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1.
Muscle biopsy samples were collected from the left middle gluteal muscle of the horses participating in day 2 (speed and endurance test) of a three day event. Six Thoroughbred horses were biopsied the day before and within 30 minutes of completion of the speed and endurance test. Serial muscle sections were reacted histochemically for myosin adenosine triphosphatase activity after acid pre-incubation to demonstrate Type I, IIA and IIB fibers and the glycogen content in the individual fibers was assessed using the periodic acid Schiff (PAS) reaction. Total glycogen in muscle was measured fluorometrically after hydrolysis to glucose. A significant decrease (P less than 0.001) in total muscle glycogen of 306.0 +/- 34.6 mmoles glucose units/kg (dry weight) (mean +/- SE) occurred when samples collected before exercise were compared to those collected following exercise. A significant decrease (P less than 0.05) in the percentage of Type I fibers having medium PAS staining intensity occurred when pre and post-exercise samples were compared. Significant decreases (P less than 0.01 and P less than 0.001 respectively) in the percentage of Type IIA and IIB fibers classified as having high PAS staining intensity occurred when post-exercise samples were compared with those pre-exercise. There were significant increases (P less than 0.01 and P less than 0.001 respectively) in the percentage of Type IIA and IIB fibers classified as having medium PAS staining intensity when the samples collected after the exercise were compared with those before the exercise.  相似文献   

2.
We evaluated differences in muscle fiber recruitment patterns between continuous and interval training to develop an optimal training program for Thoroughbred horses. Five well trained female thoroughbred horses (3–4 years old) were used. The horses performed two different exercises on a 10% inclined treadmill: 90%VO2 max for 4 min (continuous) and 90% VO2 max for 2 min × 2 times with 10-min interval (interval). Muscle samples were obtained from the middle gluteal muscle before and immediately after the exercises. Four muscle fiber types (type I, IIA, IIA/X, and IIX) were immunohistochemically identified, and the optical density of periodic acid Schiff staining (OD-PAS) in each fiber type and glycogen content of the muscle sample were determined by quantitative histochemical and biochemical procedures, respectively. No significant differences were found in the OD-PASs and glycogen contents between the continuous and interval exercises, but the decreases in OD-PAS of fast-twitch muscle fibers were obvious after interval as compared to continuous exercise. Interval exercise may be a more effective training stimulus for the glycolytic capacity of fast-twitch muscle fiber. The data about muscle fiber recruitment can provide significant insights into the optimal training program not only for thoroughbred horses, but also for human athletes.  相似文献   

3.
To find a new parameter indicating muscle fitness in Thoroughbred horses, we examined time-dependent recovery of glycogen content and sarcoplasmic reticulum (SR) Ca2+-ATPase activity of skeletal muscle after intensive treadmill running. Two repeated 50-sec running sessions (13 m/sec) were performed on a flat treadmill (approximately 90%VO2max). Muscle samples of the middle gluteal muscle were taken before exercise (pre) and 1 min, 20 min, 60 min, and 24 hr after exercise. Muscle fiber type composition was determined in the pre muscle samples by immunohistochemical staining with monoclonal antibody to myosin heavy chain. SR Ca2+-ATPase activity of the muscle and glycogen content of each muscle fiber type were determined with biochemical analysis and quantitative histochemical staining, respectively. As compared to the pre value, the glycogen content of each muscle fiber type was reduced by 15–27% at 1 min, 20 min, and 60 min after the exercise and recovered to the pre value at 24 hr after exercise test. These results indicate that 24 hr is enough time to recover glycogen content after short-term intensive exercise. The mean value of the SR Ca2+-ATPase activity showed a slight decrease (not significant) immediately after exercise, and complete recovery at 60 min after exercise. There were no significant relationship between the changes in glycogen content of each muscle fiber type and SR Ca2+-ATPase. Although further studies are needed, SR Ca2+-ATPase is not a useful parameter to detect muscle fitness, at least in Thoroughbred horses.  相似文献   

4.
To consider the optimal training programme for Thoroughbred horses, we examined the recruitment pattern of muscle fibres including hybrid muscle fibres in well-trained Thoroughbred horses. The horses performed exercise at three different intensities and durations; i.e., 100% VO2max for 4 min, 80% and 60% VO2max for 8 min on a treadmill with 10% incline. Muscle samples were obtained from the middle gluteal muscle before, during (4 min at 80% and 60% VO2max), and after exercise. Four muscle fibre types (types I, IIA, IIA/IIX, and IIX) were immunohistochemically identified, and optical density of periodic acid Schiff staining (OD-PAS) in each fibre type, and the glycogen content of the muscle sample, were determined by quantitative histochemical and biochemical procedures. The changes in OD-PAS showed that the recruitment of all fibre types were identical at the final time stage of each exercise bout, i.e., 4 min running at 100% VO2max, and 8 min running at 80% and 60% VO2max. The changes in OD-PAS of type IIA/IIX fibre were very similar to those of type IIX fibre. The recruitment of these fibres were obviously more facilitated by 4 min running at 100% VO2max than by 4 min running at 80% or 60% VO2max. Short duration with high intensity exercise, such as 4 min running at 100% VO2max or 8 min running at 80% or 60% VO2max, is effective to stimulate type IIX fibre and IIA/IIX fibres that have the fastest speed of contraction.  相似文献   

5.
REASONS FOR PERFORMING STUDY: Most racehorses are trained regularly from about age 18 months; therefore, little information is available on the effect of training in Thoroughbred foals. HYPOTHESIS: Well-controlled exercise could improve muscle potential ability for endurance running. METHODS: Thoroughbred foals at age 2 months were separated into control and training (treadmill exercise) groups and samples obtained from the middle gluteal muscle at 2 and 12 months post partum. Muscle fibre compositions were determined by histochemical and electrophoretical techniques and succinic dehydrogenase (SDH) activity was analysed in each fibre type. RESULTS: All fibre types were hypertrophied with growth and type I and IIA fibres were significantly larger in the training than the control group at age 12 months. A significant increase of SDH activity was found in type IIX muscle fibres in the training group. CONCLUSIONS: Training in young Thoroughbred horses can facilitate muscle fibre hypertrophy and increase the oxidative capacity of type IIX fibres, which could potentially enhance stamina at high speeds. POTENTIAL RELEVANCE: To apply this result to practical training, further studies are needed to determine more effective and safe intensities of controlled exercise.  相似文献   

6.
Muscle biopsies were obtained from 17 Standardbred trotters (S) and 22 Thoroughbred racehorses (T) after races which varied in length from 1200 to 2840 m. Biopsies were taken between 2 and 14 minutes from the conclusion of the race. Histochemical and biochemical analyses were performed on all muscle samples. Standardbred horses possessed fewer Type II fibers, especially Type IIB fibers, and demonstrated a higher oxidative and lower glycolytic capacity in muscle than Thoroughbred horses. Intramuscular glycogen and lac-tate concentrations were lower in Standardbred horses after racing (mean 420 and 82 mmol/kg d.w. respectively) com-pared to Thoroughbred horses (mean 545 and 148 mmol/kg d.w. respectively). Low levels of intramuscular adenosine triphosphate (ATP) (mean S 17, T 15 mmol/kg d.w.) and creatine phosphate (mean S 28, T 42 mmol/kg d.w.) were recorded in both breeds after racing. Differences in muscle enzyme activities and metabolic response to exercise between breeds were related to the different muscle fiber compositions of Standardbred and Thoroughbred horses. Within both breeds, a high percentage of Type IIB fibers was associated with a low oxidative and high glycolytic capacity in muscle and a greater lactate accumulation after racing. In Standardbred horses low intramuscular ATP concentrations post-race were associated with a high percentage of Type IIB fibers and high lactate levels. No relationship was found between placing or speed of racing and intramuscular lactate and ATP concentrations post-race. This may have been due to many other factors which affected the outcome of a race and also due to the fact that it was not known when during a race lactate accumulation and ATP depletion occurred. Since the properties of fiber types appeared to be very different, the metabolic response within individual fiber types may be more closely related to fatigue than the metabolic response measured in whole muscle.  相似文献   

7.
Skeletal muscle constitutes the largest organ system in the mammalian body and is essential for movement and force generation. Muscle tissue has the unique ability to adapt and remodel with regular exercise. Adaptation of equine contractile apparatus to exercise training with a different character occurs at the structural to the cellular and molecular levels and depends on age, breed, and sex. In Andalusian and Arabian horses from 3 months to 24 years of age, it was found that the mean cross-sectional area occupied by IIA and IIX fibers was greater in stallions than in mares. In muscle of Dutch Warmblood foals from birth to 1 year of age, a significant number of fibers coexpress either developmental and type IIa or cardiac–alpha and type I myosin heavy chain (MyHC) isoforms. Endurance training results in increased mitochondrial density, capillary supply, changes in key metabolic enzymes, and increased maximal oxygen uptake and promotes a transition from type II to type I muscle fiber. In horses, prolonged aerobic exercise training has been shown to induce a further decline in the percentage of type IIx MyHC isoform expression and an increase of type I and IIa MyHC isoform expression. Short-duration, high-intensity exercise training stimulates type IIA and hybrid (IIA/IIX) fibers. Therefore, intensive high-speed trotting facilitates muscle fiber hypertrophy and increases the oxidative capacity of type IIX fibers.  相似文献   

8.
Muscle fibre characteristics of active and inactive standardbred horses   总被引：1，自引：0，他引：1  
Muscle biopsies were taken from the middle gluteus muscle of 36 Standardbred horses. Twelve of the horses were inactive, while 24 were actively trained and raced. Twelve of the trained horses were moderate performers, with a mean racing time of 1 min 21 secs per km (741 m/min) and the other 12 were excellent performers, with a mean racing time of 1 min 16 secs per km (789 m/min). The percentage and mean area of Type I fibres were similar in all three groups of horses. Marked differences were found among the subgroups of Type II fibres. The well-trained horses had a higher proportion of Type IIA fibres and a lower proportion of the Type IIB (58 per cent IIA and 15 per cent IIB fibres in the excellent performers; 49 per cent IIA and 26 per cent IIB in the moderate performers) than the inactive horses (41 per cent IIA and 35 per cent IIB fibres). The mean area of Type II fibres was smaller in the muscle of the active horses (excellent performers: IIA, 3075 micron2; IIB, 3378 micron2) moderate performers: IIA, 3185 micron2; IIB, 4252 micron2) than in that of the inactive ones (IIA, 3714 micron2; IIB, 5935 micron2). Intramuscular substrates (glycogen and triglycerides) and the activities of enzymes used as markers for the glycolytic potential of the muscle seemed to be similar in the three groups of horses, although there were large interindividual variation.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

9.
We hypothesize that high intensity training for Thoroughbred horses that have been subjected to conventional training could further improve the metabolic properties of the middle gluteal muscle. Nine well-trained horses were subjected to high intensity (80-100% Vdot;O(2)max, 5 minx2) training for 12 weeks. Biopsy samples were obtained from the muscle before and after 4 and 12 weeks of training. Three of the 9 horses did not complete the training programme. In the remaining 6 horses, activities of succinic dehydrogenase (SDH), phosphofructokinase (PFK) and 3-hydroxy acyl CoA dehydrogenase (HAD), and the composition of myosin heavy chain isoforms were analyzed by biochemical techniques. After 12 weeks of training, a significant increase was found in PFK activity but not in the SDH and HAD activities. There were no significant changes in the composition of myosin heavy chain isoforms. The high intensity training in this study was effective at increasing glycolytic enzyme activity, indicating the possibility to improve anaerobic capacity, which potentially could contribute greatly to performance in Thoroughbred horses. This study also highlighted a fact that high intensity training should be given with the great care to prevent the skeletal muscle injuries.  相似文献   

10.
The present study aimed to clarify changes of oxidative stress and antioxidative functions in treadmill-exercised Thoroughbred horses (n=5, 3 to 7 years old), using recently developed techniques for measurement of serum d-ROMs for oxidative stress, and BAP for antioxidative markers. Also, the effect of nasogastric administration of hydrogen-rich water (HW) or placebo water preceding the treadmill exercise on these parameters was examined. Each horse was subjected to a maximum level of treadmill exercise in which the horses were exhausted at an average speed of 13.2 ± 0.84 m/sec. Blood samples were taken 4 times, immediately before the intake of HW or placebo water at 30 min preceding the treadmill exercise, immediately before the exercise (pre-exercise), immediately after the exercise (post-exercise) and at 30 min following the exercise. In all horses, both d-ROMs and BAP values significantly increased at post-exercise. The increase in d-ROMs tended to be lower in the HW trial, as compared to the placebo trial at pre-exercise. The increase in BAP was considerable at approximately 150% of the pre-exercise values in both the HW and placebo treatment trials. The BAP/d-ROMs ratio was significantly elevated at post-exercise in both treatment trials, while a significant elevation was also observed at pre-exercise in the HW trial. BAP, d-ROM, and the BAP/d-ROM ratio tended to decline at 30 min after the exercise, except BAP and BAP/d-ROMs in the placebo trial. These results demonstrate that the marked elevation of oxidative stress and anitioxidative functions occurred simultaneously in the intensively exercised horses, and suggest a possibility that HW has some antioxidative efficacy.  相似文献   

11.
The histologic and histochemical staining characteristics of the triceps brachii (long head), extensor carpi radialis, gluteus medius, vastus lateralis, biceps femoris, semimembranosus, semitendinosus, and extensor digitorum longus muscles of 8 Thoroughbreds, 2 Quarter Horses, 1 Arabian, 1 Paso Fino, and 1 Shetland Pony are described. Muscle fiber morphology, staining distribution and intensity, amount of IM connective tissue, number of IM blood vessels and IM nerves, calcium-activated adenosine triphosphatase activity (CaATPase), percentage of fibertype population, percentage of relative fibertype area, mean fiber diameter, nonspecific esterase activity, alkaline phosphatase activity, and acid phosphatase activity were evaluated, using 10 common histochemical and histologic stains. Two fiber types (I, II) and 3 subtypes (IIA, IIB, IIC) were observed, using CaATPase-, nicotinamide-adenine dinucleotide-tetrazolium reductase-, periodic acid-Schiff hematoxylin-, and nonspecific esterase-stained frozen serial muscle sections. Type I muscle fibers in general had low CaATPase activity, high oxidative capacity, low glycogen capacity, and low esterase activity. Type IIA muscle fibers had high CaATPase activity, intermediate oxidative capacity, high glycogen concentration, and high esterase activity. Type IIB fibers had high CaATPase activity, low oxidative capacity, high glycogen concentration, and a high esterase activity. Type IIC muscle fibers had high CaATPase activity, high oxidative capacity, variable glycogen concentration, and high esterase activity. Type II (IIA and IIB) muscle fibers predominated in the muscles. The percentage of muscle fiber population, mean minimal muscle fiber diameter, and percentage of relative muscle fiber area were determined for each sampled muscle. Type IIA and IIB muscle fibers predominated in the percentage of muscle fiber population and percentage of relative muscle fiber area. Type IIB muscle fibers had the greatest minimal fiber diameter, type IIA muscle fibers had intermediate minimal fiber diameter, and type I muscle fibers had the smallest minimal fiber diameter. The percentage of relative muscle fiber area was less variable (P less than or equal to 0.05) than the percentage of muscle fiber population. Mean muscle fiber diameter did not significantly differ between breeds. Alkaline and acid phosphatase activities were at low levels in all muscles biopsied and were limited to the IM connective tissue fibrocytes, macrophages, and capillaries.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

12.
1. Muscle fibre composition, capillary-fibre ratio and mitochondrial density of the Iliotibialis lateralis muscle were monitored during growth from the age of 8 weeks to sexual maturity (24 weeks) in sedentary birds and in birds subjected to regular treadmill exercise. 2. The Iliotibialis lateralis muscle consists almost exclusively of type IIA and IIB fibres with a small percentage of "unclassified" fibres. Over the 16-week period of growth there was no change in fibre composition but a marked fibre hypertrophy linked with a fall in the capillary-fibre ratio. Mitochondrial volume density increased with age but this was not significant. 3. Exercise significantly increased the IIA:IIB fibres ratio from 0.77 to 1.1 but had no significant effect on any other measured characteristics. 4. It is concluded that exercise at the intensity and duration employed (10-15 min daily, ca. 70-80% maximum oxygen consumption) has little effect on the growth and development of avian skeletal muscle although there was evidence of an increased oxidative capacity of the muscle.  相似文献   

13.
The effects of training on skeletal muscle composition were studied in four Standardbred geldings given a seven week submaximal treadmill training programme. Before the start of training, muscle biopsies were collected from the left middle gluteal muscle for the determination of muscle fibre types, oxidative capacity and capillary numbers using histochemical techniques. The concentrations of citrate synthase, 3-hydroxyacyl-CoA dehydrogenase (HAD), lactate dehydrogenase and total muscle glycogen were measured using fluorometric methods. Muscle biopsy samples were repeated after one, three, five and seven weeks of training and the same measurements performed. No significant changes were found in muscle fibre types or capillary numbers as a result of training, although there was an increase in the oxidative capacity of the Type IIB fibres after seven weeks training. After seven weeks of training there were also increases in the concentrations of citrate synthase and HAD and a decrease in lactate dehydrogenase. Before commencement of training the horses underwent a standardised submaximal exercise test and muscle glycogen concentrations were measured before and immediately after the exercise. This procedure was repeated after one, three, five and seven weeks of training. A progressive decrease in the rate of glycogen utilisation occurred throughout the period of training, which by seven weeks was 36 per cent lower than that before training.  相似文献   

14.
Blood samples from the jugular vein and muscle biopsies (gluteus medius) in 25 Standardbred trotters were obtained 5-10 min after racing. The biopsies were analysed for fibre type composition and enzymatic profile and blood samples for plasma lactate and ammonia concentrations. Muscle characteristics, plasma lactate and ammonia concentrations after racing were compared with each horse's individual performance index (IPI). The IPI is calculated annually from the individual horse's racing performance (% placing 1, 2 or 3, total annual earnings, average earning per start, and best racing record), respectively, converted to and expressed as a percentage deviation from the average record of the same sex and age group. The IPI values were 100-116. Plasma lactate concentrations were 15.0-42.7 mmol/l (mean 31.3 mmol/l) and ammonia concentrations 65-210 micromol/l (mean 141 micromol/l) after racing. Fibre type composition varied among horses (range 9-27% for Type I, 32-54% for Type IIA, and 27-46% for Type IIB). Fibre type composition, enzyme activities, plasma lactate and ammonia responses to racing were not correlated to IPI. Ten of the horses also performed a submaximal test on the track, consisting of 5 incremental 1000 m heats at approximate speeds of 9.1, 9.5, 10.0, 10.5, and 11.1 m/s. Immediately after each heat a blood sample was drawn from the jugular vein for plasma lactate analysis. Plasma lactate response to exercise differed between horses, but no correlation was seen with IPI. Muscle characteristics, plasma lactate and ammonia concentrations after racing and lactate response to a submaximal track test did not correlate with current race performance expressed as IPI in a group of horses with average or better performance capacity at the time of testing. Analysis of lactate and ammonia in blood after racing is not a valuable tool to predict an individual performance index.  相似文献   

15.
Muscle biopsies taken after exercise, in comparison to those at rest, contain increased amounts of blood and this is a particular problem in studies of the horse. The inclusion of blood in muscle will introduce an upward bias in values of pH measured in muscle homogenates. In an attempt to control this, muscle biopsy samples of the middle gluteal from Thoroughbred horses were freeze-dried and dissected free of blood before determination of pH. Following exercise, muscle pH measured after freeze-drying was similar to that measured in homogenates prepared from frozen samples. In contrast, freeze-drying appeared to increase muscle pH in samples taken at rest. This was probably the result of loss of CO2 during freeze-drying. Muscle pH determined in freeze-dried samples taken at rest and after exercise was linearly related to pyruvate and lactate content (P less than 0.001). It is concluded that muscle samples taken after exercise can be freeze-dried and dissected free from blood before determination of pH, whereas this procedure will cause an alkaline shift in samples taken at rest.  相似文献   

16.
OBJECTIVE: To determine whether adenosine pretreatment attenuates free radical production and muscle damage in ischemic and reperfused canine skeletal muscle. ANIMALS: 9 healthy mixed-breed dogs. PROCEDURE: Dogs were anesthetized, and both gracilis muscles were isolated, leaving only the major vascular pedicle intact. Saline (0.9% NaCl) solution was injected into the artery supplying the control flap, whereas adenosine (10 mg) was injected into the contralateral artery. Ischemia was induced in both flaps for 4 hours. alpha-Phenyl-N-tert-butylnitrone was administered IV to each dog 1 hour prior to reperfusion. Following 15 minutes of reperfusion, effluent blood samples from each muscle flap were obtained and processed for spin-trapping electron paramagnetic resonance (EPR) spectroscopy. Muscle biopsy specimens were obtained for histologic evaluation, and dogs were euthanatized. RESULTS: EPR spectra of strong intensity were obtained from analysis of 5 of 9 paired samples. Signals identified were characteristic of oxygen- and carbon-centered free radical adducts. Signal intensity of spectra from adenosine-treated flaps was significantly less than that of control flaps; mean signal attenuation was 36% in the adenosine-treated group. Histologic evaluation of muscle flaps did not reveal significant differences between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment of canine muscle flaps with adenosine prior to a period of ischemia reduced but did not completely attenuate free radical production after reperfusion. However, adenosine pretreatment did not affect histologic abnormalities.  相似文献   

17.
The skeletal muscle metabolism of horses with a wide range of cardiocirculatory capacities was studied during a standardised near-maximal exercise test in relation to muscle fibre composition. Although the same amount of work was performed by all horses the amount of triglycerides and glycogen utilised and lactate accumulated differed widely. Both blood and muscle lactate accumulation were positively related to the amount of glycogen utilised. These factors were in turn positively associated with the percentage of Type IIB fibres and consequently negatively associated with the percentage of Type IIA fibres. The percentage of Type IIB fibres was negatively correlated to the activities of the oxidative enzymes citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase and positively associated with the lactate dehydrogenase activity. The results indicate that the horses with a high proportion of Type IIB fibres had a lower muscle oxidative capacity and were, therefore, for energy production, more dependent upon glycolysis with subsequent lactate accumulation than horses which had a high proportion of Type IIA fibres. The different metabolic properties of the muscle fibre types indicate that the pattern of muscle fibre recruitment could have a significant effect on intramuscular substrate utilisation.  相似文献   

18.
Muscle biopsies were taken from the middle gluteal muscle of 28 Standardbred trotters, 3-4 years of age. The 13 horses in Group T were trained consistently from 18 months of age, whereas the 15 horses in Group UT were not exposed to any systematic training before 3 years of age. Group T horses had a lower percentage of Type IIB fibres (31%) than did Group UT horses (39%). Citrate synthase (CS) activity, representing oxidative capacity, was higher in Group T (72 mmol kg-1 min-1) than in Group UT (47 mmol kg-1 min-1). Biopsies were taken from 4 horses in each group when they were foals and then annually until 3-4 years of age. Results from this study indicate that regular training of Standardbreds from 18 months of age resulted in increased CS activity and a decrease in the percentage of Type IIB fibres. This study shows that training, not growth, is the main factor that induces a high oxidative capacity and a high Type IIA/IIB fibre ratio in muscle of Standardbred trotters.  相似文献   

19.
Biopsy samples were obtained from the middle gluteal muscle of 10 Thoroughbred horses undergoing a commercial race-training program. Samples were obtained before the program began and again after 6 and 12 weeks of training. All horses had raced at least once by the 12th week of training. Serial sections of muscle were examined histochemically for myosin adenosinetriphosphatase after either acid (pH 4.3 and 4.6) or alkaline (pH 10.3) preincubation, and then muscle fibers were identified as types I, IIA, IIB, or IIC. The oxidative capacity of individual fibers was assessed, using the reduced nicotinamide dinucleotide tetrazolium-reductase stain, and the number of intermyofibrillar capillaries adjacent to each fiber were counted after staining, using the alpha-amylase-periodic acid-Schiff technique. Biochemical analyses involved the fluorometric measurement of 3 enzymes--citrate synthase, 3-hydroxy-acyl coenzyme A dehydrogenase, and lactate dehydrogenase--as markers of end terminal oxidative, beta-oxidative, and glycolytic potentials, respectively. Changes in fiber-type percentages did not occur in response to training. There was a significant (P less than 0.01) increase in the percentage of type IIB fibers, having high nicotinamide dinucleotide-tetrazolium reductase staining after 12 weeks of training. Alterations in the number of capillaries adjacent to each fiber type did not occur during the training period. There were increases in the activities of both citrate synthase and 3-hydroxy-acyl coenzyme A dehydrogenase after 6 weeks (P less than 0.05) and 12 weeks (P less than 0.001) of training. Alterations in the activity of lactate dehydrogenase did not occur in response to training.  相似文献   

20.
The aim of this study was to investigate the effects of reduced muscle glycogen concentration on some physiological and metabolic responses during moderate intensity treadmill exercise in horses. Six Thoroughbred geldings were randomly allocated to 2 treatments (protocols A and B) or control in a 3 x 3 replicated Latin square design. In protocol A, horses performed low intensity exercise while horses in protocol B performed short bursts of high intensity exercise. Protocol A was designed to induce glycogen depletion mainly of slow twitch muscle fibers while protocol B aimed to deplete mainly fast twitch muscle fibers. Horses in the control group did not undergo exercise prior to the exercise test. Five hours after glycogen depletion, horses performed treadmill exercise at 60% VO2max at a treadmill slope of 10% until fatigue (20-30 min). The induced glycogen depletion prior to exercise had no significant effect on plasma glucose, insulin, or lactate concentrations during the exercise test, and there was no effect on glycogen utilization rate, although respiratory exchange ratios were lower in the glycogen-depleted groups. The VO2, heart rate and central blood temperature did not vary significantly between the protocols A and B and control throughout the exercise test. It was concluded that 20-30% depletion of glycogen concentration in the middle gluteal muscle resulted in a shift towards fat metabolism, but does not significantly affect heart rate, oxygen uptake, or concentrations of plasma glucose and lactate during moderate intensity exercise.  相似文献   

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