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.
Valberg S.The glycogen depletion patterns in the gluteus muscle of Standardbred horses were studied under different trotting intensities. After racing significant glycogen depletion was found in all Type I and IIA fibres and in a varying percentage of Type IIB fibres, depending on the individual horse. When horses performed exercise over a short distance (5 to 8 km) at three different speeds, glycogen depletion was difficult to detect for the faster speeds (10 and 8 m/sec) but notably involved a major proportion of Type I fibres at the slowest speed (6 m/sec). When exercise was prolonged over a greater ...
Physick-Sheard PW, Russell M.The objective of the study was to examine the career profile of the average racehorse in order to establish normal values for performance. Records of race performance for a population of 762 horses randomly selected from the 1972 registrations of the Canadian Standardbred Horse Society were summarized and the pattern of racing by year and month from 1974 to 1983 inclusive recorded. Results were analyzed to determine the influence of sex, gait, age, and year of first race (starting year). The transformation log (1 + X) was used to achieve normality where necessary. Of the 762 horses, 507 raced,...
Miller PA, Lawrence LM.Eight horses exercised to fatigue were used to characterize the resulting changes in blood pH, in blood lactate, free fatty acid, bicarbonate, and ammonia concentrations, and in muscle glycogen concentrations. The exercise test was conducted at a speed of 4.5 m/s on a motorized equine treadmill set at a 9% grade. At fatigue, all variables differed significantly (P less than 0.05) from base-line values. Heart rate averaged 191.1 +/- 6.5 beats/min at fatigue, and the plasma lactate concentrations increased from 7.8 +/- 0.95 mg/dl to 94.3 +/- 19.2 mg/dl. Ammonia concentrations increased from 66.7...
Pan LG, Forster HV, Kaminski RP.We assessed in ponies the adequacy of using rectal (Tre) rather than arterial temperature (Tar) under conditions common to ventilatory control experiments, i.e., CO2 breathing, thermal stress, and particularly exercise. We were interested in whether, and to what extent, Tar-Tre differences could lead to errors in arterial blood gas corrections. At control environmental temperatures (Ta) of 5 degrees C in the winter and 21 degrees C in the summer, Tar and Tre (37.1 degrees C) did not differ (P greater than 0.05). Elevating winter or summer Ta by 10-18 degrees C for 2-days or lowering summer Ta ...
Frauenfelder HC, Rossdale PD, Ricketts SW, Allen WR.Blood samples were collected twice weekly over a nine month period from 24 Thoroughbred racehorses in training at Newmarket to study the effects of daily training schedules and stage of oestrous cycle on serum enzyme levels and clinical signs of equine exertional myopathy. The sampling period extended from November to July and was performed between 16:00 h and 18:00 h so as to be at least 6 h after exercise. Serum creatine kinase, aspartate aminotransferase and plasma progestogen concentrations were measured. All horses were subjected to a similar traditional training programme. The study demo...
Leach D, Cymbaluk NF.Velocity-dependent changes in stride length and frequency were studied in 19 male foals, 6 to 8 months of age, and were related to body morphometrics. Eighteen distance and 8 angle measurements were digitized from 16-mm films of standing foals. The total mass and the percentage of total mass acting through the forelimbs were also recorded. Stride length and frequency data were extracted from 16-mm films of 239 strides of the walk, trot, and canter-gallop. Polynomial-regression analysis was used to determine the equation that best described the relationship between data of stride length or freq...
Pagan JD, Hintz HF.Energy expenditure was measured in four geldings (433 to 520 kg) during submaximal exercise on a racetrack using a mobile open-circuit indirect respiration calorimeter. A total of 304 5-min measurements of O2 consumed and CO2 produced were taken. Measurements were made with and without riders. The amount of energy expended by the horses was exponentially related to speed and was proportional to the body weight of the riderless horse or the combined weight of the horse plus rider and tack. Total energy expended by the four horses walking, trotting, cantering was best described by the equation: ...
Garcia MC, Beech J.Two identical experiments, using Standardbred and Thoroughbred horses (experiment A, n = 31; experiment B, n = 17) on a swimming regimen, were performed 1 week apart to evaluate short-term heart rate, hematologic, and endocrinologic changes. Horses were placed in 4 categories based on duration of swimming (1 to 5, greater than 5 to 10, greater than 10 to 15, and greater than 15 minutes). Heart rate, PCV, and plasma concentrations of total protein, cortisol triiodothyronine, thyroxine, insulin, and glucose of each horse were evaluated before, immediately after, and 1 hour after swimming. For ex...
Manohar M.Using radionuclide-labelled microspheres, 15 micron in diameter, we studied blood flow in the respiratory muscles (diaphragm and intercostal muscles), abdominal organs (adrenal glands, kidneys, pancreas, spleen and the small and large intestines), muscles of propulsion (gluteus medius and biceps femoris), and other working (triceps brachii and longissimus dorsi lumborum) and non-working (temporal and masseter) muscles of ponies at rest and during maximal exercise performed on a treadmill. During maximal exercise heart rate, whole body O2 consumption, cardiac output and mean aortic pressure inc...
Manohar M.Right atrial, right ventricular, and pulmonary artery pressures, along with change in pleural pressure, were determined with catheter-tipped micromanometers in two groups of ponies at rest, as well as during moderate (trot; heart rate = 180 beats . min-1) and severe (gallop; heart rate = 220 beats . min-1) exercise performed on a treadmill. Group A (n = 8) ponies served as controls, and group B ponies (n = 6) had laryngeal hemiplegia (LH) induced by sectioning the left recurrent laryngeal nerve 20-29 days before the study. It was observed that LH ponies could not gallop for more than 45-90 s. ...
Manohar M.Systemic distribution of blood flow was studied in 11 healthy adult grade ponies, using radionuclide-labeled microspheres (15 micron diameter) that were injected into the left ventricle. Measurements were made at rest, during severe exercise (SE) without furosemide, as well as during SE at 10 minutes and 120 minutes after furosemide administration (1.0 mg/kg, IV). During SE, heart rate, cardiac output, mean aortic pressure, and whole body O2 consumption were 220 +/- 4 beats/min, 720 +/- 44 ml/min/kg, 169 +/- 4 mm of Hg, and 126 +/- 9 ml of O2/min/kg, respectively. With SE performed after furos...
Manohar M.Regional distribution of brain blood flow (radionuclide labelled 15 microns diameter microspheres) and O2 supply were studied in 11 healthy adult grade ponies at rest and during severe exercise (SE) performed on a treadmill (heart rate = 220 +/- 4 beats X min-1; VO2 = 126 +/- 9 ml X min-1 X kg-1). During SE, the mean aortic pressure increased to 169 +/- 4 mm Hg and the pHa, PaCO2 and PaO2 were 7.213 +/- 0.010, 30 +/- 1 mm Hg and 85 +/- 4 mm Hg, respectively. The hemoglobin concentration increased by 59.6% with SE. Whereas blood flow increased in the cerebellar gray matter (96%), pons (39.5%) a...
Allen BV.Results of blood counts have been analysed in three-year-old racehorses in training comprising 77 colt stayers, 27 colt sprinters, 61 filly stayers and 35 filly sprinters. The distributions of haemoglobin, erythrocyte count and haematocrit were significantly higher in colt stayers compared to the other three groups. In fillies these values were also significantly higher in stayers compared to sprinters. The erythrocyte count was significantly higher in filly stayers compared to colt sprinters but there were no significant differences between haemoglobin or haematocrit values in these groups. N...
Manohar M.Eight healthy adult grade ponies were studied at rest as well as during maximal exertion carried out with and without adenosine infusion (3 microM X kg-1 X min-1 into the pulmonary artery) on a treadmill to compare levels of blood flow in respiratory muscles with those in other vigorously working muscles and to ascertain whether there remained any unutilized vasodilator reserve in respiratory muscles of maximally exercising ponies. Radionuclide-labeled 15-micron-diam microspheres, injected into the left ventricle, were used to study tissue blood flows. During maximal exertion, there were incre...
Dinger JE, Noiles EE.Eight sexually inexperienced, 2-yr-old Morgan stallions were used in a consecutive two-phase design with two groups of four stallions each. Each phase lasted 16 wk, with semen collections every 14 d. Libido scores were assigned to stallions during each semen collection. Scores ranged from zero to four, with zero indicating minimum and four representing maximum libido. In Phase 1, four stallions received daily forced exercise for 16 wk, and the remaining four stallions were confined to box stalls. In Phase 2, the previously exercised stallions were confined to box stalls, and the non-exercised ...
Dempsey JA.In summary, we have shown that the design of the pulmonary system from the architectural capacities of the lung parenchyma and respiratory muscles to the remarkable, multi-level neural integration of breathing pattern and respiratory muscle recruitment is clearly intended for the exercising state. Furthermore, the system shows remarkable capability for true adaptation, both phylogenetically and even within only a few generations within a species, when preservation of the organism's ability to survive and function is at stake. At the same time there are limits to the system's homeostatic capabi...
Robb EJ, Kronfeld DS.A 3-year-old mare repeatedly had clinical signs of rhabdomyolysis on mild exertion. Serum creatine kinase and aspartate transaminase activities were high at rest. Responses to dietary sodium bicarbonate were tested through 7 alternating periods of supplementation of a basal ration of timothy hay and oats. Physical signs; venous blood pH and gases; blood glucose and lactate; serum electrolytes, enzymes, and creatinine; and urine pH were monitored before and after exercise. Dietary sodium bicarbonate raised resting venous blood pH and bicarbonate slightly and significantly increased urine pH fro...
Evans DL, Rose RJ.The measurement of heart rate during exercise in the horse has been recommended as a means of prescribing work effort, monitoring the changes in aerobic capacity during training and as part of the clinical examination of the performance horse. The accuracy of four heart rate meters (PEH 100, PU 10, HR 14 and HRM-7) was assessed by comparison with heart rate determined by simultaneous telemetry electrocardiography (ECG) using a rapid incremental exercise test on a treadmill. Heart rate displayed by all four meters showed significant correlations with the ECG heart rate, but only two meters (PEH...
Pan LG, Forster HV, Bisgard GE, Murphy CL, Lowry TF.We investigated arterial PCO2 (PaCO2) and pH (pHa) responses in ponies during 6-min periods of high-intensity treadmill exercise. Seven normal, seven carotid body-denervated (2 wk-4 yr) (CBD), and five chronic (1-2 yr) lung (hilar nerve)-denervated (HND) ponies were studied during three levels of constant load exercise (7 mph-11%, 7 mph-16%, and 7 mph-22% grade). Mean pHa for each group of ponies became alkaline in the first 60 s (between 7.45 and 7.52) (P less than 0.05) at all work loads. At 6 min pHa was at or above rest at 7 mph-11%, moderately acidic at 7 mph-16% (7.32-7.35), and markedly...
Hodges AA, Harrison AG, Wathes CM.The heights of 89 horses were measured at the withers before and after half a furlong of trotting exercise. The mean (+/- sd) height increase after exercise was 1.75 +/- 0.86 cm and the horses returned to their resting height within seven minutes. There was no linear relationship between gain in height and pre-exercise height.
Goetz TE, Manohar M.Pressures in the right side of the heart and esophagus (pleural) have not been determined in the exercising equine subjects. In the present study, 8 healthy ponies were examined to determine the changes in these variables caused by 2 degrees of exercise done on a treadmill (heart rate:183 +/- 5 beats/min [trot] and 220 +/- 6 beats/min [canter]). Measurements were also made during both degrees of exertion 10 minutes and 120 minutes after furosemide (1.0 mg/kg) administration. It was observed that both gaits resulted in significant increases in pulmonary artery, right ventricular, and right atri...
Tschudi P.The use of the ECG to separate the different phases of the heart cycle registering other physiological signals, to evaluate the fitness and state of training of a horse and to detect a pregnancy of a mare is reported and illustrated in this text.
Kalinskiĭ MI, Kamenetskaia OV, Skorik LG, Tishchenko GN.The paper deals with possibility to regulate in a proper direction the acid-base state in race horse blood administering carbostimulin at rest and under physical exercises. The preparation is shown to favour an increase in alkaline blood reserves in race hours at rest and to prevent acidotic changes caused by physical exercises. The results obtained show a promising use of carbostimulin for the directed correction of the acid-base state of blood in race horses aimed at increasing the efficiency of the training process.
Wilson AM, Pardoe CH.Studies on horseshoe materials have been limited to the analysis of kinematic data to determine slip times and distances, since equine force plate analysis is traditionally undertaken on a rubber-surfaced force plate. The purpose of this study was to modify a force plate for measuring ground reaction forces on a road surface and report preliminary data from the system. A steel-reinforced concrete top plate of 18 mm thickness and mass 23 kg, and a 12 mm thick top plate of 6 mm bituminous macadam wear coat (road surface) contained in a tray constructed of 2 mm thick steel, mass 21 kg, were const...
Manohar M, Goetz TE, Nganwa D.Diaphragmatic O2 and lactate extraction were examined in seven healthy ponies during maximal exercise (ME) carried out without, as well as with, inspiratory resistive breathing. Arterial and diaphragmatic venous blood were sampled simultaneously at rest and at 30-s intervals during the 4 min of ME. Experiments were carried out before and after left laryngeal hemiplegia (LH) was produced. During ME, normal ponies exhibited hypocapnia, hemoconcentration, and a decrease in arterial PO2 (PaO2) with insignificant change in O2 saturation. In LH ponies, PaO2 and O2 saturation decreased well below tha...
Baillet H, Leroy D, Vérin E, Delpouve C, Boulanger J, Benguigui N, Komar J, Thouvarecq R.The present research aims at quantifying the impact of practicing a new coordination pattern with an online visual feedback on the postural coordination performed on a mechanical horse. Forty-four voluntary participants were recruited in this study. They were randomly assigned to four practice groups based on i) with or without feedback (i.e., group 1, control, did not receive the feedback; group 2, 3 and 4 received an online feedback during practice) and ii) the specific trunk/horse coordination to target during practice (group 1, target coordination = 180° (without feedback); group 2, targe...
van Weeren PR, Denoix JM.Juvenile osteochondral conditions (JOCC) have a major impact on the equine industry and include many musculoskeletal disorders of the young horse, of which osteochondrosis (OC) is the most prominent. The Breeding, Osteochondral Status and Athletic Career (BOSAC) project is the first large, comprehensive, longitudinal field study on the subject conducted in three breeds of performance horses (Thoroughbreds, Standardbred Trotters and Warmbloods) that were monitored in their natural environment where they were reared under common field conditions. The BOSAC study used a radiographic protocol desi...
Ekici S, Ozmen O.The active roles of microribonucleic acids (miRNAs) in gene regulation have made miRNAs a key point for the scientific world in the study of physiological processes. Although saliva includes the largest number of miRNAs, there is no miRNA study in saliva on horses has been found. Our study is the first study on miRNAs isolation from saliva in horses. In the present study, saliva was studied in Arabian racehorses to better understand the molecular mechanisms of expression levels that are effective in lipid metabolism of miRNAs and their target genes during the race. Identification of lipid meta...
Ingvast-Larsson C, Kallings P, Persson S, Appelgren LE, Wiese B.The pharmacokinetics of theophylline at rest and the effects on cardio-respiratory and blood lactate responses to exercise were investigated after repeated oral administrations in six healthy Standardbred horses. A dose of 5 mg/kg body weight was administered every 12 h. The binding of theophylline to plasma protein was also determined. There was good agreement between predicted and observed plasma concentrations of theophylline at steady state. The mean half-life of elimination was shown to be 17.0 +/- 2.5 h, the mean half life of absorption was 1.6 +/- 1.8 h, the apparent volume of distribut...
Brand A, Lindner A, Gerhards H, Valenchon M, Petit O.The objective of this study was to explore how the endurance of five-year-old horses, kept out on pasture all their life and ridden for the first time well into their fifth year of age, developed within one year and compared to that of six-year-old horses raised under the same conditions and to other horses. Horses were submitted to a standardized exercise test (SET) to calculate their v (velocity run under defined conditions inducing 4 mmol/L of blood lactate concentration (LA)) and v (velocity run under defined conditions inducing a heart rate of 180 beats/min). The test consisted of up to ...
Nardelli M, Lanata A, Valenza G, Sgorbini M, Baragli P, Scilingo EP.This paper reports on a novel real time index designed to assess the quality of electrocardiographic (ECG) traces recorded in a group of five horses during a submaximal treadmill test procedure. During the experimental protocol two ECG monitoring systems were simultaneously applied to the animals. The first system was equipped with textile electrodes while the second one with standard red-dot electrodes. The procedure comprised four phases with an increased treadmill velocity, specifically, Walk 1, Trot 1, Trot 2 and Gallop. Three signal quality levels have been fixed according to the amount o...
Eto D, Yamano S, Hiraga A, Miyata H.There is little information about the muscle fibre recruitment pattern during sloped and flat track running in Thoroughbred horses. Objective: To examine the glycogen depletion pattern of each muscle fibre type during running on a flat and sloped treadmill. Methods: Thirteen Thoroughbred horses (3-9 years old) were used. They were initially subjected to incremental exercise tests on a treadmill at 10 and 0% inclines in each horse to determine running speed at 90 and 60% VO2max. Needle biopsy samples were obtained from the middle gluteal muscle immediately after the running at 90% VO2max for 4 ...
Dodman NH, Lehr JL, Spaulding GL, Gavriely N.Three sheep, a foal, a pony, and a calf were anesthetized and ventilated for short periods, using a high-frequency oscillatory ventilator. The efficiency of CO2 elimination was characterized at various oscillatory frequencies (50 to 30 Hz) and various tidal volumes, although the tidal volume used was always less than the measured dead space of the animal. In general, increasing either the oscillatory frequency or tidal volume increased CO2 elimination, but increasing the tidal volume had more effect. The relationship between these 3 variables was best described by a power law equation. Ventila...
Escribano BM, Castejón FM, Santisteban R, Agüera EI, Tovar P, Vivo R, Rubio MD.Gender differences have not been shown in relation to the immune system in athletic horses. The aim of the present paper was to elucidate gender differences in the non-specific immune response of the polymorphonuclear neutrophil (PMN), plasma glucose and in hormones before and after an exercise in the lactate threshold (LT). A group of 12 Anglo-Arabian horses (6 females and 6 males, 4-7 years old) was observed. A submaximal exercise test was carried out at the LT. The results showed that males had a higher PMN percentage, plasma glucose values, Adherence index (AI) and random migration than fe...
Kaikkonen M, Hyyppä S.Like potassium (K+), caesium (Cs+) tends to concentrate intracellularly. The aim here was to determine how moderate exercise affects the uptake of Cs+ from blood plasma. Methods: After an intravenous Cs+ dose of 5 micromol kg(-1), plasma Cs+ concentration was followed for 100 min in goats and for 60 min in horses. The latter were divided into two groups, one resting and the other trotting on a treadmill (inclination 3 degrees, speed 5 m s(-1)). Results: The plasma Cs+ concentration follows a multiphase exponential decay curve, which initially could be approximated with a two-phase curve. The i...
Harmegnies NF, Duvivier DH, Vandenput SN, Art T, Lekeux PM, Votion DM.This study aimed to compare exercise-induced pulmonary perfusion redistribution in healthy vs. 'heavey' horses using scintigraphy, a minimally invasive technique. Six healthy (A) and 5 'heavey' horses in remission (B(I)) and during clinical signs of disease (B(II)) were investigated. Dimensions of the exercising pulmonary perfusion (QE) images were expressed in percent of the resting perfusion (QR) images. Computed QE to QR ratios (QE/QR) images enabled the definition of the region more perfused at exercise than at rest (R1). In all groups, exercise induced a major enlargement of the Q image b...
Frape DL.There is no clear evidence that the chronic requirement for any non-energy yielding nutrient rises in proportion as the energy requirement increases with hard work. The need for protein, and probably that for calcium, remain a function of bodyweight daily. Some proportionality with energy may exist for certain nutrients, although the evidence has not been adduced. For example, because of an increase in both the proportion and amount of propionic acid in the volatile fatty acids of caecal contents, the tissue requirement for vitamin B12 may rise with an increase in the rate of energy metabolism...
Hinchcliff KW, McKeever KH, Muir WW.The systemic haemodynamic and acid-base effects of the administration of phenylbutazone (4.4 mg kg-1 intravenously) to standing and running horses were investigated. Phenylbutazone, or a placebo, was administered to each of six mares either 15 minutes before, or after 30 minutes of a 60-minute submaximal exercise test which elicited heart rates approximately 55 per cent of maximal, and to the same horses at rest. The variables examined included the cardiac output, heart rate, systemic and pulmonary arterial pressures, right atrial and right ventricular pressures, and arterial and mixed venous ...
Hanák J, Chvátal O, Janda J.Sixty seven thoroughbred race horse of various age categories were examined electrocardiographically by bipolar leak-apex of the heart -- withers; length of training corresponded to the age categories. Basic time and voltage criteria of EKG were statistically evaluated according to electrocardiographic curves: TF = 35.1 = %/- 6.82 pulses per min., time P = 0.16 +/- 0.03 sec., PQ = 0.03 +/- 0.04 sec., QRS = 0.12 +/- +/- 0.01 sec., TQc = 0.50 sec., R = 2.83 +/- 0.63 mV, Q = 0.38 +/- 0.31 mV. Repolarization phase of the chamber complex, mainly the T wave, is the most variable component of the who...
Butudom P, Foreman JH, Kline KH, Whittem EL.Some methods of lactate (LA) measurement have not been validated appropriately for use in horses. Objective: To validate 2 LA analysers (YSI 2300 Stat Plus and TDx Lactic Acid Assay) for use with equine plasma and to compare plasma [LA] determined by the 2 methods. Methods: Both instruments were evaluated for linearity, parallelism, recovery and precision using serial dilutions of standard LA solutions and equine plasma and then comparing results with linear regression or paired t tests. Plasma [LA] results were compared in 275 blood samples collected from horses exercising at various intensit...
Soma LR, Uboh CE, Nann L, Gerber AL.The administration of sodium bicarbonate (NaHCO3) or 'milk shakes' to Standardbred horses before racing is widespread. This study analysed nonrace day (CTL) and prerace venous acid-base values from Standardbred horses racing in Pennsylvania (PA) and New Jersey (NJ). Mean +/- s.d. CTL bicarbonate (HCO3) and base excess (BE) values, for a group of horses stabled during the 1993 racing season at Pocono Downs, Pennsylvania, were 28.6 +/- 1.9 and 2.6 +/- 1.7 mmol/l, respectively. In the same population of horses, mean +/- s.d. values for prerace HCO3- and BE values were 33.1 +/- 2.8 and 7.0 +/- 2.3...
Gehlen H, Bubeck K, Stadler P.In 12 healthy warmblood horses (six trained and six untrained) the pulmonary wedge pressure and heart frequency was measured at rest and during a standardised exercise test on a treadmill. The mean pulmonary wedge pressure at rest was 14.53 +/- 2.36 mmHg. There was no significant difference in pulmonary wedge pressure either at rest or during exercise between trained and untrained horses. During walking (1.8 m/s) the mean pulmonary wedge pressure was 19.62 +/- 4.03 mmHg, during trotting (4 und 5 m/s) it was between 22.38 +/- 3.92 mmHg and 25.28 +/- 3.7 mmHg. During canter (6 m/s) and gallop (8...
Peloso JG, Stick JA, Nickels FA, Lumsden JM, Derksen FJ.A 2-year-old 400-kg Standardbred colt with a history of exercise intolerance was determined to have dorsal displacement of the soft palate (DDSP). Standing endoscopy revealed a soft, flaccid, and hypoplastic epiglottis and arytenoid cartilages that moved symmetrically and abducted fully. Lateral laryngeal radiography was used to calculate a corrected thyroepiglottic length of 6.48 cm. Videoendoscopy during exercise on a high-speed treadmill at standardized treadmill speeds was performed weekly for 3 consecutive weeks. The soft palate dorsally displaced at each examination. A sternohyoideus/ste...
Kwok WH, Choi TLS, Leung GNW, Wong ASY, Yue SK, Wan TSM, Ho ENM.The insulin-like peptide relaxin (RLX), an endogenous peptide hormone produced in human for pregnancy and reproduction, is also known to exert a range of physiological and pathological effects. Its use is banned in human sports, horseracing, and equestrian competitions due to its potential performance enhancing effect through vasodilation resulting in the increase of blood and oxygen supplies to muscles. Little is known about the biotransformation and elimination of RLX in horses. This paper describes an administration study of rhRLX-2 and its elimination in horses, and the development of sens...
McKeever KH.This article has presented information on the importance of the sympathetic nervous system in the response to exercise. The authors have reviewed the very limited information on the effects of sympathomimetic and sympatholytic drugs on exercise performance in the horse. Most of these drugs are specifically prohibited under the rules of racing, and they have significant side effects that either decrease performance or make their use dangerous to both the horse and horse-man. Additionally, all of these drugs or their metabolites are readily detected by current drug testing protocols. Further inf...
Thomason JJ, Bignell WW, Sears W.The relative contribution of a number of random and fixed variables to variation in surface strain magnitudes on the hoof capsule was assessed for healthy feet under normal conditions. Principal strains were recorded in vivo from 5 rosette gauges glued around the circumference of the right forefeet of 4 horses on 4 occasions over a 9 month period. Recordings were made at every other trimming and reshoeing. During each session, gauges were positioned with a template for repeatability. Strains were recorded at the trot and canter (at consistent speeds), for straight motion and turns, and before ...
Bain FT, Merritt AM.To investigate the possibility that a disorder of potassium balance may have a role in the development of equine rhabdomyolysis, the potassium concentration within erythrocytes (RBC [K+]) and plasma (P [K+]) was measured in 3 groups of horses: group 1, eight 2-year-old fillies that had postexercise muscle soreness within 48 hours of sample collection; group 2, ten 2-year-old fillies subjected to identical management and training conditions (as fillies of group 1) and that did not have signs of myopathy; and group 3, 32 yearlings of both sexes on the farm of origin of groups 1 and 2 that were p...
Hartley JW, Hahn AW, DeLorey M, Caldwell WM.We have developed and used a system for recording and analyzing the electrocardiogram (ECG) of the horse during exercise. The system consists of a commercial ECG transmitter telemetering a Z lead (base-apex) ECG from an exercising horse. The received data are then remodulated at an audio frequency and stored on a audio cassette recorder. Exercise protocols of up to 10 minutes are digitized using a Macintosh II computer. For rhythm analysis, a computer program to identify the various waves of the ECG uses a modification and refinement of the integrated-squared-derivative (ISD) technique. This t...
Jiang B, Rugh KS, Hatfield DG, Jiang D, Hahn AW.We have developed a digital signal analysis technique which can be used to evaluate various cardiac events in ponies and horses at rest and during exercise. The algorithm is designed to identify R-wave peaks on the surface electrocardiogram, consistent reference points on the left ventricular pressure waveform and the initiation of the QRS complex on the epicardial electrogram. We have used the technique to evaluate data from 10 horses and ponies at rest, during strenuous exercise and during experimentally-induced coronary artery occlusion. The technique provided rapid and accurate beat-by-bea...
Knight PK, Ray SP, Rose RJ.Because the haemoglobin concentration Hb[ during exercise may be at the upper limit of blood viscosity for effective oxygen delivery, we hypothesised that administration of blood would not further enhance oxygen delivery or exercise capacity. Six Thoroughbred geldings were used in 5 incremental treadmill exercise tests over a period of 4 weeks. The first test was performed 6 days prior to phlebotomy, which involved the removal of 20 ml/kg bwt of venous blood. Exercise tests were performed at 1, 8 and 15 days after blood removal. Six days after the 15 day post phlebotomy exercise test, blood fr...
Shearman JP, Hopkins WG.To evaluate the reliability of 2 time-trial protocols, 1 that involved use of a pacemaker and 1 that did not, for assessing performance of Standardbred racehorses. Methods: 3- to 7-year-old Standardbred maiden pacers. Methods: 11 Standardbred pacers were used to determine the reliability of a time-trial protocol that involved use of a galloping pacemaker. All tests were performed by a single driver. Horses were paced for an initial 1,600 m then raced and timed for the final 800 m. They were retested 9 days later. Twenty-two horses were used to determine the reliability of a time-trial protocol...
Smetzer DL, Senta T, Hensel JD.Each of nine horses was treated with amphetamine alone, with atropine alone, and with amphetamine and atropine in combination. Cardiac effects of these drugs were studied by electrocardiography during resting and exercising states and immediately after exercise. Although each treatment increased heart rate significantly during the resting state, only the amphetamine plus atropine treatment increased heart rate significantly during exercise. Decrease in heart rate immediately after exercise differed significantly for each treatment; the most rapid decrease in heart rate was found after the amph...
Haynes PF.The intent and extent of the respiratory tract examination relevant to purchase are dictated by numerous factors, including historical information, signs suggestive of respiratory tract abnormalities, intended use of the horse, and economic considerations. Following a thorough and systematic examination of the horse at rest, evaluation during and following exercise may be warranted. The physical examination should include evaluation of regional symmetry of the head, neck, and thorax; evaluation of nasal airflow and patency; palpation of the nasal septum, larynx, and trachea; examination for su...
