount of attention. It has 2 major types, central and peripheral, which may occur together or alone. Although fatigue has many strong relations with depression and sleep disorders, it is a separate entity. For the diagnosis of fatigue, self-reports and patient-reported outcomes are highly valuable tools because these methods can reflect patients' perceptions. Treating the underlying disease with newly developed direct-acting antivirals often improves the perceived fatigue. Healthy lifestyle changes are the cornerstone of the treatment.