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

The effects of three isoenergetic diets on metabolic and appetite responses to prolonged intermittent walking were investigated. Eight men undertook three 450-min walks at intensities varying between 25-30 and 50-55% of maximal O2 uptake. In a balanced design, the subjects were given breakfast, snacks, and lunch containing total carbohydrate (CHO), protein (P), and fat (F) in the following amounts (g/70 kg body mass): mixed diet, 302 CHO, 50 P, 84 F; high-CHO diet, 438 CHO, 46 P, 35 F; high-fat diet, 63 CHO, 44 P, 196 F. Substrate balance was calculated by indirect calorimetry over the 450-min exercise period. Blood samples were taken before exercise and every 45 min during the exercise period. The high-fat diet resulted in a negative total CHO balance (-140 +/- 1 g) and a lower negative fat balance (-110 +/- 33 g) than the other two diets (P < 0.05). Plasma glucagon, nonesterified fatty acids, glycerol, and 3-hydroxybutyrate were higher with the high-fat diet (P < 0.05 vs. high CHO), whereas plasma insulin was lower after high fat (P < 0.05 vs. mixed and high CHO). Subjective ratings of fatigue and appetite showed no differences between the three trials. Although diet influenced the degree of total CHO and fat oxidation, fat was the main source of energy in all trials.
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PMID:Metabolic and appetite responses to prolonged walking under three isoenergetic diets. 1196 Sep 58

The transverse (T-)tubules primarily function in conducting the action potentials that initiate excitation contraction coupling in skeletal muscle but may additionally subserve longer-term roles in volume regulation, membrane fusion and other trafficking processes. Osmotic shock thus both electrically detaches the T-tubules from surface membrane ('detubulation') and produces tubular vacuolation. The present experiments separated these effects. An established, reference osmotic shock protocol that exposed muscles to Ca2+/Mg2+-Ringer and gradual cooling to 10 degrees C after 18 min in glycerol-Ringer accomplished significant detubulation (77.5+/-13.15%, mean +/- SEM; n = 4). In contrast, a test protocol conducted entirely at room temperature using Mg2+-rather than Ca2+/ Mg2+-Ringer yielded reduced (P < 0.05, post hoc Duncan's multiple range test) detubulation indices (1.67+/-1.67%, n = 6) statistically indistinguishable from findings in fibres spared osmotic shock. Yet both osmotic shocks caused a formation of closed vacuoles, demonstrated by Sulphorhodamine B trapping, that occupied statistically similar fractions of total fibre volume (reference procedure: 14.38+/-2.7%, n = 6; test procedure: 13.36+/-2.00%, n = 22) in turn higher than determinations in control fibres (P < 0.05). The findings reconcile reports associating detubulation with vacuolation in osmotically shocked muscle [S. Nik-Zainal et al. (1999) J Muscle Res Cell Motil 20: 45-53; K.N. Khan et al. (2000) J Muscle Res Cell Motil 21: 79-90] with the persistence of tubular electrical activity in extensively vacuolated amphibian fibres following fatigue [J. Lannergren and H. Westerblad (1987) Acta Physiol Scand 129: 311-318; J. Lannergren et al. (1999) J Muscle Res Cell Motil 20: 19-32]. Furthermore test protocols produced higher densities of open vacuoles (13.38+/-2.33%, n = 9) than did reference protocols (6.66+/-1.63%, n = 20) contrary to their possible involvement in the electrophysiological changes. Abolition of tubular electrophysiological activity thus either follows or is independent of tubular vacuolation whilst sharing some of its underlying osmotic mechanisms.
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PMID:Persistent tubular conduction in vacuolated amphibian skeletal muscle following osmotic shock. 1196 71

Feeding a high-fat diet increases fat utilisation and may decrease glycogen utilisation resulting in a lower lactate production during moderate exercise. The effects of fat feeding on exercise- and lipid metabolism-associated blood variables were evaluated in 6 Standardbred horses during submaximal exercise. The horses were fed a high- (11.8% fat in total dietary dry matter) or a low-fat diet (1.5% fat) in a cross-over experiment with feeding periods of 4 weeks. At the end of each feeding period, the horses were subjected to a submaximal standardised stepwise exercise test on a treadmill. Blood samples were obtained prior to the start, during the last 10 s of each exercise step, and after recovery (40 min walking in hand). Pre-exercise test values for plasma lactate, pH, pCO2, ionised sodium, ionised potassium, ionised calcium, ionised chloride, glucose, nonesterified fatty acids and glycerol did not differ for the 2 diets. The pre-exercise concentration of triacylglycerols was significantly lower on the high- compared to the low-fat diet (mean +/- s.d. 0.17 +/- 0.06 and 0.23 +/- 0.08 mmol/l, respectively), whereas the concentrations of cholesterol (3.00 +/- 0.47 and 2.11 +/- 0.49 mmol/l, respectively), HDL cholesterol (1.80 +/- 0.18 and 1.35 +/- 0.27 mmol/l, respectively) and phospholipids (2.30 +/- 0.11 and 1.72 +/- 0.20 mmol/l, respectively) were significantly higher. There was significantly less plasma lactate accumulation during exercise when the horses were given the high-fat diet (P = 0.011). Horses on a low-fat diet had significantly different plasma lipid values when compared to being on a high-fat diet. The alterations in these values during and after moderate exercise were comparable for both diets. These results indicate that fat metabolism is significantly adapted on a high-fat diet; feeding such a diet may enhance potential performance by delaying lactate accumulation and thereby delaying the onset of fatigue.
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PMID:Exercise- and metabolism-associated blood variables in Standardbreds fed either a low- or a high-fat diet. 1240 55

We aimed to examine the effects of different energy intakes on a range of responses that are relevant to the safety of hill walkers. In a balanced design, 16 men completed a strenuous self-paced mountainous hill walk over 21 km, under either a low-energy (2.6 MJ; 616 kcal) intake (LEI) or high-energy (12.7 MJ; 3,019 kcal) intake (HEI) condition. During the hill walk, rectal temperatures were measured continuously, and blood samples for the analysis of metabolites and hormones were drawn before breakfast and immediately after the walk. Subjects also completed a battery of performance tests that included muscular strength, reaction times, flexibility, balance, and kinesthetic differentiation tests. During the LEI, mean blood glucose concentrations leveled off at the low-middle range of normoglycemia, whereas, on the HEI, they were significantly elevated compared with the LEI. The maintained blood glucose concentrations, during the LEI, were probably mediated via the marked fat mobilization, reflected by a two- to fivefold increase in nonesterified fatty acids, 3-hydroxybutyrate, and glycerol concentrations. The LEI group showed significantly slower one- and two-finger reaction time, had an impaired ability to balance, and were compromised in their ability to maintain body temperature, when compared with the HEI group. The modestly impaired performance (particularly with respect to balance) and thermoregulation during the LEI condition may increase susceptibility to both fatigue and injury during the pursuit of recreational activity outdoors.
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PMID:Physiological, metabolic, and performance implications of a prolonged hill walk: influence of energy intake. 1257 Nov 36

The amounts of water, carbohydrate and salt that athletes are advised to ingest during exercise are based upon their effectiveness in attenuating both fatigue as well as illness due to hyperthermia, dehydration or hyperhydration. When possible, fluid should be ingested at rates that most closely match sweating rate. When that is not possible or practical or sufficiently ergogenic, some athletes might tolerate body water losses amounting to 2% of body weight without significant risk to physical well-being or performance when the environment is cold (e.g. 5-10 degrees C) or temperate (e.g. 21-22 degrees C). However, when exercising in a hot environment ( > 30 degrees C), dehydration by 2% of body weight impairs absolute power production and predisposes individuals to heat injury. Fluid should not be ingested at rates in excess of sweating rate and thus body water and weight should not increase during exercise. Fatigue can be reduced by adding carbohydrate to the fluids consumed so that 30-60 g of rapidly absorbed carbohydrate are ingested throughout each hour of an athletic event. Furthermore, sodium should be included in fluids consumed during exercise lasting longer than 2 h or by individuals during any event that stimulates heavy sodium loss (more than 3-4 g of sodium). Athletes do not benefit by ingesting glycerol, amino acids or alleged precursors of neurotransmitter. Ingestion of other substances during exercise, with the possible exception of caffeine, is discouraged. Athletes will benefit the most by tailoring their individual needs for water, carbohydrate and salt to the specific challenges of their sport, especially considering the environment's impact on sweating and heat stress.
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PMID:Fluid and fuel intake during exercise. 1497 32

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 availability and exercise fatigue. Ten recreationally trained men ( n=5) and women ( n=5), with maximal oxygen consumption (VO(2max))of 51.6 (3.0) and 44.3 (1.4) ml kg(-1) min(-1), respectively, were studied on two occasions following an overnight fast, before and after n-3fa supplementation (4 g day(-1) for 4 weeks). The exercise trials consisted of a 75-min treadmill run at 60% VO(2max) followed immediately by a high-intensity incremental bout to fatigue. Measurements included exercise monitors, plasma volume (PV), triglycerides (TG), FFA, glycerol, lactate, and glucose. Free Trp and branched-chain amino acids (BCAA) were measured and correlated with time to fatigue; all blood variables were corrected for PV. Free Trp, lactate, glucose, FFA, and glycerol were not significantly different between trials, but TG ( P<0.001) and the free Trp/BCAA ratio were significantly lower after n-3fa use [1.76 (0.18)x10(-2) microg ml(-1)] versus before supplementation [2.17 (0.22), P=0.033]. There was a non-significant increase in time to fatigue after supplementation [10.2 (0.3) min] versus before n-3fa use [9.7 (0.2), P=0.068], and a tendency for higher BCAA levels after supplementation, P=0.068. However, neither free Trp nor the free Trp/BCAA ratio significantly predicted time to fatigue. In conclusion, n-3fa supplementation did not diminish free Trp concentrations or significantly improve endurance performance during a maximal bout of exercise.
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PMID:Effect of n-3 fatty acids on free tryptophan and exercise fatigue. 1505 85

To study the effects of carbohydrate (CHO) supplementation on performance changes and symptoms of overreaching, six male endurance cyclists completed 1 wk of normal (N), 8 days of intensified (ITP), and 2 wk of recovery training (R) on two occasions in a randomized crossover design. Subjects completed one trial with a 6% CHO solution provided before and during training and a 20% solution in the 1 h postexercise (H-CHO trial). On the other occasion, subjects consumed a 2% CHO solution at the same time points (L-CHO). A significant decline in time to fatigue at approximately 63% maximal power output (H-CHO: 17 +/- 3%; L-CHO: 26 +/- 7%) and a significant increase in mood disturbance occurred in both trials after ITP. The decline in performance was significantly greater in the L-CHO trial. After ITP, a significant decrease in estimated muscle glycogen oxidation (H-CHO: N 49.3 +/- 2.9 kcal/30 min, ITP 32.6 +/- 3.4 kcal/30 min; L-CHO: N 49.1 +/- 30 kcal/30 min, ITP 39.0 +/- 5.6 kcal/30 min) and increase in fat oxidation (H-CHO: N 16.3 +/- 2.4 kcal/30 min, ITP 27.8 +/- 2.3 kcal/30 min; L-CHO: N 16.9 +/- 2.6 kcal/30 min, ITP: 25.4 +/- 3.5 kcal/30 min) occurred alongside significant increases in glycerol and free fatty acids and decreases in free triglycerides in both trials. An interaction effect was observed for submaximal plasma concentrations of cortisol and epinephrine, with significantly greater reductions in these stress hormones in L-CHO compared with H-CHO after ITP. These findings suggest that CHO supplementation can reduce the symptoms of overreaching but cannot prevent its development. Decreased endocrine responsiveness to exercise may be implicated in the decreased performance and increased mood disturbance characteristic of overreaching.
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PMID:Effects of carbohydrate supplementation on performance and carbohydrate oxidation after intensified cycling training. 1515 17

Electrocortical effects of long duration exercise on cognitive function were investigated by analyzing P300 amplitude and latency changes during a 3-h cycling exercise. P300 components were measured in 12 well-trained cyclists and blood glucose, cortisol, insulin, glycerol, and free fatty acids (FFAs) epinephrine and norepinephrine were analyzed. Results indicated that P300 components were affected by exercise with a temporary increase in amplitude between the 1st and the 2nd hour and an increase in latency after 2 h of exercise concomitant with some hormonal changes, including an increase in cortisol and epinephrine and a decrease in blood glucose. These findings suggest a combined effect of arousal and central fatigue on electrocortical indices of cognitive function during acute physical exercise.
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PMID:Effects of long duration exercise on cognitive function, blood glucose, and counterregulatory hormones in male cyclists. 1519 81

Microdialysis is a technique for sampling the chemistry of the interstitial fluid of tissues and organs in animal and man. It is minimally invasive and simple to perform in a clinical setting. Although microdialysis samples essentially all small molecular substances present in the interstitial fluid the use of microdialysis in neurointensive care has focused on markers of ischemia and cell damage. The lactate/pyruvate ratio is a well-known marker of changes in the redox state of cells caused by ischemia Glycerol is an integral component of cell membranes. Loss of energy due to ischemia eventually leads to an influx of calcium and a decomposition of cell membranes, which liberates glycerol into the interstitial fluid. Thus the lactate/pyruvate ratio and glycerol have become the most important markers of ischemia and cell membrane damage. While the primary insult at the site of the accident is beyond our control, secondary insults during intensive care should be avoided by all means. Therefore, the single most important finding from microdialysis studies is the dramatic difference in the vulnerability of the penumbra surrounding a lesion as compared to normal brain tissue allowing early detection of secondary insults after traumatic brain injury as well as the onset of vasospasm after subarachnoid hemorrhage.
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PMID:Microdialysis in neurointensive care. 1528 90

Bilaterality in acute low-tone sensorineural hearing loss (ALHL) is more generally recognized than that in idiopathic sudden sensorineural hearing loss. Subjects were 274 patients diagnosed with ALHL based on criteria of a study group of the Ministry of Health, Labor and Welfare of Japan, i.e., total of 3 low tone hearing of 70dB or more and, a total of 3 high-tone hearing of 60dB or less, and treated at the departments of otolaryngology at Yamanashi University and Suwa Central Hospital. ALHL involving bilateral ears symptoms and/or bilateral hearing impairment conforming to diagnostic criteria was selected and summarized. Clinical ear symptoms, clinical test results, and hearing levels (total 3 low tone hearing, 1kHz, and total of 3 high-tone hearing) were statistically analyzed. We also reviewed Japanese clinical reports of ALHL that include bilateral cases. In 32 cases (11.7%) of 274 cases, both ear symptoms and hearing impairment were bilateral. In 22 (8.0%) of the 274, bilateral ear symptoms were present, but showed unilateral hearing loss conforming to diagnostic criteria. Another 22 (8.0%) out the 274 reported unilateral ear symptoms, but hearing tests indicated bilateral ALHL. A total of 76 cases (27.7%) of the 274 had bilaterality in either ear symptoms or hearing loss. Our review indicated that 9.0% (162 of 1803) ALHL patients were bilaterally affected, possibly indicating that AIHL includes a larger number of bilateral cases than currently assumed, if the opposite side were given a especially detailed clinical interview. Statistical analysis (Mann Whitney test, P<0.01) of hearing of unilateral cases indicated that 3 low tone hearing was more affected than 3 high-tone hearing, even on the normal side. These results indicate that ALHL tends to be bilateral, possibly due to the mechanism of pathogenesis, and also that the mechanism may include both local and general conditions. This more closely resembles Meniere's disease than idiopathic sudden sensorineural hearing loss. Both sides of bilateral cases were not usually the same in hearing patterns, glycerol test results, or prognosis. A statistically significant difference (Mann Whitney test, P<0.01) in total of 3 low tone hearing was seen between worse and better sides in bilateral cases. The degree of disease on both sides in bilateral cases thus was not always the same. Bilateral cases may result from both the influence of general conditions such as fatigue, stress, and lack of sleep and local conditions such as pathogenesis of endolymphatic hydrops that may cause differences in both ears. No clear difference was seen in clinical symptoms, hearing levels, and clinical examination, e.g., Schellong and glyceol tests, between unilateral and bilateral cases. Bilateral cases had a poorer prognosis (lower complete recovery ratio; chi2 test P<0.01) than unilateral cases. Our results indicated that cautious evaluation of opposite ear is necessary in diagnosis, treatment, and prognostication of ALHL.
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PMID:[Bilaterality in acute low-tone sensorineural hearing loss]. 1582 87


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