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Prolonged Exercise (prolonged + exercise)
Selected AbstractsIncreased fat oxidation and regulation of metabolic genes with ultraendurance exerciseACTA PHYSIOLOGICA, Issue 1 2007J. W. Helge Abstract Aim:, Regular endurance exercise stimulates muscle metabolic capacity, but effects of very prolonged endurance exercise are largely unknown. This study examined muscle substrate availability and utilization during prolonged endurance exercise, and associated metabolic genes. Methods:, Data were obtained from 11 competitors of a 4- to 5-day, almost continuous ultraendurance race (seven males, four females; age: 36 ± 11 years; cycling o2peak: males 57.4 ± 5.9, females 48.1 ± 4.0 mL kg,1 min,1). Before and after the race muscle biopsies were obtained from vastus lateralis, respiratory gases were sampled during cycling at 25 and 50% peak aerobic power output, venous samples were obtained, and fat mass was estimated by bioimpedance under standardized conditions. Results:, After the race fat mass was decreased by 1.6 ± 0.4 kg (11%; P < 0.01). Respiratory exchange ratio at the 25 and 50% workloads decreased (P < 0.01) from 0.83 ± 0.06 and 0.93 ± 0.03 before, to 0.71 ± 0.01 and 0.85 ± 0.02, respectively, after the race. Plasma fatty acids were 3.5 times higher (from 298 ± 74 to 1407 ± 118 ,mol L,1; P < 0.01). Muscle glycogen content fell 50% (from 554 ± 28 to 270 ± 25 nmol kg,1 d.w.; n = 7, P < 0.01), whereas the decline in muscle triacylglycerol (from 32 ± 5 to 22 ± 3 mmol kg,1 d.w.; P = 0.14) was not statistically significant. After the race, muscle mRNA content of lipoprotein lipase and glycogen synthase increased (P < 0.05) 3.9- and 1.7-fold, respectively, while forkhead homolog in rhabdomyosarcoma, pyruvate dehydrogenase kinase 4 and vascular endothelial growth factor mRNA tended (P < 0.10) to be higher, whereas muscle peroxisome proliferator-activated receptor , co-activator-1, mRNA tended to be lower (P = 0.06). Conclusion:, Very prolonged exercise markedly increases plasma fatty acid availability and fat utilization during exercise. Exercise-induced regulation of genes encoding proteins involved in fatty acid recruitment and oxidation may contribute to these changes. [source] Association between fatigue and failure to preserve cerebral energy turnover during prolonged exerciseACTA PHYSIOLOGICA, Issue 1 2003L. Nybo Abstract Aim: This study evaluated if the fatigue and apathy arising during exercise with hypoglycaemia could relate to a lowering of the cerebral metabolic rates of glucose and oxygen. Methods and results: Six males completed 3 h of cycling with or without glucose supplementation in random order. Cerebral blood flow, metabolism and interleukin-6 (IL-6) release were evaluated with the Kety,Schmidt technique. Blood glucose was maintained during the glucose trial, while it decreased from 5.2 ± 0.1 to 2.9 ± 0.3 mmol L,1 (mean ± SE) after 180 min of exercise in the placebo trial with a concomitant increase in perceived exertion (P < 0.05). During hypoglycaemia, the cerebral glucose uptake was reduced from 0.34 ± 0.05 to 0.28 ± 0.04 ,mol g,1 min,1, while the cerebral uptake of , -hydroxybutyrate increased to 5 ± 1 pmol g,1 min,1 (P < 0.05). The reduced glucose uptake was accompanied by a lowering of the cerebral metabolic rate of oxygen from 1.84 ± 0.19 mmol g,1 min,1 during exercise with glucose supplementation to 1.60 ± 0.16 mmol g,1 min,1 during hypoglycaemia (P < 0.05). In addition, the cerebral IL-6 release was reduced from 0.4 ± 0.1 to 0.0 ± 0.1 pg g,1 min,1 (P < 0.05). Conclusions: Exercise-induced hypoglycaemia limits the cerebral uptake of glucose, exacerbates exercise, reduces the cerebral metabolic rate of oxygen and attenuates the release of IL-6 from the brain. [source] Thyroid hormone responses to endurance exerciseEQUINE VETERINARY JOURNAL, Issue S36 2006E. A. GRAVES Summary Reasons for performing study: Limited information exists about changes in circulating thyroid hormone concentrations during prolonged endurance exercise in horses. Objective: To examine the effects of prolonged exercise on serum iodothyronine concentrations in horses performing endurance exercise of varying distances. Methods: Serum concentrations of iodothyronines were measured in horses before and after completion of 40, 56, 80 and 160 km endurance rides (Study 1); daily during a 5 day, 424 km endurance ride (Study 2); and before and for 72 h after completion of a treadmill exercise test simulating a 60 km endurance ride (Study 3). Results: In Study 1, 40 and 56 km of endurance exercise had little effect on serum iodothyronine concentrations with the exception of a 10% decrease (P<0.05) in free thyroxine (FT4) concentration after the 56 km ride. In contrast, total thyroxine (T4), total triiodothyronine (T3), FT4 and free triiodothyronine (FT3) concentrations all decreased (P<0.05) after successful completion of 80 and 160 km rides, with decreases ranging from 13,31% and 47,54% for distances of 80 and 160 km, respectively. Further, pre-ride T4 concentration was lower (P<0.05) and FT3 concentration was higher (P<0.05) in horses competing 160 km as compared to horses competing over shorter distances. In Study 2, serum concentrations of T4, T3 and reverse triiodothyronine (rT3) progressively decreased (P<0.05) over the course of the multi-day ride. In Study 3, the greatest decrease (P<0.05) in all iodothyronines was observed at 12 h of recovery, ranging from 25% for FT4 to 53% for FT3, but all thyroid hormone concentrations had returned to the pre-exercise values by 24 h of recovery. Conclusion: Endurance exercise results in transient decreases in serum iodothyronine concentrations. Potential relevance: These data are important to consider when thyroid gland function is assessed by measurement of serum iodothyronine concentrations in endurance horses. [source] Estimating fat and protein fuel from fat and muscle scores in passerinesIBIS, Issue 4 2009VOLKER SALEWSKI Fat is the prime energy source for birds during prolonged exercise, but protein is also catabolized. Estimates of the amount of catabolizable fat and protein (termed fat and protein fuel) are therefore important for studying energetics of birds. As fat and protein fuel can only be measured by sacrificing individuals or by use of technically complex methods, scoring systems were invented to estimate fat and protein fuel of birds in the field. The visible subcutaneous fat deposits and the thickness of the flight muscles are each scored on an ordinal scale but these scales do not correspond linearly to fat and protein fuel within species, which is needed for analyses such as flight range estimates. We developed an anova -type model to estimate fat and protein fuel from fat scores (FS) and muscle scores (MS) along with total mass and a size measurement. Using data from 11 337 individuals of eight passerine species (Common Nightingale Luscinia megarhynchos, Eurasian Reed Warbler Acrocephalus scirpaceus, Melodious Warbler Hippolais polyglotta, Willow Warbler Phylloscopus trochilus, Orphean Warbler Sylvia hortensis, Garden Warbler Sylvia borin, Common Whitethroat Sylvia communis, Subalpine Warbler Sylvia cantillans) mist-netted in Mauritania, West Africa, we tested for independence of FS and MS and for variation in the relationship between scores and associated mass in response to physiological state. FS, MS and third primary length (size) explained variation in body mass of all eight species analysed (R2: 0.56,0.77). The parameter estimates of the model showed that fat and protein fuel increased monotonically with increasing fat and muscle scores. In two species we found small differences in the estimates between physiological states (seasons). We evaluated our model by comparing the predicted body mass of birds with both FS and MS equal to 0 with the mean body mass of individuals mist-netted with both scores equal to zero. The values were very close. The amount of fat extracted from dead Garden and Willow Warblers was within the range of predicted fat fuel derived from the model. We conclude that our model is a useful non-invasive method to estimate simultaneously mean fat and protein fuel of small passerines and we provide recommendations on its use. [source] Blood serum branched chain amino acids and tryptophan modifications in horses competing in long-distance rides of different lengthJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 3-4 2004A. Assenza Summary During long-distance exercise, branched-chain amino acid (BCAA) catabolism could lead to an increase in the blood tryptophan/BCAA ratio and an early onset of ,central fatigue'. Based on these considerations, we studied the modifications of blood serum BCAA and tryptophan (Try) levels in 30 endurance horses competing in rides varying in distance from 20 to 72 km. From all horses, blood samples were drawn just before and just after the end of the ride. Samples were analysed for their leucine (Leu), valine (Val), isoleucine (Iso) and Try levels. Data were processed by anova, using sampling moment and ride as factors, and by LSD post hoc test. Significant differences were recorded among the different distance rides for Leu, Val, Iso, Try, Try/BCAA ratio; the same trend was recorded between samples taken at the start and the end of the race for Val and Leu. The main effect observed was an increase of BCAA levels for all rides, except the 72-km ride; for Try, a significant increase was present in all races, except the 50-km ride. The Try/BCAA ratio decreased in 20- and 50-km races and increased in the others. These data confirm that long-distance exercise involves a mobilization of BCAA. The utilization of BCAA seems to be important in prolonged exercise: in the 72-km ride, we observed a decrease in BCAA blood serum levels, while a major role of Try was indicated by its increase, resulting in a rise of the Try/BCAA ratio. [source] Sex differences in long bone fatigue using a rat modelJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2006Luisa D. Moreno Abstract Stress fractures can occur because of prolonged exercise and are associated with cyclic loading. Fatigue is the accumulated damage that results from cyclic loading and bone fatigue damage is of special concern for athletes and army recruits. Existing literature shows that the rates of stress fracture for female athletes and female army recruits are higher than their male counterparts. In this study, we used an ex vivo rat model to investigate the fatigue response of female and male bones. We determined the strain versus number of cycles to failure (S/N) for each sex and found that for a certain initial strain (5,000,7,000 µ,) female bones have shorter fatigue life. To further characterize the bone response to fatigue, we also determined the creep that occurred during the fatigue test. From the creep data, for a certain strain range, female bones accumulated greater residual strains and reached the critical strain at a faster rate. In summary, this study demonstrates that female rat bones have a lower resistance to fatigue in the absence of a physiological response such as muscle fatigue or osteogenic adaptation. From these results, we hypothesized that creep was the underlying mechanism that accounted for the fast deterioration of female bones during fatigue. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1926,1932, 2006 [source] Prevalence of Diarrhea and Enteropathogens in Racing Sled DogsJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2010E. McKenzie Background: Diarrhea is highly prevalent in racing sled dogs, although the underlying causes are poorly understood. Hypothesis: Clostridium perfringens enterotoxin (CPE) and Clostridium difficile Toxin A and B are associated with diarrhea in racing sled dogs. Animals: One hundred and thirty-five sled dogs. Methods: Freshly voided feces were obtained from 55 dogs before racing and from 80 dogs after 400 miles of racing. Samples were visually scored for diarrhea, mucus, blood, and melena. CPE and C. difficile Toxin A and B were detected by ELISA. Samples were cultured for C. perfringens, C. difficile, Campylobacter, Salmonella, and Escherichia coli 0157; Giardia and Cryptosporidium spp. were detected via immunofluorescence. Results: Diarrhea occurred in 36% of dogs during racing, and hematochezia, fecal mucus or melena, or all 3 occurred in 57.5% of dogs. Salmonella was isolated from 78.2% of dogs before racing, and from 71.3% of dogs during racing. C. perfringens and C. difficile were isolated from 100 and 58.2% of dogs before racing, and from 95 and 36.3% of dogs during racing. Dogs were more likely to test positive for CPE during than before racing (18.8 versus 5.5%, P= .021); however, no enteropathogens or their respective toxins were significantly associated with hematochezia or diarrhea. Conclusions and Clinical Importance: Sled dogs participating in long distance racing have a high prevalence of diarrhea and hematochezia that is not associated with common enteropathogens. It is possible that diarrhea and hematochezia represent the effect of prolonged exercise on the gastrointestinal tract. [source] Hypogammaglobulinemia in Racing Alaskan Sled DogsJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2010E. McKenzie Background: Serum immunoglobulin dynamics have not been studied in racing sled dogs, despite hypoglobulinemia having been reported during racing events. Hypothesis/Objectives: Hypoglobulinemia in racing sled dogs is associated with decreases in serum IgA, IgE, IgG, and IgM concentrations during prolonged exercise. Animals: One hundred and fifty-seven Alaskan sled dogs that successfully completed a 1,000 mile race. Methods: Serum was obtained from 118 sled dogs within 1 month before the race and within 12 hours after completing the race. Serum also was obtained after 4 months of rest from 51 dogs that successfully completed the race, including 12 previously sampled dogs. Serum total protein ([TP]), albumin, and globulin ([Gl]) were measured, and serum IgA, IgE, IgG, and IgM were quantified by ELISA. Results: The proportion of dogs with [Gl] , 2.2 g/dL was significantly greater immediately after racing (38 of 118 dogs, 32.2%) than before racing (21 of 118 dogs, 17.8%, P= .005). Four months after racing, [Gl] was , 2.2 g/dL in 23.5% (12 of 51) of dogs. [IgG] was significantly lower before (8.21 ± 4.95 mg/mL) and immediately after (7.97 ± 5.62) racing compared with 4 months after racing (18.88 ± 5.76). Serum [IgM] and [IgE] were higher and [IgA] was lower before racing compared with immediately after racing. Conclusions and Clinical Importance: Sled dogs participating in long-distance racing have substantial decreases in [IgG] in addition to decreases in [IgM] and [IgE]. The pronounced hypogammaglobulinemia observed in a large proportion of racing sled dogs might predispose them to infectious disease. [source] Paroxysmal exercise-induced dystonia as a presenting feature of young-onset Parkinson's diseaseMOVEMENT DISORDERS, Issue 12 2003Maria Bozi MD Abstract Paroxysmal exercise-induced dystonia (PED) is a rare, typically idiopathic familial condition, although sporadic and secondary cases have been reported. We present 2 cases where PED was the presenting feature of young-onset idiopathic Parkinson's disease (PD), preceding the onset of parkinsonian symptoms by 1.5 and 5 years, respectively. Initially, the dystonic symptoms occurred after prolonged exercise and were unilateral, affecting the foot in both patients. Over time, symptoms occurred with minimal exercise. We conclude that PED can rarely be the first and only feature of PD. © 2003 Movement Disorder Society [source] Disorders of carnitine transport and the carnitine cycle,AMERICAN JOURNAL OF MEDICAL GENETICS, Issue 2 2006Nicola Longo Abstract Carnitine plays an essential role in the transfer of long-chain fatty acids across the inner mitochondrial membrane. This transfer requires enzymes and transporters that accumulate carnitine within the cell (OCTN2 carnitine transporter), conjugate it with long chain fatty acids (carnitine palmitoyl transferase 1, CPT1), transfer the acylcarnitine across the inner plasma membrane (carnitine-acylcarnitine translocase, CACT), and conjugate the fatty acid back to Coenzyme A for subsequent beta oxidation (carnitine palmitoyl transferase 2, CPT2). Deficiency of the OCTN2 carnitine transporter causes primary carnitine deficiency, characterized by increased losses of carnitine in the urine and decreased carnitine accumulation in tissues. Patients can present with hypoketotic hypoglycemia and hepatic encephalopathy, or with skeletal and cardiac myopathy. This disease responds to carnitine supplementation. Defects in the liver isoform of CPT1 present with recurrent attacks of fasting hypoketotic hypoglycemia. The heart and the muscle, which express a genetically distinct form of CPT1, are usually unaffected. These patients can have elevated levels of plasma carnitine. CACT deficiency presents in most cases in the neonatal period with hypoglycemia, hyperammonemia, and cardiomyopathy with arrhythmia leading to cardiac arrest. Plasma carnitine levels are extremely low. Deficiency of CPT2 present more frequently in adults with rhabdomyolysis triggered by prolonged exercise. More severe variants of CPT2 deficiency present in the neonatal period similarly to CACT deficiency associated or not with multiple congenital anomalies. Treatment for deficiency of CPT1, CPT2, and CACT consists in a low-fat diet supplemented with medium chain triglycerides that can be metabolized by mitochondria independently from carnitine, carnitine supplements, and avoidance of fasting and sustained exercise. © 2006 Wiley-Liss, Inc. [source] Cortisol and IGF-1 synergistically up-regulate taurine transport by the rat skeletal muscle cell line, L6BIOFACTORS, Issue 1-4 2004Sung-Hee Park Abstract This study was undertaken to evaluate effects of exercise-induced hormones, cortisol, IGF-1, and ,-endorphin, on the regulation of taurine transport activity in rat skeletal myoblasts, L6 cells. Challenge of L6 cells with cortisol (100 nM) for 24 hrs resulted in a 165% increase in taurine transport activity, 220% increase in Vmax of the taurine transporter, and 55% increase in taurine transporter/ ,-actin mRNA level compared with untreated control cells. Neither IGF-1 (1,100 nM) nor ,-endorphin (1,20 nM), added in the incubation medium separately for 24 hrs, affected taurine uptake by L6 cells. However, when cells were co-treated with IGF-1 (10 nM) plus cortisol (100,nM), taurine transport activity (37% increase, p < 0.05), Vmax of the transporter (54%, p < 0.05), and taurine transporter/ ,-actin mRNA level were further increased compared to the value for cells treated with cortisol alone. These results suggest that taurine transport by skeletal muscle cells appear to be synergistically up-regulated during a prolonged exercise via elevated levels of cortisol and IGF-1 in muscle. [source] | |||||||||||||