AIM: The purpose of this study was to re-examine central and peripheral origins of neuromuscular fatigue after a highly strenuous eccentric exercise of the knee extensor muscles (KE) using both voluntary/evoked contractions and electromyographic recordings (EMG). METHODS: Before, and 30 min after 15 min of intermittent one-logged downhill running, maximal ...

Dialysis patients have severe exercise limitations related to metabolic disturbances, but muscle fatigue has not been well studied in this population. We investigated the magnitude and mechanisms of fatigue of the ankle dorsiflexor muscles in patients on maintenance hemodialysis. Thirty-three dialysis patients and twelve healthy control subjects performed incremental isometric ...

We investigated the effects of low frequency fatigue (LFF) on post-exercise changes in rectified surface EMG (rsEMG) and single motor unit EMG (smuEMG) in vastus lateralis muscle (n = 9). On two experimental days the knee extensors were fatigued with a 60-s-isometric contraction (exercise) at 50% maximal force capacity (MFC). ...

Choice reaction time (RT) is shorter when participants perform a choice task at the same time as a sub-maximal exercise than when they are at rest. The purpose of the present study was to determine whether such an exercise affects response execution or whether it alters processes located upstream from ...

The purpose of this investigation was to compare the effects of stretching vs. potentiation on subsequent maximal force and rate of force development capabilities of subjects in an isometric squat. Ten male collegiate athletes participated as subjects in this study. Subjects were tested during 3 separate sessions that involved joint ...

To investigate the effects of hypoxia and incremental exercise on muscle contractility, membrane excitability, and maximal Na(+)-K(+)-ATPase activity, 10 untrained volunteers (age = 20 +/- 0.37 yr and weight = 80.0 +/- 3.54 kg; +/- SE) performed progressive cycle exercise to fatigue on two occasions: while breathing normal room air ...

We explored the role of baseline characteristics of 105 patients who presented with fatigue in primary care in determining outcome following either graded exercise or cognitive-behavioural therapy. Meeting the criteria for chronic fatigue syndrome was the most powerful predictor of poor outcome and this negative effect was enhanced by greater ...

AIM: To test the hypothesis that time-wise increase in intramuscular pressure (IMP) and subsequent decrease in muscle tissue oxygenation (TO(2)) results in muscle fatigue development during a non-exhaustive, low-force contraction evidenced by changes in electromyogram (EMG) and particular mechanomyogram (MMG). METHODS: Seven subjects performed static elbow flexion at 10% maximal ...

OBJECTIVES: To investigate the effects of fluid ingestion on neuromuscular function during prolonged cycling exercise. METHODS: Eight well trained subjects exercised for 180 minutes in a moderate environment at a workload requiring approximately 60% maximal oxygen uptake. Two conditions, fluid (F) and no fluid (NF) ingestion, were investigated. RESULTS: During ...

OBJECTIVE: The aim of this study was to test whether patients with chronic fatigue syndrome (CFS) have an exercise phobia, by measuring anxiety-related physiological and psychological reactions to ordinary activity and exercise. METHODS: Patients and healthy but sedentary controls were assessed over 8 h of an ordinary day, and before, ...

We investigated whether depressed muscle Na(+)-K(+)-ATPase activity with exercise reflected a loss of Na(+)-K(+)-ATPase units, the time course of its recovery postexercise, and whether this depressed activity was related to increased Na(+)-K(+)-ATPase isoform gene expression. Fifteen subjects performed fatiguing, knee extensor exercise at approximately 40% maximal work output per contraction. ...

Very fast ramp stretches at 9.5-33 sarcomere lengths s(-1) (l0 s(-1)) stretching speed, 16-25 nm per half-sarcomere (nm hs(-1)) amplitude were applied to activated intact frog muscle fibres at tetanus plateau, during the tetanus rise, during the isometric phase of relaxation and during isotonic shortening. Stretches produced an almost linear ...

The aim of this study was to investigate the potential mechanisms underlying the efficacy of graded exercise therapy for chronic fatigue syndrome (CFS). Forty-nine CFS patients were randomized to a 12-week graded exercise programme or to standard medical care. At the end of treatment the exercise group rated themselves as ...

The aim of the present study was to evaluate static fracture loads of ProTaper Nickel-Titanium instruments that had been subjected to various degrees of cyclic fatigue. Torque and angle at failure of new instruments and instruments that had been stressed to 30, 60, or 90% of their cyclic fatigue rotations ...

OBJECTIVES: To define isometric exercise-induced pressor responses in patients with cerebrovascular accidents (CVAs) and to assess potential cardiovascular and sympathetic nervous system abnormalities during isometric exercise in CVA. DESIGN: Nonrandomized study. SETTING: University laboratory setting. PARTICIPANTS: Eight men with CVA who had documented damage of subcortical structures and 8 sex-matched ...

We hypothesized that patients with chronic obstructive pulmonary disease developing contractile fatigue of the quadriceps during cycle exercise may have characteristic metabolic and muscle features that could increase their susceptibility to fatigue, thus differentiating them from those who do not develop fatigue. We examined, in 32 patients, the fiber-type proportion, ...

This study investigated the cardiovascular response to a standard external muscle compression during concomitant muscle metaboreflex stimulation of varying intensity in human calf muscle. Eleven healthy male subjects (mean (s.d.) age, 26 (5.6) years; height, 177 (5) cm; weight, 74.3 (6.8) kg) were seated in an isometric dynamometer with the ...

Previously, long-term changes in the motor cortex have been reported after repetitive electrical nerve stimulation (rES) as well as after motor exercise. The purpose of this study was to investigate whether the effects of voluntary motor cortical drive and of rES on the motor cortical output in healthy subjects interact ...

OBJECTIVE: To date, no study has tested the reproducibility of EEG changes that occur during driver fatigue. For the EEG changes to be useful in the development of a fatigue countermeasure device the EEG response during each onset period of fatigue in individuals needs to be reproducible. It should be ...

Exercise can have profound effects on numerous biologic systems within the human body, including the central nervous system (CNS). The inherent complexity of the CNS, and the methodologic difficulties in evaluating its in vivo neurochemistry in humans, provide challenges to investigators studying the impact of exercise on the CNS. As ...

This brief review summarizes key epidemiological and experimental evidence concerning relationships between chronic physical activity and feelings of energy (vigor, vitality) and fatigue. The epidemiological studies show a positive association between the amount of typical weekly physical activity reported and the frequency with which people report feeling energetic. The randomized ...

Fatigue in the elderly population is a complex phenomenon. Although a number of factors contributing to the fatigue have been identified, its basic mechanism remains elusive. Additional research on prevalence, identification, diagnosis, severity of fatigue, and associated factors and the role of exercise as an effective treatment modality could lead ...

It is hypothesised that physical activity is controlled by a central governor in the brain and that the human body functions as a complex system during exercise. Using feed forward control in response to afferent feedback from different physiological systems, the extent of skeletal muscle recruitment is controlled as part ...

Epidemiological evidence indicates that sudden loading of the torso is a risk factor for low back injury. Accurately quantifying the time-varying loading of the spine during sudden loading events and how these loading profiles are affected by workplace factors such as fatigue, expectation, and training can potentially lead to intervention ...

AIM: Our purpose was to investigate the effect of a relaxation breathing exercise on fatigue in allogenic haemopoietic stem cell transplantation patients. BACKGROUND: Exercise is a promising approach in ameliorating the fatigue associated with cancer and its treatment. DESIGN: A randomized design with control, experimental groups being assessed pre- and ...

Electrical stimulation (ES) reverses the order of recruitment of motor units (MU) observed with voluntary muscular contraction (VOL) since under ES, large MU are recruited before small MU. The superimposition of ES onto VOL (superimposed technique: application of an electrical stimulus during a voluntary muscle action) can theoretically activate more ...

Chronic fatigue syndrome (CFS) is characterized by severe fatigue and a reduction in activity levels. The purpose of this study was to provide an overview of design, reliability, and validity of the CFS Activities and Participation Questionnaire (CFS-APQ). The CFS-APQ was constructed based on a retrospective analysis of the Karnofsky ...

The mechanism(s) of neuromuscular fatigue depends on the approach or model used to study fatigue. We evaluate the physiological and functional relevance of the fatigue quantification system, the fatigue protocols, the preparations, and muscle environmental conditions used in various models involving either artificial stimulation or voluntary exercise to induce fatigue.

BACKGROUND AND PURPOSE: This was a descriptive and exploratory study of electromyographic (EMG) activity of wrist extensor musculature specific to the extensor digitorum (ED), extensor carpi radialis brevis (ECRB) and flexor carpi radialis (FCR) in individuals with a medical diagnosis of the common work associated complaint of lateral epicondylitis (LE). ...

The response of muscle to volitional or electrically induced stimuli is affected by its contractile history. Fatigue is the most obvious effect of contractile history reflected by the inability of a muscle to generate an expected level of force. However, fatigue can coexist with post-activation potentiation (PAP), which serves to ...

Three quarters of patients who respond to treatment with the newer antidepressants still complain of fatigue. Fatigue is one of the most common and disturbing residual symptoms of depression. Increased serotonin activity in certain areas of the brain contributes to fatigue. It can be counteracted by dopaminergic agents which, interestingly, ...

BACKGROUND: Chronic fatigue syndrome (CFS) is defined by debilitating fatigue that is exacerbated by physical or mental exertion. To search for markers of CFS-associated post-exertional fatigue, we measured peripheral blood gene expression profiles of women with CFS and matched controls before and after exercise challenge. RESULTS: Women with CFS and ...

Many patients with Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP) experience excessive fatigue, which may persist for years and reduce quality of life. The authors performed a 12-week study of bicycle exercise training in 20 patients with severe fatigue, 16 with relatively good recovery from GBS, and 4 ...

This study examined the effect of whole body hyperthermia on the voluntary activation of exercised and non-exercised skeletal muscle performing a series of lengthening and shortening contractions. Thirteen subjects exercised on a cycle ergometer at 60% of maximal oxygen consumption until voluntary exhaustion in ambient conditions of approximately 40 degrees ...

A model is proposed in which the development of physical exhaustion is a relative rather than an absolute event and the sensation of fatigue is the sensory representation of the underlying neural integrative processes. Furthermore, activity is controlled as part of a pacing strategy involving active neural calculations in a ...

This study examined the effects of extended sessions of heavy intermittent exercise on quadriceps muscle fatigue and weakness. Twelve untrained volunteers (10 men and 2 women), with a peak oxygen consumption of 44.3 +/- 2.3 ml.kg(-1).min(-1), exercised at approximately 91% peak oxygen consumption for 6 min once per hour for ...

To test for evidence of a muscle pump effect during steady-state upright submaximal knee extension exercise, seven male subjects performed seven discontinuous, incremental exercise stages (3 min/stage) at 40 contractions/min, at work rates ranging to 60-75% peak aerobic work rate. Cardiac cycle-averaged muscle blood flow (MBF) responses and contraction-averaged blood ...

OBJECTIVES: To determine whether Gulf War veterans with neuromuscular symptoms that included weakness and fatigue had either 1) objective correlates for muscle weakness or fatigue; or 2) any etiologic explanation for such symptoms; and if so, 3) whether such objective measures or etiologic mechanisms were specific to Gulf War service. ...

The effects of a 20-min nap during 2 h of visual display terminal (VDT) work were examined. Ten young healthy adults took a 20-min nap or a 20-min rest I h after VDT work, followed by another 1 h of VDT work. A 20-min rest temporarily restored subjective sleepiness, but ...

OBJECTIVE: To investigate the effects of aerobic and strength exercise on motor fatigue of knee flexor and extensor muscles in subjects with multiple sclerosis (MS). DESIGN: A randomized controlled trial. SETTING: At Masku Neurological Rehabilitation Centre, Masku, and the Social Insurance Institution, Research Department, Turku, Finland. SUBJECTS: Ninety-five MS patients ...

This investigation was designed to determine if vibration during fatiguing resistance exercise would alter associated patterns of muscle activity. A cross-over design was employed with 8 subjects completing a resistance exercise bout once with a vibrating dumbbell (V) (44 Hz, 3 mm displacement) and once without vibration (NV). For both ...

Driver fatigue has been the cause of traffic accidents. Despite this, the amount of time that drivers spend within cars has been increasing due to complex city life, traffic congestion, and particular occupational requirements. Consequently, fatigue and stress cannot be avoided. In present study, in order to find out the ...

This study examined whether muscle fatigue alters the facilitatory effect of motor imagery on corticospinal excitability. We aimed to determine if post-exercise depression of potentials evoked magnetically from the motor cortex is associated with alterations in internally generated movement plans. In experiment 1, motor-evoked potentials (MEPs) were recorded from two ...

Stretch-shortening cycle (SSC)-type fatigue is associated with acute and delayed functional defects, and appears to be a useful model to reveal the flexibility of both central and reflex adjustments to the contractile failure. SSC fatigue was induced in an experimental (EXP) group (n=6) on a sledge ergometer with an exhaustive ...

OBJECTIVE: This study aimed to explore cross-sectional and longitudinal associations between pathological worry and fatigue in a working population. METHODS: In employees with very low or very high fatigue levels, psychometrics of the Penn State Worry Questionnaire (PSWQ; measuring pathological worry) and the Checklist Individual Strength (CIS; measuring fatigue) were ...

OBJECTIVE: This pilot study was designed to determine the effects of interferon beta-1a (IFNB) therapy (Avonex) on cortically evoked motor potentials (MEPs) during resting and fatigued states in individuals with multiple sclerosis (MS). METHODS: Eight women with relapsing-remitting MS (mean age 36) and mean Expanded Disability Status Scale (EDSS) score ...

The aim of the present study was to elucidate the electrophysiological manifestations of selective fast motor unit (MU) activation by electrical stimulation (ES) of knee extensor muscles. In six male subjects, test contraction measurement at 40% maximal voluntary contraction (MVC) was performed before and at every 5 min (5, 10, ...

OBJECTIVES: To investigate aspects of the validity of the total scores of the Tampa Scale for Kinesiophobia (TSK), Dutch Version, which was modified to make it an appropriate questionnaire for the assessment of kinesiophobia (fear of movement) in chronic fatigue syndrome (CFS) patients (the Dutch TSK-CFS), and, using this assessment ...

A central debate in the exercise sciences is the cause of the fatigue that develops especially during high intensity exercise of short duration. The most popular theory holds that this form of exercise is limited by a peripherally based, metabolite induced failure of skeletal muscle contractile function, independent of reduced ...

Exercise-induced loss of skeletal muscle K(+) can seriously impede muscle performance through membrane depolarization. Thus far, it has been assumed that the negative equilibrium potential and large membrane conductance of Cl(-) attenuate the loss of force during hyperkalaemia. We questioned this idea because there is some evidence that Cl(-) itself ...