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Topic:Exercise Physiology
Exercise physiology in horses involves the study of the physiological responses and adaptations of horses to physical activity. This field examines how exercise impacts various systems in the equine body, including the cardiovascular, respiratory, muscular, and metabolic systems. Researchers focus on understanding how these systems interact during different types and intensities of exercise, and how they contribute to performance and recovery. Key areas of interest include the assessment of aerobic and anaerobic capacity, muscle fiber composition, energy metabolism, and thermoregulation. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms of exercise physiology in horses, with an emphasis on performance optimization, training regimens, and the prevention of exercise-related disorders.
High-speed treadmill videoendoscopic examination of the upper respiratory tract in the horse: the results of 291 clinical cases. The purpose of the study was to describe the prevalence of upper airway abnormalities and establish if any significant associations existed between study variables and the two most frequently identified disorders; axial deviation of the aryepiglottic folds and dorsal displacement of the soft palate. The clinical records and video-recordings of all horses referred for upper respiratory tract evaluation during high-speed treadmill videoendoscopy between November 1997 and September 2003 were reviewed. Of 291 horses included in the study, 265 underwent resting endoscopy and 42% (112/265) had a rec...
Exercise training increases oxidative capacity and attenuates exercise-induced ultrastructural damage in skeletal muscle of aged horses. Exercise training improves functional capacity in aged individuals. Whether such training reduces the severity of exercise-induced muscle damage is unknown. The purpose of the present study was to determine the effect of 10 wk of treadmill exercise training on skeletal muscle oxidative capacity and exercise-induced ultrastructural damage in six aged female Quarter horses (>23 yr of age). The magnitude of ultrastructural muscle damage induced by an incremental exercise test before and after training was determined by electron microscopic examination of samples of triceps, semimembranosus, an...
Determination of peak vertical ground reaction force from duty factor in the horse (Equus caballus). Measurement of peak vertical ground reaction force (GRFz) from multiple limbs simultaneously during high-speed, over-ground locomotion would enhance our understanding of the locomotor mechanics of cursorial animals. Here, we evaluate the accuracy of predicting peak GRFz from duty factor (the proportion of the stride for which the limb is in contact with the ground). Foot-mounted uniaxial accelerometers, combined with UHF FM telemetry, are shown to be practical and accurate for the field measurement of stride timing variables, including duty factor. Direct comparison with the force plate produc...
Echocardiography and electrocardiography as means to evaluate potential performance in horses. Prediction of potential performance is one of the goals of exercise physiology investigations. When Selecting a horse for competition, one of the main objectives is to choose the one that predictably will reveal a competitive aptitude above the average. The horses used in this study underwent a two-dimensional echocardiography study and a conventional 3 leads electrocardiogram. The results show that heart score is not an appropriate index to evaluate the heart size in the horse. On the other hand, there are currently more suitable and accurate procedures such as echocardiography that allow per...
Ground reaction forces in horses trotting up an incline and on the level over a range of speeds. Although the forces required to support the body mass are not elevated when moving up an incline, kinematic studies, in vivo tendon and bone studies and kinetic studies suggest there is a shift in forces from the fore- to the hindlimbs in quadrupeds. However, there are no whole-animal kinetic measurements of incline locomotion. Based on previous related research, we hypothesized that there would be a shift in forces to the hindlimb. The present study measured the force produced by the fore- and hindlimbs of horses while trotting over a range of speeds (2.5 to 5 m s(-1)) on both level and up an...
Reproducibility of a locomotor test for trotter horses. Locomotion analysis is increasingly used to assess the gait of horses in the selection and training of equine athletes. We have developed a specific locomotor test for fast trotting harnessed horses that uses an accelerometric device. We describe here the reproducibility of the locomotor test and the validation of its use to analyse trotters on the racetrack. We measured the performance of eight horses under the same conditions three times in a single week. We then tested the influence of five tracks on the variables measured using eight different trotters every two days. The horses trotted at...
Effects of feeding meals with various soluble-carbohydrate content on muscle glycogen synthesis after exercise in horses. To determine effects of feeding diets with various soluble-carbohydrate (CHO) content on rates of muscle glycogen synthesis after exercise in horses. Methods: 7 fit horses. Methods: In a 3-way crossover study, horses received each of 3 isocaloric diets (a high soluble CHO [HC] diet, a low soluble CHO [LC] diet, or a mixed soluble CHO [MC] diet). For each diet, horses were subjected to glycogen-depleting exercise, followed by feeding of the HC, LC, or MC diet at 8-hour intervals for 72 hours. Results: Feeding the HC diet resulted in a significantly higher glycemic response for 72 hours and sign...
Electrospray ionization mass spectrometric characterization and quantitation of xanthine derivatives using isotopically labelled analogues: an application for equine doping control analysis. Isotope-dilution mass spectrometry has been employed successfully in numerous fields of analytical chemistry enabling the establishment of fast and reliable procedures. In equine sports, xanthine derivatives such as caffeine and theobromine are prohibited, and doping control laboratories analyze horse urine specimens regarding these illicit performance-enhancing drugs. Theobromine has to exceed a threshold level of 2 microg/mL, hence a robust and reliable quantitation is required. Stably deuterated theobromine and caffeine were synthesized by the reaction of xanthine or theobromine with iodome...
Variation in free jumping technique within and among horses with little experience in show jumping. To quantify variation in the jumping technique within and among young horses with little jumping experience, establish relationships between kinetic and kinematic variables, and identify a limited set of variables characteristic for detecting differences in jumping performance among horses. Methods: Fifteen 4-year-old Dutch Warmblood horses. Methods: The horses were raised under standardized conditions and trained in accordance with a fixed protocol for a short period. Subsequently, horses were analyzed kinematically during free jumping over a fence with a height of 1.05 m. Results: Within-hor...
Pulmonary artery wedge pressure measurement in healthy warmblood horses and in warmblood horses with mitral valve insufficiencies of various degrees during standardised treadmill exercise. In 12 healthy warmblood horses and 10 horses with mitral valve insufficiencies (MVI) of various degrees heart rate and pulmonary artery wedge pressure (PWP) was measured at rest and during standardised exercise on a high speed treadmill. There was a significant increase in PWP with each change in speed of the treadmill (p < 0.01). The PWP of horses with mild mitral valve regurgitation under working conditions was not significantly different compared to the healthy horses. The horses with moderate mitral valve regurgitation showed a significant higher pulmonary artery wedge pressure at rest ...
Enzyme activities in some types of peripheral leukocytes of thoroughbred race horses before and after the races. Glucose, free fatty acid (FFA), triglyceride (TG) and immunoreactive insulin (IRI) concentrations in plasma and activities of enzymes related to energy metabolism in some types of peripheral leukocytes were measured in thoroughbred race horses before and after racing. Glucose, FFA, TG and IRI concentrations and enzyme activities did not change significantly in plasma. However, the activities of cytosolic hexokinase, malate dehydrogenase (MDH), mitochondrial MDH and aspartate aminotransferase decreased significantly in leukocytes of the horses after the races. The cytosolic ratio of MDH/LDH act...
Effects of stylopharyngeus muscle dysfunction on the nasopharynx in exercising horses. Nasopharyngeal collapse has been observed in horses as a potential cause of exercise intolerance and upper respiratory noise. No treatment is currently available and affected horses are often retired from performance. Objective: To determine the effect of bilateral glossopharyngeal nerve block and stylopharyngeus muscle dysfunction on nasopharyngeal function and airway pressures in exercising horses. Methods: Endoscopic examinations were performed on horses at rest and while running on a treadmill at speeds corresponding to HRmax50, HRmax75 and HRmax, with upper airway pressures measured with ...
Blood serum branched chain amino acids and tryptophan modifications in horses competing in long-distance rides of different length. 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...
The influence of repeated arthrocentesis and exercise on matrix metalloproteinase and tumour necrosis factor alpha activities in normal equine joints. Matrix metalloproteinases (MMPs) and tumour necrosis factor alpha (TNF-alpha) may be useful as biomarkers of joint disease or inflammation. However, activity of both MMPs and TNF-alpha in synovial fluid (SF) may be influenced by nonpathological factors such as arthrocentesis or exercise. Objective: To investigate the influence of repeated arthrocentesis and exercise on MMP and TNF-alpha activities in SF from normal equine joints. Methods: SF was collected from the left metacarpophalangeal, radiocarpal and tarsocrural joints of 16 horses. Eight of these horses were subsequently subjected to an ...
Use of multifrequency bioelectrical impedance analysis for estimation of total body water and extracellular and intracellular fluid volumes in horses. To evaluate the use of multifrequency bioelectrical impedance analysis (MF-BIA) for estimating total body water (TBW), extracellular fluid volume (ECFV), and intracellular fluid volume (ICFV) in horses. Methods: 9 healthy mares. Methods: TBW and ECFV were measured by use of deuterium oxide and sodium bromide dilution techniques, respectively. Intracellular fluid volume was calculated as the difference between TBW and ECFV. Concurrently, MF-BIA recordings were obtained by use of 4 anatomic electrode positions and 3 measurements of length. Models for MF-BIA data were created for all combinations...
Effect of an external nasal dilator strip on cytologic characteristics of bronchoalveolar lavage fluid in Thoroughbred racehorses. To determine the effects of an external nasal dilator strip on cytologic characteristics of bronchoalveolar lavage (BAL) fluid in racing Thoroughbreds. Methods: Clinical trial. Methods: 23 Thoroughbred racehorses in active training. Methods: Each horse raced on 2 occasions: once while wearing an external nasal dilator strip and once while not. Bronchoalveolar lavage was performed 12 to 18 hours after each race, and BAL fluid was analyzed for RBC and leukocyte counts and hemosiderin content. Results: Mean +/- SEM count of RBCs in BAL fluid when horses raced without the nasal dilator strip (84.6...
Effects of ribose supplementation on selected metabolic measurements and performance in maximally exercising Thoroughbreds. The objective of this study was to investigate the effects of ribose supplementation on blood ammonia-N, plasma lactic acid, plasma glucose, volume of oxygen consumption (VO2), heart rate, and performance in Thoroughbred geldings performing a maximal treadmill standardized exercise test (SET). The hypothesis tested was that ribose supplementation would decrease ammonia-N and lactic acid accumulation during exercise, and improve performance. Eight Thoroughbred geldings were assigned randomly to one of two groups: glucose or ribose. The glucose group received 0.15 g glucose/kg of BW, and the rib...
Ventilatory dynamics and control of blood gases after maximal exercise in the Thoroughbred horse. Despite enormous rates of minute ventilation (Ve) in the galloping Thoroughbred (TB) horse, the energetic demands of exercise conspire to raise arterial Pco(2) (i.e., induce hypercapnia). If locomotory-respiratory coupling (LRC) is an obligatory facilitator of high Ve in the horse such as those found during galloping (Bramble and Carrier. Science 219: 251-256, 1983), Ve should drop precipitously when LRC ceases at the galloptrot transition, thus exacerbating the hypercapnia. TB horses (n = 5) were run to volitional fatigue on a motor-driven treadmill (1 m/s increments; 14-15 m/s) to study the ...
Evaluation of serum concentrations of biochemical markers of bone metabolism and insulin-like growth factor I associated with treadmill exercise in young horses. To evaluate changes in serum concentrations of biochemical markers of bone metabolism and insulin-like growth factor I (IGF-I) associated with treadmill exercise in young horses. Methods: 12 two-year-old Thoroughbred mares. Methods: During a 20-week study period, 6 horses were exercised on a treadmill 3 times a week (exercise group) and 6 horses received walking exercise 6 days a week (controls). Serum concentrations or activity of biochemical markers and IGF-I were assessed biweekly. Bone mineral density and content of the first phalanx were measured by dual-energy X-ray absorbiometry (DEXA) ...
Effect of high intensity training on anaerobic capacity of middle gluteal muscle in Thoroughbred horses. 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)...
NaHCO(3) does not affect arterial O(2) tension but attenuates desaturation of hemoglobin in maximally exercising Thoroughbreds. The objective of the present study was to examine the effects of preexercise NaHCO(3) administration to induce metabolic alkalosis on the arterial oxygenation in racehorses performing maximal exercise. Two sets of experiments, intravenous physiological saline and NaHCO(3) (250 mg/kg i.v.), were carried out on 13 healthy, sound Thoroughbred horses in random order, 7 days apart. Blood-gas variables were examined at rest and during incremental exercise, leading to 120 s of galloping at 14 m/s on a 3.5% uphill grade, which elicited maximal heart rate and induced pulmonary hemorrhage in all horses ...
Liquid chromatography/electrospray ionization tandem mass spectrometric screening and confirmation methods for beta2-agonists in human or equine urine. Electrospray ionization (ESI) mass spectra of 19 common beta(2)-agonists were investigated in terms of fragmentation pattern and dissociation behavior of the analytes, proving the origin of fragment ions and indicating mechanisms of charge-driven and charge-remote fragmentation. Based on these data, liquid chromatographic/ESI tandem mass spectrometric (LC/ESI-MS/MS) screening and confirmation methods were developed for doping control purposes. These procedures employ established sample preparation steps including either acidic or enzymatic hydrolysis, alkaline extraction and, in the case of eq...
Effect of controlled exercise on middle gluteal muscle fibre composition in Thoroughbred foals. Most racehorses are trained regularly from about age 18 months; therefore, little information is available on the effect of training in Thoroughbred foals. Objective: 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...
Ca2+ ATPase in Dutch warmblood foals compared with Na+, K+ ATPase: intermuscular differences and the effect of exercise. We studied the effects of exercise without or with a subsequent period on pasture on Ca2+ ATPase concentration in foal skeletal muscle, and compared the results with those previously reported on Na+, K+ ATPase. Ca2+ ATPase was measured in homogenates as Ca2+-dependent steady-state phosphorylation from [gamma-32P]ATP. From day 7 after birth, 24 foals were divided into three groups: (i) staying in a box stall (Box); (ii) staying in a box stall with an exercise programme of an increasing number of sprints per day (Exercise); and (iii) staying on pasture (Pasture). Half of the foals (12 with four ...
Rehydration fluid temperature affects voluntary drinking in horses dehydrated by furosemide administration and endurance exercise. To determine whether temperature of rehydration fluid influences voluntary rehydration by horses, six 2-3-year-old horses were dehydrated (4-5% body weight loss) by a combination of furosemide administration and 30 km of treadmill exercise. For the initial 5 min following exercise, horses were offered a 0.9% NaCl solution at 10, 20, or 30 degrees C. Subsequently, after washing and cooling out, voluntary intake of water at 10, 20, or 30 degrees C from 20 to 60 min after exercise was measured. Fluid intake (FI) during the first 5 min of recovery was 9.8+/-2.5,12.3+/-2.1 and 9.7+/-2.0L (p>0.05...
Do Thoroughbred and Standardbred horses have similar increases in pulmonary vascular pressures during exertion? To test the hypothesis that the pulmonary vascular pressures of Thoroughbred and Standardbred horses behave similarly during exertion. Measurements were made on 5 Thoroughbred and 5 Standardbred horses on a treadmill at rest and during 3-minute exercise intervals at speeds predicted to produce 75%, 90%, and 100% maximal heart rate. Left forelimb acceleration, heart rate, esophageal pressure, and pulmonary artery pressure were measured continuously. Pulmonary capillary and wedge pressures were measured during intermittent occlusion of the pulmonary artery. Breathing rate and gait frequency were...
Effect of moderate exercise immediately followed by induced hyperglycemia on gene expression and content of the glucose transporter-4 protein in skeletal muscles of horses. To determine the effect of a single bout of exercise and increased substrate availability after exercise on gene expression and content of the glucose transporter-4 (GLUT-4) protein in equine skeletal muscle. Methods: 6 healthy adult Thoroughbreds. Methods: The study was designed in a balanced, randomized, 3-way crossover fashion. During 2 trials, horses were exercised at 45% of their maximal rate of oxygen consumption for 60 minutes after which 1 group received water (10 mL/kg), and the other group received glucose (2 g/kg, 20% solution) by nasogastric intubation. During 1 trial, horses stood...
Significance of affinity and cooperativity in oxygen binding to hemoglobin of horse fetal and maternal blood. The physiological significance of the position and shape of the oxygen equilibrium curve (OEC) of horse hemoglobin (Hb) is considered from the viewpoint of oxygen (O2) transport efficiency and the effectiveness of the Bohr effect. In horse fetal and maternal bloods, their physiological O2 affinities are nearly optimized with respect to the effectiveness of the Bohr shift occurring at the O2 release site, when it is measured by the change in O2 saturation per unit change in P50. With relatively low cooperativity (n=2.69) of horse Hb under physiological conditions, the effectiveness of the Bohr ...
