Exercise in horses encompasses the physical activities that horses engage in, either through natural behaviors or structured training programs. These activities impact a horse's musculoskeletal, cardiovascular, and respiratory systems, influencing overall health and performance. Exercise can vary in intensity, duration, and frequency, and its effects are studied to understand conditioning, endurance, and recovery processes in equines. Research in this field often focuses on the physiological adaptations to different types of exercise, the prevention of exercise-related injuries, and the optimization of training regimens for various equestrian disciplines. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological, biomechanical, and health-related aspects of exercise in horses.
Van den Hoogen BM, van de Lest CH, van Weeren PR, Lafeber FP, Lopes-Cardozo M, van Golde LM, Barneveld A.The purpose of this study was to determine whether changes in the synovial fluid (SF) induced by in vivo loading can induce an alteration in the metabolic activity of chondrocytes in vitro. Therefore, SF was collected from ponies after a period of box rest and after they had exercise for a week. Normal, unloaded articular cartilage explants were cultured in 20% solutions of these SFs for 4 days and chondrocyte activity was determined by glycosaminoglycan (GAG) turnover. In explants cultured in post-exercise SF, GAG synthesis was enhanced and GAG release was diminished when compared to cultures...
Constable PD, Hinchcliff KW, Muir WW.To compare the accuracy of anion gap (AG) and strong ion gap (SIG) for predicting unmeasured strong ion concentration in plasma and serum from horses. Methods: 6 well-trained Standardbred horses undergoing high-intensity exercise (experimental study) and 78 horses and ponies that underwent i.v. administration of lactic acid or endotoxin, and endurance, submaximal, or high-intensity exercise. Methods: Anion gap was calculated as AG = (Na+ + K+) - (Cl- + HCO3-), and SIG was calculated, using the simplified strong ion model, whereby SIG (mEq/L) = 2.24 x total protein (g/dl)/(1 + 10(6.65-pH)) - AG...
Manohar M, Goetz TE.To examine regional distribution of blood flow in the brain of horses at rest and during exercise. Methods: 9 clinically normal horses. Methods: Regional brain blood flow was measured using radionuclide-labeled 15-microns-diameter microspheres injected into the left ventricle, while reference blood samples were obtained from the aorta. Results: At rest, cerebral cortex and caudate nuclei received significantly higher blood flow, compared with cerebral white matter. A similar perfusion heterogeneity existed in the cerebellum. In the brain stem, a gradual tapering of blood flow from thalamus-hyp...
Tyler CM, Golland LC, Evans DL, Hodgson DR, Rose RJ.Thirteen standard-bred horses were trained intensively for 34 weeks and detrained for 6 weeks to study skeletal muscle adaptations to prolonged training, overtraining and detraining. Training included endurance (phase 1, 7 weeks), high-intensity (phase 2, 9 weeks) and overload training (OLT) (phase 3, 18 weeks). During phase 3, horses were divided into two groups, OLT and control (C), with OLT horses performing greater intensities and durations of exercise than C horses. Overtraining was evident in OLT horses after week 31 and was defined as a significant reduction in treadmill run time in res...
Harris PA, Marlin DJ, Gray J.In order to investigate the effect of age, sex and month on the response of plasma aspartate aminotransferase (AST) and creatine kinase (CK) to exercise, blood samples were collected once a month between March and September from a group of 40 2- and 3-year-old (2yo and 3yo) thoroughbred racehorses (kept under the same managemental regimen) at rest before exercise (PRE) and at 2 (2H) and 24 h (24H) post-exercise. The absolute change in activities between the 2H and PRE samples (2H delta) and the 24H and PRE samples (24H delta) was also calculated. Age had a significant effect on all measured an...
Alfredson H, Hedberg G, Bergström E, Nordström P, Lorentzon R.To evaluate whether the type of weight-bearing loading subjected to the skeleton during horseback-riding was associated with differences in bone mass and muscle strength of the thigh, we investigated bone mass and isokinetic muscle strength in 20 female horse riders (age 17.9 +/- 0.6 years) who were riding 7.0 +/- 3.4 hours/week, and 20 nonactive females (age 17.8 +/- 1.1 years). The groups were matched according to age, weight, and height. Areal bone mineral density was measured in total body, head, lumbar spine, right femoral neck, Ward's triangle, and trochanter, the whole dominant and nond...
Schroter RC, Marlin DJ, Denny E.Exercise-induced pulmonary haemorrhage (EIPH) in horses, although of major welfare and economic importance worldwide, is of uncertain cause. It is accepted that the dorsocaudal region of the lung is particularly prone to the condition, but present theories of causation cannot satisfactorily explain the mechanism or pattern of occurrence. We propose that EIPH results from locomotory impact induced trauma; the mechanism being similar to that producing lung tissue damage following thoracic impact injury. In impact injury, the localised impulsive load on the chest wall is transmitted by pressure w...
Cheung TK, Warren LK, Lawrence LM, Thompson KN.Surface electrodes were used to record electromyographic (EMG) activity of the long digital extensor muscle on the right hindlimb of 8 Thoroughbred horses for 8 s at the walk and 8 s at the trot before (unfatigued) and after (fatigued) an exercise test. The exercise test was performed on a motorised treadmill set on a 10% grade. Each test started at a speed of 6 m/s which was increased by 1 m/s each minute until the horse fatigued as indicated by its inability to keep pace with the treadmill with minimal encouragement. Observations were made on the horses prior to conditioning (untrained state...
Manohar M, Goetz TE.The present study was carried out to examine the effects of nitric oxide synthase inhibition with Nomega-nitro-L-arginine methyl ester (L-NAME) on the right atrial as well as on the pulmonary arterial, capillary, and venous blood pressures of horses during rest and exercise performed at maximal heart rate (HRmax). Experiments were carried out on seven healthy, sound, exercise-trained Thoroughbred horses. Using catheter-tip manometers, with signals referenced at the point of the shoulder, we determined phasic and mean right atrial and pulmonary vascular pressures in two sets of experiments [con...
Hinchcliff KW, McKeever KH.The effect of blood volume repletion after frusemide administration on the right atrial and pulmonary artery pressure responses of horses to exercise has not been reported. We examined right atrial and pulmonary artery pressure and plasma atrial natriuretic peptide concentration (ANP) responses to an incremental exercise test in 6 Standardbred mares. Horses were treated, in a 3 way cross over design, with isotonic saline, frusemide (1 mg/kg bwt, i.v.), and frusemide followed 3 h later by lactated Ringer's solution (12 ml/kg bwt, i.v.). Three and a half hours after saline or frusemide administr...
Potard US, Leith DE, Fedde MR.Thoroughbred (TB) and draft horses (DH) have long been selected for tasks of very different intensities and force-speed relationships. To study their adaptations, we measured O2 consumption and related variables in three TB and four DH during progressive exercise tests on a level treadmill. The horses exerted a draft force of 0, 5, 10, 15, or 20% of their body weight at speeds that increased by 2 m/s every 3 min until they could not maintain that speed. We found that TB could exert the same draft forces as DH and, at each force, TB achieved about twice the speed, twice the external power, and ...
Hopkins SR, Bayly WM, Slocombe RF, Wagner H, Wagner PD.During short-term maximal exercise, horses have impaired pulmonary gas exchange, manifested by diffusion limitation and arterial hypoxemia, without marked ventilation-perfusion (VA/Q) inequality. Whether gas exchange deteriorates progressively during prolonged submaximal exercise has not been investigated. Six thoroughbred horses performed treadmill exercise at approximately 60% of maximal oxygen uptake until exhaustion (28-39 min). Multiple inert gas, blood-gas, hemodynamic, metabolic rate, and ventilatory data were obtained at rest and 5-min intervals during exercise. Oxygen uptake, cardiac ...
Carrier TK, Estberg L, Stover SM, Gardner IA, Johnson BJ, Read DH, Ardans AA.To determine whether a two-month or longer period without official high-speed workouts (lay-up) is associated with humeral or pelvic fracture in Thoroughbred racehorses. Methods: Reprospective study. Methods: Thoroughbred racehorses in California that were euthanatized because of a complete humeral or pelvic fracture. Methods: Age, sex, activity, number of lay-ups, number of days from a race or official timed workout to fracture, number of days from end of last lay-up to fracture, mean duration of lay-ups, and total number of days in race training were compared between horses with humeral frac...
Valentine BA, Hintz HF, Freels KM, Reynolds AJ, Thompson KN.To determine whether feeding a low-carbohydrate, high-fat diet would decrease severity of exercise-induced muscle injury in horses with exertional rhabdomyolysis. Methods: 19 horses with a history of exertional rhabdomyolysis. Methods: Case series. Methods: Specimens of the semitendinosus or semimembranosus muscle were obtained for histologic examination, and serum creatine kinase (CK) and aspartate transaminase (AST) activities 4 hours after exercise were determined. Horses were then fed a low-carbohydrate, high-fat diet, and serum CK and AST activities 4 hours after exercise were reevaluated...
Breidenbach A, Schlumbohm C, Harmeyer J.The aim of the present study was to investigate the importance of putative regulatory factors of the calcium (Ca) and inorganic phosphate (P(i)) homeostatic system in the horse. The concentrations of Ca, P(i), vitamin D metabolites, parathyroid hormone (PTH), the activity of the alkaline phosphatase (AP) and the concentration and binding properties of vitamin D binding protein (DBP) were measured in the plasma. In addition, the ability of the renal cortex to hydroxylate calcidiol into 24,25(OH)2D3 and 1,25(OH)2D3 was evaluated in vitro. The plasma concentration of Ca (3.2 +/- 0.15 mmol.L-1, N ...
Chou CC, Chen CL, Asbury AC, Webb AI, Vickroy TW.To develop an ELISA that is sensitive and suitable for measurement of immunoreactive acepromazine (ACP) in horse serum and urine and to determine the acute effects of exercise on immunoreactive ACP values in Thoroughbreds. Methods: 12 healthy Thoroughbreds (5 mares, 5 geldings, 2 stallions), aged 2 to 8 years. Methods: A commercially available antibody and a horseradish peroxidase-conjugated oxime derivative of immunoreactive ACP were used to develop a one-step ELISA. Horses were used in a crossover design study to evaluate possible effects of treadmill exercise on serum and urine ACP concentr...
Maxson-Sage A, Parente EJ, Beech J, Lindborg S, May LL, Teleis DC.To determine the effect of exercise on arterial blood gas tensions and upper airway and cardiac function in clinically normal Quarter Horses and horses heterozygous and homozygous for hyperkalemic periodic paralysis (HYPP). ANIMALS AND PROCEDURE: 5 clinically normal Quarter Horses, and 5 heterozygous and 2 homozygous HYPP-affected horses were examined before, during, and after exercise on a high-speed treadmill. Arterial blood gas tensions, ECG, and echocardiogram were obtained prior to exercise. Upper airway endoscopy, collection of arterial blood samples, and continuous electrocardiography w...
Baptiste KE.The equine guttural pouch is a large, air-filled diverticulum of the auditory tube whose function is not clear. Since the horse does not possess a known, well-developed brain-cooling mechanism that could satisfy cerebral thermoregulatory demands, an hypothesis is proposed that respiratory air enters the guttural pouches, when needed, to ventilate and cool the internal carotid arteries (ICA). Experiments were initially carried out on nine cadavers, where blood flow was mimicked with warmed saline propelled by peristaltic pumps. Subsequent experiments were conducted on an anaesthetized horse whe...
Weiss DJ, Evanson OA, Fagliari JJ, Valberg S.To determine whether platelets become activated and form platelet-neutrophil aggregates during near-maximal treadmill exercise in horses. Methods: 4 Thoroughbreds. Methods: Horses were subjected to 4 standardized exercise tests on a treadmill, and blood samples were collected before exercise, at treadmill speed of 12 m/s, and 5 minutes after exercise. Flow cytometric techniques were used to identify activated platelets, and flow cytometric and microscopic techniques were used to identify platelet-neutrophil aggregates. Results: Platelet-neutrophil aggregates increased from 2.8 +/- 0.4% at rest...
Nyman S, Kokkonen UM, Dahlborn K.To investigate effects of hydration status and exercise intensity on plasma atrial natriuretic peptide (ANP) concentration in exercising horses. Methods: 4 trained Standardbreds. Methods: Horses performed a 40-minute exercise test at 65 to 70% maximal heart rate (HRmax; no incline) and a 12-minute test at approximately 90% HRmax (3.5 degrees incline). The 40-minute test was performed with ad libitum access to drinking water (normohydration), after water had been withheld for 24 hours (dehydration), and 30 minutes after 12 L of water at body temperature had been given via nasogastric tube (hype...
Jimenez M, Hinchcliff KW, Farris JW.The responses of the plasma concentrations of catecholamines and cortisol in horses to varied relative intensities of exertion were examined. The plasma concentrations of cortisol, epinephrine and norepinephrine increased significantly (p < 0.05) with exertion. The plasma cortisol concentrations at relative work intensities of 48.3% +/- 1.4%, 82.3% +/- 2.0% and 99.6% +/- 0.4% of VO2max were 114%, 124%, and 126%, respectively, of those at rest, whereas the plasma epinephrine concentrations were 239%, 772% and 3483%, and the norepinephrine concentrations were 138%, 255%, and 1121% of the valu...
Kingston JK, Bayly WM.Exercise in horses is associated with a wide variety of physiological changes in fluid, electrolyte and acid base balance. The integration of physiologic and physiochemical mechanisms acts to minimize alterations in pH and enhance removal of carbon dioxide produced by exercising muscles. This article provides a description of the changes that take place during exercise and how these changes affect acid-base balance in the horse.
Sosa León LA.One of the most common consequences of prolonged exercise is fluid and electrolyte depletion. Fluid and electrolyte losses during exercise may limit the horse's performance and, in extreme cases, jeopardize its health. To avoid or treat the deleterious effects of dehydration, fluid and electrolyte supplementation is essential. This article provides recommendations for fluid and electrolyte supplementation for horses involved in endurance-related events.
Guthrie AJ, Lund RJ.Metabolic HP is extremely high during exercise in horses. Thermoregulation in horses is primarily dependent on evaporative heat loss from sweating in particular. Under thermoneutral conditions, these mechanisms are sufficient to allow horses to perform high-intensity exercise for long periods. Under thermally stressful conditions, particularly in high ambient humidity, the efficiency of evaporative heat loss mechanisms is compromised and may result in horses developing hyperthermia. Early recognition and vigorous treatment are essential to limit the consequences of heat stress in horses. Metic...
McCutcheon LJ, Geor RJ.In the horse, sweat is produced by apocrine glands which are present over most haired and nonhaired skin. Although sweat secretion is initiated under a number of circumstances, the central drive for sweating in response to a thermal stimulus is the primary mechanism for its production. Sweating is an essential and primary mechanism for heat dissipation during exercise or exposure to hot ambient conditions. The rate of sweat production will reflect the interaction of numerous factors, including exercise intensity, ambient conditions, state of hydration, and the training or heat acclimation stat...
Flaminio MJ, Rush BR.In horses, fluid losses of 10L to 15L per hour can occur during endurance exercise under hot environmental conditions. The horse's sweat is hypertonic with respect to plasma, and large amounts of sodium, chloride and potassium are lost during prolonged exercise. Horses that reach exhaustive syndrome often show pronounced increases in plasma protein concentration. This could be an indication of failure of the compensatory fluid shift from the intracellular compartment caused by severe dehydration. Thorough physical examination by the ride veterinarian allows early recognition of dehydration and...
White SL.Horses competing in 3-day, combined-training events develop a metabolic acidosis that is partially compensated for by a respiratory alkalosis immediately after phases B and D. By the end of phase C and 30 minutes to 2 hours after phase D, the acidosis is resolved by the oxidation of lactate, and a metabolic alkalosis prevails. A reduction in TBW and cation content occurs, which often is not replenished 12 to 24 hours after the event, even though the serum or plasma concentration of various constituents may be within normal limits. Hypochloremia and hypocalcemia, however, may persist 12 or more...
McKeever KH.Exercise places large demands on the equine cardiovascular system which are further complicated by environmental factors. In many respects, performance is limited by fluid and electrolyte stores and the ability to maintain cardiovascular and thermoregulatory stability in the face of severe sweat losses. Studies in the exercising horse have been primarily descriptive or associative, with only a limited number seeking to identify physiologic mechanisms associated with the control of fluid and electrolyte balance. More mechanistic studies are needed to fully understand the integration of the card...
Foreman JH.Exhaustion occurs in most equestrian sports, but it is more frequent in events that require sustained endurance work such as endurance racing, three-day eventing, trial riding, and hunting. Exhaustion is also more likely when an unfit, unacclimatized, or unsound horse is exercised. Mechanisms that contribute to exhaustion include heat retention, fluid and electrolyte loss, acid-base imbalance, and intramuscular glycogen depletion. Clinical signs include elevated temperature, pulse, and respiratory rate; depression; anorexia; unwillingness to continue to exercise; dehydration; weakness; stiffne...
Wiemer P, Ugahary F.A 6-year-old trotter gelding presented with exercise intolerance and swelling of the left side of the head during exercise and grazing. The complaints were caused by a complete thrombosis of the left jugular vein. In this case report a surgical approach is described in which a bypass was created with a synthetic vascular graft. After treatment the horse was capable of racing at his former level. The patency of the synthetic graft was 11 months.
Art T, Lekeux P, Gustin P, Desmecht D, Amory H, Paiva M.The purpose of the present work was to measure the pulmonary inertance (IL) in ponies and to analyze its potential influence on the mechanics of breathing and on their aptitude to increase ventilation during exercise. Five healthy ponies 2.4-4 yr old [mean wt 255 +/- 15 (SE) kg] were used. On the one hand, inertance of the respiratory system (Irs) was computed from the value of the resonant frequency (fr) measured by the forced oscillation technique. On the other hand, respiratory airflow, tidal volume (VT), and transpulmonary pressure (PL) changes were recorded while the ponies were performin...
Graham-Thiers PM, Kronfeld DS, Kline KA, Sklan DJ.A restricted protein diet supplemented with amino acids and fat may reduce the acidogenic effects of exercise. Twelve Arabian horses were assigned to a 2 x 2 factorial experiment: two fat levels: 0 or 10 g/100 g added corn oil and two crude protein levels: 7.5 g/100 g (supplemented with 0.5% L-lysine and 0.3% L-threonine) or 14.5 g/100 g. The experiment began with a 4-wk diet accommodation period followed by a standard exercise test consisting of six 1-minute sprints at 7 m/s. Horses were interval trained for 11 wk followed by another exercise test with sprints at 10 m/s. Blood samples were ta...
Murray JK, Senior JM, Singer ER.Short format 3-day events were introduced in 2004. Anecdotal reports suggested that horses were more tired on completion of the cross-country phase of short format events when compared with horses completing the cross-country phase of long format competitions, despite the absence of Phases A, B and C. Objective: To compare the physiological parameters and haematological parameters of horses that had completed the cross-country phase of a short format (SF) and a long format (LF) CCI 2* competition. Methods: During a CCI 2* competition 69 competitors took part in the short format and 74 in the l...
Roethlisberger-Holm K.Recording of intratracheal pressure during exercise as a method for evaluating upper airway obstruction in the horse has previously been carried out on the treadmill. In the present study the method was applied to normal horses, outdoors under field conditions, to assess its usefulness for analysis of respiratory problems mainly occurring under racing conditions. The horses examined performed a standardized exercise test during which the intratracheal pressure was recorded with a tape recorder receiving amplified signals from a transducer connected to a percutaneously inserted intratracheal ca...
Hyyppä S, Saastamoinen M, Reeta Pösö A.Low muscle glycogen at the beginning of exercise may adversely affect performance, increase protein degradation and contribute to the onset of fatigue. As horses are sometimes required to compete on consecutive days both in racing and endurance types of competition, optimal muscle glycogen repletion may improve performance on the day following a race day. The purpose of this experiment was to study the effects of fat supplementation on repletion of muscle glycogen. Twelve Finnhorses performed an exercise test on a treadmill, and 2 and 4 h later they received hay and concentrate (Trial A). Two ...
Paine SW, Harding C, Waller CC, Zemenova J, Viljanto M, Habershon Butcher J, Hincks PR.Calcium dobesilate (CD) is a synthetic venoactive drug used in veterinary medicine to treat equine navicular disease. Etamsylate is a haemostatic agent used in horses for the treatment of exercise-induced pulmonary haemorrhage. Both etamsylate and CD dissociate in the circulatory system with 2,5-HBSA as the active drug. The aim of the research was to be able to provide detection time (DT) advice from pharmacokinetic (PK) studies in Thoroughbred horses to better inform trainers, and their veterinary surgeons, prescribing these substances for treatment of Thoroughbred racehorses. Two (pilot stud...
Whitton RC, Murray RC, Buckley C, Goodship AE, Lekeux P.Training results in marked modelling of the subchondral bone of the carpus, but the effect of training on the subchondral bone of the distal tarsal joints is unknown. The aim of this study was to determine whether training influenced modelling of the third and central tarsal bones in Thoroughbred horses. Twelve untrained Thoroughbred horses were divided into 2 groups. Group 1 underwent a 19 week progressive training regimen on a high speed treadmill. Group 2 were walked for 40 min daily. Images of left tarsi were obtained by magnetic resonance imaging (MRI) with a 0.5 Tesla superconducting mag...
Vervuert I, Coenen M, Wedemeyer U, Chrobok C, Harmeyer J, Sporleder HP.Physical exercise is known to affect calcium homeostasis in horses, but there is little information on the hormonal regulation of calcium metabolism during exercise. In order to evaluate the effects of exercise and training on calcium homeostasis and intact plasma parathyroid hormone, 7 untrained Standardbred horses were studied in a 6 week training programme. These horses were accustomed to running on the treadmill 3 weeks before onset of training and were exercised on a high-speed treadmill with an initial incremental standardised exercise test (SET 1: 6 incremental steps of 5 min duration e...
Ülke ÇG, Deniz SI, Nureddin Ç.Metacarpal tendon diseases are important problems that may cause a decrease in performance and even may finish sport life in equine athletes. In this study, it was aimed to evaluate the ratio of return to races and the time of staying away from races and also to detect the prognostic value of ultrasonographic findings in Thoroughbred and Arabian racehorses with metacarpal flexor tendon injury or peritendonitis. Of 120 cases, 84 (70.0%) returned to races. Among these, 82.1% had tendonitis (69/84) and 17.9% peritendonitis (15/84). Among the cases being unable to return to races, 91.7% had tendon...
Siciliano PD, Kawcak CE, McIlwraith CW.Twelve Quarter Horses, 18 to 24 mo of age and having an average body weight of 460+/-12 kg, were randomly assigned to one of two exercise treatments (control and exercise) to study the effect of initiation of exercise training in young horses on vitamin K status. The control treatment consisted of hand-walking the horses 7 min/d and 5 d/wk for 180 d. Exercise consisted of the following treadmill exercise regimen: 2 min at 4.5 to 5.4 m/s, 3 min at 13.4 to 14.3 m/s, and 2 min at 4.5 to 5.4 m/s on 5 d/wk for 180 d. Both groups were allowed free access to brome grass hay (273 mg of phylloquinone/1...
Todhunter RJ, Freeman KP, Yeager AE, Lust G.This study assessed the effects of postoperative exercise and intra-articular polysulfated glycosaminoglycan (PSGAG) on the repair of osteochondral defects in the carpal joints of ponies. Eighteen ponies with normal carpi had osteochondral defects (mean dimensions 2.4 cm x 0.9 cm) created arthroscopically on the dorsal aspect of the distal articular surface of the radial carpal bone. The ponies were randomized (while balancing for age [range, 2 to 15 years; median, 5.0 years]) to two groups--nine ponies were exercised and nine were stall confined. Beginning at surgery, six ponies in each group...
Knych HK, Stanley SD, Harrison LM, Mckemie DS.The use of corticosteroids, such as betamethasone, in performance horses is tightly regulated. The objective of the current study was to describe the plasma pharmacokinetics of betamethasone as well as time-related urine and synovial fluid concentrations following intra-articular administration to horses. Twelve racing-fit adult Thoroughbred horses received a single intra-articular administration (9 mg) of a betamethasone sodium phosphate and betamethasone acetate injectable suspension into the right antebrachiocarpal joint. Blood, urine, and synovial fluid samples were collected prior to and...
Herbst AC, Coleman MC, Macon EL, Brokman A, Stromberg AJ, Harris PA, Adams AA.Information on the management and health of US senior horses (≥15 years of age) is currently limited. Objective: Provide information on (1) primary use of US senior horses, (2) reasons and risk factors for horse retirement, (3) exercise management, (4) prevalence of low muscle mass and (5) risk factors for, and owner-perceived consequences of, low muscle mass. Methods: Online survey. Methods: Survey responses from 2717 owners of U.S.-resident senior horses (≥15 years of age) were analysed descriptively and inferentially, using ordered and binomial logistic regression, ANOVA and the Kru...
Davie AJ, Evans DL, Hodgson DR, Rose RJ.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 f...
Holcombe SJ, Derksen FJ, Stick JA, Robinson NE, Boehler DA.To compare tracheal and pharyngeal inspiratory and expiratory pressures achieved during 60 seconds of nasal occlusion in standing horses with pressures achieved in horses during intense exercise. Methods: 5 Standardbreds. Methods: Tracheal and pharyngeal inspiratory and expiratory pressures were obtained from 5 horses during 60 seconds of nasal occlusion and compared with tracheal and pharyngeal pressures achieved during incremental treadmill exercise tests in which horses ran at 50, 75, and 100% of the speed that resulted in maximal heart rate (HRmax). Results: Significant difference was not ...
Davidson EJ, Martin BB, Parente EJ.3 racehorses were evaluated because of poor performance or abnormal noise originating from the upper portion of the respiratory tract. Results: During maximal exercise, initial dynamic videoendoscopy of the upper respiratory tract revealed complete arytenoid cartilage abduction in 2 horses and incomplete but adequate abduction of the left arytenoid cartilage in 1 horse. Subsequent exercising endoscopic evaluation revealed severe dynamic collapse of the left arytenoid cartilage and vocal fold in all 3 horses. Results: 2 horses were treated with prosthetic left laryngoplasty and raced successful...
Rose RJ, Schlierf HA, Knight PK, Plummer C, Davis M, Ray SP.In a crossover study, either a placebo paste or N,N-dimethylglycine was administered orally at a dose rate of 1.2 mg/kg twice daily for five days to six thoroughbred horses, with bodyweights ranging from 424 to 492 kg. Using previously determined regression equations for oxygen uptake (VO2) against speed for each horse, a standardised exercise test was given with speeds equivalent to fixed percentages of the maximum oxygen uptake (VO2max). The test consisted of two minutes at speeds equivalent to approximately 40 per cent and 50 per cent VO2max, and one minute at speeds that produced approxima...
Crabill MR, Honnas CM, Taylor DS, Schumacher J, Watkins JP, Snyder JR.A review of medical records was used to identify 10 horses in which stringhalt developed subsequent to trauma to the dorsal metatarsus. Six horses developed stringhalt within 3 months after injury, 3 horses developed stringhalt > 3 months after injury, and time from injury to stringhalt was unknown for 1 horse. Horses were treated with exercise, including daily hand-walking with pasture turnout, followed by lunging; or surgically, using lateral digital extensor myotenectomy. Of the horses treated with exercise, 1 had resolution of stringhalt, 2 improved but had residual stringhalt, and 1 ha...
Stoiber B, Zach C, Izay B, Windberger U.In situations where capillary perfusion in skeletal muscles is limited, changes in blood flow play an important role. Especially alterations in intrinsic erythrocyte factors like red cell aggregation and deformability would increase blood flow resistance. In our study we investigated whether whole blood and plasma viscosity influence exercise tolerance during submaximal training and whether a difference can be realized between trained and untrained standardbred trotters. Venous blood from 42 healthy adult trotters (20 horses at the beginning of their training and 22 well trained horses) was in...
Shaffer SK, Stover SM, Fyhrie DP.Focal bone lesions are often found prior to clinically relevant stress-fractures. Lesions are characterized by low bone volume fraction, low mineral density, and high levels of microdamage and are hypothesized to develop when bone tissue cannot sufficiently respond to damaging loading. It is difficult to determine how exercise drives the formation of these lesions because bone responds to mechanical loading and repairs damage. In this study, we derive steady-state rate constants for a compartment model of bone turnover using morphometric data from fractured and non-fractured racehorse proximal...
Aguilera-Tejero E, Garfia B, Estepa JC, López I, Mayer-Valor R, Rodríguez M.To determine effects of exercise on blood ionized calcium (Ca2+) and plasma parathyroid hormone (PTH) concentrations in horses and to compare the effects of exercise-induced and EDTA-induced hypocalcemia on PTH secretion. Methods: 17 horses entered in a show jumping competition and 5 horses given EDTA. Methods: Blood Ca2+ and plasma PTH concentrations were measured before and after exercise in the 17 horses entered in the jumping competition. In the other 5 horses, concentrations were measured during infusion of EDTA IV. Results: Exercise resulted in a significant decrease in blood Ca2+ concen...
Rooney JR.Sacroiliac arthrosis is a major cause of "hiking" lameness (often, so-called "stifle lameness") in Standardbred horses. The cause of this arthrosis is found in the moment forces generated as horses negotiate unbanked and underbanked turns and in the forces generated on cambered racing surfaces. The prediction is that such lameness could be virtually eliminated if racetrack and training track turns were properly banked and camber held to a minimum.
McDonnell SM, Love CC, Martin BB, Reef VB, Kenney RM.Two mature breeding stallions were evaluated because of specific ejaculatory dysfunction, and each was found to have aortic-iliac thrombosis occluding 60 to 70% of the aortic lumen. In each case, the stallion had strong libido, normal mounting, and vigorous initial thrusting. With continued exertion, thrusting became weak and dismount was awkward. Treatment aimed at maximizing sexual arousal before mounting and reducing hind limb pain and exertion during breeding allowed these stallions to continue breeding. A program of gradually increasing daily exercise also was associated with improved bre...
McDonough P, Kindig CA, Ramsel C, Poole DC, Erickson HH.In healthy man, conditions that change muscle O2 delivery affect the achievable maximum rate of O2 uptake as well as the metabolic (e.g. lactate threshold, LT) and gas exchange (e.g. gas exchange threshold, Tge) responses to incremental exercise. Inclined (I) compared to level (L) running increases locomotory muscle EMG at a given speed in the horse, indicative of elevated metabolic demand. To our knowledge, the effect of treadmill incline on VO2,max, LT and Tge has not been addressed in the exercising quadruped. We used blood sampling and breath-by-breath expired gas analysis to test the hypo...
Hernlund E, Egenvall A, Peterson ML, Mahaffey CA, Roepstorff L.Increased knowledge of the influence of stride type on hoof impact accelerations for fore and hind limbs could lead to a more complete picture of hoof-ground interactions in equine athletes. Hoof accelerations were quantified for each hoof of five show jumping horses using two orthogonal single axis ± 250 g accelerometers. Accelerations were recorded when cantering horses jumped fences of varying types (upright and oxer) and heights (90-130 cm) on three different surface conditions. Strides were identified as normal canter strides, take-off strides and landing strides. Descriptive hoof impact...
Weiss DJ, Richwagen K, Evanson OA.To evaluate the contribution of hematocrit and RBC deformability to pulmonary vascular pressures of racehorses. Methods: Pony lungs were isolated and right and left lungs were perfused separately with blood. The effects of changing hematocrit and of pentoxifylline treatment were evaluated. Methods: 11 healthy mixed-breed ponies. Methods: Ponies were anesthesized, blood was collected, and lungs were removed and perfused with blood at constant flow rate. Results: Increasing the hematocrit from 35% to 65% resulted in increases in pulmonary arterial pressure (53%, 45%), capillary shear stress (45%...
Smith JE, Erickson HH, Debowes RM, Clark M.Five horses were exercised at 10m/sec at a 3 degree incline for 2 mins. Packed cell volume, erythrocyte count, haemoglobin concentration, mean corpuscular volume, plasma protein, total white cell count and lymphocytes increased significantly in blood samples taken after exercise, compared with those taken before exercise; but mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration decreased. Erythrocytes were more resistant to osmotic stress after exercise, but their shape and degree of deformity were unaffected by exercise.
Hall GM, Adrian TE, Bloom SR, Lucke JN.Venous blood samples were collected before and immediately after an 80 km ride and a 42 km race. They were analysed for blood glucose and lactate, and for plasma non-esterified fatty acids, insulin, pancreatic glucagon, pancreatic polypeptide, gastrin, gastric inhibitory peptide, somatostatin and vasoactive intestinal polypeptide concentrations. The 80 km ride was associated with marked hypoglycaemia and a slight lactic acidaemia together with an increase in plasma glucagon, somatostatin, pancreatic polypeptide and vasoactive intestinal polypeptide values. The 42 km race produced hyperglycaemi...
Mitten LA, Hinchcliff KW, Pate JL, Kohn CW, McKeever KH.Exertion has an effect on plasma, serum, and/or urine prostanoid concentrations in many species. We investigated the effect of exercise intensity on plasma prostaglandin concentrations during and after exercise in horses. Six Thoroughbreds completed 4 trials: 3 exercise trials (low-, medium-, and high-speed) and 1 nonexercise (control) trial on a high-speed treadmill. Blood samples were collected from a jugular catheter before, during, and after exercise. The PCV and blood lactate, plasma protein, plasma prostacyclin (6-keto-PGF1 alpha), thromboxane B2 (TXB2), and prostaglandin E2 (PGE2) conce...
Williams RJ, Marlin DJ, Smith N, Harris RC, Haresign W, Davies Morel MC.To determine the effects of exercise, high heat and humidity and acclimation on plasma adrenaline, noradrenaline, beta-endorphin and cortisol concentrations, five horses performed a competition exercise test (CET; designed to simulate the speed and endurance test of a three-day event) in cool dry (CD) (20 degrees C/40% RH) and hot humid (30 degrees C/80% RH) conditions before (pre-acclimation) and after (post-acclimation) a 15 day period of humid heat acclimation. Plasma adrenaline and noradrenaline concentrations pre-acclimation were significantly increased compared with exercise in the CD tr...
