OBJECTIVE: To evaluate motor cortex excitability changes by transcranial magnetic stimulation (TMS) following repetitive muscle contractions in patients with multiple sclerosis (MS); to state whether a typical pattern of post-exercise motor evoked potentials (MEPs) is related to clinical fatigue in MS. METHODS: In 41 patients with definite MS (32 with ...

The objective of this study was to explore the nature of fatigue in cancer patients with advanced stages of disease undergoing chemotherapy and concurrently participating in a 6-week multidimensional exercise programme (physical exercise, relaxation, massage and body-awareness training). Semi-structured qualitative interviews were conducted with 23 patients between 18 and 65 ...

Muscle functional MRI (mfMRI) has been proposed as a tool for noninvasively measuring the metabolic and hemodynamic responses to muscle activation, but its theoretical basis remains unclear. One challenge is that it is difficult to isolate individually those variables affecting the magnitude and temporal pattern of the mfMRI response. Therefore, ...

BACKGROUND: 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 ...

Fatigue is an inevitable consequence of physical activity; yet its biological cause remains uncertain. During exercise, a polypeptide messenger molecule interleukin-6 (IL-6) is actively produced. Previously, the administration of recombinant IL-6 (rhIL-6) induced a heightened sensation of fatigue in healthy humans at rest. In contrast, anti-IL-6 receptor antibodies reduced the ...

It is a popular belief that exercise performance is limited by metabolic changes in the exercising muscles, so called peripheral fatigue. Exercise terminates when there is a catastrophic failure of homoeostasis in the exercising muscles. A revolutionary theory is presented that proposes that exercise performance is regulated by the central ...

Visual analogue scale has been shown to reflect subjective feelings but rarely has it been used for musculoskeletal fatigue so in the present study VAS ratings were used to quantify musculoskeletal fatigue. A total of 20 students underwent a fatigue protocol (M age=21.3 yr., SD= 1.0). A series of randomized ...

The purpose of this study was to estimate the level of muscular activation and muscle fatigue of the low back muscles during the performance of an intermittent prone back extension (PBE) exercise. Forty-one healthy students (24 males and 17 females) lying prone on a bench with the legs fixed performed ...

The contribution of central and peripheral factors to muscle fatigue were quantified following a high-intensity uphill running exercise. Eight male volunteers performed an intermittent exercise at 120 % of maximal aerobic speed on a treadmill with an 18 % grade. Electrically evoked and voluntary contractions of the knee extensors and ...

Resistance exercise can result in both potentiating and fatiguing responses. These responses can acutely affect performance, which may affect subsequent exercise sessions in the same day. The purpose of this investigation was to study the acute neuromuscular responses to two high intensity training sessions in the same day. Twelve recreationally ...

PURPOSE: This study investigated the time course of contractile and neural alterations of knee extensor (KE) muscles during a long-duration running exercise. METHODS: Nine well-trained triathletes and endurance runners sustained 55% of their maximal aerobic velocity (MAV) on a motorized treadmill for a period of 5 h. Maximal voluntary contraction ...

Falls from heights resulting from a loss of balance are a major concern in the occupational setting. Previous studies have documented a deleterious effect of lower extremity fatigue on balance. The purpose of this study was to investigate the effect of lumbar extensor fatigue on balance during quiet standing. Additionally, ...

Following forceful exercise that leads to muscle fatigue, the size of muscle evoked responses (MEPs) generated by transcranial magnetic stimulation (TMS) in the exercised muscle is depressed over a prolonged period. Strong evidence implicates intracortical mechanisms in this depression. As well as evoking MEPs in contralateral muscles, TMS also reduces ...

PURPOSE: To evaluate whether muscle contraction-induced variability of limb femoral arterial blood flow (FABF) can be reduced with longer sampling durations. This was assessed in relation to muscle contraction-relaxation cycles (CRcycles) during steady-state, one-legged, dynamic knee-extensor exercise (KEE) at varying "exercise intensities" and "contraction frequencies." METHODS: Eleven male subjects performed ...

BACKGROUND/PURPOSE: The authors studied gastrointestinal motility in a patient with total intestinal aganglionosis (TIA) and the effect of octreotide (OCT) on ileal motility in this patient. METHODS: The 3200-g girl received ileostomy at 50 cm proximal to the ileocecal site and jejunostomy at 15 cm distal to the ligament of ...

This study tested the hypothesis that skeletal muscle contraction activates nuclear factor-kappaB (NF-kappaB), a putative regulator of muscle protein breakdown. Muscle biopsies were obtained from the vastus lateralis of healthy humans before, immediately after, and 1 h after fatiguing resistance exercise of the lower limbs. Biopsies were analyzed for nuclear ...

OBJECTIVE: To determine the effect of yoga and of aerobic exercise on cognitive function, fatigue, mood, and quality of life in multiple sclerosis (MS). METHODS: Subjects with clinically definite MS and Expanded Disability Status Score less than or equal to 6.0 were randomly assigned to one of three groups lasting ...

The purpose of this research was to provide more definitive support for the hypothesis that prolonged muscle activation at high intensities increases voluntary activation deficits. Interpolated twitch responses were evoked during maximal and sub-maximal voluntary contractions of the soleus muscle in 10 college-aged students. Maximal voluntary contractions (MVC), maximal muscle ...

AIM: The purpose of this study was to examine the effect of fatigue resulting from supramaximal dynamic exercise on cerebral cortex activity. METHODS: Five healthy male subjects (age 24.6+/-0.4 years, body weight 62.9+/-1.1 kg, height 175.3+/-1.2 cm, and maximal O2 uptake per body mass 48.4+/-1.3 ml/kg/min) participated in this study. ...

Previous studies have suggested that during sustained maximal voluntary and evoked contractions, decreasing activation rates may minimize fatigue. The idea of gradually decreasing stimulation frequency to preserve force during fatiguing isometric contractions has, however, recently been challenged. The primary purpose of this study was to test the effectiveness of decreasing ...

It has been suggested that the effects of old age on the ability to resist fatigue may be task dependent. To test one aspect of this hypothesis, we compared the neuromuscular responses of nine young (26 +/- 4 yr, mean +/- SD) and nine older (72 +/- 4 yr) healthy, ...

The objective of this study was to investigate whether a warm-up consisting of a series of maximal contractions would augment the force and activation of subsequent leg extensor contractions. Both voluntary and evoked isometric contractions were tested to determine the mechanisms underlying the response. Nine subjects were tested for twitch, ...

This study was designed to evaluate the suitability of nonlinear recurrence quantification analysis (RQA) in assessing electromyograph (EMG) signals during dynamic exercise. RQA has been proven to be effective in analyzing nonstationary signals. The subject group consisted of 19 male patients diagnosed with low back pain. EMG signals were recorded ...

To test whether there is a regional difference in the exercise pressor reflex within a given muscle, we investigated the relationship between the inflection points of cardiovascular responses and muscle oxygenation during exercise. Seven subjects performed incremental exercise, which consisted of incremental 30-s static knee extensions, each separated by 30 ...

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) ...

We investigated the effects of physical fatigue produced by swimming exercise on learning the Morris water maze in BALB/c mice. We measured the escape latency in the maze immediately after the swimming exercise. The control group was soaked in the water but not fatigued. For easier tasks, like one with ...

Free tryptophan (Trp), which is augmented by liberated free fatty acids (FFA) from adipose tissue, can induce mental fatigue via serotonin during exercise. Since an attenuation in FFA has been observed with omega-3 fatty acid (n-3fa) use, our purpose was to examine the effect of n-3fa supplementation on free Trp ...

Accumulation of K+ in skeletal muscle interstitium during intense exercise has been suggested to cause fatigue in humans. The present study examined interstitial K+ kinetics and fatigue during repeated, intense, exhaustive exercise in human skeletal muscle. Ten subjects performed three repeated, intense (61.6+/-4.1 W; mean+/-SEM), one-legged knee extension exercise bouts ...

Magnetic stimulation of the motor cortex with electromyographic recordings from exercising muscles has shown corticospinal excitability to be depressed following exercise. We now investigate whether this depression spreads to non-exercising muscles and its influence on performance. Healthy volunteers made unilateral biceps curls to exhaustion and, in another later session, for ...

During exercise, activation of the sympathetic nervous system causes reflex renal vasoconstriction. The effects of aging on this reflex are poorly understood. This study evaluated the effects of age on renal vasoconstrictor responses to handgrip. Seven older (65 +/- 9 yr) and nine younger (25 +/- 2 yr) subjects were ...

This review addresses cerebral metabolic and neurohumoral alterations during prolonged exercise in humans with special focus on associations with fatigue. Global energy turnover in the brain is unaltered by the transition from rest to moderately intense exercise, apparently because exercise-induced activation of some brain regions including cortical motor areas is ...

OBJECTIVE: In an attempt to examine whether impairments in cardiorespiratory fitness are associated with daily functioning in patients with chronic fatigue syndrome (CFS), this study addresses the correlations between exercise capacity and activity limitations/participation restrictions. DESIGN: Prospective observational study. SETTING: An outpatient tertiary care, chronic fatigue clinic at the Vrije ...

Muscle blood flow (MBF) and muscle oxygen saturation (SmO(2)) were measured at eight locations (four proximal, four distal) over a 4 x 8 cm(2) area of the vastus lateralis at rest and immediately after isometric, maximal quadriceps contraction using multichannel, frequency-domain, near-infrared spectroscopy. A venous occlusion was applied 20 s ...

The major symptom of chronic fatigue syndrome is extreme fatigue and an increase in fatigue following exertion. Many patients reduce physical activity to avoid such fatigue and thus become increasingly weak and less fit. Exercise testing does not exacerbate symptoms. Even though a fair amount of variability exists in symptoms ...

This study investigated the effects of prolonged exercise performed in normoxia (N) and hypoxia (H) on neuromuscular fatigue, membrane excitability, and Na+-K+ -ATPase activity in working muscle. Ten untrained volunteers [peak oxygen consumption (Vo2peak) = 42.1 +/- 2.8 (SE) ml x kg(-1) x min(-1)] performed 90 min of cycling during ...

Exercise has been shown to cause an increase in the concentration of brain serotonin (5-hydroxytryptamine, 5-HT) in humans and experimental animals. The increase in brain serotonin coincides with the onset of fatigue and is referred to as "central fatigue". Experiments in humans and animals involving serotonin receptor agonists have demonstrated ...

The exacerbation of symptoms after exercise differentiates Chronic fatigue syndrome (CFS) from several other fatigue-associated disorders. Research data point to an abnormal response to exercise in patients with CFS compared to healthy sedentary controls, and to an increasing amount of evidence pointing to severe intracellular immune deregulations in CFS patients. ...

Experiments with electrophysiology of the heart have been essential for the progress in diagnostics and pharmacotherapy of cardiovascular diseases. The aim of the study was to establish the influence of a new propranolol analogue on mechanical and bioelectrical activity of the rabbit heart in vitro. In the experiment, propranolol (1-isopropylamino-3-[1-naphthoxy]-2-propanol ...

We questioned if a non-linear increase in ventilation defining a ventilatory threshold (V(Th)) accompanied the electromyographic (EMG) signs of neuromuscular fatigue. Indeed, the intramuscular accumulation of metabolites may activate the afferent nervous pathways responsible for both the 'muscle wisdom' phenomenon and the respiratory centre activation. During inframaximal (50%) handgrip sustained ...

BACKGROUND: Define covariates of cerebrospinal corticotropin-releasing hormone (CRH) levels in normal humans. CRHCSF was measured in 9 normal subjects as part of an intensive study of physiological responses stressors in chronic pain and fatigue states. CRHCSF was first correlated with demographic, vital sign, HPA axis, validated questionnaire domains, baseline and ...

During constant-load exercise above the lactate threshold, oxygen-uptake kinetics deviate from the pattern seen below the threshold, with an additional, delayed component superimposed on the monoexponential pattern. It was hypothesised that this slow component is due to the progressive recruitment of type II muscle fibres. Oxygen uptake was measured for ...

The role of muscle potentiation in overcoming low-frequency fatigue (LFF) as it developed during submaximal voluntary exercise was investigated in eight males (age 26.4 +/- 0.7 years, mean +/- SE) performing isometric leg extension at approximately 30% of maximal voluntary contraction for 60 min using a 0.5-duty cycle (1 s ...

The influence of different work-to-rest (W:R) ratios during fatigue induced by maximal eccentric contractions is unknown. The present study sought to expand the understanding of the task-dependent nature of eccentric contractions, and the associated fatigue, during exercise and acute as well as extended recovery periods. Using a Biodex multi-joint dynamometer, ...

The purpose of this study was to examine neuromuscular factors that may contribute to post exercise force loss and subsequent recovery after exhaustive stretch-shortening cycle (SSC) exercise. Six subjects were fatigued on a sledge apparatus by 100 maximal rebound jumps followed by continuous submaximal jumping until complete exhaustion. Exercise-induced changes ...

The purpose of the present study was to relate the expected inter-subject variability in voluntary drive of the knee extensor muscles during a sustained isometric contraction to the changes in firing rates of single motor units. Voluntary activation, as established with superimposed electrical stimulation was high (range: 91-99%, n=8) during ...

This study aimed to verify if the level of biceps femoris antagonist activity measured during isometric knee extension was affected by the individual degree of adiposity in 14 young healthy subjects of both genders aged between 18 and 24. Surface EMG signals were recorded from the biceps femoris muscle of ...

Most patients with cancer experience fatigue, a severe activity-limiting symptom with a multifactorial origin. To avoid cancer-related fatigue, patients are frequently advised to seek periods of rest and to reduce their amount of physical activity. This advice is reminiscent of that formerly given to patients with heart disease. However, such ...

The authors studied standard autonomic function tests and measures of heart rate variability in 60 patients with multiple sclerosis (MS) and correlated results with the Fatigue Severity Scale and the Modified Fatigue Impact Scale. The authors found that autonomic responses correlated with fatigue resembling a hypoadrenergic orthostatic response, possibly due ...

It is unknown whether changes in corticomotor excitability follow exercise in healthy humans. We hypothesized that a fall in the diaphragm and quadriceps motor-evoked potential (MEP) amplitude elicited by transcranial magnetic stimulation of the motor cortex would occur after an incremental exercise task. In 11 healthy subjects, we measured transdiaphragmatic ...

The production of reactive oxygen species in skeletal muscle is linked with muscle fatigue. This study investigated whether the antioxidant compound N-acetylcysteine (NAC) augments time to fatigue during prolonged, submaximal cycling exercise. Seven men completed a double-blind, crossover study, receiving NAC or placebo before and during cycling exercise, comprising 45 ...