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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We hypothesized that muscle fiber bundles produce reactive oxygen intermediates and that reactive oxidant species contribute to muscular fatigue in vitro. Fiber bundles from rat diaphragm were mounted in chambers containing Krebs-Ringer solution. In studies of intracellular oxidant kinetics, bundles were loaded with 2',7'-dichlorofluorescin, a fluorochrome that emits at 520 nm when oxidized; emissions were quantified using a fluorescence microscope. Emissions from unstimulated muscles increased over time (P < 0.001). Accumulation of fluorescence was slowed by addition of catalase (P < 0.001) or superoxide dismutase (P < 0.001) and was accelerated by repetitive muscular contraction (P < 0.05). To determine effects of reactive oxygen intermediates on fatigue, curarized bundles were stimulated to contract isometrically; force was measured. Catalase, superoxide dismutase, and dimethyl sulfoxide were screened for effects on low- and high-frequency fatigue. Antioxidants inhibited low-frequency fatigue [after 5 min of repetitive contractions, force at 30 Hz was 20% greater than control (P < 0.015)] and increased the variability of fatigue at 30 Hz (P < 0.03). Antioxidants did not alter high-frequency (200-Hz) fatigue. We conclude that 1) diaphragm fiber bundles produce reactive oxygen intermediates, including O2-. and H2O2; 2) muscular contraction increases intracellular oxidant levels; and 3) reactive oxygen intermediates promote low-frequency fatigue in this preparation.
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PMID:Reactive oxygen in skeletal muscle. I. Intracellular oxidant kinetics and fatigue in vitro. 147 54

Twelve male subjects, ages 18-32, performed low, moderate, and high intensity systemic treadmill exercise to examine its effect on isometric strength and fatigue of the handgrip muscles. Baseline handgrip values were recorded, as well as maximal oxygen uptake and ventilatory threshold (VT), to determine the intensity for each of the three exercise conditions. Task A involved a 10-min treadmill run at 20% below VT, task B was given at VT, and task C was 20% above VT. Immediately following the endurance treadmill run the subjects were given a 2-min isometric contraction at maximum intensity. Heart rate and blood pressure were also measured. No significant differences were found between control measures and the strength and endurance variables. Rates of fatigue were similar for all conditions, and heart rate and blood pressure remained elevated during the handgrip fatigue task. It is concluded that isometric strength and endurance of non-involved muscles are not affected by prior endurance exercise.
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PMID:The effects of treadmill running on the isometric fatigue of the handgrip muscles. 148 15

Seven healthy subjects exercised to exhaustion on a bicycle ergometer at a power output corresponding to 70% of maximum oxygen uptake after administration of either a placebo or 20 mg of paroxetine, a serotonin re-uptake inhibitor. Exercise time after paroxetine (median 94 min; range 84-127 min) was less (P < 0.05) than after placebo (median 116 min; range 86-133 min). The metabolic and cardiorespiratory responses to exercise were the same in both trials. This result supports the suggestion that there is a central component to fatigue which is mediated by the activity of serotoninergic neurones.
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PMID:Evidence for a possible role of 5-hydroxytryptamine in the genesis of fatigue in man: administration of paroxetine, a 5-HT re-uptake inhibitor, reduces the capacity to perform prolonged exercise. 148 48

This report describes a case of epinephrine predominant pheochromocytoma successfully managed intraoperatively with an infusion of diltiazem. A 50-yr-old woman with a 10-yr history of diabetes mellitus was admitted to the hospital because of thirst and general fatigue. A cystic left adrenal tumor was found on computed tomographic scan. Although resting plasma catecholamine levels were normal, plasma norepinephrine and epinephrine levels obtained from the left adrenal vein were 1.6 ng.ml-1 (normal, 0.04-0.35) and 6.2 ng.ml-1 (normal, less than 0.12), respectively. Diltiazem was administered i. v. at a rate of 3 micrograms.kg-1.min-1 before induction of anesthesia. Anesthesia was induced with enflurane 2-3% and nitrous oxide in oxygen, followed by tracheal intubation facilitated with vecuronium. Anesthesia was maintained with enflurane 1-3% and nitrous oxide in oxygen. Paralysis was maintained with vecuronium. Hypertension during the manipulation of the tumor was controlled by increasing the inspired concentration of enflurane or by increasing the infusion rate of diltiazem to 5 micrograms.kg-1.min-1. There was no tachyarrhythmia. The infusion of diltiazem was continued until the draining vein from the tumor had been ligated. Hypotension, after removal of the tumor, was treated by the rapid infusion of fluid. Plasma norepinephrine and epinephrine levels during tumor manipulation were 1.18 ng.ml-1 and 6.57 ng.ml-1, respectively.
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PMID:[Use of diltiazem in the anesthetic management of epinephrine predominant pheochromocytoma]. 149 89

Exercise performance and dyspnea in COPD patients have been shown to be improved with supplemental oxygen, although the exact mechanisms resulting in the improvement are still unclear. The purpose of the present study was to investigate a possible relationship between ventilatory muscle function and sensation of dyspnea (modified Borg Scale) during exercise on 20% O2 and 30% O2. Eight patients with COPD (FEV1 1.06 L +/- 0.30 L) exercised on a treadmill two times breathing compressed air or 30% oxygen with a one hour rest in between. The electrical activity of the diaphragm (EMGdi) was recorded with esophageal electrodes, and that of the sternomastoid muscle (EMGsm) was recorded from the fine wire electrodes. The ratio of high frequency (150 to 350 Hz) to low frequency (20 to 47 Hz) power (H/L) of EMGdi was analyzed to assess diaphragmatic fatigue, which was defined as a 20% fall of H/L ratio from the control value. Flow, volume, O2 Saturation (SaO2), esophageal pressure (Pes) and transdiaphragmatic pressure (Pdi) were measured. Tension time index (TTdi) was calculated from Pdi and the ratio of inspiratory time to total time for one cycle (Ti/Ttot). At rest, we measured maximal esophageal pressure (Pesmax), maximal transdiaphragmatic pressure (Pdimax), maximal integrated EMGdi (EMGdimax) and EMGsm (EMGsmmax). Incremental exercise was discontinued by dyspnea. The walking distance achieved was increased in all patients on 30% O2. Dyspnea and desaturation were significantly improved on 30% O2 breathing, and the onset of diaphragmatic fatigue was delayed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Dyspnea and ventilatory muscle function during exercise on air and oxygen breathing in patients with chronic obstructive pulmonary disease (COPD)]. 150 86

Two patients with obstructive sleep apnoea syndrome are reported where the initial presenting complaint was of lingual ulceration. This unusual presentation has not been reported previously. Both patients experienced frequent apnoeic episodes during sleep with a profound fall in the arterial oxygen saturation. It is postulated that the lingual ulceration resulted from repeated trauma to the tongue by the teeth as the patient made violent inspiratory efforts at the termination of an apnoeic episode. The diagnosis of sleep apnoea syndrome was based upon suggestive symptoms of snoring, morning fatigue and day-time somnolence plus a minimum of 15 apnoeic episodes per hour of sleep. The first-line investigations of this condition are available in all district general hospitals and a diagnosis of sleep apnoea syndrome obtained. Referral to a regional sleep study centre may be appropriate prior to the commencement of therapy. Management is predominantly medical, consisting of weight loss and the administration of nocturnal nasal continuous positive airways pressure.
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PMID:Obstructive sleep apnoea syndrome presenting as lingual ulceration. 151 Sep 3

The purpose of this investigation was to determine whether the concept of the critical power could be applied to competitive swimming by using critical swimming speed (CS) as determined both in the swimming flume (CS-flume) and in the normal swimming pool (CS-pool) and whether CS could be utilized as a practical index for assessing a swimmer's endurance performance. CS defined as the swimming speed which could be theoretically maintained continuously without exhaustion was expressed as the slope of a regression line between swimming distance (D) and its duration (T) obtained at various swimming speeds. Eight highly trained swimmers were instructed to swim until onset of fatigue at four predetermined swimming speed levels in the swimming flume and at maximal effort over four different swimming distances in the swimming pool. In the results of CS-flume and CS-pool, the regression relations between D and T were expressed in the general form, D = a+b x T, with r2 being higher than 0.998 (p less than 0.01), respectively. These results both from the flume and the pool indicated extremely good linearity. Furthermore, maximal oxygen uptake (VO2max) during the incremental exercise test, swimming speed corresponding 4 mM of blood lactate concentration (V-OBLA) and mean velocity in the 400 m freestyle (V-400) were measured on each subject.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A simple method for determining critical speed as swimming fatigue threshold in competitive swimming. 152 52

The purpose of this study was to compare respiratory responses with moderate and slow rates of unsupported arm exercise (UAE) with a newly developed electromechanical device. Twenty-one patients with chronic obstructive pulmonary disease (COPD) were studied. Exercise endurance limits, metabolic, ventilatory and sensation outcomes were determined at rest prior to exercise and at end-exercise endurance limits. Increases from baseline rest for both exercise rates were observed in: oxygen uptake, carbon dioxide production, inspiratory flow, minute ventilation, respiratory rate, dyspnea, respiratory effort, and arm fatigue. Endurance limits were similar for both rates of UAE. These data provide standards against which UAE in COPD can be evaluated.
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PMID:Standardization of a device to measure unsupported arm exercise endurance in chronic obstructive pulmonary disease. 152 10

Subjects cycled at a work load calculated to elicit 75% of maximal oxygen uptake on two occasions: the first to fatigue (34.5 +/- 5.3 min; mean +/- SE), and the second at the same workload and for the same duration as the first. Biopsies were obtained from the quadriceps femoris muscle before and immediately after exercise, and 5 min post-exercise. Before the first experiment, muscle glycogen was lowered by a combination of exercise and diet, and before the second, experiment muscle glycogen was elevated. In the low glycogen condition (LG), muscle glycogen decreased from 169 +/- 15 mmol glucosyl units kg-1 dry wt at to rest to 13 +/- 6 after exercise. In the high glycogen condition (HG) glycogen decreased from 706 +/- 52 at rest to 405 +/- 68 after exercise. Glycogen synthase fractional activity (GSF) was always higher during the LG treatment. During exercise in the HG condition, those subjects who cycled for less than 35 min (n = 3) had GSF values in muscle which were lower than at rest, whereas those subjects who cycled for greater than 35 min (n = 4) had values which were similar to or higher than at rest. Thus the change in GSF in muscle during HG was positively related to the exercise duration (r = 0.94; y = 254-17x + 0.3x2; P less than 0.001) and negatively related to the glycogen content at the end of exercise (r = -0.82; y = 516-2x + 0.001x2; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of low glycogen on glycogen synthase in human muscle during and after exercise. 152 22

Exercise performance in essential hypertension (EH) and its relations to blood pressure (BP) response and left ventricular hypertrophy (LVH) were studied. Twenty-three patients with mild to moderate EH and 12 controls underwent symptom-limited (except BP elevation more than 250 mm Hg) ergometer exercise. Exercise performance was evaluated by the oxygen uptake (VO2/kg) at anaerobic threshold (AT) and at peak exercise (Peak). Left ventricular geometry and function, and left ventricular mass index (LVMI) were measured using echocardiography. The endpoints of 12 patients (group A) and controls were fatigue. The endpoints of 11 patients (group B) were BP elevation. Though both group A and group B had concentric hypertrophy, group B showed severe LVH compared to group A and controls. The VO2/kg at AT or at Peak was not different among the three groups. Neither BP response or LVMI correlated with exercise performance in EH. We conclude that exercise performance is not disturbed in EH; that BP response to exercise is not related to exercise performance in EH; and that concentric LVH may be a compensatory mechanism to maintain exercise capacity against exaggerated BP elevation in EH.
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PMID:Exercise performance in essential hypertension with special reference to blood pressure response and left ventricular hypertrophy. 153 18


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