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

A novel, simple, rapid, sensitive and reproducible microassay is described for determination of myoglobin and hemoglobin content of myocardial and skeletal muscle biopsy specimens from various mammals, birds and fish. As little as 50 mg of tissue is needed and myoglobin concentrations lower than 1 mg% can be detected. Myoglobin and hemoglobin are separated at alkaline pH by ammonium sulfate extraction followed by ultrafiltration. Heme content is determined by absorption of the Soret band when the hemoprotein extract is visibly colored or more sensitively by its peroxidase activity when the extract has low color. The heme reacts with tertiary-butyl hydroperoxide and orthotolidine to generate a blue color. Hemoglobin content is correlated with myoglobin content and is related to aerobic capacity and blood flow to the tissue. Myoglobin content varied over 5 orders of magnitude up to 7 per cent of the weight of tissue, whereas hemoglobin content varied over 2 orders of magnitude up to 6 per cent of tissue weight. Myoglobin content is increased in species with high basal metabolic rate, high physical activity, prolonged diving capacity, fatigue resistance, and red muscle, whereas it is decreased in white muscle, iron-deficient animals, animals with sedentary lifestyles, and in animals and tissues with small fiber diameters such as avian or fish hearts.
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PMID:Rapid, simple and sensitive microassay for skeletal and cardiac muscle myoglobin and hemoglobin: use in various animals indicates functional role of myohemoproteins. 132 34

CO binding kinetics to the homodimeric myoglobin (Mb) from Nassa mutabilis has been investigated between pH 1.9 and 7.0. Protonation of the proximal imidazole at low pH (less than or equal to 3.0) and the consequent cleavage of the HisF8NE2-Fe proximal bond brings about a approximately 20-fold increase of the second-order rate constant for CO binding. This process displays a pKa = 4.0 +/- 0.2, significantly higher than that observed in all other deoxygenated hemoproteins investigated up to now. Such a feature underlies a decreased energy for the HisF8NE2-Fe proximal bond in the unliganded form and it also appears supported by resonance Raman spectroscopy in the low frequency region of the Fe(II) deoxygenated hemoprotein. Further, the pH-rate profile of N. mutabilis Mb, like that of the homodimeric hemoglobin (Hb) from Scapharca inaequivalvis (Coletta, M., Boffi, A., Ascenzi, P., Brunori, M. and Chiancone, E. (1990) J. Biol. Chem. 265, 4828-4830), can be described only by assuming a concerted proton-linked transition with n = 1.8 +/- 0.1. Such a characteristic suggests, also on the basis of the amino acid sequence homology between N. mutabilis Mb and S. inaequivalvis Hb in the region forming the subunit interface, that the interaction mechanism is similar for the two homodimeric proteins, and drastically different Hb in the region forming the subunit interface, that the interaction mechanism is similar for the two homodimeric proteins, and drastically different from that operative in other hemoproteins.
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PMID:Alteration of the proximal bond energy in the unliganded form of the homodimeric myoglobin from Nassa mutabilis. Kinetic and spectroscopic evidence. 173 75

The purpose of this study was to evaluate the effects of 6 weeks of low-intensity continuous exercise training (CE; 40 min at 50% VO2peak, 3 days/week) and high-intensity interval exercise training (IE: 10 x 2 min at VO2peak, 3 days/week) on the parameters of the power-endurance time relationship for cycle ergometry. The hyperbolic relationship between power and endurance time was linearized by expressing the power against the inverse of time, as described by Whipp et al. (22). This model consists of two parameters: theta f, a fatigue threshold reflecting the capability for sustained aerobic power, and W', a constant postulated to reflect a finite energy store (i.e., those factors comprising the O2 deficit: Phosphagen stores, anaerobic glycogenolysis, myoglobin O2 stores). Prior to training, test-retest reliability coefficients (r2) for theta f and W' were 0.92 and 0.62, respectively (P less than 0.01). Training resulted in significant (P less than 0.01) increases in theta f for both CE [27 +/- 3 W (13.4%) increase] and IE [33 +/- 5 W (15.0%) increase], with no difference between groups. Increases in theta f were not dependent upon improvements in VO2peak. W' was not changed significantly in either group after training. However, a significant negative correlation between the training-induced changes in theta f and W' (R = 0.76; P less than 0.01) was obtained. The minimum intensity threshold for exercise training necessary to elicit increases in theta f has yet to be identified, but is at least as low as 50% of VO2peak.
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PMID:Effects of continuous and interval training on the parameters of the power-endurance time relationship for high-intensity exercise. 325 31

The clinical symptoms of 55 patients with primary fibromyalgia (PF) were studied and compared with 30 patients with rheumatoid arthritis (RA). The PF patients expressed a more intense feeling of illness than did the RA patients. Stiffness occurred just as often in PF as in RA. Trigger points occurred less frequently in RA patients. Muscular fatigue appeared to be one of the most disabling symptoms in PF. Neurophysiological studies indicated that the fatigue was at least partly of central origin. Ischemic forearm exercise test gave no evidence of impaired glycogenolysis. Laboratory investigation revealed normal 25-hydroxyvitamin D, cobalamin, folate, estrogen, testosterone, and myoglobin in the PF patients.
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PMID:Primary fibromyalgia. A clinical and laboratory study of 55 patients. 346 25

In sports, vitamins along with minerals, particularly iron, and the energy nutrients such as carbohydrates, are considered especially important. Frequently single or multiple vitamins in combination with other active substances such as iron, other minerals or carbohydrates are administered. In sports, vitamins are added to carbohydrate mixtures or electrolytes enriched with vitamins are offered and frequently used. There is no doubt that due to the numerous effects of vitamins, a connection must exist between the vitamin status and athletic performance capability. It can be concluded that vitamin deficiencies have a negative effect on physical and mental performance. The release of energy can only attain its maximum output when the organism has the required substances at its disposal. Iron is of central importance among these active substances, since its presence in haemoglobin is essential for the transport of oxygen and carbon dioxide, makes it possible for myoglobin to function as an oxygen supply depot and guarantees the functioning of internal respiration in the respiratory chain and various key enzymes. Muscle training increases not only the respiratory chain but also several other iron-rich enzymes. This makes even more astonishing the fact that a variety of recently published articles report on iron deficiency among athletes. The effect of the iron deficiency with anaemia (sports anaemia) is manifest in a reduction of aerobic capacity with an increase in lactate acidosis, greater fatigue, loss of appetite, muscular cramps and vasomotor disturbances.
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PMID:[Effect of vitamins and iron on performance and recovery in humans and in sports anemia]. 360 97

The fast-twitch extensor digitorum longus (EDL) and the slow-twitch soleus muscle of the rat consist of heterogeneous fiber populations. EDL muscle fibers differ in size, mitochondrial content, myoglobin concentration, and thickness of the Z line. The sarcoplasmic reticulum, on the other hand, is richly developed in all fibers, with only small variation. Myofibrils are clearly circumscribed at both the A and I band level. The soleus muscle is composed primarily of fibers with moderate mitochondrial content and myoglobin concentration. In most fibers the sarcoplasmic reticulum is poorly developed, with the exception of the portion of reticulum in phase with the Z line. As a consequence the myofibrillar fields are amply fused together. Contacts between sarcoplasmic reticulum and T system are discontinuous and may occur in the form of "dyads" instead of the typical triad structure. In a small proportion of soleus muscle fibers the organization and development of the sarcoplasmic reticulum is similar to that of EDL muscle fibers, with prominent fenestrated collars at the H band level. In these fibers mitochondria are larger and more abundant. The results are correlated with physiological studies on motor units in the same and in similar rat muscles. It is suggested that the variable structural pattern of rat muscle fibers is related to two distinct physiological parameters, speed of contraction and resistance to fatigue.
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PMID:Relations between structure and function in rat skeletal muscle fibers. 551 49

Patients with neuromuscular diseases have low levels of cardiovascular fitness and they fatigue rapidly during daily activities. The purpose of this investigation was to determine whether patients with slowly-progressive or non-progressive neuromuscular diseases could complete a 12-wk training program without untoward responses, and develop cardiovascular training adaptations. All eight patients completed the training program with better than 90% compliance. Resting creatine kinase and myoglobin in the group as a whole showed no change with training, though two patients did have definite elevations after training. Their VO2max increased by 25 +/- 5% with training and their relative increase in VO2max was not different from that of healthy subjects undergoing the same training. Heart rate reductions during submaximal exercise were somewhat delayed or non-existent in the two patients with Charcot-Marie-Tooth disease, a hereditary neuropathy. However, the six patients with myopathies had heart rate adaptations similar to those in healthy subjects. Thus, some patients with slowly-progressive or non-progressive neuromuscular diseases can undergo exercise training and in many cases demonstrate adaptations not different from those in healthy subjects. Patients with different diseases, however, need not respond uniformly, in terms of training adaptations or markers of muscle damage. Therefore, each disease must be considered individually.
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PMID:Effect of training on the exercise responses of neuromuscular disease patients. 651 64

Near infrared spectroscopy (NIRS) is a noninvasive technique of monitoring tissue oxygen saturation by detecting changes in tissue absorbance of two wavelengths (850 and 760 nm) reflecting the relative oxygenation of hemoglobin and myoglobin. Aim of the present study was to determine whether changes in skeletal muscle oxygen saturation during incremental exercise detected by NIRS can reflect an impared oxygen delivery and an early onset of anaerobic metabolism in patients with chronic heart failure (CHF). We studied 19 subjects (mean age 43 +/- 16 years). Seven patients had a history of CHF with a diagnosis of ischemic cardiomyopathy (Group A) and 12 were healthy sedentary (Group B). All patients had a history of dyspnea on exertion (NY-HA II), peripheral edema, pulmonary rales and cardiac gallop sounds over the last 6 months. They were in sinus rhythm and stable clinical condition in the last 3 months. They were well matched regarding age, sex and body surface area. All subjects performed an incremental work rate test in a ramp pattern on a upright cycle ergometer until volitional fatigue. Gas exchange was measured breath by breath with a metabolic chart. Muscle oxygenation was determined, transcutaneously, during the exercise test over the vastus lateralis muscle with NIRS. At peak exercise, work rate, VO2, anaerobic threshold (LAT), heart rate and systolic blood pressure were significantly lower in Group A compared to Group B (92 +/- 28 vs 232 +/- 17 watts; 14 +/- 2 vs 21 +/- 2 ml/kg/min; 868 +/- 225 vs 1317 +/- 354 ml/min; 149 +/- 7 vs 172 +/- 18 b/min; 145 +/- 18 vs 195 +/- 21 mm Hg, respectively; p < 0.0001 for all). In both groups, as work rate increased, tissue oxygenation initially either remained constant near resting levels or decreased. In both groups, muscle oxygenation decreased more steeply near the work rate where lactic acidosis (LAT) was detected. However, patients with CHF had an earlier acceleration in muscle deoxygenation compared to the other group, indicating a premature onset of anaerobic metabolism. Moreover, Group A had a flatter increase in both heart rate and systolic blood pressure and a steeper slope of oxygenation profile at all matched workloads compared to normals (Group A: -0.13 +/- 0.03 ml/min; Group B: -0.06 +/- 0.015 ml/min; p < 0.0001). The LAT correlated with the work rate at which the rate of tissue O2 desaturation accelerated (r = 0.94; p < 0.0001).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Near infrared spectroscopy and changes in skeletal muscle oxygenation during incremental exercise in chronic heart failure: a comparison with healthy subjects. 764 20

Patients with chronic heart failure (CHF) are frequently limited by muscle fatigue resulting from impaired skeletal muscle blood flow. Accordingly, we assessed working skeletal muscle oxygenation in such patients using near-infrared (NIR) spectroscopy. Nine normal subjects (mean age 52 years) and 12 patients with CHF (mean age 60 years) were studied. NIR spectroscopy was used to monitor relative changes in oxygenated hemoglobin (Hb) and myoglobin (Mb) (oxy Hb/Mb), deoxygenated Hb and Mb (deoxy Hb/Mb), and total (oxy + deoxy) Hb and Mb (total Hb/Mb) contents in the vastus lateralis muscle at rest, during warm-up (0 W, 30 cycles/min for 3 min), incremental maximal supine bicycle exercise (ramp protocol, 15 W/min, 50 cycles/min), and recovery. At peak exercise the patients exhibited reduced heart rate, systolic blood pressure, peak exercise oxygen consumption (VO2; 15 +/- 3.0 ml/kg/min vs 32 +/- 8.5 ml/kg/min), and workload (99 +/- 23.4 W vs 183 +/- 68.4 W) as compared with the normal subjects. The respiratory quotient was comparable in both groups. In the normal subjects, oxy Hb/Mb was increased from the warm-up period to the early phase of exercise, followed by a progressive decrease to peak exercise. In the recovery phase, oxy Hb/Mb was increased abruptly. For these patients, change in oxy Hb/Mb followed a pattern similar to that seen in normal subjects, and oxy Hb/Mb was decreased earlier in contrast to that in the normal subjects. There was a significant difference in the change of oxy Hb/Mb during warm-up, early phase exercise, and recovery between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Assessment of working skeletal muscle oxygenation in patients with chronic heart failure. 790 Jun 19

Patients with fibromyalgia often complain of fatigue and pain during exercise and of worsening of pain days after exercise. The aim of the study described here was to determine if abnormal changes in potassium or lactate could be observed during an exercise test in fibromyalgia. Whether an abnormal incline in plasma creatine kinase or myoglobin could be observed days after the test was studied also. Fifteen female fibromyalgia patients and 15 age- and sex-matched controls performed a stepwise incremental maximal bicycle-ergometer test. Blood samples were collected from a catheter in a cubital vein. The changes in heart rate, potassium levels, and haematocrit during the exercise test were similar in the two groups. The maximal obtained lactate concentration was 4.2 mmol l-1 (3.5-5.6) in the patients as compared to 4.9 mmol l-1 (3.9-5.9) in the controls (NS). The estimated anaerobic threshold of 2 mmol l-1 was reached at a heart rate of 124 min-1 in the patients with fibromyalgia as compared to 140 min-1 in the controls (P = 0.02). In relation to workload, the patients scored higher on a Borg scale for perceived exertion during exercise, but if the Borg score was related to lactate no significant difference was found. The patients reported 86% and 79% of maximal pain in the thighs on the visual analogue scale 1 and 2 days after the test, but the creatine kinase and myoglobin concentrations were not increased.
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PMID:Biochemical changes in relation to a maximal exercise test in patients with fibromyalgia. 820 47


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