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Topic:Lactate
Lactate is a byproduct of anaerobic metabolism, produced when glucose is broken down for energy in the absence of sufficient oxygen. In horses, lactate levels can increase during intense physical exertion, such as racing or other high-performance activities. Elevated lactate concentrations are often associated with muscle fatigue and can provide insights into a horse's exercise physiology and conditioning status. Monitoring lactate levels can aid in assessing the horse's fitness, recovery, and adaptation to training. This page compiles peer-reviewed research studies and scholarly articles that explore the production, regulation, and implications of lactate in equine exercise physiology and performance.
The isolated perfused equine skin flap. Preparation and metabolic parameters. A model for the study of equine cutaneous physiology, pharmacology, and toxicology was developed. Four 4 x 12 cm and twenty-one 6 x 12 cm single-pedicle axial pattern skin flaps based on the caudal superficial epigastric artery, and eight 6 x 12 cm flaps based on the saphenous artery and medial saphenous vein, were raised and sutured in a tubed configuration. On day 2, each flap was removed, the artery was cannulated, and the flap was perfused with a modified Krebs-Ringer's albumin-based medium for at least 6 hours. Flap viability was assessed by glucose use, lactate production, and histologic...
Metabolic responses to ammonium acetate infusion in exercising horses. The relationship between elevated plasma ammonia (NH3) levels, fatigue development and muscle metabolism were examined in horses during a submaximal fatigue test. Eight Quarter Horse mares were intravenously infused prior to exercise with either sodium acetate (control) or ammonium acetate (AMINF), and exercised to fatigue on an 11% grade treadmill, carrying 27 kg of lead. Time to fatigue was not different (P greater than 0.05) between groups. Intramuscular NH3 and lactate increased (P less than 0.001) during exercise; however, the treatment did not (P greater than 0.05) affect either. A treat...
Clenbuterol plasma concentrations after repeated oral administration and its effects on cardio-respiratory and blood lactate responses to exercise in healthy Standardbred horses. To evaluate the effects of clenbuterol on cardio-respiratory parameters and blood lactate relation to exercise tolerance, experimental horses performed standardized exercise tests on a high-speed treadmill before and after administration of the drug. Clenbuterol was administered in feed to six healthy Standardbreds at a dose rate of 0.8 micrograms/kg b.wt twice daily for 5.5 days. Each horse was tested twice, without and with a respiratory mask, during two consecutive days. One week elapsed between the baseline tests without drug and the tests with clenbuterol treatment (each horse served as i...
Dietary protein level and energy metabolism during treadmill exercise in horses. Six conditioned Quarter Horse mares were used in a crossover design to assess the effect of the dietary protein level on intramuscular and hepatic glycogen and lactate, oxygen uptake and blood lactate, pyruvate and free fatty acids. After a 2-wk adaptation period to either a 9.0% (control) or an 18.5% crude protein diet, each horse performed an exercise test. The horses were exercised for 15 min on an 11% grade treadmill at 4.5 m/sec. The exercise test was performed 3-4 h after a meal. Venous, arterial and mixed-venous blood samples were taken simultaneously at rest and during exercise. Muscle...
Diaphragmatic energetics during prolonged exhaustive exercise. The present study was carried out to examine diaphragmatic O2 extraction and lactate and ammonia production during prolonged exhaustive exercise. Experiments were performed on nine healthy exercise-conditioned ponies in which catheters had been implanted in the phrenic vein previously. Blood-gas variables and lactate and ammonia concentrations were determined on simultaneously obtained arterial and phrenic-venous blood samples at rest and during 30 min of exertion at 15 mph + 7% grade (heart rate, 200 beats/min; approximately 90% of maximum). Arterial O2 tension and saturation were maintained ...
Changes in some haematological and metabolic indices in young horses during the first year of jump-training. Effects of an 18 min exercise test, on three separate occasions during a one year jump-training programme, was studied in seven horses. Determinations were carried out on venous blood for packed cell volume, haemoglobin, total protein, lactate and pyruvate, glucose, free fatty acids, insulin, glucagon, blood gases, bicarbonate, pH, aldolase, aspartate aminotransferase and alanine amino-transferase. Exercise caused a slight increase in lactate and pyruvate, total protein, aldolase, alanine aminotransferase, pO2, bicarbonate and pH. Glucose, free fatty acids and pCO2 levels decreased. Training c...
Quantitative buffy coat analysis related to adrenocortical function in horses during a three-day event competition. This study was carried out to investigate stress induced in a cross-country by measuring plasma cortisol and to compare the changes in cortisol level with the leucocytic changes measured with the quantitative buffy coat (QBC) analysis, which is a new method applicable in field conditions for the evaluation of haematological parameters in horses. Seven healthy horses competing in a national three-day event were investigated. Venous blood was sampled under resting condition, 2 min and 180 min after the completion of the cross-country and analysed for haematological parameters, plasma cortisol, p...
Ventilatory compensation for lactacidosis in ponies: role of carotid chemoreceptors and lung afferents. We investigated changes in arterial PCO2 (PaCO2) and pulmonary ventilation (VE) in normal, carotid chemoreceptor-denervated, and hilar nerve-denervated ponies during intravenous lactic acid infusion at rest and treadmill exercise at 1.8 mph-5% grade (mild) and 1.8 mph-15% grade (moderate). Lactic acid, (0.5 M) infusion of 0.10, 0.13, and 0.20 ml.min-1.kg-1 at rest and mild and moderate exercise increased arterial [H+] linearly throughout the 10 min of acid infusion. At 10 min of infusion, arterial [H+] had increased approximately 20 nmol/l (0.2 pH units) for each condition and group. Under mos...
Exercise induced hormonal and metabolic changes in Thoroughbred horses: effects of conditioning and acepromazine. Nine Thoroughbred horses were assessed to determine the normal response of insulin, glucose, cortisol, plasma potassium (K) and erythrocyte K through conditioning and to exercise over 400 and 1,000 m. In addition, adrenaline, noradrenaline, cortisol, plasma K, erythrocyte K and L-lactate concentrations were evaluated in response to maximal exercise with and without the administration of acepromazine. Conditioning caused no obvious trends in plasma K, erythrocyte K, insulin or glucose concentration. Serum cortisol increased (P less than 0.05) from the initial sample at Week 1 to Weeks 4 and 5 (...
Comparison of yearling, two-year-old and adult Thoroughbreds using a standardised exercise test. The purpose of this study was to compare exercise measurements in yearling, two-year-old and adult Thoroughbreds using a standardised treadmill incremental exercise test. Peak oxygen consumption (VO2 peak: 128.0 +/- 2.1, 140.0 +/- 2.1, 163.7 +/- 3.4; ml/kg/min +/- se, P less than 0.05), peak packed cell volume (PCV peak: 0.50 +/- 0.01, 0.58 +/- 0.01, 0.64 +/- 0.01 litres/litre +/- se, P less than 0.05) and the maximum number of steps completed in the exercise test (STEPmax: 7.7 +/- 0.1, 8.1 +/- 0.1, 8.6 +/- 0.1; steps +/- se, P less than 0.05) increased with age and degree of physical activity...
Heart rate, blood biochemistry and performance of horses competing in a 100 km endurance ride. To determine whether a clinical examination was adequate to assess the fitness of horses in an endurance ride, and to characterise the relationship between a clinical assessment of the horse's fitness and its blood biochemistry, 23 horses were monitored before, during and after an 87 to 100 km endurance ride. Blood samples were taken before the ride, at three checkpoints on the ride, immediately after the ride and one day later for the determination of packed cell volume, total protein, lactate, glucose, non-esterified fatty acids, creatine phosphokinase, aspartate aminotransferase and plasma ...
Myocardial blood flow, metabolism, and function with repeated brief coronary occlusions in conscious ponies. Studies were performed in the conscious pony instrumented with a Doppler flow probe and hydraulic occluder on the left anterior descending coronary artery (LAD), sonomicrometry crystals and intraventricular micromanometer in the left ventricle, and catheters in the left atrium and anterior interventricular vein. Two-minute LAD occlusions were performed every 30 min continuously or during working hours. Data on release of catabolites (potassium, hydrogen ions, and lactate) and norepinephrine from the initially dysfunctional region were obtained periodically during a regimen of 445 +/- 56 occlus...
Exercise induced alterations in the serum muscle enzymes, erythrocyte potassium and plasma constituents following feed withdrawal or furosemide and sodium bicarbonate administration in the horse. Six thoroughbreds were used in each of three trials to examine the effect of potassium depletion on exercise-associated muscle damage. Horses were exercised after a control period (Treatment 1), a 72-hour fast (Treatment 2), and furosemide and sodium bicarbonate (Treatment 3). During the preexercise period, feed withdrawal for 72 hours caused decreases in body weight, plasma sodium, chloride, and serum calcium. There were no changes in plasma potassium, erythrocyte potassium, or serum creatine phosphokinase (CK) activity. Furosemide and sodium bicarbonate administration resulted in a decrease ...
Muscle ATP loss and lactate accumulation at different work intensities in the exercising Thoroughbred horse. The effect of 2 min treadmill exercise, at speeds of 6-12 m.s-1 on an incline of 5 degrees, upon muscle adenine nucleotide loss and lactate accumulation was studied in six Thoroughbred horses. Minimal change occurred in the adenosine triphosphate (ATP) content of the middle gluteal muscle at speeds of 10 m.s-1 or less, but significant loss (up to 47%) had occurred in all horses by 12 m.s-1. The decline in ATP significantly correlated with the accumulation of muscle lactate, beginning shortly after the accumulation of 40 mmol.kg-1 dry muscle lactate. Decline in muscle ATP was mirrored closely b...
The influence of metabolic alkalosis upon exercise metabolism in the thoroughbred horse. Six thoroughbred horses exercised on a motorised treadmill on two separate occasions at a speed of 11 or 12 m.s-1 for up to 2 min. 4 h prior to exercise each horse was given a 21 test solution of sodium bicarbonate (NaHCO3; 0.6 g.kg-1 body mass) or a control solution of water by nasogastric intubation, the order of administration of the two solutions was randomised. Blood samples (n = 15) were obtained before and during the 4 h after intubation, during exercise and for 30 min after exercise. NaHCO3 ingestion resulted in changes in pre-exercise acid-base status. The changes in blood lactate and...
Diurnal changes in lactic and pyruvic acid levels and pH values in foals during the first 13 weeks of their life and in their lactating mothers. 1. The diurnal changes in the levels of lactic (LA) and pyruvic (PA) acids and values of pH were studied in standard-bred mares and their foals, for 13 weeks of foal life, throughout 2 years. 2. The studies began when a foal was 7 days old and were repeated every 2 weeks until foals reached 13 weeks of age. 3. Blood samples were taken every 4 hr for one day, each second week. 4. In the LA, PA levels and pH values no diurnal rhythm was stated in lactating mares during study periods. 5. In foals the diurnal rhythm in LA and PA occurred in the 3rd month of their life, with the acrophase at night ...
Diaphragm does not produce ammonia or lactate during high-intensity short-term exercise. To ascertain whether costal diaphragm engages in ammonia and lactate production (like limb muscles) during high-intensity short-term exercise, experiments were carried out on six healthy trained ponies in which phrenic venous catheters had been implanted 5-9 days earlier. Simultaneous anaerobically obtained blood samples from abdominal aorta and the phrenic vein at rest and during 4 min of exertion at 32 km/h and at a 7% grade were analyzed for blood-gas variables as well as lactate and ammonia concentrations using standard procedures. At rest, heart rate was 47 +/- 4 beats/min and the diaphra...
Clinical exercise testing in the normal thoroughbred racehorse. To evaluate normal cardiorespiratory and metabolic responses of Thoroughbred horses to a standardised treadmill exercise test, we examined 28 horses ranging in age from 1 to 4 years. The group consisted of eight yearlings, eight 2-year-olds and twelve 3 and 4-year-olds. All horses except the yearlings were in training, and either racing or ready to race, at the time of examination. None of the horses had histories of performance problems. On the first day the horses received a full physical examination, resting electrocardiogram, upper respiratory tract endoscopy and either one or two acclimat...
Respiratory and metabolic responses in the horse during moderate and heavy exercise. Thoroughbred horses were exercised to fatigue on a treadmill at 62% and 100% of their VO2max. Hypoxemia occurred at the onset of exercise under both exercise conditions. This hypoxemia persisted to fatigue during the heavy exercise but progressively diminished as the exercise continued and had disappeared by the end of exercise at the lighter load. As a result of the hypoxemia the oxygen content of arterial blood during exercise at VO2max was 17% below its carrying capacity. However, under both experimental conditions the CaO2 still exceeded that of rest owing to an elevation in hemoglobin con...
The stress response to anaesthesia in ponies: barbiturate anaesthesia. Information on the equine stress response to anaesthesia and surgery is sparse but offers a promising approach to elucidating the high anaesthetic risk in this species. Previous work has shown that halothane anaesthesia induces substantial metabolic and endocrine changes. This paper reports the effects of barbiturate anaesthesia. Anaesthesia was induced with thiopentone in six ponies and no further agents were given. They stood within 30 mins. On another occasion, these animals, and three further ponies, were anaesthetised with pentobarbitone and anaesthesia was maintained for 2 h. No surgery ...
Effect of acute acidemia on blood biochemical variables in healthy ponies. L-Lactic acid and D,L-lactic acid infusion in ponies resulted in metabolic acidosis with high anion gap (AG). Increased AG was explained entirely by increased blood L- and D-lactate concentrations. Hydrochloric acid infusion caused metabolic acidosis with decreased AG. Saline (NaCl) infusion caused mild metabolic acidosis, with no significant change in AG. Plasma K+ concentration was decreased by all types of infusions, with a maximum of 0.50, 0.25, 0.40, 0.50 mmol/L below baseline at the end of infusion in the L-lactic acid-, D,L-lactic acid-, HCl-, and NaCl-infused ponies, respectively. Only...
Metabolic and hormonal changes associated with arthroscopic surgery in the horse. The effect of general anaesthesia and arthroscopic surgery on blood glucose and lactate, plasma non-esterified fatty acids, insulin, beta-endorphin and cortisol was investigated in seven horses. Animals were premedicated with xylazine and anaesthesia was induced with guaifenesin and sodium thiamylal and maintained with halothane vaporised in oxygen. Blood samples were collected in the pre-, intra- and post operative period. Induction of anaesthesia was associated with a transient hyperglycaemia and a significant rise in plasma insulin levels. Plasma insulin values fell during surgery but showe...
Blood biochemical response to sodium bicarbonate infusion during sublethal endotoxemia in ponies. Hypertonic NaHCO3 infusion caused blood volume expansion, increased blood bicarbonate concentration, and delayed the onset of hypophosphatemia in ponies with endotoxemia. However, NaHCO3 infusion did not normalize blood pH, and it increased blood L-lactate concentration, and caused hypokalemia, hypernatremia, and hyperosmolality. The deleterious effects of NaHCO3 infusion in endotoxemia ponies outweighed the beneficial effects. The role of hypertonic NaHCO3 given IV for treatment of endotoxemia in equids must be reevaluated.
Partial pressures of oxygen and carbon dioxide, pH, and concentrations of bicarbonate, lactate, and glucose in pleural fluid from horses. Samples of pleural fluid from 20 horses with effusive pleural diseases of various causes were evaluated; samples from 19 horses were used for the study. There were differences for pH (P = 0.001) and partial pressure of oxygen (PO2) between arterial blood and nonseptic pleural fluid (P = 0.0491), but there were no differences for pH, PO2, partial pressure of carbon dioxide (PCO2), and concentrations of bicarbonate (HCO3-), lactate, and glucose between venous blood and nonseptic pleural fluid. Paired comparisons of venous blood and nonseptic pleural fluid from the same horse indicated no differe...
A comparative study of interval and conventional training in thoroughbred racehorses. Eight horses with previous racing experience were used in a comparative study of training methods for Thoroughbred racehorses. They were randomly assigned to two groups of four horses each. One group was trained using an interval training method (IT) and the other using conventional training (CT) methods. Peak heart rates, heart rate recovery curves, peak plasma lactate levels, plasma lactate clearance rates and run times were used to evaluate differences in the training methods. Peak heart rates, heart rate recovery curves, and run times were not significantly different between the groups. Ho...
Application of a standardised treadmill exercise test for clinical evaluation of fitness in 10 thoroughbred racehorses. Clinical exercise stress testing is an important diagnostic tool for evaluating exercise intolerance and degree of fitness in human athletes. The purpose of this paper was to describe the methodology necessary to perform a clinical exercise test and report the results of performance evaluations on 10 Thoroughbred racehorses using this test. The test utilised an open flow gas analysis system for ease of use with untrained horses and a fast time response lactate analyser for rapid data analysis. Exercise test measurements used to evaluate fitness included peak oxygen consumption (mean VO2peak = ...
Effect of show jumping on heart rate, blood lactate and other plasma biochemical values. This study investigated some physiological responses to exercise performed by a horse during show jumping. The effects of jumping on heart rate (HR), blood lactate (LA) and some other blood values were studied in nine normal horses participating at the Belgian Junior Championship. Venous blood was sampled before and immediately after the show jumping and was analysed for packed cell volume, LA, blood glucose (GLU), total plasma protein, bicarbonate, sodium, potassium (K+), chloride, calcium and activities of plasma lactate dehydrogenase, creatine phosphokinase (CK) aspartate amino transferase ...
Methodology and repeatability of a standardised treadmill exercise test for clinical evaluation of fitness in horses. This paper describes the methodology necessary to perform a clinical exercise test and the expected variability in an individual horse's exercise test measurements based on comparing the results of two repetitions of the test with six horses. The exercise test measurements were obtained with an open flow respiratory gas analysis system, fast time response lactate analyser and an on-board heart rate monitor during an incremental inclined treadmill exercise test. With the exception of peak venous lactate concentration (LACpeak), the results indicate that the mean variability in peak oxygen consu...
Effects of treadmill elevation on heart rate, blood lactate concentration and packed cell volume during graded submaximal exercise in ponies. Six ponies performed a standardised exercise test on a motorised treadmill at each of three randomly assigned treadmill elevations (1, 4, or 7 degrees). The exercise test consisted of four, 4 min increments of increasing treadmill speed from 1.0 to 3.4 m/sec. Heart rate, blood lactate concentration, and packed cell volume (PCV) were determined, during the last min of each exercise level, and at 4 and 12 mins post exercise. Regardless of treadmill elevation, no differences were observed in pre-exercise heart rate (49 +/- 2) beats/min), lactate (1.2 +/- 0.1 mM), and PCV (0.32 +/- 0.01 litres. Du...
Standardized exercise test and daily heart rate responses of thoroughbreds undergoing conventional race training and detraining. Ten healthy sedentary male Thoroughbreds with previous race training experience were studied for 14 weeks. Horses were trained for 9 weeks, using a program designed after those used commonly in the United States. Horses were trained conventionally by slow trotting (250 m/min) for 2 weeks and galloping (390 to 450 m/min) for 4 weeks, followed by 3 weeks of galloping (440 to 480 m/min) and intermittent sprinting exercises (breezes) at distances between 600 and 1,000 m (900 to 950 m/min). The horses were then pasture rested for 5 weeks. A standardized exercise test (SET) involving an 800-m gallop...
